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Atmospheric Environment (v.69, #)

Editorial board (pp. i).

Characterisation of the local topsoil contribution to airborne particulate matter in the area of Rome (Italy). Source profiles by A. Pietrodangelo; R. Salzano; E. Rantica; C. Perrino (pp. 1-14).

Elemental profiles of the local resuspended natural topsoil of Rome area have been studied. Relevant compositional differences were observed either among main geological domains and rock types of this area (volcanics, flysch, marlstone, travertine) or between the two considered dimensional fractions (50 μm and PM₁₀ resuspended from the former). A significant enrichment in trace metals (especially Pb, Ni and Cr) has been observed in the PM₁₀ resuspended fraction of either volcanics or sedimentary outcropping rocks; volcanics show larger trace metals enrichment than sedimentary. Profiles of this study have been compared with signatures of natural crustal dust of African origin (collected either in situ or at European receptor sites, including Rome and other sites in the Latium region) and with signatures of road dust, properly selected from literature. This comparison was performed for source apportionment goals, with the aim of improving discrimination among signatures of local and non-local natural crustal materials.Elemental ratios of major and trace elements of geochemical relevance were used for the comparative study. Mg/Ca and Ti/Ca ratios appear successful in separating, by dispersion diagram, the resuspended fraction of local Rome geological topsoil from road dust and from long-range transported dust from Africa.► We report source profile of the PM₁₀ fraction of local natural topsoil in Rome area. ► Chamber resuspension and EDXRF technique were used for PM₁₀ collection and analysis. ► PM₁₀ differentiates from raw topsoil for its higher trace metals content. ► Our profiles were compared with literature signatures of African dust and road dust. ► Mg/Ca and Ti/Ca ratios separate Rome natural crustal PM₁₀, African dust and road dust.

Keywords: Particulate matter; Resuspension; Local topsoil; Source signature; Elemental ratio; Rome

Impact of urban pollution emitted in Warsaw on aerosol properties by O. Zawadzka; K.M. Markowicz; A. Pietruczuk; T. Zielinski; J. Jaroslawski (pp. 15-28).

This paper presents the analyses of the long-term observations of aerosol optical thickness (AOT) and concentrations of particulate matter with an aerodynamic diameter <10 μm (PM₁₀) in the Warsaw extended area. The AOT was observed between 2005 and 2011 in Warsaw and in Belsk (about 45 km away from Warsaw) with hand-held Microtops (Warsaw) and CIMEL (Belsk) sun photometers. The PM₁₀ concentrations were measured at three Warsaw stations as well as in Belsk. The ground-based observations, and the satellite data from the Moderate Resolution Imaging Spectroradiometer (MODIS) provided information about the influence of Warsaw emissions on the AOT. The estimated effect is about 0.02 (at 500 nm) based on the sun photometers' comparisons and 0.03 (at 550 nm) based on the MODIS results. Relatively small impact of Warsaw emissions on the AOT (about 10–15%) is consistent with the PM₁₀ data. The mean PM₁₀ differences, estimated during the same time as sun photometer measurements, for Warsaw Ursynow (a residential area) and Belsk was only 5.7 μg m⁻³ (13%), and for Warsaw Targowek (a mixed shopping and residential area) and Belsk was about 9.8 μg m⁻³ (20%). For the station located in the central Warsaw, near to the street with the heavy traffic, the difference in the long-term mean of the PM₁₀ was significantly larger and reached 22.1 μg m⁻³ (36%). Finally, an extreme smoke event observed on 4 April 2009, when favorable weather conditions led to the differences in the AOT between Warsaw and Belsk in a range of 0.11–0.2 (at 500 nm) has been described.► Negligible urban impact on Angstrom exponent. ► Monthly means of AOT and PM₁₀ are anticorrelated. ► During favorable weather conditions urban impact increases up to 50%.

Keywords: Aerosol; Aerosol optical thickness; Particulate matter; PM; ₁₀; Urban pollution; Sun photometer; Microtops; CIMEL; MODIS

Numerical simulation of observed submesoscale plume meandering under nocturnal drainage flow by B.S. Sandeepan; P.T. Rakesh; R. Venkatesan (pp. 29-36).

Bimodal plume shapes are occasionally observed in the series of tracer release experiments conducted at Hanford known as Hanford 67. These particular cases have not been studied so far. A possible reason for the bimodal shape could be the nocturnal submesoscale meandering of wind over the valley terrain. This study investigates the ability of state of art nested numerical model (WRF-ARW) to dynamically down scale up to submesoscale range (10 km in space and less than one hour in time) to simulate the meandering wind flow. The simulated wind field is used to drive a Lagrangian particle dispersion model, FLEXPART-WRF for plume simulation. From the study it is confirmed that the reason for this bimodal plume pattern is the wind meandering with periodicity of the order of ∼30 min having physical origin in the nocturnal drainage flow. Further, it is observed that the above submesoscale motion could be simulated using WRF model by reducing the grid size to 1 km in the horizontal plane.► Simulation of submesoscale wind meandering under drainage flow using WRF model. ► Analysis of Hanford, 1967 tracer release experiment data. ► Simulation of observed bimodal plume pattern using FLEXPART-WRF.

Keywords: WRF; FLEXPART-WRF; Dispersion modeling; Submesoscale; Meandering

A study of the temporal dynamics of ambient particulate matter using stochastic and chaotic techniques by Hwa-Lung Yu; Yuan-Chien Lin; Bellie Sivakumar; Yi-Ming Kuo (pp. 37-45).

Temporal dynamics of particulate matter (PM) concentration are affected by a variety of complex physical and chemical interactions among ambient pollutants and various exogenous factors (e.g. meteorological variables). Consequently, the dynamics of PM concentration can be considered either as a stochastic process or as a deterministic process. Many studies have applied stochastic and chaotic approaches independently to study the dynamics of PM concentration. However, none of them has compared these two complementary approaches for verification and possible confirmation of the outcomes. The present study makes an attempt to address this issue, through application of the dynamic factor analysis (DFA) (a stochastic method) and the correlation dimension (CD) method (a chaotic method) to study the temporal dynamics of ambient pollutants. More specifically, these two methods are employed to identify the number of variables dominantly governing the dynamics of PM concentration, with analysis of PM10, PM2.5, and ten other variables observed at the Hsing-Chuang station in Taipei (Taiwan). The results from the two methods are found to be consistent, with the DFA method suggesting eight common trends among the observed time series and the CD method suggesting eight variables dominantly governing the dynamics of both PM10 and PM2.5. This study provides an excellent example for the utility of both stochastic and chaotic approaches in modeling atmospheric and environmental systems, as these approaches not only shed light in their own ways but also complement each other in capturing the salient characteristics of such systems, especially from the perspective of simplified modeling.► PM10, PM2.5 and their associated ambient pollutants are investigated by both stochastic and chaotic methods. ► Both stochastic and chaotic methods reveal eight dominant underlying temporal dynamics of PM10 and PM2.5. ► Multivariate dynamic factor analysis identifies the common trends among the ambient pollutants. ► Correlation dimension method identifies the deterministic dynamics without linear assumption.

Keywords: Particulate matter; Temporal dynamics; System identification; Dynamic factor analysis; Correlation dimension

Effects of the meteorological variability on regional air quality in East Asia by Jaein I. Jeong; Rokjin J. Park (pp. 46-55).

We examine the effects of the meteorological variability on O₃ and SO₄²⁻–NO₃⁻–NH₄⁺ aerosol concentrations in East Asia using 3-D chemical transport model (GEOS-Chem) simulations for the period of 1985–2006. The model was driven by the GEOS assimilated meteorology with the emission estimates from the Streets et al. inventory with annual scale factors of Regional Emission inventory in Asia (REAS). Over the past two decades precursor emissions have been dramatically increased. Our model simulations however show strong non-linear responses of oxidation products to the increases of those precursors. The analysis of simulated results shows significant effects of meteorological variability on O₃ and SO₄²⁻–NO₃⁻–NH₄⁺ concentrations. Springtime O₃ concentration has been generally increased over the past two decades mainly due to increases in anthropogenic precursors emissions but concurrent changes in meteorology including decreases of cloud covers and increases of temperature further enhance O₃ increases in East Asia. Our analysis reveals that changes in meteorology account for 30% of total O₃ increases in East Asia over the past two decades. On the contrary, increases in mixing depth suppress increases of (NH₄)₂SO₄ concentrations in summer but decreases in mixing depth in winter result in enhancement of NH₄NO₃ aerosols concentrations up to 4 μg m⁻³ in eastern China. Effects of meteorological variability on SO₄²⁻–NO₃⁻–NH₄⁺ aerosol concentrations are thus seasonally dependent such as a decrease in summer by 4% but an increase by 7% in winter over the past two decades. This result indicates that the meteorological conditions have changed more favorable for the PM air quality degradation in winter.► Examine the effects of the meteorological variability on regional air quality. ► Cloudiness and temperature account for 30% of total O₃ increases in East Asia. ► Increases in mixing depths suppress increases of (NH₄)₂SO₄ in summer. ► Decreases in mixing depths in winter result in enhancement of NH₄NO₃.

Keywords: Air pollution; Meteorological variability; Ozone; Secondary inorganic aerosol; Chemical transport model

Critical loads and H⁺ budgets of forest soils affected by air pollution from oil sands mining in Alberta, Canada by Kangho Jung; Scott X. Chang; Yong Sik Ok; M.A. Arshad (pp. 56-64).

