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Atmospheric Environment (v.65, #)

Editorial board (pp. i).

Haagen-Smit Prize 2012 (pp. a1-a2).

High-resolution measurement of ammonia emissions from fertilization of vegetable and rice crops in the Pearl River Delta Region, China by Weiwei Gong; Yisheng Zhang; Xiaofeng Huang; Shengji Luan (pp. 1-10).

Loss of ammonia (NH₃) as a result of intensive N fertilization, especially due to agronomic practices in South China, is not well characterized. To investigate mechanisms and characteristics of NH₃ volatilization after urea application, an on-line monitoring system, with 30-min data resolution, was used to study vegetable and rice fields from January 2009 to September 2010. Ammonia emissions and concurrent meteorological conditions were monitored for up to 20 days after fertilization in 12 experiments. Standard recovery test results indicated that the on-line measurement system was both stable and accurate. The NH₃ emission factors (EFs) related to broadcast (soil surface) basal dressing and top dressing to Brassica rapa L. were 23.6% and 21.3%, respectively. The NH₃ EFs from holing basal dressing and broadcasting top dressing for lettuce were 17.6% and 24.0%, respectively. The NH₃ EFs for early rice in parallel broadcast basal dressing process were 10.7% and 14.2%, while in parallel top dressing process were 24.0% and 22.6%, respectively. The NH₃ EFs for late rice were 15.4% and 21.0% in parallel broadcasting basal dressing process, while 13.2% and 17.6% in parallel top dressing process. Emission of NH₃ from vegetable and rice fields occurred mainly in the first 2–3 weeks after fertilization. Ammonia emission flux was positively correlated with air temperature and soil temperature in the majority of the experiments. Relationships between NH₃ emissions and humidity, soil moisture or wind speed were explored, which were not consistent among all tests. Ammonia emission in vegetable and rice fields was primarily associated with temperature. High-resolution data, such as those gathered in the current investigation, will contribute to a more thorough quantitative understanding of the relationship between fertilizer application, environmental conditions, and NH₃ volatilization which, in turn, will improve the accuracy of atmospheric modeling on local, regional and global scales.► In-situ measurement on ammonia emissions were carried out by self-designed system. ► NH₃ emission fluxes with 30-min data resolution from vegetable and rice fields were obtained. ► The real-time meteorological conditions of the experiment area were monitored. ► Ammonia emission flux was positively correlated with temperature in most experiments.

Keywords: Ammonia emission; Vegetable and rice field; Emission flux; Emission factor

Positive matrix factorization of a 32-month series of daily PM_2.5 speciation data with incorporation of temperature stratification by Mingjie Xie; Ricardo Piedrahita; Steven J. Dutton; Jana B. Milford; Joshua G. Hemann; Jennifer L. Peel; Shelly L. Miller; Sun-Young Kim; Sverre Vedal; Lianne Sheppard; Michael P. Hannigan (pp. 11-20).

