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Atmospheric Environment (v.67, #)

Editorial board (pp. i).

Fast determination of 3-ethenylpyridine as a marker of environmental tobacco smoke at trace level using direct atmospheric pressure chemical ionization tandem mass spectrometry by Cheng-Yong Jiang; Shi-Hao Sun; Qi-Dong Zhang; Jun-Hui Liu; Jian-Xun Zhang; Yong-Li Zong; Jian-Ping Xie (pp. 1-7).

A method with atmospheric pressure chemical ionization tandem mass spectrometry (APCI-MS/MS) was developed and applied to direct analysis of Environmental Tobacco Smoke (ETS), using 3-ethenylpyridine (3-EP) as a vapour-phase marker. In this study, the ion source of APCI-MS/MS was modified and direct analysis of gas sample was achieved by the modified instrument. ETS samples were directly introduced, via an atmospheric pressure inlet, into the APCI source. Ionization was carried out in positive-ion APCI mode and 3-EP was identified by both full scan mode and daughter scan mode. Quantification of 3-EP was performed by multiple reaction monitoring (MRM) mode. The calibration curve was obtained in the range of 1–250 ng L⁻¹ with a satisfactory regression coefficient of 0.999. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.5 ng L⁻¹ and 1.6 ng L⁻¹, respectively. The precision of the method, calculated as relative standard deviation (RSD), was characterized by repeatability (RSD 3.92%) and reproducibility (RSD 4.81%), respectively. In real-world ETS samples analysis, compared with the conventional GC–MS method, the direct APCI-MS/MS has shown better reliability and practicability in the determination of 3-EP at trace level. The developed method is simple, fast, sensitive and repeatable; furthermore, it could provide an alternative way for the determination of other volatile pollutants in ambient air at low levels.Display Omitted► A novel direct APCI-MS/MS method has been developed for monitoring of 3-EP in ETS. ► ETS sampling was carried out using a new gas sampler without any external forces. ► The APCI source was modified to allow the direct introduction of ETS samples. ► Advantages of the method: simplicity, high speed, good sensitivity and repeatability.

Keywords: 3-Ethenylpyridine; Atmospheric pressure chemical ionization; Mass spectrometry; Environmental tobacco smoke

Sea ice in the Arctic Ocean: Role of shielding and consumption of methane by Xin He; Liguang Sun; Zhouqing Xie; Wen Huang; Nanye Long; Zheng Li; Guangxi Xing (pp. 8-13).

Sources and sinks of methane, one of the most important greenhouse gases, have attracted intensive attention due to its role in global warming. We show that sea ice in the Arctic Ocean regulates methane level through two mechanisms, shielding of methane emission from the ocean, and consumption of methane. Using a static chamber technique, we estimated that the methane flux from under-ice water was 0.56 mg(CH₄) m⁻² d⁻¹ on average in central Arctic Ocean, relatively higher than that in other oceans, indicating considerable methane storage in this region under sea ice. Average methane flux on under-ice water was higher than that above sea ice, which suggests that sea ice could limit methane emission. In addition, negative fluxes on sea ice suggest that there are methane consuming processes, which are possibly associated with both photochemical and biochemical oxidation. Our results provide a general understanding about how sea ice in Arctic affects regional and global methane balance.► We compared methane fluxes under two conditions, with and without ice cover. ► There is considerable methane potentially storing in central Arctic Ocean. ► Sea ice limits methane emission in Arctic. ► Sea ice absorbs methane in atmosphere potentially related to both photochemical and biochemical oxidation.

Keywords: Methane; Central Arctic Ocean; Sea ice; Under-ice water

Size-resolved comprehensive characterization of airborne particulate matter by E. Cuccia; D. Massabò; V. Ariola; M.C. Bove; P. Fermo; A. Piazzalunga; P. Prati (pp. 14-26).

An update of a methodology to extract both the size-segregated source apportionment of atmospheric aerosol and the size distribution of each detected element or compound, is presented. The approach is based on the parallel use of standard low-volume samplers to collect particulate matter (PM) and of an Optical Particle Counter (OPC). The methodology was introduced and validated in previous works for the average size distribution of elemental components of PM: it has now been extended to PM compounds such as ions and carbonaceous aerosol (namely, organic end elemental carbon, OC and EC). Furthermore, the methodology has been now adopted in the frame of a field campaign, proving that it is able to provide not only an average size distribution but also information on the time evolution of the size distribution of specific PM species. Samples were collected in the urban area of Genoa (Italy) and their composition was measured by Energy Dispersive X-ray Fluorescence (ED-XRF), Ion Chromatography (IC) and Thermo-optical analysis. Positive Matrix Factorization (PMF) was applied to time series of daily concentration values in PM10 and PM2.5 (i.e. fraction of PM mass with aerodynamic diameter lower that 10 μm and 2.5 μm, respectively) to identify major PM sources, and both PM mass concentration and size-segregated particle number concentration were apportioned. Seven and six sources were respectively resolved in PM10 and PM2.5, with processes related to secondary aerosol formation accounting for about 53% and 57% of PM levels in the two fractions. The new methodology is complementary to size-segregated PM sampling, and it was actually tested against a 13-stage nanoMOUDI cascade impactor. Size distributions obtained with the new methodology and directly measured by the nanoMOUDI turned out to be in good agreement ( R² > 0.60) with discrepancies observed forSO42− only.► Size distribution of aerosol components has been obtained without using impactors. ► The new methodology can follow the temporal evolution of aerosol size distribution. ► Validation of in-field data against a 13-stage cascade impactor has been performed.

Keywords: Particulate matter; Size distribution; Optical counter; Positive matrix factorization

Polycyclic aromatic hydrocarbons and hopanes in PM1 aerosols in urban areas by K. Křůmal; P. Mikuška; Z. Večeřa (pp. 27-37).

The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs), 4 hopanes and ααα (20 R)-cholestane in PM1 aerosol samples were measured in two cities of the Czech Republic (Brno and Šlapanice) in winter and summer season of 2009 and 2010. Daily PM1 aerosol samples were collected on pre-fired quartz fibre filters.Mass concentrations of PM1 aerosols were higher in winter than in summer both in Brno and Šlapanice during both 2009 and 2010.The mean total PAH concentrations (∑ 16 PAHs) in PM1 aerosol was 22.2 ng m⁻³ in Brno and 21.0 ng m⁻³ in Šlapanice during winter period 2009 while the mean total PAH concentrations was 5.01 ng m⁻³ in Brno and 5.41 ng m⁻³ in Šlapanice in summer 2009. In winter 2010, the mean total PAH concentrations was 39.8 ng m⁻³ and 38.7 ng m⁻³ in Brno and Šlapanice whereas, in summer 2010, the mean total PAH concentrations was 1.68 ng m⁻³ and 1.52 ng m⁻³ at the same localities.The mean total concentrations of four hopanes and a sterane were much smaller than those for PAHs. On the contrary, the difference between the mean total concentrations of hopanes and sterane in winter and summer season was not so large as it was found for PAHs.Analysis of source specific molecular markers and diagnostic ratios of PAHs and hopanes were employed to identify the main emission sources of these compounds. Diagnostic ratios imply that during winter the origin of PAHs was mainly from coal/biomass burning while hopanes originate mainly from coal combustion. During summer season, traffic is proposed as the main emission source of particulate PAHs and hopanes.Organic and elemental carbon were analysed in collected PM1 samples too. Organic carbon contributes significantly to the total mass of PM1 aerosols ranging from 24 to 31% in winter season and from 21 to 29% in summer season.► Analysis of 16 PAHs, 4 hopanes and ααα (20 R)-cholestane in PM1 aerosols. ► Winter and summer samples of 2009 and 2010 in Brno and Šlapanice. ► Molecular markers and diagnostic ratios for identification of emission sources. ► Traffic and combustion of coal and wood identified as main emission sources of PM1.

Keywords: PAHs; Hopanes; Diagnostic ratio; Coal combustion; Traffic; PM1

Airborne particle concentrations at schools measured at different spatial scales by G. Buonanno; F.C. Fuoco; L. Morawska; L. Stabile (pp. 38-45).

Potential adverse effects on children health may result from school exposure to airborne particles. To address this issue, measurements in terms of particle number concentration, particle size distribution and black carbon (BC) concentrations were performed in three school buildings in Cassino (Italy) and its suburbs, outside and inside of the classrooms during normal occupancy and use. Additional time resolved information was gathered on ventilation condition, classroom activity, and traffic count data around the schools were obtained using a video camera. Across the three investigated school buildings, the outdoor and indoor particle number concentration monitored down to 4 nm and up to 3 μm ranged from 2.8 × 10⁴ part cm⁻³ to 4.7 × 10⁴ part cm⁻³ and from 2.0 × 10⁴ part cm⁻³ to 3.5 × 10⁴ part cm⁻³, respectively. The total particle concentrations were usually higher outdoors than indoors, because no indoor sources were detected. I/O measured was less than 1 (varying in a relatively narrow range from 0.63 to 0.74), however one school exhibited indoor concentrations higher than outdoor during the morning rush hours. Particle size distribution at the outdoor site showed high particle concentrations in different size ranges, varying during the day; in relation to the starting and finishing of school time two modes were found. BC concentrations were 5 times higher at the urban school compared with the suburban and suburban-to-urban differences were larger than the relative differences of ultrafine particle concentrations.► Airborne particle and black carbon concentrations were measured at three schools. ► Spatial and temporal variations of particles at three different scales were analyzed. ► Concentrations at urban schools scale are higher than background ones due to traffic. ► Building lowers the particle concentration experienced by children in the schools. ► A 30% indoor spatial variation in concentration at schools facing a trafficked street.

Keywords: Particle number concentration; Traffic emissions; Airborne particle spatial variation; School; Children exposure

Impact of nesting resolution jump on dynamical downscaling ozone concentrations over Belgium by D. Lauwaet; P. Viaene; E. Brisson; T. van Noije; A. Strunk; S. Van Looy; B. Maiheu; N. Veldeman; L. Blyth; K. De Ridder; S. Janssen (pp. 46-52).

Global air quality datasets with a coarse resolution have to be downscaled to become useful for regional interpretation, for instance by applying dynamical downscaling. Here, the downscaling ability of the regional air quality model AURORA (Air quality modelling in Urban Regions using an Optimal Resolution Approach) for surface ozone concentrations is evaluated over a model domain covering a large part of Belgium. The impact of two different one-way nesting resolution jumps is studied. Additionally, the effect of horizontal grid spacing on the simulation results is investigated. Model evaluation against measurements from a number of urban/suburban and rural background stations and a gridded interpolation map shows that the model is capable of reproducing the observed temporal and spatial patterns. The results indicate that the two applied nesting resolution jumps are comparably successful in simulating the surface ozone concentrations, despite the large resolution jump (25–3 km) in one of the approaches. The impact of horizontal resolution on the modelled time series at different types of locations is relatively small, with the average difference around 1% of the mean concentrations. However, the benefits of the higher resolution express themselves in the spatial correlations and temporal variances of the simulation results.► Surface ozone concentrations were downscaled over Belgium. ► Model evaluation showed the capability of reproducing observed concentrations. ► Two different nesting resolution jumps were found to be comparably successful. ► Impact of a resolution increase is relatively small.