We investigated the critical load (CL) and exceedance (EX) of sulfur (S) deposition, temporal changes in soil chemistry, and H⁺ budget of soils in plots dominated by Pinus banksiana (jack pine) or Populus tremuloides (trembling aspen, aspen) in two acid-sensitive watersheds to assess the risk of soil acidification by S emissions from oil sands mining in the Athabasca oil sands region (AOSR), Canada. The CLs and EXs were determined by two methods: one was based on bulk deposition and the other based on total deposition (as a sum of bulk deposition and interception deposition). The CLs ranged from 223 to 711 mol_c ha⁻¹ yr⁻¹ based on bulk deposition. Those values were similar to that obtained based on total deposition. However, EXs based on bulk deposition were significantly lower ( p < 0.001) than those based on total deposition due to the relative increase ofSO42− concentrations in interception deposition, indicating that EXs based on bulk deposition only could underestimate the risk of soil acidification in the AOSR. The S deposition did not exceed CLs in the long-term for both methods. The pH in the forest floor increased and availableSO42− (as the sum of soluble and adsorbedSO42−) in the forest floor and surface mineral soils increased in both jack pine and aspen stands between 2005 and 2010. The H⁺ budget ranged from −289 to −130 mol_c ha⁻¹ yr⁻¹ in jack pine stands and from −510 to −371 mol_c ha⁻¹ yr⁻¹ in aspen stands. Our results suggest that 1) soils in the studied forest stands have recovered from acidification based on the increasing soil pH over time and the negative H⁺ budget, and 2) the risk of soil acidification should be assessed by CL and EX calculated based on total deposition.► Proportion of SO₄^2- was greater in interception than in bulk deposition. ► Exceedance of S deposition was underestimated if based on bulk deposition only. ► Sulfur deposition was lower than critical loads in the studied watersheds. ► The studied forest soils were recovering from previous acidification.

Keywords: Athabasca oil sands; Critical load; H; ⁺; budget; Interception deposition; S deposition; Soil acidification

Ultrafine particle concentrations in and around idling school buses by Qunfang Zhang; Heidi J. Fischer; Robert E. Weiss; Yifang Zhu (pp. 65-75).

Unnecessary school bus idling increases children's exposure to diesel exhaust, but to what extent children are exposed to ultrafine particles (UFPs, diameter < 100 nm) in and around idling school buses remains unclear. This study employed nine school buses and simulated five scenarios by varying emissions source, wind direction, and window position. The purpose was to investigate the impact of idling on UFP number concentration and PM_2.5 mass concentration inside and near school buses. Near the school buses, total particle number concentration increased sharply from engine off to engine on under all scenarios, by a factor of up to 26. The impact of idling on UFP number concentration inside the school buses depended on wind direction and window position: wind direction was important and statistically significant while the effect of window positions depended on wind direction. Under certain scenarios, idling increased in-cabin total particle number concentrations by a factor of up to 5.8, with the significant increase occurring in the size range of 10–30 nm. No significant change of in-cabin PM_2.5 mass concentration was observed due to idling, regardless of wind direction and window position, indicating that PM_2.5 is not a good indicator for primary diesel exhaust particle exposure. The deposition rates based on total particle number concentration inside school bus cabins varied between 1.5 and 5.0 h⁻¹ across nine tested buses under natural convection conditions, lower than those of passenger cars but higher than those of indoor environments.► Five scenarios were simulated to assess their impacts on UFP levels in and around idling school bus. ► Idling increased total particle number concentration near the school buses under all scenarios. ► The impact of idling on in-cabin UFP number concentrations depended on wind direction and window position. ► The deposition rates inside school cabins were lower than those of passenger cars but higher than those of indoor environments.

Keywords: Ultrafine particles; PM; _2.5; School bus; Wind direction; Window position; Deposition rate

Modeling the effects of a solid barrier on pollutant dispersion under various atmospheric stability conditions by Jonathan T. Steffens; David K. Heist; Steven G. Perry; K. Max Zhang (pp. 76-85).

There is a growing need for developing mitigation strategies for near-road air pollution. Roadway design is being considered as one of the potential options. Particularly, it has been suggested that sound barriers, erected to reduce noise, may prove effective at decreasing pollutant concentrations. However, there is still a lack of mechanistic understanding of how solid barriers affect pollutant transport, especially under a variety of meteorological conditions. In this study, we utilized the Comprehensive Turbulent Aerosol Dynamics and Gas Chemistry (CTAG) model to simulate the spatial gradients of SF₆ concentrations behind a solid barrier under a variety of atmospheric stability conditions collected during the Near Road Tracer Study (NRTS08). We employed two different CFD models, RANS and LES. A recirculation zone, characterized by strong mixing, forms in the wake of a barrier. It is found that this region is important for accurately predicting pollutant dispersion, but is often insufficiently resolved by the less complex RANS model. The RANS model was found to perform adequately away from the leading edge of the barrier. The LES model, however, performs consistently well at all flow locations. Therefore, the LES model will make a significant improvement compared to the RANS model in regions of strong recirculating flow or edge effects. Our study suggests that advanced simulation tools can potentially provide a variety of numerical experiments that may prove useful for roadway design communities to intelligently design roadways, making effective use of roadside barriers.► The LES and k– ɛ RANS models are employed to model how a solid barrier affects dispersion. ► Modeling results are evaluated against the NRTS08 dataset. ► LES performs consistently well under all atmospheric conditions. ► The k– ɛ RANS model cannot fully capture the edge and recirculation.

Keywords: Pollutant dispersion; Flow recirculation; CFD; Modeling

Carbon emissions in Mediterranean shrubland wildfires: An experimental approach by Elisa Garcia-Hurtado; Jorge Pey; M. Jaime Baeza; Arnaud Carrara; Joan Llovet; Xavier Querol; Andrés Alastuey; V. Ramon Vallejo (pp. 86-93).

Forest fire emissions modify the chemical composition of the atmosphere and the earth's climate system. The Ayoraburning experiment was designed to assess and quantify fire emissions from Mediterranean shrublands. A number of gaseous pollutants and particulate matter metrics (CO₂, CO, CH₄, PM_2.5) were measured during 3 burning replicates by using real-time monitors. Quantification of carbon emissions released during the experiments showed that 71% was CO₂, 26% CO, 3% CH₄, and only 0.3% was particulate carbon. Emission factors obtained for CO₂, CO and CH₄ were 1257 ± 40, 453 ± 28 and 46 ± 12 g kg⁻¹ dry matter, respectively, and combustion efficiencies ranged from 0.46 to 0.99. The experiments allowed the estimation of carbon emission in the different fire phases. Thus, 25% of carbon was sampled in the flaming phase and 75% of C in the smoldering phase.Current natural greenhouse gas (GHG) emission inventories in Mediterranean countries underestimate the actual emissions from forest fires since they do not consider forest shrub understory and shrublands and since they assume that the CO₂ emitted is offset by forest re-growth.Our results may be used to improve current forest-fire emission inventories in southern Europe with special emphasis on shrublands.► The experiments were performed to guarantee the conditions of a real fire. ► In situ monitoring measures have allowed estimating the percentage of carbon sampled. ► Low combustion efficiencies due to the structural composition of the shrubs. ► Experimental emission data will improve the information in emission inventories.

Keywords: Emission factor; Shrubland; Combustion efficiency; Carbon contribution; Emission inventory

Critical review and meta-analysis of ambient particulate matter source apportionment using receptor models in Europe by C.A. Belis; F. Karagulian; B.R. Larsen; P.K. Hopke (pp. 94-108).

A review was conducted of the published literature on source apportionment of ambient particulate matter (PM) in Europe using receptor models (RMs). Consistent records were identified for source contribution estimates of PM mass concentrations for 272 records and of organic carbon (OC) in PM for 60 records. Over the period 2000–2012, a shift was observed in the use of RMs from principal component analysis, enrichment factors, and classical factor analysis to Positive Matrix Factorization while Chemical Mass Balance is still topical.Following a meta-analysis of the published results, six major source categories for PM were defined that comprise almost all individual sources apportioned in Europe: atmospheric formation of secondary inorganic aerosol (SIA), traffic, re-suspension of crustal/mineral dust, biomass burning, (industrial) point sources, and sea/road salt. For the OC fraction, the three main source categories were: atmospheric formation of secondary organic aerosol, biomass burning, and fossil fuel combustion. The geographical and seasonal variations of these sources are mapped and discussed.A special analysis of PM concentrations that exceed the current European air quality limits indicated SIA and traffic as the most important source categories to target for abatement throughout the year together with biomass burning during the cold season.► Receptor models evolve towards tools with refined uncertainty treatment. ► Positive Matrix Factorization and Chemical Mass Balance are the most used models. ► Gas-to-particle conversion is the main PM mass and particulate organic carbon source. ► To abate exceedances, secondary inorganic and traffic are the main sources to target. ► More long term speciated PM datasets would foster source identification studies.

Keywords: PM; ₁₀; PM; _2.5; Particulate matter; Source apportionment; Receptor models; Europe; Exceedances; Carbonaceous fraction; Particulate organic carbon

Insights into PM₁₀ sources in Houston, Texas: Role of petroleum refineries in enriching lanthanoid metals during episodic emission events by Ayşe Bozlaker; Birnur Buzcu-Güven; Matthew P. Fraser; Shankararaman Chellam (pp. 109-117).