This study presents source apportionment results for PM_2.5 from applying positive matrix factorization (PMF) to a 32-month series of daily PM_2.5 compositional data from Denver, CO, including concentrations of sulfate, nitrate, bulk elemental carbon (EC) and organic carbon (OC), and 51 organic molecular markers (OMMs). An optimum 8-factor solution was determined primarily based on the interpretability of the PMF results and rate of matching factors from bootstrapped PMF solutions with those from the base case solution. These eight factors were identified as inorganic ion, n-alkane, EC/sterane, light n-alkane/polycyclic aromatic hydrocarbon (PAH), medium alkane/alkanoic acid, PAH, winter/methoxyphenol and summer/odd n-alkane. The inorganic ion factor dominated the reconstructed PM_2.5 mass (sulfate + nitrate + EC + OC) in cold periods (daily average temperature <10 °C; 43.7% of reconstructed PM_2.5 mass) whereas the summer/odd n-alkane factor dominated in hot periods (>20 °C; 53.1%). The two factors had comparable relative contributions of 26.5% and 27.1% in warm periods with temperatures between 10 °C and 20 °C. Each of the seven factors resolved in a previous study (Dutton et al., 2010b) using a 1-year data set from the same location matches one factor from the current work based on comparing factor profiles. Six out of the seven matched pairs of factors are linked to similar source classes as suggested by the strong correlations between factor contributions ( r = 0.89–0.98). Temperature-stratified source apportionment was conducted for three subsets of the data in the current study, corresponding to the cold, warm and hot periods mentioned above. The cold period (7-factor) solution exhibited a similar distribution of reconstructed PM_2.5 mass as the full data set solution. The factor contributions of the warm period (7-factor) solution were well correlated with those from the full data set solution ( r = 0.76–0.99). However, the reconstructed PM_2.5 mass was distributed more to inorganic ion, n-alkane and medium alkane/alkanoic acid factors in the warm period solution than in the full data set solution. For the hot period (6-factor) solution, PM_2.5 mass distribution was quite different from that of the full data set solution, as illustrated by regression slopes as low as 0.2 and as high as 4.8 of each matched pair of factors across the two solutions.► Positive matrix factorization (PMF) was applied to a 32-month series of PM_2.5 data. ► Temperature stratified subsets of the data were also analyzed by using PMF. ► Environmental parameters were used to help the identification of resolved factors.

Keywords: Source apportionment; Positive matrix factorization; Organic molecular markers; Temperature-stratified; Reconstructed PM; _2.5; mass

Calibration of the Ogawa passive ozone sampler for aircraft cabins by Seema Bhangar; Brett C. Singer; William W. Nazaroff (pp. 21-24).

Elevated ozone levels in aircraft cabins would pose a health hazard to exposed passengers and crew. The Ogawa passive sampler is a potentially useful tool for measuring in-cabin ozone levels. Accurate interpretation of measured values requires knowing the effective collection rate of the sampler. To calibrate the passive sampler for the aircraft-cabin environment, ozone was measured simultaneously with an Ogawa sampler and an active ozone analyzer that served as a transfer standard, on 11 commercial passenger flights, during Feb–Apr 2007. An empirical pressure-independent effective collection rate that can be used to convert nitrate mass to ozone mixing ratio was determined to be 14.3 ± 0.9 atm cm³ min⁻¹ (mean ± standard error). This value is similar to estimates from other applications where airflow rates are low, such as in personal monitoring and in chamber studies. This study represents the first field calibration of any passive sampler for the aircraft cabin environment.Display Omitted► Passive samplers can facilitate ozone monitoring in aircraft cabins. ► We report the first field calibration of the Ogawa sampler in aircraft cabins. ► Ozone was actively and passively measured on 11 flights in Spring 2007. ► We estimate an in-flight effective collection rate of 14.3 ± 0.9 atm cm³ min⁻¹. ► The estimated sampling rate is similar to others from environments with low airflow.

Keywords: Passive sampling; Transportation; Ozone; Effective collection rate

Tropospheric column O₃ and NO₂ over the Indian region observed by Ozone Monitoring Instrument (OMI): Seasonal changes and long-term trends by Liji Mary David; Prabha R. Nair (pp. 25-39).

Monthly mean tropospheric column O₃ and NO₂ retrieved from Ozone Monitoring Instrument on board Aura for the period December 2007 to November 2008 have been analysed to study the spatial and seasonal variations at selected locations over the Indian landmass and surrounding oceanic region. The annual change in tropospheric O₃ and NO₂ over the study region was ∼15–20 DU and ∼0.03–0.1 DU, respectively. Latitudinal gradient of −0.84 DU/° and 0.005 DU/°, respectively has been estimated for O₃ and NO₂ over this region. High levels of O₃ were measured over parts of Arabian Sea and Bay of Bengal owing to transport from adjacent landmass. The dependence of O₃ on NO₂, solar radiation, cloud cover, rainfall, fire count, outgoing longwave radiation and boundary layer height (BLH) were investigated in detail along with the airflow pattern and airmass back trajectory analysis. There were regional variations in O₃ seasonal patterns associated with differences in NO₂, availability of solar radiation and prevailing airmass. BLH plays a role in the seasonal variation of tropospheric O₃. The long-term trend in tropospheric O₃ over a period of ten years has been examined for the different regions and both positive and negative trends were observed.► Spatial variation of tropospheric ozone and NO₂ over the Indian landmass and adjoining ocean. ► Role of precursors and meteorology. ► Long-term trends.