Keywords: AURORA; COSMO–CLM; Ozone; Downscaling; Nesting; Resolution

Study of tropospheric CO and O₃ enhancement episode over Indonesia during Autumn 2006 using the Model for Ozone and Related chemical Tracers (MOZART-4) by Shuchita Srivastava; Varun Sheel (pp. 53-62).

An intense biomass burning event occurred over Indonesia in Autumn of 2006. We study the impact of this event on the free tropospheric abundances of carbon monoxide (CO) and ozone (O₃) using MOPITT (Measurements of Pollution In The Troposphere) observations, ozonesonde measurements and 3D chemistry transport model MOZART (Model for Ozone and Related chemical Tracers). MOPITT observations showed an episode of enhanced CO in the free troposphere over the Indonesian region during October–November 2006. This feature is reproduced well by MOZART. The model mass diagnostics identifies the source of enhanced CO mixing ratio in the free troposphere (100–250 ppbv) as due to convective processes. The implication of the fire plume on the vertical distribution of O₃ over Kuala Lumpur has been studied. The tropospheric O₃ increased over this location by 10–25 ppbv during Autumn 2006 as compared to Autumn 2005 and 2007. The MOZART model simulation significantly underestimated this tropospheric O₃ enhancement. The model is run both with and without Indonesian biomass burning emissions to estimate the contribution of fire emission in CO and O₃ enhancement. Biomass burning emission is found to be responsible for an average increase in CO by 104 ± 56 ppbv and O₃ by 5 ± 1 ppbv from surface to 100 hPa range. The model results also showed that biomass burning and El Niño related dynamical changes both contributed (∼4 ppbv–12 ppbv) to the observed increase in tropospheric O₃ over the Indonesian region during Autumn 2006.► Study of CO distribution over Indonesia during a fire event using MOPITT and MOZART. ► Assessing role of convection, advection and chemistry on CO budget over Indonesia. ► Quantification of O₃ enhancement due to biomass burning emission and large scale transport.

Keywords: Carbon monoxide; Ozone; Indonesia; Biomass burning; Chemical transport model

Heterogeneous reactions of gaseous hydrogen peroxide on pristine and acidic gas-processed calcium carbonate particles: Effects of relative humidity and surface coverage of coating by Yue Zhao; Zhongming Chen; Xiaoli Shen; Dao Huang (pp. 63-72).

Atmospheric aging appears to alter physical and chemical properties of mineral dust aerosol and thus its role as reactive surface in the troposphere. Yet, previous studies in the atmosphere have mainly focused on the pristine surfaces of mineral dust aerosol, and the reactivity of aged mineral dust toward atmospheric trace gases is poorly recognized. This work presents the first laboratory investigation of heterogeneous reactions of gaseous hydrogen peroxide (H₂O₂), an important atmospheric oxidant, on the surfaces of HNO₃ and SO₂-processed calcium carbonate particles as surrogates of atmospheric mineral dust aged by acidic trace gases. It is found that the processing of the calcium carbonate particles with HNO₃ and SO₂ has a strong impact on their reactivity toward H₂O₂. On HNO₃-processed particles, the presence of nitrate acts to either decrease or increase H₂O₂ uptake, greatly depending on RH and surface coverage of nitrate. On SO₂-processed particles, the presence of surface sulfite appears to enhance the intrinsic reactivity of the mineral particles due to its affinity for H₂O₂, and the uptake of H₂O₂ increases significantly relative to the pristine particles, in particular at high RH. The mechanisms for heterogeneous reactions of H₂O₂ with these processed particles are discussed, as well as their potential implications on tropospheric chemistry. The results of our study suggest that the reactivity of mineral dust aerosol toward H₂O₂ and maybe other trace gases is markedly dependent on the chemical composition and coverage of the coatings as well as ambient RH, and thus will vary considerably in different polluted air masses.► First kinetic study of H₂O₂ uptake on acidic gas-aged mineral dust. ► H₂O₂ uptake on calcium carbonate is highly related to acidic gas aging. ► H₂O₂ favors sulfate formation on mineral dust particularly at high RH. ► Atmospheric aging of mineral dust should be considered in atmospheric models.

Keywords: Atmospheric hydrogen peroxide; Heterogeneous reactions; Calcium carbonate; Mineral dust; Atmospheric aging

Emission of unintentionally produced polychlorinated biphenyls (UP-PCBs) in China: Has this become the major source of PCBs in Chinese air? by Song Cui; Hong Qi; Li-Yan Liu; Wei-Wei Song; Wan-Li Ma; Hong-Liang Jia; Yong-Sheng Ding; Yi-Fan Li (pp. 73-79).

There are two kinds of primary emissions of PCBs to the atmosphere; one is primary emissions due to intentionally produced PCBs (IP-PCBs), and the other is due to unintentionally produced PCBs (UP-PCBs). This paper presents UP-PCB emissions in China from 1950 to 2010. The total UP-PCB emissions in the 61 years were estimated to be 146.1 t, approximately 98.1% of which were from cement (132.5 t) and steel industries (6.3 t). The emissions from Chinese coking industry were 115 kg from 1950 to 2010, less than 0.1% of the total UP-PCB emissions in China. Both the temporal and spatial trends of these UP-PCB emissions were investigated. The UP-PCB emissions started to increase quickly at the middle of 1980s due to the fast and continuously developing cement and steel industries in China, and exceeded IP-PCB emissions possibly during the beginning of 2000s. The spatial pattern of UP-PCB emissions was in general consistent with the population distribution pattern, indicating the anthropogenic nature of the UP-PCB emissions. The gridded Chinese emission inventories for UP-PCBs from cement and steel industries on a 1/6° latitude and 1/4° longitude resolution were also compiled. The gridded UP-PCB emissions in 2005 were compared with PCB air concentrations measured by our group (IJRC-PTS) in 2005, and a significant correlation between these 2 datasets was found for the rural sites, but not for the urban sites. It is most likely that these UP-PCB emissions were a major source for PCB in Chinese rural air, and possibly responsible for the increase of PCBs in Chinese air as a whole from 2004 to 2008, reported in recent publications. To our knowledge, this is the first dataset of the Chinese UP-PCB emissions spanning 61 years from 1950 to 2010, and also the first gridded emission inventories for UP-PCBs on a national scale.Display Omitted► The first emission inventories of UP-PCBs in China were conducted. ► From 1950 to 2010, total UP-PCB emissions in China were estimated at 146 t. ► Spatial pattern of UP-PCBs was consistent with population distribution pattern. ► UP-PCBs predominated in rural areas and IP-PCBs in urban centers. ► UP-PCBs seem to have overtaken IP-PCBs as a major source of PCBs in China.

Keywords: PCB air concentrations; Unintentionally produced POPs; Emission inventories; China

A simplified method for assessing particle deposition rate in aircraft cabins by Ruoyu You; Bin Zhao (pp. 80-84).

Particle deposition in aircraft cabins is important for the exposure of passengers to particulate matter, as well as the airborne infectious diseases. In this study, a simplified method is proposed for initial and quick assessment of particle deposition rate in aircraft cabins. The method included: collecting the inclined angle, area, characteristic length, and freestream air velocity for each surface in a cabin; estimating the friction velocity based on the characteristic length and freestream air velocity; modeling the particle deposition velocity using the empirical equation we developed previously; and then calculating the particle deposition rate. The particle deposition rates for the fully-occupied, half-occupied, 1/4-occupied and empty first-class cabin of the MD-82 commercial airliner were estimated. The results show that the occupancy did not significantly influence the particle deposition rate of the cabin. Furthermore, the simplified human model can be used in the assessment with acceptable accuracy. Finally, the comparison results show that the particle deposition rate of aircraft cabins and indoor environments are quite similar.

Keywords: Aerosol; Aircraft cabin; Deposition; Indoor air quality (IAQ)

Relative rate coefficients of OH radical reactions with CF₃CFCClCF₃ and CF₃CHCHCH₂OH. Ozone depletion potential estimate for CF₃CFCClCF₃ by Juan Pablo Aranguren Abrate; Ignacio Pisso; Silvina Anahí Peirone; Pablo Marcelo Cometto; Silvia Irene Lane (pp. 85-92).

The relative rate method was used to determine the rate coefficients for the reactions of OH radicals with CF₃CFCClCF₃ ( k₁) and CF₃CHCHCH₂OH ( k₂). Experiments were carried out at (298 ± 2) K and atmospheric pressure using ultra pure air or ultra pure nitrogen as the gas bath. The k₁ value was measured relative to those of chloroethane and ethane, and the k₂ value was measured relative to those of cyclohexene and 1-pentene. The following rate coefficients were derived in units of cm³ molecule⁻¹ s⁻¹: k₁ = (3.3 ± 0.9) × 10⁻¹³ and k₂ = (3.3 ± 0.9) × 10⁻¹¹. This is the first experimental determination of k₁ and k₂. The rate coefficients were used to estimate the atmospheric lifetimes for the studied haloalkenes considering the OH-initiated oxidation process. The ozone depletion potential (ODP) for CF₃CFCClCF₃ was estimated following a recently-developed technique based on Lagrangian trajectories, which takes into account the time and location of the release of the short-lived halogenated species.Display Omitted► Reaction rate constants for OH with CF₃CFCClCF₃ and CF₃CHCHCH₂OH were determined. ► Atmospheric lifetimes of CF₃CFCClCF₃ and CF₃CHCHCH₂OH were estimated. ► ODP calculations for CF₃CFCClCF₃ were performed. ► ODP of CF₃CFCClCF₃ depends on emission scenarios. ► ODP of CF₃CFCClCF₃ is of minor importance, but not zero.

Keywords: OH radical; Rate coefficient; Atmospheric chemistry; Halogenated alkenes; Ozone depletion potential; Lagrangian trajectories

Cl atom initiated oxidation of 1-alkenes under atmospheric conditions by M. Walavalkar; A. Sharma; H.D. Alwe; K.K. Pushpa; S. Dhanya; P.D. Naik; P.N. Bajaj (pp. 93-100).

In view of the importance of the oxidation pathways of alkenes in the troposphere, and the significance of Cl atom as an oxidant in marine boundary layer (MBL) and polluted industrial atmosphere, the reactions of four 1-alkenes (C6–C9) with Cl atoms are investigated. The rate coefficients at 298 K are measured to be (4.0 ± 0.5), (4.4 ± 0.7), (5.5 ± 0.9) and (5.9 ± 1.7) × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹ for 1-hexene, 1-heptene, 1-octene and 1-nonene, respectively. The quoted errors include the experimental 2σ, along with the error in the reference rate coefficients. From the systematic increase in the rate coefficients with the number of carbon atoms, an approximate value for the average rate coefficient for hydrogen abstraction per CH₂ group in alkenes is estimated to be (4.9 ± 0.3) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹. Based on these rate coefficients, the contribution of Cl atom reactions towards the degradation of these molecules is found to be comparable to that of OH radical reactions, under MBL conditions. The products identified in gas phase indicate that Cl atom addition occurs mainly at the terminal carbon, leading to the formation of 1-chloro-2-ketones and 1-chloro-2-ols. The major gas phase products from the alkenyl radicals (formed by H atom abstraction) are different positional isomers of long chain enols and enones. A preference for dissociation leading to an allyl radical, resulting in aldehydes, lower by three carbon atoms, is indicated. The observed relative yields suggest that in general, the increased contribution of the reactions of Cl atoms towards degradation of 1-alkenes in NOx free air does not result in an increase in the generation of small aldehydes (carbon number < 4), including chloroethanal, as compared to that in the reaction of 1-butene.► Reports the rate coefficients of Cl reactions with1-alkenes (C6–C9) at 298 K. ► Cl contributes as much as OH towards the degradation of 1-alkenes in MBL. ► Increased role of H abstraction in higher alkenes. ► No increase in dissociation and generation of small aldehydes (C < 4). ► Major gas phase products in NO_x free air are 1-chloro-2-ones/ols; enones; enols.