Petroleum refineries may emit large quantities of pollutants during non-routine operations that include start-ups and shutdowns, planned maintenance, and unplanned equipment failures. The Texas Commission on Environmental Quality (TCEQ) tracks such events by requiring industries to self-report estimates of these emissions because they often have a detrimental impact on local air quality and potentially, public health. An inventory of non-routine episodic emission events is available via TCEQ's website. However, there is on-going concern that such episodic emissions are sometimes under-reported or even not cataloged. Herein, we present concentrations of 42 main group, transition, and lanthanoid elements in 114 time-resolved (3 or 6 h) samples collected over a 1-month period. We also develop strategies to identify aerosol sources using elemental tracers and compare source apportionment (performed by positive matrix factorization) based on ambient measurements to inventoried non-routine emission events. Through interpretation of key marker elements, five sources impacting concentrations of metals in PM₁₀ were identified and calculated to contribute 73% of the measured PM₁₀ mass. On average, primary emissions from fluidized-bed catalytic cracking (FCC) units negligibly contributed to apportioned PM₁₀ mass. However, 35 samples were identified as impacted by transient PM₁₀ emissions from FCC units because of elevated levels of lanthanoid metals and their ratios. Only 31 of these 35 samples coincided with self-reported non-routine emission events. Further, roughly half of the emission event self-reports detailed only emissions of gaseous pollutants. Based on this, we posit that not all PM₁₀ emission events are reported and even self-reported emission events are incomplete – those that only catalog gaseous pollutants may also include unreported PM emissions.Display Omitted► The elemental composition of over 100 time-resolved PM₁₀ samples is reported. ► Episodic industrial emissions are shown to transiently enrich particulate metals. ► ICP-MS and PMF identified gaps in TCEQ's emission event inventory database. ► Trace metals measurements assist in independently monitoring industrial emissions. ► FCC emission events significantly increase lanthanoids concentrations in aerosols.

Keywords: PM; ₁₀; Trace metals; Positive matrix factorization; Non-routine emissions; Petrochemical industries; Rare earth elements

Light absorption of black carbon aerosol and its enhancement by mixing state in an urban atmosphere in South China by Zi-Juan Lan; Xiao-Feng Huang; Kuang-You Yu; Tian-Le Sun; Li-Wu Zeng; Min Hu (pp. 118-123).

The effects of black carbon (BC) aerosol on climate warming have been the study focus in the recent decade, and the reduction of BC is now expected to have significant near-term climate change mitigation. Large uncertainties of BC optical properties, however, still exist and seriously restrict the ability to quantify BC's climate effects. In this study, advanced instrumentation (a three-wavelength photoacoustic soot spectrometer (PASS-3) and a single particle soot photometer (SP2)) were used to measure black carbon aerosol and analyze its optical properties in a mega-city in South China, Shenzhen, during the summer of 2011. The results indicated that the average BC mass concentration was 4.0 ± 3.1 μg m⁻³ during the campaign, accounting for ∼11% of the total PM_2.5 mass concentration. The PM_2.5 light absorption at 405, 532 and 781 nm was 37.1 ± 28.1, 25.4 ± 19.0 and 17.6 ± 12.9 Mm⁻¹, respectively. The average absorption Angstrom exponent of PM_2.5 in visual spectrum (AAE_{405–781 nm}) was 1.1 ± 0.1 during the campaign, indicating that the light absorbing carbon mainly came from vehicular emissions, with little contributions from biomass burning emissions. The mass absorption efficiency (MAE) of BC at 532 nm ranged from 5.0 to 8.5 m² g⁻¹ during the campaign, with an average of 6.5 ± 0.5 m² g⁻¹, and showed an obvious diurnal pattern with high values in the daytime. The average percentage of internally mixed BC was 24.3 ± 7.9% during the campaign, showing significant positive correlation relationship with the MAE of BC. More quantitative data analysis indicated that the internally mixed BC would amplify MAE by about 7% during the campaign, which stands in accordance with the new finding of a very recent Science magazine paper (Cappa et al., 2012) that the BC absorption enhancement due to internal mixing in the real atmosphere is relatively low, in apparent contrast to theoretical model predictions.► Black carbon (BC) aerosol was characterized with advanced on-line instruments. ► The BC light absorption at 3 wavelengths was obtained using photoacoustic method. ► The enhancement of BC light absorption by mixing state is evaluated quantitatively.

Keywords: Photoacoustic soot spectrometer; Single particle soot photometer; Absorption Angstrom exponent; Mass absorption efficiency; Mixing state

Seasonal variation in basal emission rates and composition of mono- and sesquiterpenes emitted from dominant conifers in Japan by Sou N. Matsunaga; Shigeru Niwa; Tomoki Mochizuki; Akira Tani; Dai Kusumoto; Yasuhiro Utsumi; Tsutomu Enoki; Tsutom Hiura (pp. 124-130).

Biogenic volatile organic compounds (BVOCs) are known to play an important role in atmospheric chemistry due to their high reactivity and high emission rates. Therefore, in recent decades, many efforts have been made to estimate the emission rates, composition and allocation of the BVOCs. Monoterpenes (MNTs) and sesquiterpenes (SQTs) are major groups of BVOCs and mainly emitted from coniferous trees. There is quite a few reports discussing the seasonality of basal emission rate, which is a normalized emission rate at a set of standard conditions (e.g. temperature, light intensity), of the BVOCs. Three field measurements were conducted using branch enclosure techniques to determine MNTs and SQTs emission measured from mature trees of Cryptomeria japonica and Chamaecyparis obtusa, which are the most dominant trees in Japan and account for about 40–50% of Japanese forest in leaf amount throughout the four seasons in southern Japan in 2010. The results are compared with the measurements for the same compound classes obtained at a suburban area of Tokyo, Japan in 2009. The seasonal variation in the basal emissions of MNTs from both tree species at Shiiba did not show significant seasonal changes. For both tree species, the variations in the basal emission of MNTs differ in the two sites, while those of SQTs showed relatively similar variations. Chemical composition of SQTs showed clear and continued seasonal variations, while MNTs did not show any clear seasonal variation for these tree species at both sites. It can be hypothesized that the emissions of BVOC classes (e.g. MNTs and SQTs) depend on leaf age. In this paper, we discuss about the seasonal variations in the basal emission rates and chemical compositions of BVOCs obtained from the two dominant coniferous tree species in Japan based on nine field measurement campaigns conducted at two different sites.► Basal emission rates of monoterpenes and sesquiterpenes have seasonal variations. ► The two sites showed different seasonal patterns in the BVOC emission. ► Composition of sesquiterpene emission also had seasonal variations.

Keywords: Monoterpenes; Sesquiterpenes; Biogenic volatiles; Atmosphere; Seasonal variation; BVOC composition

Estimate of dry deposition fluxes of nutrients over the East China Sea: The implication of aerosol ammonium to non-sea-salt sulfate ratio to nutrient deposition of coastal oceans by Li Zhu; Ying Chen; Lin Guo; Fujiang Wang (pp. 131-138).

Atmospheric deposition is one of important sources for nutrients to the surface ocean. Previous estimates for dry deposition fluxes of nutrients have mainly employed a single-mode particle model, and here we attempt to use size-segregated samples collected at Huaniao Island of the East China Sea (ECS) and dry deposition velocities derived from particle size and meteorological conditions of each sampling day. The dry deposition fluxes of NO₃⁻, NH₄⁺, and SP are estimated to be 6080, 10,006, and 26 μmol m⁻² yr⁻¹ respectively over the ECS using size-segregated samples. It is found that assuming a constant deposition velocity could overestimate the dry flux of NO₃⁻ by a factor of 6 while underestimate the flux of NH₄⁺, which would alter the dry flux ratio ofNH4+/NO3− from 1.6 to 0.1 with potential effects on the primary production and phytoplanktonic structure in the ECS. For coastal oceans influenced significantly by NH₃ sources, aerosol NH₄⁺ to non-sea-salt (nss-) SO₄²⁻ ratio could be high and excess NH₄⁺ may drag 34–54% of NO₃⁻ to fine mode aerosols, which may cause a large overestimation of dry flux of NO₃⁻ over the ocean by assuming its deposition velocity similar to that of coarse particle.► Dry depositions of nutrients are the highest in spring and the lowest in summer over the ECS. ► Assuming a constant deposition velocity may overestimate dry flux of NO₃⁻. ► High NH₄⁺/SO₄²⁻ ratio implies the existence NO₃⁻ in fine mode aerosols. ► Atmospheric input of DIN could support over 20% of the new production.

Keywords: Dry deposition flux; Nutrients; East China Sea; Ammonium; Non-sea-salt sulfate

Influence of biogenic pollen on optical properties of atmospheric aerosols observed by lidar over Gwangju, South Korea by Young Min Noh; Detlef Müller; Hanlim Lee; Tae Jin Choi (pp. 139-147).

For the first time, optical properties of biogenic pollen, i.e., backscatter coefficients and depolarization ratios at 532 nm were retrieved by lidar observations. The extinction coefficient was derived with the assumption of possible values of the extinction-to-backscatter (lidar) ratio. We investigate the effect of the pollen on the optical properties of the observed atmospheric aerosols by comparing lidar and sun/sky radiometer measurements carried out at the lidar site. The observations were made with a depolarization lidar at the Gwangju Institute of Science & Technology (GIST) in Gwangju, Korea (35.13°N, 126.50°E) during an intensive observational period that lasted from 5 to 7 May 2009. The pollen concentration was measured with a Burkard trap sampler at the roof top of the Gwangju Bohoon hospital which is located 1 km away from the lidar site. During the observation period, high pollen concentrations of 1360, 2696, and 1952 m⁻³ day⁻¹ were measured on 5, 6, and 7 May, respectively. A high lidar depolarization ratio caused by biogenic pollen was only detected during daytime within the planetary boundary layer which was at 1.5–2.0 km height above ground during the observational period. The contribution of biogenic pollen to the total backscatter coefficient was estimated from the particle depolarization ratio. Average hourly values of pollen optical depth were retrieved by integrating the pollen extinction coefficients. We find average values of 0.062 ± 0.037, 0.041 ± 0.028 and 0.067 ± 0.036 at 532 nm on 5, 6, and 7 May, respectively. The contribution of pollen optical depth to total aerosol optical depth was 2–34%. The sun/sky radiometer data show that biogenic pollen can affect optical properties of atmospheric aerosol by increasing aerosol optical depth and decreasing the Ångström exponent during daytime during the season of high pollen emission.► For the first time, optical properties of biogenic pollen were retrieved by lidar. ► Pollen particles were only detected during daytime within the PBL. ► Pollen particles result in the increase of aerosol optical depth. ► Pollen particles decrease the Ångström exponent of aerosol during pollen periods. ► The contribution of biogenic pollen to the total aerosol optical depth was 2–34%.