Keywords: Tropospheric O; ₃; Tropospheric NO; ₂; Indian region; Transport

The behaviour of traffic produced nanoparticles in a car cabin and resulting exposure rates by Pouyan Joodatnia; Prashant Kumar; Alan Robins (pp. 40-51).

The aim of this study is to assess particle number concentrations (PNCs) and distributions (PNDs) in a car cabin while driving. Further objectives include the determination of the influence of particle transformation processes on PNCs, PNDs and estimation of PNC related exposure. On-board measurements of PNCs and PNDs were made in the 5–560 nm size range using a fast response differential mobility spectrometer (DMS50), which has a response time of 500 ms. Video records of the traffic ahead of the experimental car were also used to correlate emission events with measured PNCs and PNDs. A total of 30 return trips was made on a 2.7 km route during morning and evening rush hours, with journey times of 7 ± 2 and 10 ± 3 min, respectively. The average PNC for the set of morning journeys, 5.79 ± 3.52 × 10⁴ cm⁻³, was found to be nearly identical to the average recorded during the afternoon, 5.95 ± 4.67 × 10⁴ cm⁻³. Average PNCs for individual trips varied from 2.42 × 10⁴ cm⁻³ to 2.18 × 10⁵ cm⁻³, mainly due to changes in the emissions affecting the experimental car (e.g. when the experimental car was following another vehicle). The largest one second averaged PNC during a specific event, 1.85 × 10⁶ cm⁻³, was found to be over 30-times greater than the overall average of 5.87 ± 4.06 × 10⁴ cm⁻³. Correlation of video records and concentration data indicated that close proximity to a preceding vehicle led to a clear increase in PNCs of freshly emitted nucleation mode particles. The evolution of normalised PNDs demonstrated that dilution was the dominant transformation process in the car cabin. The deposition of inhaled particles in the lung was estimated on the basis of either the size-resolved distribution or the total PNC. In general, the two methods yielded similar results but differences up to 30% were noted in some cases, with the latter method giving the lower values. Overall, the results reflect the importance of size-resolved measurements for deriving accurate evaluations of exposure rates, as well as identifying emissions from nearby traffic as the cause of short-term elevations of PNCs and hence dose rates.► Freshly emitted nanoparticles were found in the car cabin. ► High frequency measurements are needed for better PNC estimation. ► Dilution was found to be the dominant process in car cabin. ► PNC levels in car cabin increased significantly in traffic congestion zones. ► Exposure doses to temporal PNC peaks were up to 380% more than average dose rate.

Keywords: Car cabin exposure; Nanoparticles dispersion; Number and size distribution; Ultrafine particles; Vehicle emissions

Seasonal and temporal characterization of dissolved organic matter in rainwater by proton nuclear magnetic resonance spectroscopy by Pamela J. Seaton; Robert J. Kieber; Joan D. Willey; G. Brooks Avery Jr.; Joshua L. Dixon (pp. 52-60).

Dissolved organic carbon in rainwater was concentrated by two separate techniques and characterized by¹H-NMR. The total¹H-NMR integral of lyophilized rainwater was higher in every rain sample than that of C18 solid phase extracted samples and always contained a higher percentage integral in the region of protons bound to carbon atoms singly bound to oxygen (H–C–O), such as alcohols, polyols and carbohydrate-like compounds. C18 extracted samples had higher % integral in the alkyl region, consistent with reverse phase extraction of more hydrophobic components in rainwater. Differences in both the¹H-NMR integration and spectral pattern of lyophilized rainwater samples were especially apparent between spring and winter rains, with spring samples having higher percent carbohydrate (H–C–O) signal and winter rains having higher percent alkyl protons and a spectral pattern consistent with the presence of saturated fatty acids. Spring rains are characterized by lower % Alkyl signal coupled with higher % H–C–O than all other events while marine winter events appear in regions characterized by relatively high % Alkyl and average % H–C–O, consistent with increased abundance of fatty acids or fatty acid oxidation products. The¹H-NMR data presented in this manuscript are important because they provide spectral data relating to the source and chemical characteristics of dissolved organic carbon in rainwater as a function of season and air mass back trajectory.► NMR spectra and integrations show great variability between rain events. ► Season and storm origin influence rainwater NMR spectral pattern and intensity. ► Spring rains contained a high percentage of carbohydrate like components. ► Marine winter rains had a high alkyl signal. ► Anthropogenic (phthallic and terephthallic acids) and biogenic signals were observed.