Keywords: 1-Alkenes; Cl atom reactions; Rate coefficients; Tropospheric lifetimes; Aldehyde formation

A GIS based emissions inventory at 1 km × 1 km spatial resolution for air pollution analysis in Delhi, India by Sarath K. Guttikunda; Giuseppe Calori (pp. 101-111).

In Delhi, between 2008 and 2011, at seven monitoring stations, the daily average of particulates with diameter <2.5 μm (PM_2.5) was 123 ± 87 μg m⁻³ and particulates with diameter <10 μm (PM₁₀) was 208 ± 137 μg m⁻³. The bulk of the pollution is due to motorization, power generation, and construction activities. In this paper, we present a multi-pollutant emissions inventory for the National Capital Territory of Delhi, covering the main district and its satellite cities – Gurgaon, Noida, Faridabad, and Ghaziabad. For the base year 2010, we estimate emissions (to the nearest 000's) of 63,000 tons of PM_2.5, 114,000 tons of PM₁₀, 37,000 tons of sulfur dioxide, 376,000 tons of nitrogen oxides, 1.42 million tons of carbon monoxide, and 261,000 tons of volatile organic compounds. The inventory is further spatially disaggregated into 80 × 80 grids at 0.01° resolution for each of the contributing sectors, which include vehicle exhaust, road dust re-suspension, domestic cooking and heating, power plants, industries (including brick kilns), diesel generator sets and waste burning. The GIS based spatial inventory coupled with temporal resolution of 1 h, was utilized for chemical transport modeling using the ATMoS dispersion model. The modeled annual average PM_2.5 concentrations were 122 ± 10 μg m⁻³ for South Delhi; 90 ± 20 μg m⁻³ for Gurgaon and Dwarka; 93 ± 26 μg m⁻³ for North-West Delhi; 93 ± 23 μg m⁻³ for North-East Delhi; 42 ± 10 μg m⁻³ for Greater Noida; 77 ± 11 μg m⁻³ for Faridabad industrial area. The results have been compared to measured ambient PM pollution to validate the emissions inventory.► An emissions inventory for PM, SO₂, NO_x, CO, and VOCs for Delhi, India. ► Resources for activity data utilized for emissions inventory. ► A gridding inventory at 1 km × 1 km spatial resolution and 1 h temporal resolution. ► Validation of the inventory via particulate dispersion modeling.

Keywords: Megacity; Urban; Air Quality Management; Dispersion modeling

Development of a new LOPAP instrument for the detection of O₃ in the atmosphere by S. Peters; I. Bejan; R. Kurtenbach; S. Liedtke; G. Villena; P. Wiesen; J. Kleffmann (pp. 112-119).

A simple O₃-LOPAP (Long Path Absorption Photometer) instrument for the selective detection of O₃ in the atmosphere is presented, which is mainly intended to be used as an extension of a recently developed NO₂-LOPAP. O₃ is sampled in a stripping coil by a selective chemical reaction with the highly absorbing Indigo dye. The reduction of the optical absorption of the dye is detected in a liquid core waveguide. The instrument has a detection limit of 0.4 ppbv, an accuracy of 10%, a precision of 2% for 6 min time resolution and allows the absolute quantification of O₃ according to Lambert–Beer's law. Interferences towards nitrogen oxides (NO and NO₂), N₂O₅, H₂O₂ and several VOCs were quantified in the laboratory and found to be negligible for atmospheric conditions. The new instrument was successfully validated against a commercial UV-absorption instrument during an urban field campaign and against the FTIR technique in a smog chamber under complex photosmog conditions. For the UV-absorption instrument significant positive interferences towards aromatic species were observed in the smog chamber.► A simple instrument for the detection of O₃ is presented. ► Sensitive, selective and absolute quantification by Lambert–Beer's law. ► Single interferences studied can be negligible for atmospheric conditions. ► Successful validation in the atmosphere and in a complex smog chamber experiment.

Keywords: Ozone; Instrument development; Interferences; Intercomparison

CCN estimates from bulk hygroscopic growth factors of ambient aerosols during the pre-monsoon season over Central Nepal by Prabhakar Shrestha; Ana P. Barros; Andrei Khlystov (pp. 120-129).

Aerosol size distribution (ambient and dried) and chemical composition were measured simultaneously using two Scanning Mobility Particle Sizers (SMPSs) and filters during the pre-monsoon season (April–June 2009) at two locations in Central Nepal: Dhulikhel, an urban site in the Kathmandu valley, and Besisahar, a rural village in the Marsyangdi valley. Diameter growth factors (DGF) were estimated using the larger mode (around 100 nm) of the aerosol size distributions. The measured DGF suggest that the aerosols were in metastable state below 80% RH owing to the strong diurnal cycle of relative humidity (RH) at Dhulikhel, while no discernible growth was observed for Besisahar. Assuming ideal behavior of water-soluble organic compounds and using their fraction as determined by water extraction of filters produced the best agreement for a two-component hygroscopic growth model with the observed DGFs. This finding together with the DGF and chemical composition data were used to determine the aerosol bulk hygroscopicity parameter,κ. Theκ parameter suggests that aerosols in this region are less hygroscopic than aerosols reported in previous studies from other regions. The estimatedκ and the vertically scaled aerosol size distribution were then used to estimate the CCN spectra. These are the first estimates of CCN spectra from ground-based observations for the Central Himalaya region.► Aerosol Hygroscopicity and CCN spectra estimated for Central Nepal. ► DGF and Chemical Composition data used for hygroscopicity estimates. ► Aerosols found to be less hygroscopic and in metastable state. ► Two-component hygroscopic growth model used to explain growth factor. ► Effect of WSOC solubility on CCN estimates also addressed.

Keywords: Hygroscopicity; Aerosol size distribution; CCN; Nepal

Influence of measurement frequency on the evaluation of short-term dose of sub-micrometric particles during indoor and outdoor generation events by M. Manigrasso; L. Stabile; P. Avino; G. Buonanno (pp. 130-142).

Aerosol generation events due to combustion processes are characterized by high particle emissions in the nucleation mode range. Such particles are characterized by very short atmospheric lifetimes, leading to rapid decay in time and space from the emission point. Therefore, the deposited fraction of inhaled particles (dose) also changes. In fact, close to the emission source, high short-term peak exposures occur. The related exposure estimates should therefore rely on measurements of aerosol number-size distributions able to track rapid aerosol dynamics.In order to study the influence of the time resolution on such estimates, simultaneous measurements were carried out via Scanning Mobility Particle Sizer (SMPS) and Fast Mobility Particle Sizer (FMPS) spectrometers during particle generation events in both indoor (cooking activities) and outdoor (airstrip and urban street canyons) microenvironments. Aerosol size distributions in the range 16–520 nm were measured by SMPS and FMPS at frequencies of 0.007 s⁻¹ and 1 s⁻¹, respectively. Based on the two datasets, respiratory dosimetry estimates were made on the basis of the deposition model of the International Commission on Radiological Protection.During cooking activities, SMPS measurements give an approximate representation of aerosol temporal evolution. Consequently, the related instant doses can be approximated to a fair degree. In the two outdoor microenvironments considered, aerosol size distributions change rapidly: the FMPS is able to follow such evolution, whereas the SMPS is not. The high short-term peak concentrations, and the consequent respiratory doses, evidenced by FMPS data are hardly described by SMPS, which is unable to track the fast aerosol changes. The health relevance of such short peak exposures has not been thoroughly investigated in scientific literature, therefore, in the present paper highly time-resolved and size-resolved dosimetry estimates were provided in order to deepen this aspect.► During aerosol generation events high short term peak exposures occur. ► Generation events in indoor/outdoor microenvironments are compared. ► Low (SMPS 0.007 Hz) and high (FMPS 1 Hz) frequency measurements were performed. ► SMPS/FMPS give similar instant doses in conditions of approximately steady aerosol. ► 1-Hz measurements (FMPS) are required to describe the instant dose fast evolution.

Keywords: Respiratory particle deposition; Short-term exposure; Measurement frequency; FMPS; SMPS

Seasonal and geographic effects on predicting personal exposure to nitrogen dioxide by time-weighted microenvironmental model by Kiyoung Lee; Jiseon Yeom; Chungsik Yoon; Wonho Yang; Bu-Soon Son; Jun Min Jeon; Seung-Do Yu; Choong-Hee Park (pp. 143-148).

The purposes of this study were to investigate the impact of microenvironment concentrations on personal exposure by season and city, and to develop statistical models to predict personal exposure to nitrogen dioxide (NO₂). Personal exposures, residential indoor, residential outdoor and workplace indoor levels of NO₂ were measured in four cities in Korea (Seoul, Daegu, Asan and Suncheon) using a passive sampler for five weekdays. The measurements were conducted in summer and winter during 2008–2009. Average personal NO₂ exposures were 20.5 ppb in summer and 18.6 ppb in winter. The average personal exposures of NO₂ and residential indoor levels were the highest in Seoul and the lowest in Suncheon both summer and winter. Personal exposure was significantly different by season. Personal exposure was significantly correlated with residential indoor concentration in all cities. The personal exposure estimated by residential indoor, workplace indoor and outdoor levels explained 38% and 41% of the measured personal exposure variance in summer and winter, respectively. The low correlation may be due to the longer time spent in other microenvironments in the Korean population. Personal exposure was significantly correlated with working day and city. Correlation between the estimated personal exposure and measured personal exposure was significantly associated with the season and city. The model can provide reasonable estimation of population exposure with appropriate microenvironmental concentrations and time activity data. However, season- and city-specific models should be considered.► Impact of microenvironments on personal exposure was different by season and city. ► Personal exposures by the subject groups were similar despite different time activity. ► Time spent in other indoor microenvironments causes higher exposure in summer. ► Microenvironmental model explanation was less than that in Western countries.

Keywords: Nitrogen dioxide; Microenvironmental model; Regional difference; Season; Time activity

Modelling ozone stomatal flux of wheat under mediterranean conditions by I. González-Fernández; V. Bermejo; S. Elvira; D. de la Torre; A. González; L. Navarrete; J. Sanz; H. Calvete; H. García-Gómez; A. López; J. Serra; A. Lafarga; A.P. Armesto; A. Calvo; R. Alonso (pp. 149-160).

Correct estimation of leaf-level stomatal conductance ( g_sto) is central for current ozone (O₃) risk assessment of wheat yield loss based on the absorbed O₃ phytotoxic dose (POD). The g_sto model parameterizations developed in Europe must be checked in the different climatic regions where they are going to be applied in order to reduce the uncertainties associated with the POD approach.This work proposes a new g_sto model parameterization for estimating POD of Triticum aestivum and Triticum durum under Mediterranean conditions, based on phenological observations over 25 years and g_sto field measurements during 5 growing seasons. Results show that POD in the Mediterranean area might be higher than previously estimated. However, caution must be paid when assessing the risk of yield loss for wheat in this area since field validation of O₃ impacts is still limited.► Models to estimate ozone deposition flux need to be tested in the field. ► A new ozone flux model parameterization for Mediterranean wheat is proposed. ► Modelled ozone flux for Mediterranean wheat was higher than previously estimated. ► Regional model parameterizations are more suitable for ozone risk assessment. ► Field validation of ozone effects on wheat yield in Southern Europe is still scarce.