Keywords: Pollen; Lidar; Depolarization ratio; Optical depth; Ångström exponent

Evaluating environmental modeling and sampling data with biomarker data to identify sources and routes of exposure by Hyeong-Moo Shin; Thomas E. McKone; Deborah H. Bennett (pp. 148-155).

Exposure to environmental chemicals results from multiple sources, environmental media, and exposure routes. Ideally, modeled exposures should be compared to biomonitoring data. This study compares the magnitude and variation of modeled polycyclic aromatic hydrocarbons (PAHs) exposures resulting from emissions to outdoor and indoor air and estimated exposure inferred from biomarker levels. Outdoor emissions result in both inhalation and food-based exposures. We modeled PAH intake doses using U.S. EPA's 2002 National Air Toxics Assessment (NATA) county-level emissions data for outdoor inhalation, the CalTOX model for food ingestion (based on NATA emissions), and indoor air concentrations from field studies for indoor inhalation. We then compared the modeled intake with the measured urine levels of hydroxy-PAH metabolites from the 2001–2002 National Health and Nutrition Examination Survey (NHANES) survey as quantifiable human intake of PAH parent-compounds. Lognormal probability plots of modeled intakes and estimated intakes inferred from biomarkers suggest that a primary route of exposure to naphthalene, fluorene, and phenanthrene for the U.S. population is likely inhalation from indoor sources. For benzo(a)pyrene, the predominant exposure route is likely from food ingestion resulting from multi-pathway transport and bioaccumulation due to outdoor emissions. Multiple routes of exposure are important for pyrene. We also considered the sensitivity of the predicted exposure to the proportion of the total naphthalene production volume emitted to the indoor environment. The comparison of PAH biomarkers with exposure variability estimated from models and sample data for various exposure pathways supports that both indoor and outdoor models are needed to capture the sources and routes of exposure to environmental contaminants.► We modeled PAHs intake from multiple exposure pathways. ► Predicted PAH intake were compared to observed intake from NHANES samples. ► The total modeled intake was within a factor of 3.4 of the median observed intake. ► Evaluation of both indoor and outdoor exposures is needed to evaluate biomarkers.

Keywords: Polycyclic aromatic hydrocarbons; Biomarker; Environmental modeling; Exposure routes; Food intakeAbbreviations; ASPEN; Assessment System for Population Exposure Nationwide; CDC; Centers for Disease Control; EPA; Environmental Protection Agency; LOD; limit of detection; NATA; National Air Toxics Assessment; NHANES; National Health and Nutrition Examination Survey; PAH; polycyclic aromatic hydrocarbons

Emissions characterization and regulatory compliance at an industrial complex: An integrated MM5/CALPUFF approach by K. Ghannam; M. El-Fadel (pp. 156-169).

This paper couples the meteorological Mesoscale Model (MM5) with the non-steady state CALPUFF modelling system in a short range dispersion context to assess regulatory compliance with air quality standards in a coastal urban area with complex terrain. For this purpose, an inventory of CO, NO_x, and PM₁₀ emissions from an industrial complex, highway and quarrying activity was developed using emission factors reported by the US Environmental Protection Agency (USEPA) and the European Environment Agency (EEA). Multiple emission scenarios were then simulated to test the representativeness of the obtained emission factors using statistical analysis of predictions against year-round field measurements. At the validated emission rates, CALPUFF simulations showed an acceptable ability to predict the upper end of observed concentrations and reproduced field measurements at several locations. Statistical analysis revealed that sources are likely to be emitting at conservative estimates (worst-case efficiency of control equipment and fuel quality), with total CO, NO_x and PM₁₀ emissions reaching 913 g s⁻¹ (19% by highway and 81% by industries), 1266 g s⁻¹ (63% by highway and 37% by industries) and 2970 g s⁻¹ (93% by industries and 7% by quarries), respectively.► MM5/CALPUFF were integrated for a regulatory compliance assessment at a multi-stack complex. ► Multiple CO, NO_x and PM₁₀ emission scenarios were simulated to validate source emissions. ► Statistical analysis established that sources are emitting at highest emission factors. ► CALPUFF simulated observed peak levels and reproduced field measurements.

Keywords: Emission factors; Regulatory compliance; Cement industry

Experimental measurement of cooling tower emissions using image processing of sensitive papers by J. Ruiz; A.S. Kaiser; M. Ballesta; A. Gil; M. Lucas (pp. 170-181).

Cooling tower emissions are harmful for several reasons such as air polluting, wetting, icing and solid particle deposition, but mainly due to human health hazards (i.e. Legionella). There are several methods for measuring drift drops. This paper is focussed on the sensitive paper technique, which is suitable in low drift scenarios and real conditions. The lack of an automatic classification method motivated the development of a digital image process algorithm for the Sensitive Paper method. This paper presents a detailed description of this method, in which, drop-like elements are identified by means of the Canny edge detector combined with some morphological operations. Afterwards, the application of a J48 decision tree is proposed as one of the most relevant contributions. This classification method allows us to discern between stains whose origin is a drop and stains whose origin is not a drop. The method is applied to a real case and results are presented in terms of drift and PM₁₀ emissions. This involves the calculation of the main features of the droplet distribution at the cooling tower exit surface in terms of drop size distribution data, cumulative mass distribution curve and characteristic drop diameters. The Log-normal and the Rosin–Rammler distribution functions have been fitted to the experimental data collected in the tests and it can been concluded that the first one is the most suitable for experimental data among the functions tested (whereas the second one is less suitable). Realistic PM₁₀ calculations include the measurement of drift emissions and Total Dissolved Solids as well as the size and number of drops. Results are compared to the method proposed by the U.S. Environmental Protection Agency assessing its overestimation. Drift emissions have found to be 0.0517% of the recirculating water, which is over the Spanish standards limit (0.05%).► An improved digital image process in order to measure the emissions has been developed. ► The Rosin–Rammler distribution function do not provide consistent curve fits. ► The Log-normal has proven to be the most suitable function for fitting experimental data among the ones tested. ► AP-42 method overestimates the PM₁₀ emitted by the tower. ► Drift, Total Dissolved Solids and the distribution of diameters (size and number) is required for a precise PM₁₀ evaluation.

Keywords: Cooling tower emissions; Sensitive paper; Canny edge detector; Log-normal distribution function

Particulate matter dynamics in naturally ventilated freestall dairy barns by H.S. Joo; P.M. Ndegwa; A.J. Heber; J.-Q. Ni; B.W. Bogan; J.C. Ramirez-Dorronsoro; E.L. Cortus (pp. 182-190).

Particulate matter (PM) concentrations and ventilation rates, in two naturally ventilated freestall dairy barns, were continuously monitored for two years. The first barn (B1) housed 400 fresh lactating cows, while the second barn (B2) housed 835 non-fresh lactating cows and 15 bulls. The relationships between PM concentrations and accepted governing parameters (environmental conditions and cattle activity) were examined. In comparison with other seasons, PM concentrations were lowest in winter. Total suspended particulate (TSP) concentrations in spring and autumn were relatively higher than those in summer. Overall: the concentrations in the barns and ambient air, for all the PM categories (PM_2.5, PM₁₀, and TSP), exhibited non-normal positively skewed distributions, which tended to overestimate mean or average concentrations. Only concentrations of PM_2.5 and PM₁₀ increased with ambient air temperature ( R² = 0.60–0.82), whereas only concentrations of TSP increased with cattle activity. The mean respective emission rates of PM_2.5, PM₁₀, and TSP for the two barns ranged between 1.6–4.0, 11.9–15.0, and 48.7–52.5 g d⁻¹ cow⁻¹, indicating similar emissions from the two barns.► Particulate matter concentrations and ventilation rates in dairy barns were monitored for two years. ► Concentrations of PM_2.5, PM₁₀, and TSP, exhibited non-normal positively skewed distributions. ► The respective emission rates of PM_2.5, PM₁₀, and TSP ranged between 1.6–4.0, 11.9–15.0, and 48.7–52.5 g d⁻¹ cow⁻¹. ► Concentrations of PM_2.5 and PM₁₀ increased with ambient air temperature ( R² = 0.60–0.82). ► Concentrations of TSP (but not of PM_2.5 and PM₁₀) tended to increase with cattle activity.

Keywords: Air quality; Air pollution; Animal agriculture; Dairy operations; Emission rates

Estimate of methane release from temperate natural wetlands using ENVISAT/SCIAMACHY data in China by Xiuying Zhang; Hong Jiang; Xuehe Lu; Miaomiao Cheng; Xiaomin Zhang; Xinhui Li; Linjing Zhang (pp. 191-197).