Keywords: Rainwater; ¹; H-NMR; Dissolved organic compounds; Seasonal trajectory variability; Back trajectory variability

Volatile organic compound emissions from elephant grass and bamboo cultivars used as potential bioethanol crop by E. Crespo; M. Graus; J.B. Gilman; B.M. Lerner; R. Fall; F.J.M. Harren; C. Warneke (pp. 61-68).

Volatile organic compound (VOC) emissions from elephant grass ( Miscanthus gigantus) and black bamboo ( Phyllostachys nigra) were measured online in semi-field chamber and plant enclosure experiments during growth and harvest using proton-transfer reaction mass spectrometry (PTR-MS), proton-transfer reaction ion-trap mass spectrometry (PIT-MS) and gas chromatography-mass spectrometry (GC–MS). Both cultivars are being considered for second-generation biofuel production. Before this study, no information was available on their yearly VOC emissions. This exploratory investigation shows that black bamboo is a strong isoprene emitter (daytime 28,516 ng g_dwt⁻¹ h⁻¹) and has larger VOC emissions, especially for wound compounds from the hexanal and hexenal families, than elephant grass. Daytime emissions of methanol, acetaldehyde, acetone + propanal and acetic acid of black bamboo were 618, 249, 351, and 1034 ng g_dwt⁻¹ h⁻¹, respectively. In addition, it is observed that elephant grass VOC emissions after harvesting strongly depend on the seasonal stage. Not taking VOC emission variations throughout the season for annual and perennial species into account, may lead to an overestimation of the impact on local air quality in dry periods. In addition, our data suggest that the use of perennial grasses for extensive growing for biofuel production have lower emissions than woody species, which might be important for regional atmospheric chemistry.► We determine the VOC emissions of two potential biofuels: elephant grass and bamboo. ► VOC emissions after harvesting strongly depend on the seasonal stage. ► Perennial grasses have lower emissions than woody species with implications for air quality.

Keywords: Volatile organic compounds; Biofuel; Elephant grass; Bamboo

Short-term effects of daily air pollution on mortality by Wan Rozita Wan Mahiyuddin; Mazrura Sahani; Rasimah Aripin; Mohd Talib Latif; Thuan-Quoc Thach; Chit-Ming Wong (pp. 69-79).

The daily variations of air pollutants in the Klang Valley, Malaysia, which includes Kuala Lumpur were investigated for its association with mortality counts using time series analysis. This study located in the tropic with much less seasonal variation than typically seen in more temperate climates. Data on daily mortality for the Klang Valley (2000–2006), daily mean concentrations of air pollutants of PM₁₀, SO₂, CO, NO₂, O₃, daily maximum O₃ and meteorological conditions were obtained from Malaysian Department of Environment. We examined the association between pollutants and daily mortality using Poisson regression while controlling for time trends and meteorological factors. Effects of the pollutants (Relative Risk, RR) on current-day (lag 0) mortality to seven previous days (lag 7) and the effects of the pollutants from the first two days (lag 01) to the first eight days (lag 07) were determined. We found significant associations in the single-pollutant model for PM₁₀ and the daily mean O₃ with natural mortality. For the daily mean O₃, the highest association was at lag 05 (RR = 1.0215, 95% CI = 1.0013–1.0202). CO was found not significantly associated with natural mortality, however the RR's of CO were found to be consistently higher than PM₁₀. In spite of significant results of PM₁₀, the magnitude of RR's of PM₁₀ was not important for natural mortality in comparison with either daily mean O₃ or CO. There is an association between daily mean O₃ and natural mortality in a two-pollutants model after adjusting for PM₁₀. Most pollutants except SO_2, were significantly associated with respiratory mortality in a single pollutant model. Daily mean O₃ is also important for respiratory mortality, with over 10% of mortality associated with every IQR increased. These findings are noteworthy because seasonal confounding is unlikely in this relatively stable climate, by contrast with more temperate regions.► We model the association of air pollution and mortality using Poisson regression. ► RR for each pollutant was obtained for every IQR increase at different lag times. ► O₃, CO and PM₁₀ were the important pollutants associated with natural mortality. ► All pollutants except SO₂ were associated with respiratory mortality. ► Those who have respiratory diseases are at higher risk of mortality.