Keywords: Triticum aestivum; Triticum durum; Phenology; Stomatal conductance; Ozone risk assessment; Phytotoxic ozone dose

Measurement and modeling of indoor air pollution in rural households with multiple stove interventions in Yunnan, China by Zohir Chowdhury; Luke Campanella; Christen Gray; Abdullah Al Masud; Jessica Marter-Kenyon; David Pennise; Dana Charron; Xia Zuzhang (pp. 161-169).

In the developing world, indoor air pollution (IAP) created from solid fuel used in traditional biomass cook stoves is a leading contributor of poor respiratory health, global burden of disease, and greenhouse pollutant emissions. In the present study, we piloted an experimental cross-sectional monitoring and evaluation design with 30 households in rural Lijiang and Deqin counties in northwest Yunnan province, China. This approach offers the ability to examine the effectiveness of improved cook stove (ICS) programs with a much smaller sample size than the typical population based pre- and post-intervention study that requires a large sample representative of the population. Continuous PM_2.5 was measured with the UCB (currently known as UCB-PATS) and the TSI DustTrak and continuous CO was measured with the HOBO CO logger. Using the traditional method of cooking and heating, mean 24-h PM_2.5 and CO concentrations in the kitchen were measured in the range of 0.15–0.71 mg m⁻³ for PM_2.5 and 3.0–11 ppm for CO. These concentrations were compared to using a combination of improved stoves in the kitchen where PM_2.5 and CO concentrations were measured in the range of 0.08–0.18 mg m⁻³ for PM_2.5 and 0.7–5.5 ppm for CO. These concentrations yielded statistically significant reduction in IAP when replacing the traditional fireplace or traditional stove with an improved stove combination. Finally, we show a strong correlation between CO and PM_2.5 ( R² = 0.72–0.76). The combination of this experimental design along with the monitoring and evaluation protocol presented here may provide a robust framework to rapidly assess the effectiveness of ICS interventions in progress.Display Omitted► An experimental design may be used for evaluation of improved cook stoves projects. ► CO may be used as a proxy for PM_2.5 when using biomass fuels in cook stoves. ► Improved cook stove installation in China significantly reduces both PM_2.5 and CO. ► Alternative clean energy is used with improved cook stoves to reduce fuel use.

Keywords: PM; _2.5; CO; Indoor air pollution; Cook stove emissions; Biomass burning; Monitoring and evaluation; China

Contribution of grazing to soil atmosphere CH₄ exchange during the growing season in a continental steppe by Shiming Tang; Chengjie Wang; Andreas Wilkes; Pei Zhou; Yuanyuan Jiang; Guodong Han; Mengli Zhao; Ding Huang; Philipp Schönbach (pp. 170-176).

Degradation of steppes induced by overgrazing may affect the uptake of atmospheric methane (CH₄) by soil sinks. However, uncertainty is associated with the very limited knowledge of gas fluxes in rapidly degrading steppe. In this study, we investigated the effects of grazing on CH₄ uptake during the growing season in three types of steppe (meadow steppe, typical steppe and desert steppe and) in Inner Mongolia, China, to quantify and compare CH₄ uptake in steppe ecosystems under different grazing management conditions. The CH₄ fluxes were measured using an automatic cavity ring-down spectrophotometer at three steppe locations that differed primarily in grazing intensity. The results indicated that steppe soils were CH₄ sinks throughout the growing season. CH₄ uptake at all sites averaged 7.98 kg CH₄-C ha⁻¹ yr⁻¹ (ranging from 1.53 to 18.74 kg CH₄-C ha⁻¹ yr⁻¹), of which approximately 43.8% occurred in the desert steppe. CH₄ uptake in the desert steppe increased 20.4% and 51.2% compared with the typical steppe and meadow steppe, respectively. Light grazing (LG) of steppe did not significantly change CH₄ uptake compared with un-grazed (UG) steppe, but moderate and heavy grazing (MG, HG) reduced CH₄ uptake significantly (by 6.8–37.9%, P < 0.05). These findings imply that reducing the grazing pressure on steppe would help increase the atmospheric CH₄ sinks in steppe soils. Our results suggest that HG exerts a considerable negative impact on CH₄ uptake in a continental steppe. Further studies involving year-round, intensive measurements of CH₄ uptake are needed.► Soil CH₄ uptakes during the growing season were affected by the types of steppe. ► Overgrazing has exerted a considerable negative impact on CH₄ uptake. ► CH₄ uptakes were mainly driven by stocking rate, soil temperature and moisture.

Keywords: Methane uptake; Stocking rate; Growing season; Continental steppe; Inner Mongolia

Theoretical study on the OH-initiated atmospheric reaction of 1,1,1-trichloro-2,2-bis(4-chlorophenyl) ethane (DDT) by Jing Bai; Wenbo Yang; Chenxi Zhang; Yuyang Zhao; Chen Gong; Xiaomin Sun; Qingzhu Zhang; Wenxing Wang (pp. 177-183).

p, p′-DDT is a member of the widely used organochlorine pesticides. In this paper, the mechanism for the OH-initiated reaction of p, p′-DDT is studied at the MPWB1K/6–311 + G(3df,2p)//MPWB1K/6–31 + G(d,p) level. The OH addition reaction to the C₂ atom and H abstraction reaction from alkyl are energetically favorable pathways in OH-initiated reactions of DDT. On the basis of the quantum chemical information, the Rice–Ramsperger–Kassel–Marcus (RRKM) theory is used to calculate the rate constants over the temperature range of 200–800 K. The OH addition reaction is dominant according to the branching ratio, and the atmospheric lifetime of p, p′-DDT is 7.9 days. This work provides a comprehensive understanding of the OH-initiated atmospheric degradation of p, p′-DDT which is helpful for experiments and risk assessment.The branching ratio of each reaction among the OH-initiated reaction from 200 to 800 K (a: OH radical addition; b: H atoms abstraction; c: addition reaction vs abstraction reaction.Display Omitted► The OH-initiated reactions include H-abstracted and OH addition reaction. ► The Non-Arrhenius formulas of rate constants with the temperature are fitted. ► The rate constant of DDT relative to OH radical is 1.50 × 10⁻¹² cm³ molecule⁻¹ s⁻¹.

Keywords: p; ,; p; ′-DDT; OH radical; Chemical mechanism and kinetic property; Rate constants; Atmospheric lifetime

Air quality and public health impacts of UK airports. Part II: Impacts and policy assessment by Steve H.L. Yim; Marc E.J. Stettler; Steven R.H. Barrett (pp. 184-192).

The potential adverse human health impacts of emissions from UK airports have become a significant issue of public concern. We produce an inventory of UK airport emissions – including emissions from aircraft landing and takeoff operations, aircraft auxiliary power units (APUs) and ground support equipment (GSE) – with quantified uncertainty. Emissions due to more than 95% of UK passenger enplanements are accounted for. We apply a multi-scale air quality modelling approach to assess the air quality impacts of UK airports. Using a concentration-response function we estimate that 110 (90% CI: 72–160) early deaths occur in the UK each year (based on 2005 data) due to UK airport emissions. We estimate that up to 65% of the health impacts of UK airports could be mitigated by desulphurising jet fuel, electrifying GSE, avoiding use of APUs and use of single engine taxiing. Two plans for the expansion of UK airport capacity are examined – expansion of London Heathrow and new hub airport in the Thames Estuary. Even if capacity is constrained, we find that the health impacts of UK airports still increases by 170% in 2030 due to an increasing and aging population, increasing emissions, and a changing atmosphere. We estimate that if Heathrow were to be expanded as per previous UK Government plans, UK-wide health impacts in 2030 would increase by 4% relative to the 2030 constrained case, but this increase could become a 48% reduction if emissions mitigation measures were employed. We calculate that 24% of UK-wide aviation-attributable early deaths could be avoided in 2030 if Heathrow were replaced by a new airport in Thames Estuary because the location is downwind of London, where this reduction occurs notwithstanding the increase in aircraft emissions. A Thames hub airport would (isolated from knock-on effects at other airports) cause 60–70% fewer early deaths than an expanded Heathrow, or 55–63% fewer early deaths than an unexpanded Heathrow. Finally, replacing Heathrow by a Thames Estuary airport combined with emissions mitigation measures would reduce UK-wide aviation-attributable early deaths by 56% in 2030 while increasing aircraft movements, which would represent aviation causing about the same level of adverse health impacts as today in absolute terms. We note that because aviation emissions are included in the EU Emissions Trading Scheme, all options are CO₂-neutral in terms of direct emissions (but not climate-neutral).► UK airport emissions are estimated for the present-day and 2030 scenarios. ► 2030 Scenarios considered include expanding Heathrow and a new Thames Hub airport. ► A multi-scale approach to assessing air quality impacts of airports is used. ► The air quality and public health impacts of UK airports are estimated. ► A Thames Hub airport results in lower health impacts than Heathrow expansion.

Keywords: Aviation; Airports; Aircraft; Emissions; Air quality; Particulate matter; Dispersion

A decade of⁷Be and²¹⁰Pb activity in surface aerosols measured over the Western Iberian Peninsula by Ana Cristina Carvalho; Mário Reis; Lídia Silva; Maria José Madruga (pp. 193-202).

This work presents the analysis of⁷Be and²¹⁰Pb continuously measured near Lisbon, Portugal, and their correlation with meteorological parameters, between 2001 and 2010. The values are compared against other similar works over the Iberian Peninsula and Eastern Mediterranean countries. Relative Humidity shows the strongest correlation sign, negative. Higher⁷Be activity was found in the years 2001, 2003, 2007 and 2009 being the year 2001 a singular one regarding extremes. The use of⁷Be as a stratospheric tracer can be interesting to enhance the radionuclide sample frequency due to the meso to local scale of this phenomenon.► A decadal of⁷Be and²¹⁰Pb activity are analysed over Lisbon Portugal. ► The mean value for entire⁷Be time series was 4.0 mBq m⁻³. ► Higher⁷Be activity were found in the years 2001, 2003, 2007 and 2009. ► The year 2001 ws a singular one regarding⁷Be activity extreme values. ►⁷Be activity show negative correlation sign with relative humidity.

Keywords: Natural radionuclides; Atmospheric tracers; Gamma spectrometry; Aerosols

Kinetics and products of HONO interaction with TiO₂ surface under UV irradiation by Atallah El Zein; Yuri Bedjanian; Manolis N. Romanias (pp. 203-210).