Since wetlands are the largest natural sources of atmospheric CH₄, it is important to estimate the CH₄ emissions from natural wetlands at regional scale and over a long time period. The annual CH₄ efflux from temperate natural wetlands excluding water surface in China was estimated, based on atmospheric CH₄ concentrations from SCIAMACHY/ENVISAT. The atmospheric CH₄ concentrations showed obvious seasonal cycles, and CH₄ emission from natural wetlands dominated the temporal variations of CH₄ concentrations in north China, accounting for about 67.94% of the variations of CH₄ concentrations. The chemical transport model, MOZART-4 (Model for Ozone and Related Chemical Tracers, version 4), was used to simulate the space-borne CH₄ column concentrations to the surface level, and then the relationship between surface concentrations and emissions of CH₄ from natural wetlands was simulated by a linear regression model. The results showed that the estimated annual budget of CH₄ emission from natural wetlands in the temperate zone of China was about 4.76 Tg CH₄, which was within the range of 2.38–4.91 Tg CH₄ estimated by spatial distribution of wetland and the published CH₄ release fluxes during the 1990s–2000s. This demonstrated that the method of using space-borne CH₄ column concentrations to estimate CH₄ emissions from natural wetlands was reliable.► Natural wetland emission dominates seasonal variation of atmospheric CH₄. ► MOZART-4 is used to simulate the space-borne XCH₄ columns to the surface level. ► Relationship between surface CH₄ concentrations and emissions from wetland is simulated by a linear regression model. ► The estimated CH₄ emission from natural wetlands in temperate zone of China is 4.76 Tg CH₄ yr⁻¹.

Keywords: Atmospheric methane; SCIAMACHY/ENVISAT; Temperate wetlands

Assessment of changing meteorology and emissions on air quality using a regional climate model: Impact on ozone by L. Coleman; D. Martin; S. Varghese; S.G. Jennings; C.D. O'Dowd (pp. 198-210).

A regional climate model is used to assess changes in atmospheric ozone for the years 2030, 2050 and 2100 relative to 2006 brought about by changes in meteorology and emissions. The simulations are evaluated against ozone measurements for 2006, exhibiting good agreement between the model-predicted measurements and the measured annual cycles. Under the RCP6 emission scenario used in these simulations, average ozone mixing ratios are set to reduce by 2.0 ppb over domains encompassing Europe and the North East Atlantic between 2006 and 2100 with the most significant decrease occurring after 2050 due to the pattern in changing emissions. Peak reductions of more than 8 ppb are observed during summer time over mainland Europe by 2100. Model output was studied for three relevant sub-domains, namely the North East Atlantic, Ireland and Europe. The relative contribution of changes in both emissions and meteorology is assessed. Over the whole domain, changing emissions are predominantly responsible for changes in surface ozone; although over the North East Atlantic domain, the changing emissions do not perturb surface ozone trends and the decrease in 2100 levels is entirely attributable to changing meteorology.► Future simulations indicate that ozone levels will decrease under the RCP6 emission storyline. ► This reduction is most significant after 2050 when the most significant changes in emissions occur. ► An analysis of the ozone variance illustrates a significant decrease in extreme ozone events.

Keywords: Ozone; Changing meteorology; RCP emission scenarios

The effect of varying primary emissions on the concentrations of inorganic aerosols predicted by the enhanced UK Photochemical Trajectory Model by Roy M. Harrison; Alan M. Jones; David C.S. Beddows; Richard G. Derwent (pp. 211-218).

An enhanced Photochemical Trajectory Model (PTM) has been used to simulate concentrations of secondary inorganic aerosol (for the purposes of this work, sulphate, nitrate, chloride and ammonium) in PM₁₀ over a two-month period at a rural site in central southern England (Harwell). Judged against a base year of 2007, emissions of precursor gases, SO₂, NO_x and NH₃ have been varied over plausible ranges, occurring across the UK only, mainland Europe only, or the whole of Europe. The model is able to reproduce observed non-linearities and shows that abatement is less than proportional in all cases. Additionally, abatement of sulphur dioxide leads to increased nitrate concentrations. The combination of a weak response of nitrate to reductions in NO_x emissions, and the effect of sulphur dioxide reductions in increasing nitrate is consistent with the very small recent observed trends in nitrate concentrations over the UK. A scenario for 2020 in which emissions of SO₂, NO_x and NH₃ fall to 64%, 75% and 96% respectively of their 2007 baseline levels across the whole of Europe shows a reduction of 2 μg m⁻³ in secondary inorganic aerosol which is 13% below the baseline case for a two month period in 2007, due mostly to a fall in sulphate and ammonium. As this was a relatively high pollution period, it is estimated that over a full year, the reduction is more likely to be around 1 μg m⁻³.Display Omitted► Secondary inorganic aerosol has been simulated for a site in central southern England. ► Non-linearities in precursor–pollutant relationships are well reproduced. ► In line with some other model studies, abatement of sulphur dioxide leads to increased nitrate. ► Low response of nitrate aerosol to NO_x reductions is predicted. ► Total reduction of secondary inorganic components of about 1 μg m⁻³ between 2007 and 2020 is predicted.

Keywords: Secondary inorganic aerosol; Sulphate; Nitrate; Trajectory model

Multi-zone modeling of size-resolved outdoor ultrafine particle entry into a test house by Donghyun Rim; Andrew Persily; Steven Emmerich; W. Stuart Dols; Lance Wallace (pp. 219-230).

Airborne particle entry into buildings is important for human exposure to particles and associated health effects. The present study investigated the entry of size-resolved outdoor ultrafine particles into a test building under three different ventilation scenarios using a multi-zone airflow and contaminant transport model. Simulations of the entry of outdoor ultrafine particles into a residential test building were performed and validated with measurement data. The study results show that accurate particle deposition and penetration inputs are required to predict the time-varying particle concentrations in buildings. For closed-window conditions, both deposition and penetration have significant effects on modeling UFP transport, while deposition is more important than penetration for open-window conditions. As the window opening area increases, the filtering effect of the building envelope decreases and more outdoor particles enter the building through window openings. The study results also show that the indoor–outdoor (I–O) concentration ratio is a strong function of particle size and building operating conditions. The comparison between measurements and prediction suggests that a multi-zone particle transport model can provide insight into particle entry into buildings under various weather and building operating scenarios.► We model entry of outdoor ultrafine particles into a multi-zone building. ► Indoor–outdoor relationship varies with particle size and window opening area. ► Multi-zone model can predict reasonably entry of ultrafine particles into a building. ► Deposition and penetration should be considered to model particle transport.

Keywords: Ultrafine particles; Indoor–outdoor relationship; Multi-zone modeling; CONTAM

Atmospheric mercury depletion events at the Dead Sea: Spatial and temporal aspects by Christopher W. Moore; Daniel Obrist; Menachem Luria (pp. 231-239).

Atmospheric cycling over the saline Dead Sea is highly dynamic due to high atmospheric BrOx (Br + BrO) concentrations. Elevated atmospheric BrOx concentrations cause large and frequent atmospheric mercury (Hg) depletion events (AMDEs), whereby the normally dominant gaseous Hg(0) drops well below global background levels and oxidized forms – particularly Hg(II)_gaseous – increase dramatically. The high BrOx concentrations also cause ozone (O₃) depletion events (ODEs), and the corresponding depletions of Hg(0) and O₃ provide strong evidence that Dead Sea AMDEs are linked to active halogen chemistry. We conducted two measurement campaigns in the Dead Sea basin (summer 2009 and winter 2009/2010), and here provide: spatial and temporal data on atmospheric levels of Hg(0), Hg(II) (gaseous and particulate), and O₃; Dead Sea water methyl-Hg and total-Hg concentrations; and an evaluation of the performance of current Hg measurement techniques under the particularly high atmospheric Hg(II) concentrations found at the Dead Sea. AMDEs (Hg(0) <1.0 ng m⁻³) occurred on 20 of 29 days in summer, of which eight events were very strong (<0.5 ng m⁻³); in winter, they occurred on eight of 20 days, of which four were very strong. Although all AMDEs occurred when BrO levels (measured by LP-DOAS) were enhanced, only four and three of the strong AMDEs (in summer and winter, respectively) showed corresponding ODEs, while other events showed no corresponding O₃ concentration declines. This indicated that AMDEs can occur without detectable ODEs, even though BrOx chemistry is considered to drive AMDEs. We attribute these patterns to the fact that Hg concentrations seem more sensitive to active halogen chemistry than O₃ which occurs at concentrations orders of magnitude higher and also shows photochemical daytime production. A second observation site some 400 m above the Dead Sea surface showed that AMDEs and ODEs occur throughout the Dead Sea basin and are not limited to the shore, although their frequency was lower (four events with levels <1.0 ng m⁻³ in winter). Total-Hg and methyl-Hg concentrations of the Dead Sea water were not enhanced in spite of the regular occurrence of AMDEs, with methyl-Hg concentrations below detection limits and total-Hg concentrations below 5 ppt. We further found that even at high Hg(II)_gaseous concentrations, the commonly-used Tekran Model 2537 Hg vapor analyzer predominantly measures Hg(0) – as opposed to total gaseous Hg (TGM: GEM + Hg(II_gaseous); and that at high Hg(II)_gaseous levels, the Tekran speciation unit experiences enhanced system blank levels because glassware possibly has difficulty fully retaining Hg(II).► AMDEs were strong in both seasons and some occurred regionally at the Dead Sea. ► Some AMDEs occurred without subsequent ozone depletion, despite halogen controls. ► Total-Hg and methyl-Hg were not enhanced despite high occurrence of AMDEs. ► Tekran 2537 measures Hg(0) only. ► Tekran speciation unit has higher blanks under higher Hg(II) concentrations.