Keywords: Relative risk; Health; Mortality; O; ₃; CO; PM; ₁₀; Klang Valley; Malaysia

Acetone in the atmosphere of Hong Kong: Abundance, sources and photochemical precursors by H. Guo; Z.H. Ling; K. Cheung; D.W. Wang; I.J. Simpson; D.R. Blake (pp. 80-88).

Intensive field measurements were carried out at a mountain site and an urban site at the foot of the mountain from September to November 2010 in Hong Kong. Acetone was monitored using both canister air samples and 2,4-dinitrophenylhydrazine cartridges. The spatiotemporal patterns of acetone showed no difference between the two sites ( p > 0.05), and the mean acetone mixing ratios on O₃ episode days were higher than those on non-O₃ episode days at both sites ( p < 0.05). The source contributions to ambient acetone at both sites were estimated using a receptor model i.e. Positive Matrix Factorization (PMF). The PMF results showed that vehicular emission and secondary formation made the most important contribution to ambient acetone, followed by the solvent use at both sites. However, the contribution of biogenic emission at the mountain site was significantly higher than that at the urban site, whereas biomass burning made more remarkable contribution at the urban site than that at the mountain site. The mechanism of oxidation formation of acetone was investigated using a photochemical box model. The results indicated that i-butene was the main precursor of secondary acetone at the mountain site, while the oxidation of i-butane was the major source of secondary acetone at the urban site.► Ambient acetone was mainly caused by vehicular emission and secondary formation in Hong Kong. ► i-Butene was the main precursor of secondary acetone at the mountain site. ► Oxidation of i-butane was the major source of secondary acetone at the urban site.

Keywords: Acetone; Positive Matrix Factorization; Photochemical box model; Hong Kong

A wind tunnel study on the effect of thermal stability on flow and dispersion of rooftop stack emissions in the near wake of a building by Mohamed F. Yassin (pp. 89-100).

The effect of atmospheric thermal stability on wind flow and dispersion of rooftop stack emissions in the near wake of a building in an urban environment is investigated using stratified wind tunnel experiments. Experiments with varying stratifications (stable: Ri_B and Re_b = 0.023 & 5.1 × 10³, neutral: Ri_B and Re_b = 0.0 & 5.8 × 10³, and unstable: Ri_B and Re_b = −0.016 & 6.6 × 10³) were conducted using an isolated cubical building model. Tracer gas (C₂H₄) was released from a stack on the building roof. Flow, temperature and dispersion fields were analyzed and measured using a split film, a cold-wire thermometer, and high-response flame ionization detector. Thermal diffusion was examined at different distances downwind of the leeward side of the building model. Flow and dispersion characteristics studied included mean velocity, turbulence intensity, mean and fluctuation concentrations in the near wake of the building. The results indicate that when atmospheric stratification is unstable, flow separation decreases and longitudinal turbulence intensity increases in the near wake region. When this stratification is stable, vertical velocity and vertical turbulence intensity increase in the near wake region. There is an increase in concentrations with stable conditions, and a decrease in concentrations with unstable conditions in the near wake region.► Study on flow and dispersion of rooftop stack emissions in the near wake region. ► Varying atmospheric stratifications were stable, neutral and unstable conditions. ► Vertical velocity increases under stable conditions. ► Longitudinal turbulence intensity increases under unstable conditions. ► Concentration increases with stable condition and decreases with unstable condition.