The interaction of HONO with UV irradiated TiO₂ solid films was studied using a low pressure flow reactor (1–10 Torr of Helium) combined with a modulated molecular beam mass spectrometer for monitoring of the gaseous species involved. The reactive uptake of HONO to TiO₂ was studied in absence of O₂ in the reactor as a function of HONO concentration ([HONO]₀ = (0.5–5.0) × 10¹² molecule cm⁻³), relative humidity (RH = 0.001–60%) and temperature ( T = 275–320 K). The measured initial uptake coefficient ( γ₀) of HONO on TiO₂ surface was independent of the HONO concentration and showed slight inverse dependence on temperature (activation factor = −1390 ± 150 K) and relative humidity: γ₀ = 6.9 × 10⁻⁴ (RH)^−0.3 (at T = 280 K, calculated using BET surface area, 30% uncertainty). NO₂ and NO were observed as products of the HONO reaction with UV irradiated TiO₂ surface with sum of their yields corresponding to nearly 100% of the nitrogen mass balance. The yields of the NO and NO₂ products were found to be (48 ± 7) and (52 ± 8) %, respectively, independent of relative humidity, temperature and concentration of HONO under experimental conditions used. The HONO loss on mineral aerosol during daytime (calculated with uptake data for HONO on TiO₂ surface in presence of UV irradiation) appears to be of minor importance compared with HONO photolysis in the atmosphere.► Reactive uptake of HONO to UV irradiated TiO₂ surface was studied. ► Uptake coefficient was measured as function of temperature and relative humidity. ► NO₂ and NO were observed as reaction products with 52 and 48% yields, respectively. ► Daytime HONO loss on mineral aerosol is of minor importance in the atmosphere.

Keywords: TiO; ₂; HONO; Heterogeneous reaction; Uptake coefficient; Products

Evaluation of backward Lagrangian stochastic (bLS) model to estimate gas emissions from complex sources based on numerical simulations by Wei Wang; Wenqing Liu; Tianshu Zhang; Manyan Ren (pp. 211-218).

The focus of the paper is application of an inverse-dispersion technique based on a backward Lagrangian stochastic (bLS) model in order to calculate gas-emission rates from industrial complexes. While the bLS technique is attractive for these types of sources, the bLS calculation must assume a spatial configuration for the source. Therefore, results are presented herein of numerical simulations designed to study the sensitivity of emissions calculations to the assumption of source configuration for complex industrial sources. We discuss how measurement fetch, concentration sensor height, and optical path length influence the accuracy of emission estimation. Through simulations, we identify an improved sensor configuration in order to reduce emission-calculation errors caused by an incorrect source-configuration assumption. It is concluded that, with respect to our defined source, the optimal measurement fetch may be between 200 m and 300 m; also, the ideal measurement height is probably between 2.0 m and 2.5 m. With choices within these two ranges, a path length of about 200 m is adequate, and greater path lengths, above 200 m, result in no substantial improvement in emission calculations.► We study emission calculation sensitivity to source configuration using bLS model. ► Moving far away from complex sources may reduce the emission calculation error. ► We may require larger measurement distance for sources with higher height. ► Higher measurement height may be a rational choice for large area source. ► Path length above 200 m yields no substantial improvement in emission calculations.In order to examine the sensitivity of emission calculations based on a bLS model to the assumption of source configuration for industrial complex sources using numerical simulation, we constructed ten source configurations in a hypothetical industrial site, consisting of two area sources and one or more elevated point sources, each emitting tracer at different rates. The above plot is one of the source configurations, and the straight lines with arrows illustrate the positions of line-average concentration sensor. We discuss how measurement fetch, concentration sensor height, and optical path length influence the accuracy of emission estimation.Display Omitted

Keywords: Lagrangian stochastic model; Inverse dispersion technique; Gas emissions; Complex sources; Source configuration; Sensor configuration

Estimating the influence of lightning on upper tropospheric ozone using NLDN lightning data and CMAQ model by Lihua Wang; M.J. Newchurch; Arastoo Pour-Biazar; Shi Kuang; Maudood Khan; Xiong Liu; William Koshak; Kelly Chance (pp. 219-228).

Lightning is a particularly significant NO_x source in the middle and upper troposphere where it affects tropospheric chemistry and ozone. Because the version-4 Community Multiscale Air Quality Modeling System (CMAQ) does not account for NO_x emission from lightning, it underpredicts NO_x above the mixed layer. In this study, the National Lightning Detection Network™ (NLDN) lightning data are applied to the CMAQ model to simulate the influence of lightning-produced NO_x (LNO_x) on upper tropospheric NO_x and subsequent ozone concentration. Using reasonable values for salient parameters (detection efficiency ∼95%, cloud flash to ground flash ratio ∼3, LNO_x production rate ∼500 mol N per flash), the NLDN ground flashes are converted into total lightning NO_x amount and then vertically distributed on 39 CMAQ model layers according to a vertical-distribution profile of lightning N mass. This LNO_x contributes 27% of the total NO_x emission during 15 July ∼7 September 2006. This additional NO_x reduces the low-bias of simulated tropospheric O₃ columns with respect to OMI tropospheric O₃ columns from 10 to 5%. Although the model prediction of ozone in upper troposphere improves by ∼20 ppbv due to lightning-produced NO_x above the southeastern and eastern U.S.A., the improved ozone prediction is still ∼20–25 ppbv lower than ozonesonde measurements.► Not accounting for lightning NO_x, CMAQ underpredicts NO_x above the mixed layer. ► We estimate LNO_x emissions based on NLDN ground flashes and applied it to CMAQ. ► LNO_x contributes 27% of the total NO_x emission during 15 July–7 September 2006. ► LNO_x improves upper tropospheric O₃ by ∼20 ppbv above the southeastern and eastern U.S.A. ► The improved ozone prediction is still ∼20–25 ppbv lower than ozonesonde measurements.

Keywords: LNO; _x; CMAQ; Ozone; Lightning; NLDN; OMI; IONS06

Parametric laws to model urban pollutant dispersion with a street network approach by L. Soulhac; P. Salizzoni; P. Mejean; R.J. Perkins (pp. 229-241).

This study discusses the reliability of the street network approach for pollutant dispersion modelling in urban areas. This is essentially based on a box model, with parametric relations that explicitly model the main phenomena that contribute to the street canyon ventilation: the mass exchanges between the street and the atmosphere, the pollutant advection along the street axes and the pollutant transfer at street intersections. In the first part of the paper the focus is on the development of a model for the bulk transfer street/atmosphere, which represents the main ventilation mechanisms for wind direction that are almost perpendicular to the axis of the street. We then discuss the role of the advective transfer along the street axis on its ventilation, depending on the length of the street and the direction of the external wind. Finally we evaluate the performances of a box model integrating parametric exchange laws for these transfer phenomena. To that purpose we compare the prediction of the model to wind tunnel experiments of pollutant dispersion within a street canyon placed in an idealised urban district.► We discuss the street network approach for pollutant dispersion modelling in urban areas. ► We identify two main mechanisms for the street ventilation. ► A new model for the street/atmosphere turbulent transfer is proposed. ► A model for the advective transfer along the street axis is analysed. ► Both models are tested against wind tunnel measurements.

Keywords: Air pollution; Street canyon ventilation; Street network; Street intersection; Urban dispersion models

Testing of models of stomatal ozone fluxes with field measurements in a mixed Mediterranean forest by S. Fares; G. Matteucci; G. Scarascia Mugnozza; A. Morani; C. Calfapietra; E. Salvatori; L. Fusaro; F. Manes; F. Loreto (pp. 242-251).

Mediterranean forests close to urban areas are exposed to polluted plumes loaded with tropospheric ozone. This is the case of Castelporziano Estate, a 6000 ha Mediterranean forest 25 km from Rome downtown on the coast of the Mediterranean Sea. In September 2011 we started an intensive field campaign aimed at investigating ozone deposition from a mixed Mediterranean forest, mainly composed by Quercus suber, Quercus ilex, Pinus pinea. Measurements at canopy level with the eddy covariance technique were supported by a vegetation survey and the measurement of all environmental parameters which allowed to calculate stomatal ozone fluxes. Leaf-level measurements were used to parameterize models to calculate stomatal conductance based on a Jarvis-type and Ball–Berry approach. We show changes in magnitude of ozone fluxes from a warm (September) to a cold period (October–December). Stomatal component explained almost the totality of ozone fluxes during the cold days, but contributed only up to 50% to total ozone deposition during warm days, suggesting that other sinks (e.g. chemistry in the gas-phase) play a major role. Modeled stomatal ozone fluxes based on a Jarvis-type approach (DO3SE) correlated with measured fluxes better than using a Ball–Berry approach. A third model based on a modified Ball–Berry equation was proposed to account for the non-linear dependency of stomatal conductance on relative humidity. This research will help the development of metrics for ozone-risk assessment and advance our understanding of mixed Mediterranean forests in biosphere–atmosphere exchange.► Flux of H₂O, CO₂, O₃ was measured with Eddy Covariance in a Mediterranean Forest. ► Stomata explained almost the totality of ozone fluxes during the cold days. ► Non-stomatal ozone deposition was the main ozone sink during warm days. ► Modeled Gs based on a Jarvis-type approach correlated well measured Gs. ► A model based on a modified Ball–Berry equation was proposed.

Keywords: Ozone fluxes; Stomatal conductance models; GPP; Mediterranean forest

Nanoparticle emissions from 11 non-vehicle exhaust sources – A review by Prashant Kumar; Liisa Pirjola; Matthias Ketzel; Roy M. Harrison (pp. 252-277).

Nanoparticle emissions from road vehicles have been studied extensively in the recent past due to their dominant contribution towards the total airborne particle number concentrations (PNCs) found in the urban atmospheric environment. In view of upcoming tighter vehicle emission standards and adoption of cleaner fuels in many parts of the world, the contribution to urban nanoparticles from non-vehicle exhaust sources (NES) may become more pronounced in future. As of now, only limited information exists on nanoparticle emissions from NES through the discretely published studies. This article presents critically synthesised information in a consolidated manner on 11 NES (i.e. road–tyre interaction, construction and demolition, aircraft, ships, municipal waste incineration, power plants, domestic biomass burning, forest fires, cigarette smoking, cooking, and secondary formation). Source characteristics and formation mechanisms of nanoparticles emitted from each NES are firstly discussed, followed by their emission strengths, airborne concentrations and physicochemical characteristics. Direct comparisons of the strengths of NES are not straightforward but an attempt has been made to discuss their importance relative to the most prominent source (i.e. road vehicles) of urban nanoparticles. Some interesting comparisons emerged such as 1 kg of fast and slow wood burning produces nearly the same number of particles as for each km driven by a heavy duty vehicle (HDV) and a light duty vehicle, respectively. About 1 min of cooking on gas can produce the similar particle numbers generated by ∼10 min of cigarette smoking or 1 m travel by a HDV. Apportioning the contribution of numerous sources from the bulk measured airborne PNCs is essential for determining their relative importance. Receptor modelling methods for estimation of source emission contributions are discussed. A further section evaluates the likely exposure risks, health and regulatory implications associated with each NES. It is concluded that much research is needed to provide adequate quantification of all nanoparticle sources, and to establish the relative toxicity of nanosize particles from each.► Nanoparticle emissions from 11 non-vehicle exhaust sources (NES) are reviewed. ► Limited information exists but encouraging progress made to characterise NES. ► No air quality regulations exist currently to control nanoparticle exposure. ► Physicochemical characterisation and exposure to NES derived nanoparticles needed. ► Relative toxicity and contribution of NES produced nanoparticles unknown.

Keywords: Particle number concentrations; Non-exhaust emissions; Number size distributions; Exposure risks and regulation; Outdoor ultrafine particle formation

Particulate matter concentrations and their related metal toxicity in rural residential environment of semi-arid region of India by David D. Massey; Aditi Kulshrestha; Ajay Taneja (pp. 278-286).