Keywords: Atmospheric mercury depletion events; Dead Sea; Mercury speciation; Atmospheric halogens; Bromine; Tekran instruments

Indoor–outdoor relationships of airborne particles and nitrogen dioxide inside Parisian buses by Romain Molle; Sophie Mazoué; Évelyne Géhin; Anda Ionescu (pp. 240-248).

This study evaluated passengers' exposure to traffic air pollution inside the articulated buses of the line 91 in Paris during 10 working days in May, 2010. Twenty articulated buses were studied on 32 routes in order to determine the influence of the sampling position on the pollutant concentrations. This parameter is still poorly known for the rigid buses and is even less known for the articulated ones. However this parameter must be studied for articulated buses because the greater length may cause a pollutant concentration gradient in the cabin. Portable devices were used to measure pollutants in the presence of passengers from 8 a.m. to 9 a.m. and from 4 p.m. to 5 p.m., time periods corresponding to the peak traffic and travellers. PM_2.5 mass concentration, particle number concentration between 0.3 and 20 μm and nitrogen dioxide concentration were simultaneously measured on three positions inside the buses (front, middle and rear) in order to study the spatial distribution of these compounds. These measurements inside the buses were compared to the outdoor concentrations at the same moment of the day provided by the Parisian air quality monitoring network; they were also compared to the results of a previous monitoring campaign performed in 2008. The results obtained during the 2010 campaign revealed that in-cabin NO₂ mean concentrations were 1.5–3.5 times higher than the outside concentration levels; a maximum concentration of 234 ± 40 μg m⁻³ was found in the rear position (location of the engine and exhaust gas). Mean in-cabin PM_2.5 mass concentrations varied from one week to another one, but they were globally the same at the three positions inside the instrumented buses. In order to determine the impact of outdoor levels, correlations have been calculated between the results measured inside the buses and those measured by the outdoor air monitoring stations. The highest Pearson correlation coefficient was 0.29 for NO₂ data whereas the highest Pearson correlation coefficient between in-cabin PM_2.5 mass concentrations and outdoor levels was 0.96. The higher indoor/outdoor correlation of PM_2.5 compared to NO₂ may result from the high variation of PM_2.5 outdoors. Otherwise, this low indoor/outdoor correlation of NO₂ can highlight a source of pollution other than the outdoor air.► Two monitoring campaigns were conducted to analyse air quality inside Diesel buses. ► Typical buses of Paris Public Transport (RATP) were instrumented. ► Spatial distribution of traffic pollutants (PM_2.5 and NO₂) is studied inside the buses. ► In-cabin/outdoor concentrations were compared.

Keywords: Indoor air quality; Diesel bus; PM; _2.5; Nitrogen dioxide; Aerosol

Spatio-temporal variations in columnar aerosol optical properties over Bay of Bengal: Signatures of elevated dust by V. Sreekanth; Padmavati Kulkarni (pp. 249-257).

Multiyear all-season characterization of the columnar optical properties of aerosols over Bay of Bengal (BoB) has been carried out using simultaneous data from MODIS and TOMS satellite sensors. Significant spatio-temporal heterogeneity has been observed in the columnar aerosol optical properties over BoB. Latitudinally, MODIS derived Aerosol optical depths (AOD), its Small mode fraction (SMF, except pre-monsoon) has shown increasing trends towards northern latitudes of BoB. A pocket of high Aerosol Index (AI) values has been observed over the north-western part of BoB during pre-monsoon. Longitudinally, the variations in the aerosol properties are subdued comparatively. SMF values tend to increase weakly towards eastern longitudes during all the seasons. Variations in the aerosol properties are parameterised using best fit analytical functions. By simultaneous examination of AI, AOD and SMF, it has been inferred that the aerosol load responsible for the higher values of AI over BoB during pre-monsoon is dominated by the transported UV-absorbing dust.► Large spatio-temporal heterogeneity in aerosol optical properties over BoB. ► Signatures of transported dust aerosols over BoB. ► Subdued longitudinal variations compared to latitudinal variations.

Keywords: Spatio-temporal heterogeneity; Aerosol index; UV-absorbing dust

Levels of phthalate esters in settled house dust from urban dwellings with young children in Nanjing, China by Qi Zhang; Xiao-Mei Lu; Xiao-Ling Zhang; Yong-Gang Sun; Dong-Mei Zhu; Bing-Ling Wang; Ren-Zheng Zhao; Zheng-Dong Zhang (pp. 258-264).

To investigate the levels and possible determinants of phthalate esters (PEs) in settled house dust from urban dwellings with young children, dust was collected from 215 urban houses in Nanjing, China, and 145 outdoor settled dust samples were collected nearby. Six PEs were measured by gas chromatography/mass spectrometry. All PEs were detected in the dust from approximately 90% of the houses, with the exception of dioctyl phthalate (DOP), which had only a 59% detection rate. Di-2-ethylhexyl phthalate (DEHP) and di-n-butyl phthalate (DBP) were the most abundant PEs, with geometric means of 110 and 16.4 μg g⁻¹, respectively, and maximal concentrations 9950 and 2150 μg g⁻¹. Factor analysis showed that DBP, DEHP and benzyl butyl phthalate (BBP) might come from the same source and were significantly influenced by the use of solid-wood floor wax. High BBP, DEHP, DOP and total PE levels were associated with indices of dampness, and high DOP was associated with humidifier use. In conclusion, six PEs are ubiquitous in urban settled house dust in Nanjing, China, and both plastic materials and cosmetic and personal care products are important sources. Flooring material, dampness and humidifier use potentially influence house dust PE levels.► Phthalate esters (PEs) were measured in settled house dust from urban dwellings. ► Di-2-ethylhexyl phthalate and di-n-butyl phthalate are the most abundant. ► Solid-wood flooring wax and cosmetic and personal care products are two PE sources. ► Flooring material, dampness and humidifier use potentially influence PE levels.

Keywords: Urban house dust; Phthalate ester; Child exposure

Atmospheric deposition of polycyclic aromatic hydrocarbons (PAHs) to a coastal site of Hong Kong, South China by Fobang Liu; Yue Xu; Junwen Liu; Di Liu; Jun Li; Gan Zhang; Xiangdong Li; Shichun Zou; Senchao Lai (pp. 265-272).

Dry and wet deposition of atmospheric particles is a dominant pathway for PAHs to the coastal environments. Very few studies have been conducted to quantify the contribution of atmospheric deposition to PAH levels in the coastal regions. In this study, PAHs were analyzed in samples collected during a year-round campaign using atmospheric (gas and particle) and depositional samples at a coastal site South China. The average PAH particle deposition fluxes observed calculated 260 ± 190 ng m⁻² d⁻¹. Remarkable seasonal variations were recorded in the total PAH deposition fluxes, with higher deposition fluxes in the dry seasons and lower fluxes in the wet seasons. The temporal trend of deposition fluxes was influenced by PAH concentration in the aerosols and changes in meteorological parameters, such as temperature, rainfall, and wind speed etc. Dry deposition velocities of individual PAH compound ranged from 0.02 to 1.03 cm s⁻¹, and there was a decrease pattern in dry deposition velocity with increasing molecular weight of PAHs. The annual mean washout ratio, defined as the ratio between the particle-associated concentrations of PAHs in precipitations and aerosols, was 3.4 × 10⁵ in this study. Washout ratios decreased with increasing rainfall frequency and reached a consistent level afterward. The contribution of atmospheric deposition to PAH concentrations in the sediments was estimated to be 30%–40% in the coastal regions of South China.► Particle phase concentrations and meteorological factors influenced PAH deposition. ► Higher PAH particle scavenging efficiencies occurred during the dry season. ► Rainfall frequency decreased the particle washout ratios before reaching constant. ► The contribution of atmospheric deposition to the coastal sediments was 30%–40%.

Keywords: Polycyclic aromatic hydrocarbons; Atmospheric deposition; Coastal site; Sediment

Current status and future trends of SO₂ and NO_x pollution during the 12th FYP period in Guiyang city of China by Hezhong Tian; Peipei Qiu; Ke Cheng; Jiajia Gao; Long Lu; Kaiyun Liu; Xingang Liu (pp. 273-280).

In order to investigate the future trends of SO₂ and NO_x pollution in Guiyang city of China, the MM5/CALMET/CALPUFF modeling system is applied to assess the effects of air pollution improvement that would result from reduction targets for SO₂ and NO_x emissions during the 12th Five-Year Plan (2011–2015). Three scenarios are established for the objective year 2015 based on the reference emissions in base year 2010. Scenario analysis and modeling results show that emissions are projected to increase by 26.5% for SO₂ and 138.0% for NO_x in 2015 Business-As-Usual (BAU) relative to base year 2010, respectively, which will lead to a substantial worsening tendency of SO₂ and NO_x pollution. In comparison, both the 2015 Policy Reduction (PR) and 2015 Intensive Policy Reduction (IPR) scenarios would contribute to improve the urban air quality. Under 2015 PR scenario, the maximum annual average concentration of SO₂ and NO_x will reduce by 54.9% and 31.7%, respectively, relative to the year 2010, with only 2.1% of all individual gridded receptors exceed the national air quality standard limits; while the maximum annual average concentrations of SO₂ and NO_x can reduce further under 2015 IPR scenario and comply well with standards limits. In view of the technical feasibility and cost-effectiveness, the emission reduction targets set in the 2015 PR scenario are regarded as more reasonable in order to further improve the air quality in Guiyang during the 12th FYP period and a series of comprehensive countermeasures should be effectively implemented.► Current status of SO₂ and NO_x pollution are assessed for base year 2010. ► CALPUFF modeling is evaluated by comparing observed and simulated concentrations. ► Three emission scenarios are analyzed for the projected year 2015. ► Reasonable air pollutant emission control targets are proposed during the 12th FYP. ► Comprehensive countermeasures must be implemented to ensure air quality improvement.