The concentration of PM_10, PM_5.0, PM_2.5 and PM₁ were measured in the indoor–outdoor environment of rural homes of North central part of India during winter, summer and rainy seasons for the time duration of October 2007 to March 2009. Seven trace metals (Pb, Cd, Ni, Fe, Cr, Mn and Cu) were also determined in PM_2.5 from October 2007 to March 2009 in the indoor–outdoor environment. During the study period the annual average concentration for PM_10, PM_5.0, PM_2.5 and PM₁ in indoor and outdoor were 242.53 μg m⁻³ and 217.76 μg m⁻³, 203.57 μg m⁻³ and 180.42 μg m⁻³, 164.60 μg m⁻³ and 143.07 μg m⁻³, 106.23 μg m⁻³ and 105.17 μg m⁻³ respectively. Concentrations of PM₁₀ and PM_2.5 have been compared with prescribed WHO standards and NAAQS standards of India and were found to be much higher. Significant seasonal variations of particulate pollutants were obtained using the monthly average concentration of coarse and fine particulate matter. Indoor/outdoor ratios at the rural sites were also determined with the meteorological parameters like temperature, humidity, wind speed and air exchange rate. Chromium was found to have the highest excess cancer risk in a risk evaluation using an Integrated Risk Information System. Three factors each in indoor and outdoor environment of rural site have been identified using Principal Component Analysis & Positive Matrix Factorization.► Concentration of indoor–outdoor particles emissions in rural India determined. ► Particulate toxicity in terms of trace metals in PM_2.5 was examined. ► The PM ratios with meteorological parameters and air exchange rate are discussed. ► Exposure concentration is greatly affected by cooking and smoking sources. ► Risk assessment related to particulate pollutant were evaluated.

Keywords: PM concentrations; Seasonal variation; Indoor/outdoor ratios; Meteorological parameters and air exchange rate; Multivariate statistical analysis; Excess cancer risk

Ozone and its projection in regard to climate change by Ani Melkonyan; Patrick Wagner (pp. 287-295).

In this paper, the dependence of ozone-forming potential on temperature was analysed based on data from two stations (with an industrial and rural background, respectively) in North Rhine-Westphalia, Germany, for the period of 1983–2007. After examining the interrelations between ozone, NO_x and temperature, a projection of the days with ozone exceedance (over a limit value of a daily maximum 8-h average≥120 μg m⁻³ for 25 days per year averaged for 3 years) in terms of global climate change was made using probability theory and an autoregression integrated moving average (ARIMA) model. The results show that with a temperature increase of 3 K, the frequency of days when ozone exceeds its limit value will increase by 135% at the industrial station and by 87% at the rural background station.► Ozone dependence on NO_x and temperature at industrial and rural stations. ► Prediction of number of days with ozone exceedances in terms of climate change. ► Frequency of bad ozone days increases by 135% at the industrial station. ► Frequency of bad ozone days increases by 87% at the rural station. ► Ozone forming potential is significantly higher in rural areas than in urban ones.

Keywords: Ozone production; NO; _x; - and VOC-limited regimes; Probability of ozone exceedances; Limit values; ARIMA model; Global climate change; North Rhine-WestphaliaAbbreviations; NRW; North Rhine-Westphalia; NO; nitric oxide; NO; ₂; nitrogen dioxide; O; ₃; ozone; LANUV; Environmental State Agency for Nature, Environment and Consumer Protection; VOC; volatile organic compounds; NMVOC; non-methane volatile organic compounds; AVOC; anthropogenic volatile organic compounds; BVOC; biogenic volatile organic compounds; WALS; Duisburg–Walsum; EGGE; Horn-Bad Meinberg Egge; IPCC; Intergovernmental Panel on Climate Change; SRES; Special Report on Emission Scenarios

Effectiveness of sulfur and boron isotopes in aerosols as tracers of emissions from coal burning in Asian continent by Masahiro Sakata; Tomomi Ishikawa; Satoshi Mitsunobu (pp. 296-303).

The atmospheric concentrations and isotopic compositions of sulfur and boron were measured for aerosol samples (water soluble fraction) collected from April 2004 to March 2006 at two sites on the Japan Sea coast. SO₄²⁻ originating from sea salts in the aerosols was negligible (only 1–2% of the total SO₄²⁻). The atmospheric concentrations of nonsea-salt SO₄²⁻ (S_nss) and total B (B_T) were scattered widely, but the concentration ratio B_T/S_nss was relatively high during winter and relatively low during summer. Moreover, aerosols during winter were characterized by a high δ³⁴S (δ³⁴S_nss) of nonsea-salt SO₄²⁻ and a low δ¹¹B (δ¹¹B_T) of total B, whereas aerosols during summer were characterized by a low δ³⁴S_nss and a high δ¹¹B_T. A negative correlation ( r² = 0.34, p < 0.001) was observed between δ³⁴S_nss and δ¹¹B_T in aerosols from the two sites, suggesting that those values are governed primarily by a mixing of two end-members. On the basis of air trajectory analysis, the first end-member is the air mass from “Northern China (>30°N)”, whereas the second end-member is the air mass from “Japan and the Pacific Ocean”. It is likely that SO₄²⁻ and B in the air mass from northern China are strongly affected by coal burning, which satisfactorily reflects the characteristics of δ³⁴S and δ¹¹B (i.e., high δ³⁴S and low δ¹¹B) of coals formed in this region. Thus, both sulfur and boron isotopes in aerosols are effective as tracers of emissions from coal burning in northern China mainly during winter when the air mass from this region is dominant. On the other hand, the results of source identification suggested that the major sources of SO₄²⁻ and B in the air mass from Japan and the Pacific Ocean are oil combustion in Japan and ocean sea salts, respectively.► δ³⁴S and δ¹¹B were measured for aerosol samples collected on the Japan Sea coast. ► Aerosols during winter are characterized by a high δ³⁴S and a low δ¹¹B. ► Aerosols during winter are strongly affected by coal burning in northern China. ► S and B isotopes in aerosols are effective tracers of coal burning emissions.

Keywords: Long-range transport of air pollutants; Asian continent; Coal burning; Sulfur isotopes; Boron isotopes; Tracers

A sequential factorial analysis approach to characterize the effects of uncertainties for supporting air quality management by S. Wang; G.H. Huang; A. Veawab (pp. 304-312).

This study proposes a sequential factorial analysis (SFA) approach for supporting regional air quality management under uncertainty. SFA is capable not only of examining the interactive effects of input parameters, but also of analyzing the effects of constraints. When there are too many factors involved in practical applications, SFA has the advantage of conducting a sequence of factorial analyses for characterizing the effects of factors in a systematic manner. The factor-screening strategy employed in SFA is effective in greatly reducing the computational effort. The proposed SFA approach is applied to a regional air quality management problem for demonstrating its applicability. The results indicate that the effects of factors are evaluated quantitatively, which can help decision makers identify the key factors that have significant influence on system performance and explore the valuable information that may be veiled beneath their interrelationships.► A sequential factorial analysis was proposed to examine the effects of uncertainty. ► Influence of a number of factors of interest was studied in a systematic manner. ► A factor-screening strategy was used to reduce the computational effort. ► Interactive effects of parameters and constraints on model outputs were analyzed.

Keywords: Air quality management; Factorial analysis; Modeling; Uncertainty

New indices for the spatial validation of plume forecasts with observations of smoke plumes from grassfires by Joaquín E. Blanco; Guillermo J. Berri (pp. 313-322).

The purpose of this work is to propose new indices for the spatial validation of hazardous plumes forecast, and apply and test them with data of a case study. One, the Plume-Overlap-Area Hit index, is a modification of a widely used index that considers the overlap area between observed and forecast plumes. The other one, the Plume-Mean-Orientation Hit index, introduces a new concept in plume forecast validation, i.e., the mean direction of plume propagation. These two indices are combined in a new two-dimensional Combined-Direction-Area Hit index. The new indices are applied to the spatial validation of smoke plume forecast for a case study of uncontrolled grassfires that took place during April and May 2008 in the La Plata River region in South America. Operational models at the Argentine National Meteorological Service (SMN) are employed to produce the plume forecast. The HIRHYLTAD dispersion model is used to forecast the smoke plumes, employing the Eta/SMN meteorological forecast model outputs. The forecast plumes are compared to the observed plumes in high-resolution MODIS imagery from AQUA and TERRA satellites, from which a total of 59 smoke plumes are identified. The study concludes that the presented methodology that employs operational meteorological models and simplified dispersion models can be used to produce reasonably accurate forecasts of the areas affected by the smoke plumes that originate in forest and grassland fires, particularly in cases when limited information is available about the fires. Although the present study is specifically applied to smoke plumes, the validation technique with the proposed indices can be of utility to study pollutant plumes of diverse nature.► We introduce new indices for the spatial validation of forecast plumes. ► One of them measures agreement in direction between observed and forecast plumes. ► All indices are evaluated in a case study of grassfires in Argentina during 2008. ► Useful methodology that can be applied to different plume types, not only smoke.

Keywords: Plume forecast; Dispersion model; Validation index; Case study; Smoke

Characterization of secondary organic aerosol generated from ozonolysis of α-pinene mixtures by Hardik S. Amin; Meagan L. Hatfield; Kara E. Huff Hartz (pp. 323-330).

In the atmosphere, multiple volatile organic compounds (VOCs) co-exist, and they can be oxidized concurrently and generate secondary organic aerosol (SOA). In this work, SOA is formed by the oxidation (in presence of excess ozone) of mixtures containing α-pinene and other VOCs. The VOC mixtures were made so their composition approached a commercially-available α-pinene-based essential oil, Siberian fir needle oil. The SOA products were sampled using filters, solvent extracted and analyzed by gas chromatography/mass spectrometry with trimethylsilyl derivatization. The individual product yields for SOA generated from α-pinene changed upon the addition of other VOCs. An increase in concentration of non-reactive VOCs (bornyl acetate, camphene, and borneol) lead to a decrease in individual product yields of characteristic α-pinene SOA products. Although these experiments were carried out under higher VOC and ozone concentrations in comparison to the atmosphere, this work suggests that the role of non-reactive VOCs should be explored in SOA products formation.► Secondary organic aerosol from volatile organic compound mixtures was characterized. ► Mixtures included a commercially available essential oil. ► Product yields were measured as a function of mixture composition. ► Changes in products yields were observed as the composition was changed.

Keywords: VOC mixtures ozonolysis; Secondary organic aerosol; GC/MS characterization; Siberian fir needle oil

Recent tropospheric ozone changes – A pattern dominated by slow or no growth by S.J. Oltmans; A.S. Lefohn; D. Shadwick; J.M. Harris; H.E. Scheel; I. Galbally; D.W. Tarasick; B.J. Johnson; E.-G. Brunke; H. Claude; G. Zeng; S. Nichol; F. Schmidlin; J. Davies; E. Cuevas; A. Redondas; H. Naoe; T. Nakano; T. Kawasato (pp. 331-351).