Keywords: SO; ₂; and NO; _x; pollution; Modeling; Emission reduction; CALPUFF; Scenario analysis; Guiyang

Hygroscopic properties of oxalic acid and atmospherically relevant oxalates by Qingxin Ma; Hong He; Chang Liu (pp. 281-288).

Oxalic acid and oxalates represent an important fraction of atmospheric organic aerosols, however, little knowledge about the hygroscopic behavior of these particles is known. In this study, the hygroscopic behavior of oxalic acid and atmospherically relevant oxalates (H₂C₂O₄, (NH₄)₂C₂O₄, CaC₂O₄, and FeC₂O₄) were studied by Raman spectrometry and vapor sorption analyzer. Under ambient relative humidity (RH) of 10–90%, oxalic acid and these oxalates hardly deliquesce and exhibit low hygroscopicity, however, transformation between anhydrous and hydrated particles was observed during the humidifying and dehumidifying processes. During the water adsorption process, conversion of anhydrous H₂C₂O₄, (NH₄)₂C₂O₄, CaC₂O₄, and FeC₂O₄ to their hydrated particles (i.e., H₂C₂O₄·2H₂O, (NH₄)₂C₂O₄·H₂O, CaC₂O₄·H₂O, and FeC₂O₄·2H₂O) occurred at about 20% RH, 55% RH, 10% RH, and 75% RH, respectively. Uptake of water on hydrated Ca-oxalate and Fe-oxalate particles can be described by a multilayer adsorption isotherm. During the dehumidifying process, dehydration of H₂C₂O₄·2H₂O and (NH₄)₂C₂O₄·H₂O occurred at 5% RH while CaC₂O₄·H₂O and FeC₂O₄·2H₂O did not undergo dehydration. These results implied that hydrated particles represent the most stable state of oxalic acid and oxalates in the atmosphere. In addition, the assignments of Raman shift bands in the range of 1610–1650 cm⁻¹ were discussed according to the hygroscopic behavior measurement results.► Hygroscopic behavior of oxalic acid and oxalates were studied under ambient conditions. ► No deliquescence and dehydration for oxalates was observed. ► All samples studied exhibited hydration during humidifying process. ► It suggests that the most stable state for oxalic acid and oxalates is hydrated particles in the atmosphere.

Keywords: Oxalates; Hygroscopic behavior; Vapor sorption analyzer; Raman spectroscopy

The origin of ambient particulate matter concentrations in the Netherlands by Carlijn Hendriks; Richard Kranenburg; Jeroen Kuenen; René van Gijlswijk; Roy Wichink Kruit; Arjo Segers; Hugo Denier van der Gon; Martijn Schaap (pp. 289-303).

Particulate matter poses a significant threat to human health. To be able to develop effective mitigation strategies, the origin of particulate matter needs to be established. The regional air quality model LOTOS-EUROS, equipped with a newly developed labeling routine, was used to establish the origin of PM₁₀ and PM_2.5 in the Netherlands for 2007–2009 at the source sector level, distinguishing between national and foreign sources. The results suggest that 70–80% of modeled PM₁₀ and 80–95% of PM_2.5 in the Netherlands is of anthropogenic origin. About 1/3 of anthropogenic PM₁₀ is of Dutch origin and 2/3 originates in foreign countries. Agriculture and transport are the Dutch sectors with the largest contribution to PM₁₀ mass in the Netherlands, whereas the foreign contribution is more equally apportioned to road transport, other transport, industry, power generation and agriculture. For the PM_2.5 fraction, a larger share is apportioned to foreign and anthropogenic origin than for PM₁₀, but the same source sectors are dominant. The national contribution to PM levels is significantly higher in the densely populated Randstad area than for the country on average and areas close to the borders. In general, the Dutch contribution to the concentration of primary aerosol is larger than for secondary species. The sectoral origin varies per component and is location and time dependent. During peak episodes, natural sources are less important than under normal conditions, whereas especially road transport and agriculture become more important.► The PM origin in the Netherlands was established using a Chemistry Transport Model. ► 70–80% of modeled PM₁₀ and 80–95% of PM_2.5 is of anthropogenic origin., 1/3 of which comes from domestic sources. ► The domestic contribution to anthropogenic PM is 1/3, mainly from agriculture and transport. ► The foreign contribution is equally divided over 5 sectors. ► During episodes road transport and agriculture contribute more mass than on average.

Keywords: Particulate matter; Source apportionment; Chemistry transport model; The Netherlands

Sea spray and the atmospheric transport of nonylphenol ethoxylates. A combined laboratory, field and modeling study by Mark A. McInnes; David A. Ellis; Eva M. Webster; Andrew Peters (pp. 304-312).

Nonylphenol ethoxylates (NPEOs) are environmentally ubiquitous non-ionizing surfactants that show a preference for the air–water interface. They are therefore potentially subject to enhanced transport by aqueous aerosols. The extent to which aqueous aerosols affect the overall environmental fate and behavior of NPEOs is investigated with a combination of laboratory and field experiments and mathematical modeling. Aqueous aerosol droplets were generated in a laboratory-based experimental system. Aqueous aerosols were measured to have concentrations of NPEOs at least four times greater than in the bulk source water.The concentration of nonylphenol and nonylphenol monoethoxylate in aqueous aerosols off the coast of Bermuda were 4.3–19.2 times higher than in coastal water and open water collected from the Bermuda Atlantic Time Series sampling site. Coastal water showed higher concentrations than open water samples ranging from 36 to 51 ng L⁻¹ and 14 to 21 ng L⁻¹ respectively. Depth profiling showed a loss of detection below 300 m. Aqueous aerosol enrichment was demonstrated and relative atmospheric concentrations ranged from 0.28 to 1.8 ng m⁻³. A generic marine model was developed using independent North Sea data to estimate the relative potential for NPEO transfer within spray droplets to the atmosphere and subsequently into the gas phase by volatilization. The results were compared to the estimated direct volatilization from the surface of a natural water body. The upward mass flux of NPEOs by direct volatilization was comparable in magnitude to the fluxes due to spray generation, depending on the wind speed and droplet sizes. The experimental results and the model calculations were illustratively applied to reported NPEO concentrations in the North Sea. Aerosol generation provides a feasible mechanism for atmospheric transport of NPEOs and their degradation products, nonylphenols (NPs).► Laboratory-generated spray NPEO concentrations 4 times greater than source water. ► NPEO entering the gas phase through spray is comparable to direct volatilization. ► Natural wave action caused 4.3–19.2 NPEO enhancement relative to source water. ► Spray contributes to atmospheric NPEO burden and subsequent atmospheric transport.

Keywords: Aqueous spray; Chemical environmental fate; Surfactant; Air–water transfer; Medium-distance transport potential; Atlantic Ocean

The aerosol forcing efficiency in the UV region and the estimation of single scattering albedo at a typical West European site by E. Nikitidou; A. Kazantzidis; V. De Bock; H. De Backer (pp. 313-320).

The measurements of aerosol optical depth, total ozone and UV irradiance from a Brewer spectrophotometer located at Uccle, Belgium, were used to estimate, for the first time at a typical site in Western Europe, the aerosol radiative forcing efficiency (the forcing performed per unit of aerosol optical depth). The study was performed at selected solar zenith angles during the period July 2006–May 2010. In the 300–360 nm spectral region, the highest values were revealed at 30° (−6.9 ± 0.9 W m⁻²), while at 60° the RFE was almost 2.5 times lower (−2.7 ± 0.1 W m⁻²). In the UV-B region (300–315 nm), the RFE value at 60° (−0.069 ± 0.005 W m⁻²) was 5 times lower than the corresponding value at 30° (−0.35 ± 0.04 W m⁻²). Extending previous studies for the estimation of aerosol single scattering albedo in UV-A wavelengths down to 340 nm, an attempt was made, taking advantage of the Brewer measurements, to provide estimates at low UV-A wavelengths and in the UV-B region. The estimated monthly averages of the Brewer single scattering albedo at 320 nm are in very close agreement (within ±0.01) with measurements at 440 nm from a collocated CIMEL sunphotometer. Due to increased measurement uncertainties and the effect of ozone absorption, large differences between the two instruments were found at 306.5 nm. For the rest of wavelengths, average differences up to 0.03 were revealed.► The aerosol radiative forcing efficiency is estimated in the UV at Uccle, Belgium. ► The study takes advantage of the AOD measurements at the Brewer wavelengths. ► The single scattering albedo is calculated at low UV-A and in the UV-B region. ► The estimated monthly SSA means from Brewer at 320 nm agree well with CIMEL at 440 nm.

Keywords: Aerosol forcing efficiency; UV; Single scattering albedo

Mass specific optical absorption coefficient of HULIS aerosol measured by a four-wavelength photoacoustic spectrometer at NIR, VIS and UV wavelengths by Noémi Utry; Tibor Ajtai; Ágnes Filep; Máté Dániel Pintér; András Hoffer; Zoltán Bozoki; Gábor Szabó (pp. 321-324).

The mass specific optical absorption coefficient (MAC) of Humic-Like Substances (HULIS), isolated from a fine aerosol fraction (PM1) collected at a typical Central European rural background site (Kpuszta) was measured in the re-dispersed aerosol phase at 1064, 532, 355 and 266 nm wavelengths by our recently developed four wavelength photoacoustic spectrometer. It is found to be practically negligible in the visible (0.03 m² g⁻¹ @532 nm), while in the ultraviolet (4.9 m² g⁻¹ @266 nm) it becomes comparable with that of black carbon (BC), a major absorbing fraction of the ambient aerosol. This type of wavelength dependency was already hypothesized for HULIS aerosol, but it was proved previously only by indirect measurements on HULIS samples dissolved in the aqueous phase. On the other hand, the other generally accepted hypothesis, that this wavelength dependency can be described by a single, wavelength independent absorption Angström-exponent (AAE) is not justified by the presented measurements.

Keywords: Optical absorption; Angström exponent; Photoacoustic; HULIS

Collection efficiency and interstage loss of nanoparticles in micro-orifice-based cascade impactors by Chun-Nan Liu; Amit Awasthi; Yi-Hung Hung; Chuen-Jinn Tsai (pp. 325-333).

In this study, two micro-orifice-based cascade impactors, including the micro-orifice uniform deposit impactor (MOUDI, MSP Model 110) and the NCTU micro-orifice cascade impactor (NMCI), were tested for the collection efficiency and interstage loss of nanoparticles. In the NMCI, new nozzle plates with smooth nozzle shape made by the LIGA (Lithography, Electroplating, and Molding) process were used to replace the 7th–10th stages in one of the MOUDI. Test results show that after adjusting proper S/W ratios (S: jet to plate distance, W: nozzle diameter) to 2.52, 3.01, 13.44, and 24.75 for the 7th, 8th, 9th and 10th stage of the NMCI, respectively, and 5.56, 11.18, 9.3, and 10.9 for the 7th, 8th, 9th and 10th stage of the MOUDI, respectively, the cutoff aerodynamic diameters ( d_pa50) are close to the nominal values given in Marple et al. (1991). Different S/W ratios are needed due to differences in the nozzle shape and nozzle diameter between two cascade impactors. Total interstage loss of nanoparticles from the inlet to the 6th–10th stage of the MOUDI exists due to the convection-diffusion mechanism, which increases with decreasing d_pa. For the MOUDI, total loss is 2.9–15.3 % ( d_pa: 105.8 to 15.4 nm) for the inlet to the 6th stage and it increases to 20.1–26.1 % ( d_pa: 23 to 15.4 nm) for the inlet to the 10th stage, respectively. Similar but slightly lower loss also exists in the NMCI. Field comparison tests in the ambient air show that mass size distributions measured by the MOUDI agree well with those of the NMCI. Finally, nozzle clogging tests using high concentration incense smokes indicate that the NMCI has a much less tendency for particles to clog in the nozzles than the MODUI.► Nanoparticle loss occurs in lower stages of the micro-orifice cascade impactors. ► Nozzle plates with step-shape nozzle results in possible nozzle clogging. ► New NMCI with nozzles of smooth nozzle shape prevents nozzle clogging. ► New NMCI can facilitate accurate mass size distribution measurement of aerosols.

Keywords: Nanoparticle; Cascade impactor; Particle loss

Long term climatology of particulate matter and associated microphysical and optical properties over Dibrugarh, North-East India and inter-comparison with SPRINTARS simulations by Binita Pathak; Pradip Kumar Bhuyan; Jhuma Biswas; Toshihiko Takemura (pp. 334-344).

The long term climatology of PM₁₀ and PM_2.5 concentrations for the five year period from June 2007–March 2012 is studied using measurements made with a Quartz Crystal Microbalance Impactor over Dibrugarh, North-East India. The PM₁₀ and PM_2.5 exhibit similar seasonal variability with maximum concentration in winter and minimum in monsoon seasons. The PM₁₀ concentration is mainly attributed to PM_2.5 with minimal contribution from PM_10–2.5. The long term monthly mean PM₁₀ and PM_2.5 concentrations shows maximum value in late winter and early pre-monsoon. This temporal variability is positively correlated with the MODIS retrieved fire counts associated mostly with the biomass burning activities and negatively correlated with rainfall. PM₁₀ and PM_2.5 gradually increased from 2007 to 2010 and decreased thereafter. An overall slow decreasing trend in PM₁₀ and PM_2.5 concentrations together with black carbon (BC) concentrations has been observed. The examination of microphysical and optical properties also reveals the dominance of PM_2.5 aerosols. Higher percentage contributions of BC to both PM₁₀ and PM_2.5 are observed in post-monsoon season followed by winter. The inter-comparison of measured PM and BC concentrations with SPRINTARS simulation reveals that model underestimates the measurements except in pre-monsoon. The discrepancy might have arisen due to the topography of the location and inadequate emission inventory for the climate zone.► The long term climatology indicates PM_2.5 is the principal contributor to the PM₁₀ over Dibrugarh, North-East India. ► Maximum PM concentrations are positively correlated with fire counts over NE India and negatively correlated with rainfall. ► A slow decreasing trend in the PMs and BC concentrations has been observed during the study period. ► The SPRINTARS model underestimates the measured concentrations of PMs and BC except in pre-monsoon season.

Keywords: Aerosols; PM; ₁₀; PM; _2.5; QCM; SPRINTARS

Remote sensing of exposure to NO₂: Satellite versus ground-based measurement in a large urban area by Matthew J. Bechle; Dylan B. Millet; Julian D. Marshall (pp. 345-353).

Remote sensing may be a useful tool for exploring spatial variability of air pollution exposure within an urban area. To evaluate the extent to which satellite data from the Ozone Monitoring Instrument (OMI) can resolve urban-scale gradients in ground-level nitrogen dioxide (NO₂) within a large urban area, we compared estimates of surface NO₂ concentrations derived from OMI measurements and US EPA ambient monitoring stations. OMI, aboard NASA's Aura satellite, provides daily afternoon (∼13:30 local time) measurements of NO₂ tropospheric column abundance. We used scaling factors (surface-to-column ratios) to relate satellite column measurements to ground-level concentrations. We compared 4138 sets of paired data for 25 monitoring stations in the South Coast Air Basin of California for all of 2005. OMI measurements include more data gaps than the ground monitors (60% versus 5% of available data, respectively), owing to cloud contamination and imposed limits on pixel size. The spatial correlation between OMI columns and corrected in situ measurements is strong ( r=0.93 for annual average data), indicating that the within-urban spatial signature of surface NO₂ is well resolved by the satellite sensor. Satellite-based surface estimates employing scaling factors from an urban model provide a reliable measure (annual mean bias: −13%; seasonal mean bias: <1% [spring] to −22% [fall]) of fine-scale surface NO₂. We also find that OMI provides good spatial density in the study region (average area [km²] per measurement: 730 for the satellite sensor vs. 1100 for the monitors). Our findings indicate that satellite observations of NO₂ from the OMI sensor provide a reliable measure of spatial variability in ground-level NO₂ exposure for a large urban area.► We estimate satellite-based surface NO₂ concentrations from the OMI sensor. ► We compare OMI estimates with ground-based in situ measurements in a large urban area. ► Within-urban spatial signature of surface NO₂ is well resolved by OMI column measurements. ► OMI provides a useful dataset for exploring the epidemiological impact of urban air pollution. ► OMI measurements may be a useful tool for exploring NO₂ variability between urban locations.

Keywords: OMI; Nitrogen dioxide; Urban air quality; Remote sensing; Exposure

Measurements of surface cloud condensation nuclei and aerosol activity in downtown Shanghai by Chunpeng Leng; Tiantao Cheng; Jianmin Chen; Renjian Zhang; Jun Tao; Guanghan Huang; Shuping Zha; Meigen Zhang; Wen Fang; Xiang Li; Ling Li (pp. 354-361).

Cloud condensation nuclei (CCN) and aerosols were measured continuously at an urban site of Shanghai in the period of September 2010–August 2011. Over the entire campaign, annual averages of CCNs at 0.2–1.0% supersaturation (SS) roughly ranged from 4000 cm⁻³ to 8000 cm⁻³. CCNs (0.2% SS) varied in a remarkable pattern on monthly or seasonal time scales, showing higher in spring and winter and lower in summer and autumn. High CCN events occurred frequently in spring (21 out of 30 days) and winter (19 out of 30 days) rather than other seasons. The diurnal variation of CCNs popularly showed a pronounced bi-modal pattern in spring, summer and winter while a uni-modal pattern in autumn. The apparent activation diameter was below 100 nm at 0.8% SS regardless of their chemical composition, whereas few particles in diameter smaller than 30 nm were activated. The activation ratio (CCN/CN) at 0.8% SS varied within 0.1–0.9 with an average of 0.47. The CCN activity of CN particles indicated a strong dependence on first aerosol size, which can explain its fundamental changes, and second aerosol chemical composition. High CCN levels were usually observed in the period of particulate pollution (e.g. haze), during which CCN increased up 2.0 times in hazy days higher than clear days, revealing a significant influence of aerosols on CCN in the atmospheric planet boundary.► Annual mean CCN concentrations at supersaturation 0.2–1.0% ranged from 4000 cm⁻³ to 8000 cm⁻³. ► Seasonal CCNs followed a sequence of spring > winter > summer > autumn. ► CCN closely linked with aerosol size distribution and chemical composition, among which size was most important. ► CCN activation was averaged at 0.47 and the averaged apparent activation diameter was below 100 nm at 0.8% SS. ► Air from different origins have influence on CN and sequent CCN.

Keywords: Cloud condensation nuclei; Aerosol; Activity; Urban

Corrigendum to “The influence of emission sources and meteorological conditions on SO₂ pollution in Mongolia” [Atmos. Environ. 61C (2012) 542–549] by Munkh-Erdene Luvsan; Ruei-Hao Shie; Tseden Purevdorj; Lkhagvasuren Badarch; Barkhasragchaa Baldorj; Chang-Chuan Chan (pp. 362-362).

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