Longer-term (i.e., 20–40 years) tropospheric ozone (O₃) time series obtained from surface and ozonesonde observations have been analyzed to assess possible changes with time through 2010. The time series have been selected to reflect relatively broad geographic regions and where possible minimize local scale influences, generally avoiding sites close to larger urban areas. Several approaches have been used to describe the changes with time, including application of a time series model, running 15-year trends, and changes in the distribution by month in the O₃ mixing ratio. Changes have been investigated utilizing monthly averages, as well as exposure metrics that focus on specific parts of the distribution of hourly average concentrations (e.g., low-, mid-, and high-level concentration ranges). Many of the longer time series (∼30 years) in mid-latitudes of the Northern Hemisphere, including those in Japan, show a pattern of significant increase in the earlier portion of the record, with a flattening over the last 10–15 years. It is uncertain if the flattening of the O₃ change over Japan reflects the impact of O₃ transported from continental East Asia in light of reported O₃ increases in China. In the Canadian Arctic, declines from the beginning of the ozonesonde record in 1980 have mostly rebounded with little overall change over the period of record. The limited data in the tropical Pacific suggest very little change over the entire record. In the southern hemisphere subtropics and mid-latitudes, the significant increase observed in the early part of the record has leveled off in the most recent decade. At the South Pole, a decline observed during the first half of the 35-year record has reversed, and O₃ has recovered to levels similar to the beginning of the record. Our understanding of the causes of the longer-term changes is limited, although it appears that in the mid-latitudes of the northern hemisphere, controls on O₃ precursors have likely been a factor in the leveling off or decline from earlier O₃ increases.► O₃ at mid-latitudes of the N.H. is flat or declining in the last 10–15 years. ► O₃ in S.H. subtropics and mid-latitudes increased earlier but has leveled off. ► 15-year moving trends reveal changes in both high and low O3 concentrations. ► Precursor (NO_x) reductions in Europe and N.A. likely contribute to O₃ decline.

Keywords: Troposphere ozone; Trends; Changes in concentration distribution

Atmospheric turbidity determined by the annual cycle of the aerosol optical depth over north-center Spain from ground (AERONET) and satellite (MODIS) by Y.S. Bennouna; V.E. Cachorro; B. Torres; C. Toledano; A. Berjón; A.M. de Frutos; I. Alonso Fernández Coppel (pp. 352-364).

The present study focuses on the characterization of aerosol seasonal variability over the northern continental region of the Iberian Peninsula based on remotely sensed aerosol optical properties, and in particular the aerosol optical depth (AOD) and Ångström exponent (Alpha) parameters. For this region, a representative annual cycle of these parameters was built based on data from the AERONET-RIMA station of Palencia (Spain, 42N, 4.5W) for the period 2003–2011. The results also examine in details the interannual variability during the whole period. The ability of satellite to reproduce the seasonal patterns and anomalies, is investigated using the MODIS (Moderate Resolution Imaging Radiometer) for the same period. MODIS instantaneous fields are validated against ground-based sunphotometer data, and the differences between monthly values are estimated. The site of Palencia is characterized by a daily AOD (440 nm) of 0.15 ± 0.10 and Alpha (440–870 nm) of 1.29 ± 0.35 on average, thus presenting values typical of a clean continental background. The seasonal pattern corresponds to mid-high turbidity values of the AOD during a period starting in mid-spring to the end of the summer (max 0.19), and a lower AOD during fall and winter months (min 0.09). When using MODIS data, the overall results for Palencia give a higher (by ∼25%) AOD (470 nm) with 0.19 ± 0.15 and a much lower (by ∼50%) Alpha (470–660 nm) of 0.70 ± 0.20. These numbers reflect substantial differences, with overestimations of the monthly means that can be almost double those of AERONET in the summer months. However MODIS satisfactorily reproduces the increase–decrease cycle in the AOD. These large differences tend to be more attributed to the aerosol models used in the MODIS algorithm rather than to the sampling difference between ground and satellite in this season. Despite the poor sampling in winter and the small AOD (<0.1) observed over the area, the best agreement between satellite and ground is found during this period. The seasonal pattern of the Ångström exponent derived from MODIS was found to be very different from that of AERONET, the former showing apparently no consistency with the latter. Given the aforementioned values and the fact that the AERONET Alpha value for 470–660 nm is 1.41 ± 0.37 (wavelengths used in the comparison with MODIS), we can conclude that the Alpha derived from MODIS is not representative of the aerosol type characterizing this region of the globe.► The site of Palencia (Spain) is characterized by a clean continental background. ► On average the daily AERONET AOD is 0.15 ± 0.10 and Ångström exponent 1.29 ± 0.35. ► Mid-high turbidity values in summer and spring contrast with winter. ► The best agreement MODIS/AERONET is found when the AOD is low during winter months. ► MODIS Ångström exponent is not representative for the region of “Castilla y León”.

Keywords: Aerosols; MODIS; AERONET; Aerosol optical depth (AOD)

An improved method for the quantification of SOA bound peroxides by Anke Mutzel; Maria Rodigast; Yoshiteru Iinuma; Olaf Böge; Hartmut Herrmann (pp. 365-369).

An improvement is made to a method for the quantification of SOA-bound peroxides. The procedure is based on an iodometric-spectrophotometric method that has been commonly used for the determination of peroxides in a wide range of biological and environmental samples. The improved method was applied to determine the peroxide content of laboratory-generated SOA from α-pinene ozonolysis. Besides main improvements for the detection conditions, the use of more environmentally sound solvents is considered instead of carcinogenic solvents. In addition to the improved method for peroxide determination, the present study provides evidence for artefact formation caused by ultrasonic agitation for the extraction of organic compounds in SOA filter samples. The concentration of SOA-bound peroxides in the extracts from ultrasonic agitation were up to three times higher than those from a laboratory orbital shaker under the same extraction conditions, indicating peroxide formation caused by acoustic cavitation during extraction. In contrast, pinic acid, terebic acid and terpenylic acid showed significantly lower concentrations in the sample extract prepared using ultrasonic agitation, indicating that these compounds react with OH radicals that are formed from acoustic cavitation. Great care should be taken when extracting SOA samples and the use of ultrasound should be avoided.

Keywords: Peroxides; Secondary organic aerosol; α-Pinene; Ozonolysis

On the impact of the vertical resolution on chemistry-transport modelling by Laurent Menut; Bertrand Bessagnet; Augustin Colette; Dmitry Khvorostiyanov (pp. 370-384).

This paper presents a sensitivity analysis of the modelling of air pollutant concentrations in the surface layer with the WRF/CHIMERE models. The influence of the vertical resolution near the surface is studied. The simulations are carried out over two periods (winter and summer 2009) over the Paris area. Three model configurations are used: (i) the CHIMERE mesh used for the PREVAIR forecast (8 levels from 995 to 500 hPa), (ii) a mesh refined along the whole vertical axis (20 levels from 995 to 500 hPa) and (iii) a mesh with a refinement near the surface (9 levels from 999 to 500 hPa). The results are discussed in terms of differences on surface concentrations between the reference case and an improved resolution. Adding a point close to the surface appears to be important mainly for high nocturnal concentrations in very stable boundary layers. Refining the vertical mesh, with 20 levels instead of 8, enables to model new structures in the well mixed boundary layer, but with a moderate impact at the surface. It is shown that the different model configurations lead to changes of a few μg m⁻³ at most, showing that the vertical mesh is not the most sensitive factor in chemistry-transport modelling when results are compared to surface measurements. This finding validates the fact that a simplified vertical mesh is suitable for air quality forecasting even if an improved vertical resolution close to the ground is important to take into account the urban increment.► Regional atmospheric composition modelling. ► Sensitivity of the model vertical resolution. ► Impact on surface pollutants concentrations. ► Improvement of the analysis/forecast CHIMERE model.

Keywords: Atmospheric pollution; Chemistry-transport modelling; Sensitivity to vertical resolution

Exploratory data analysis of PAH, nitro-PAH and hydroxy-PAH concentrations in atmospheric PM₁₀-bound aerosol particles. Correlations with physical and chemical factors by Ana Isabel Barrado; Susana García; Yolanda Castrillejo; Enrique Barrado (pp. 385-393).

A method is proposed to determine PAHs, OH-PAHs and nitro-PAHs in samples of PM₁₀ particulate matter based on liquid chromatography with fluorescence detection, and applied to quantify such compounds over a 14-month period in a semiurban area of a large city (Madrid, Spain). A clear seasonal trend was observed in the levels of the compounds. The mean overall concentration of all the PAHs determined was 1250 pg m⁻³; with levels rising in the colder months to 2062 pg m⁻³ and descending in the warm months to 725 pg m⁻³. The same effect was observed for the OH-PAHs, showing a mean of 83 pg m⁻³ and values of 153 pg m⁻³ and 36 pg m⁻³ in the colder and warmer months, and for the nitro-PAHs, with a mean of 132 pg m⁻³ and levels of 162 pg m⁻³ and of 112 pg m⁻³ in the colder and warmer months, respectively. These trends were confirmed in the statistical analysis, which clearly revealed the difference between PAH levels in the months April–September compared to October–December or January–March. Correlations were also found between PAH patterns and those of their hydroxy- and nitro derivatives, as well as between both derivatives. Negative correlation was observed between O₃ and OH-PAH levels and direct correlation between the presence of nitrogen oxides in the atmosphere and nitro-PAHs in the particulate matter.Display Omitted► 12 PAHs, 2 OH-PAHs and 5 nitro-PAHs were monitored in PM₁₀ atmospheric samples. ► Variations were found to be related to weather conditions (temperature & pressure). ► Concentrations were higher for the colder months and lower for the warmer period. ► Increased concentrations of ozone/temperature caused disappearance of PAHs families. ► Positive correlations were observed between nitrogen oxides and nitro-PAHs.

Keywords: Air; Particulate matter; Polycyclic aromatic hydrocarbons; Hydroxy-PAHs; Nitro-PAHs; Liquid chromatography

Wet and dry deposition of particles associated metals (Cd, Pb, Zn, Ni, Hg) in a rural wetland site, Marais Vernier, France by O. Connan; D. Maro; D. Hébert; P. Roupsard; R. Goujon; B. Letellier; S. Le Cavelier (pp. 394-403).

Atmospheric transport plays an important role in the transfer of pollutants to ecosystems. During such transport, the atmospheric aerosol is one of the key factors in terms of deposition. Over 18 months, we studied the concentrations of Zn, Pb, Ni, Cd, Hg in air and precipitations in a wetland site in the north west of France. The objective of this study was to characterise the quantities transferred by dry and wet deposition. An eddy correlation technique was used to measure dry deposition velocities and determine the dry deposition fluxes from atmospheric concentration. In this site, wet deposition is almost always preponderant, except for Pb and Cd over several months. Measurements in the air and in rainwater are low and show that the site is protected from important anthropogenic influences, with levels that can be considered as background levels. In terms of deposition fluxes, the configuration of the site and the meteorological conditions (low wind speeds, low thermal fluxes) lead to low dry depositions. Wet depositions, although more important are also relatively low compared to the literature, directly linked to the pluviometry during the study period.► Measurements of trace metals in air and rainwater on a wetland site. ► Estimation of dry and wet deposition fluxes. ► Use of eddy correlation method to obtain dry deposition velocity. ► Results show that dry deposition are superior to dry deposition. ► Measurement shows low concentrations with levels that can be considered as background.

Keywords: Metals; Wet and dry deposition; Aerosols; Wetland; Eddy correlation

Air quality impacts of a scheduled 36-h closure of a major highway by David C. Quiros; Qunfang Zhang; Wonsik Choi; Meilu He; Suzanne E. Paulson; Arthur M. Winer; Rui Wang; Yifang Zhu (pp. 404-414).

Elevated concentrations of ultrafine particles (UFPs, <0.1 μm) are commonly found near roadways. On the July 16–17, 2011 weekend, a section of a major Los Angeles freeway, the I-405, was closed for 36 h. We measured UFPs and other pollutants at two fixed locations, one upwind and one downwind, and at various distances from I-405 using a mobile measurement platform (MMP) on Fridays, Saturdays, and Sundays before, during, and after closure. On the closure Saturday on July 16, I-405 traffic flow was reduced by ∼90% relative to non-closure Saturday observations. Downwind of I-405, fixed-site measurements showed the following reductions: 83% of particle number concentration (PNC), 36% of PM_2.5, and 62% of black carbon. Fixed-site measurements showed daily average UFP size distributions were bimodal for non-closure conditions (nucleation modes ∼20 nm, accumulation modes ∼60 nm), but only showed an accumulation mode ∼50 nm during closure. Spatial measurements from the MMP confirmed no nucleation mode was detected at any location 0–300 m downwind during closure. In 2011, non-closure particle emission factors were 5.0, 2.7, and 3.4 × 10¹³ particles vehicle⁻¹ km⁻¹ for Friday through Sunday respectively. After accounting for instrumental and traffic flow differences, weekday PNC in 2011 was 60% lower than 2001 at the same study location. During the closure event, regional freeway traffic was reduced compared to four selected control Saturdays. Eight stationary monitoring stations throughout the South Coast Air Basin showed PM_2.5 was reduced between 18 and 36% relative to the same control days. The outcome of this natural experiment during the I-405 closure confirms that substantial traffic reduction can improve local and regional air quality in sprawled urban regions such as Los Angeles, CA.Display Omitted► Air pollutants were examined around the time of a major planned freeway closure. ► On the closure day, particle number concentration (PNC) downwind of the freeway was reduced by 83%. ► On the closure day, PM_2.5 decreased by 18–36% across the South Coast Air Basin. ► Weekday downwind PNC decreased by 60% between 2001 and 2011.

Keywords: Near-roadway; Traffic restriction; Freeway closure; Ultrafine particle; PM; _2.5

Atmospheric dry and wet nitrogen deposition on three contrasting land use types of an agricultural catchment in subtropical central China by Jianlin Shen; Yong Li; Xuejun Liu; Xiaosheng Luo; Hong Tang; Yangzhu Zhang; Jinshui Wu (pp. 415-424).

Atmospheric emissions of reactive nitrogen (N) species are at high levels in China in recent years, but few studies have employed N deposition monitoring techniques that measure both dry and wet deposition for comprehensive evaluation of the impacts of N deposition on ecosystems. In this study, to quantify the total N deposition, both dry and wet N depositions were monitored using denuder/filter pack systems, passive samplers and wet-only samplers at three sites with different land use types (forest, paddy field and tea field) in a 135-km² catchment in subtropical central China from September 2010 to August 2011. At the three sampling sites, the annual mean concentrations of total N (the sum ofNH4+,NO3− and DON) in rainwater were 1.2–1.6 mg N L⁻¹, showing small variation across sites. Annual mean concentrations of total N (the sum of NH₃, NO₂, HNO₃, particulateNH4+ andNO3−) in the air were 13–18 μg N m⁻³. High NH₃ concentrations in the air were observed at the agricultural sites of tea and paddy fields, indicating significant NH₃ emissions from N fertiliser application; and high NO₂ concentrations were found at the upland sites of forest and tea field, suggesting high NO emissions from soils due to high N deposition or high N fertiliser input. The annual total N deposition for the three sites of paddy field, tea field and forest was estimated as 22, 34 and 55 kg N ha⁻¹ yr⁻¹, in which the dry N deposition components contributed to 21%, 36% and 63% of the annual total N deposition, respectively. The annual deposition of reduced N species was 1.1–1.8 times of the annual deposition of oxidised N species. To minimise the adverse effects of atmospheric N deposition on natural/semi-natural ecosystems, it is crucial to reduce the reactive N emissions from anthropogenic activities (e.g., N fertiliser application, animal production and fossil fuel combustion) in subtropical central China.► Major atmospheric reactive N species were observed in an agricultural catchment in subtropical central China. ► N deposition was 22–55 kg N ha⁻¹ yr⁻¹, with dry deposition contributing 21%–63 % of the total deposition. ► N fertiliser application and animal production were main sources for NH₃ and NH₄⁺. ► Soil NO emission may contribute a large quantity to the NO₂ in the air.

Keywords: NH; ₃; NO; ₂; HNO; ₃; Ammonium; Nitrate; Nitrogen deposition

Tracking of atmospheric release of pollution using unmanned aerial vehicles by Václav Šmídl; Radek Hofman (pp. 425-436).

Tracking of an atmospheric release of pollution is usually based on measurements provided by stationary networks, occasionally complemented with deployment of mobile sensors. In this paper, we extend the existing concept to the case where the sensors are carried onboard of unmanned aerial vehicles (UAVs). The decision theoretic framework is used to design an unsupervised algorithm that navigates the UAVs to minimize the selected loss function. A particle filter with a problem-tailored proposal function was used as the underlying data assimilation procedure.A range of simulated twin experiments was performed on the problem of tracking an accidental release of radiation from a nuclear power plant in realistic settings. The main uncertainty was in the released activity and in parametric bias of the numerical weather forecast. It was shown that the UAVs can complement the existing stationary network to improve the accuracy of data assimilation. Moreover, two autonomously navigated UAVs alone were shown to provide assimilation results comparable to those obtained using the stationary network with more than thirty sensors.► An algorithm for navigation of UAVs tracking atmospheric release is pro-posed. ► Dynamics of the release is unknown and estimated on-line on a fine time scale. ► Time varying biases of the numerical weather forecast are estimated. ► Assimilation methodology is based on the sequential Monte Carlo. ► Twin experiments performed on a release of radiation with realistic setting.

Keywords: Data assimilation; Atmospheric dispersion model; Sequential Monte Carlo; Sensor positioning; Mutual information

Impact of biomass burning sources on seasonal aerosol air quality by Fabienne Reisen; C.P. (Mick) Meyer; Melita D. Keywood (pp. 437-447).

In the Huon Valley, Tasmania, current public perception is that smoke from regeneration burning is the principal cause of pollution events in autumn. These events lead to exceedences of national air quality standards and to significant health impacts on the rural population. To date there is little data on the significance of the impact.The aim of the study was to quantitatively assess the seasonal atmospheric particle loadings in the Huon Valley and determine the impact of smoke pollution. The study monitored fine (PM_2.5) and coarse (PM₁₀) particle concentrations and their chemical composition at two locations in the Huon Valley, Geeveston, an urban site and Grove, a rural site, between March 2009 and November 2010.The monitoring program clearly showed that biomass burning was a significant source of PM_2.5 in the Huon Valley, leading to exceedences of the 24 h PM_2.5 Ambient Air Quality National Environment Protection Measures advisory standard on a number of occasions. Significant increases of PM_2.5 concentrations above background occurred during periods of prescribed burning as well as during the winter season. Although the intensity of emissions from prescribed burns (PB) and residential woodheaters (WH) was similar, emissions from WH were the largest source of PM_2.5, with a contribution of 77% to the ambient PM_2.5 load compared to an 11% contribution from PB. The results have also shown a greater impact on air quality at the urban site than at the rural site, indicating that PM_2.5 concentrations are primarily influenced by localised sources rather than by regional pollution.The potential impact on local residents of the high PM concentrations during the PB and WH season was assessed. WH pollution is largely a persistent night-time issue in contrast to PB events which generally occur during the day and are of short duration. Due to the long persistence of high PM concentrations in winter, indoor PM concentrations are unlikely to be substantially lower than outdoor ones. However plume strikes are usually of shorter duration and therefore it may be possible to avoid exposure to PB events by remaining indoors.► Impact of biomass burning sources on air quality is assessed for an urban and rural site in Tasmania. ► Both chemical and PMF analysis confirmed that biomass combustion was a major source of PM_2.5. ► Emissions from residential woodheaters were the largest source of PM_2.5, compared to prescribed burns. ► PM_2.5 concentrations are influenced by localised sources rather than by regional pollution.

Keywords: Particulate matter; Levoglucosan; Prescribed burns; Residential wood burning; Biomass; Huon Valley Tasmania

Long-term observations of saccharides in remote marine aerosols from the western North Pacific: A comparison between 1990–1993 and 2006–2009 periods by Jing Chen; Kimitaka Kawamura; Cong-Qiang Liu; Pingqing Fu (pp. 448-458).

Anhydrosugars (galactosan, mannosan and levoglucosan), sugars (xylose, fructose, glucose, sucrose and trehalose) and sugar alcohols (erythritol, arabitol, mannitol and inositol) were measured in the aerosol samples collected in a remote island (Chichi-Jima, Japan) in the western North Pacific from 1990 to 1993 and from 2006 to 2009. Total concentrations of anhydrosugars, the biomass burning tracers, were 0.01–5.57 ng m⁻³ (average 0.76 ng m⁻³) during 1990–1993 versus 0.01–7.19 ng m⁻³ (0.64 ng m⁻³) during 2006–2009. Their seasonal variations were characterized by winter/spring maxima and summer/fall minima. Such a seasonal pattern should be caused by the enhanced long-range atmospheric transport of biomass burning products and terrestrial organic matter (such as higher plant detritus and soil dust) from the Asian continent in winter/spring seasons, when the westerly or winter monsoon system prevails over the western North Pacific. Sugars and sugar alcohols showed different seasonal patterns. The monthly mean concentrations of erythritol, arabitol, mannitol, inositol, fructose, glucose and trehalose were found to be higher in spring/summer and lower in fall/winter during both 1990–1993 and 2006–2009 periods, indicating an enhanced biogenic emission of aerosols in warm seasons. Interestingly, saccharides showed a gradual decrease in their concentrations from 1991 to 1993 and an increase from 2006 to 2009. In addition, the monthly averaged concentrations of sugars and sugar alcohols showed maxima in early summer during 1990–1993, which occurred about 1–2 months earlier than those during 2006–2009. Such a clear seasonal shift may be attributable to the changes in the strength of westerly and trade wind systems during two periods.► Analysis of 12 sugar compounds in marine aerosols at Chichi-Jima Island. ► Long-term observations were performed during 1990–1993 and 2006–2009. ► The levels of arabitol and mannitol generally increased from 2006 to 2009. ► Biomass burning is a minor contributor to the remote marine aerosols.

Keywords: Marine aerosols; Long-term trends; Levoglucosan; Mannitol; Chichi-Jima Island

Corrigendum to “Diurnal and annual variation of the sensation distance of odour emitted by livestock buildings calculated by the Austrian odour dispersion model (AODM)” [Atmos. Environ. 34 (2000) 4839–4851] by Günther Schauberger; Martin Piringer; Erwin Petz (pp. 459-460).

Corrigendum to “A sensitivity study of separation distances calculated with the Austrian Odour Dispersion Model (AODM)” [Atmos. Environ. 41 (2007) 1725–1735] by Martin Piringer; Erwin Petz; Inga Groehn; Günther Schauberger (pp. 461-462).

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