Keywords: Atmospheric diffusion; Dispersion emissions; Rooftop stack; Thermal stability; Wake region

Application of 2D-GCMS reveals many industrial chemicals in airborne particulate matter by Mohammed S. Alam; Charles E. West; Alan G. Scarlett; Steven J. Rowland; Roy M. Harrison (pp. 101-111).

Samples of airborne particulate matter (PM_2.5) have been collected in Birmingham, UK and extracted with dichloromethane prior to analysis by two-dimensional GC separation and TOFMS analysis. Identification of compounds using the NIST spectral library has revealed a remarkable diversity of compounds, some of which have not been previously reported in airborne analyses. Groups of compounds identified in this study include a large number of oxygenated VOC including linear and branched compounds, substituted aromatic compounds and alicyclic compounds, oxygenated polycyclic aromatic and alicyclic compounds, organic nitrogen compounds, branched chain VOC and substituted aromatic VOC, phthalates, organo-phosphates and organo-sulphate compounds. Many of the compounds identified are mass production chemicals, which due to their semi-volatility enter the atmosphere and subsequently partition onto pre-existing aerosol. Their contribution to the toxicity of airborne particulate matter is currently unknown but might be significant. The diverse industrial uses and potential sources of the identified compounds are reported.Display Omitted► Daily PM_2.5 samples were collected at an urban background site. ► Aerosol samples were analysed using GC × GC-TOFMS. ► Results reveal a remarkable range of compounds present, where 1500 peaks are detected. ► We identify natural and industrial chemicals that have not been focused on previously. ► Some of the detected compounds may contribute to the toxicity of urban particulate matter.

Keywords: 2D GCMS; Airborne chemicals; Industrial chemicals; Plasticisers; Fire retardants

Nitrous oxide emissions from Chinese maize–wheat rotation systems: A 3-year field measurement by Yanjiang Cai; Weixin Ding; Jiafa Luo (pp. 112-122).

Nitrous oxide (N₂O) fluxes were measured over a 3-year period (2004–2007) in a long-term experimental field. The objectives of the study were to evaluate the interannual variation of N₂O emissions from a maize–wheat rotation, under different fertilizer regimes and to determine the key controlling factors. The study involved four treatments: compost (OM), half compost N plus half inorganic fertilizer-N (HOM), inorganic fertilizer-N (NPK), and control (CK) where no N application. The mean annual N₂O emission over a 3-year period was 0.30 ± 0.11 kg N₂O–N ha⁻¹ in the CK treatment, but increased to 1.61 ± 0.10 kg N₂O–N ha⁻¹ in the HOM treatment, 2.13 ± 0.15 kg N₂O–N ha⁻¹ in the OM treatment, and 2.76 ± 0.19 kg N₂O–N ha⁻¹ in the NPK treatment. Differences were significant among treatments. The N₂O emission factors of the applied OM, NPK and HOM were 0.61 ± 0.02, 0.82 ± 0.10 and 0.44 ± 0.04%, respectively, at a rate of 300 kg N ha⁻¹ year⁻¹, indicating that the combined application of compost with inorganic fertilizer significantly reduced N₂O emission. Over a maize–wheat rotation year, more than 65% of the annual N₂O emission occurred during the maize growing season. There was a large interannual variation in N₂O emission in all treatments, albeit not significant either during the maize growing season or at an inter-year scale. This interannual variation was mainly attributable to differences in soil moisture after basal fertilizer application, and irrigation and/or heavy rainfall events immediately following basal fertilization could induce more N₂O production than pre-irrigation before plowing. The HOM treatment had higher N fertilizer use efficiency and lowest yield-scaled N₂O emissions compared with the OM and NPK treatments. We therefore argue that the combined application of half compost N plus half fertilizer-N will mitigate N₂O emissions from soils in the North China plain.► There was a large interannual variation in N₂O emission from agricultural field. ► Interannual variation was due to different soil moisture after basal fertilizer application. ► Irrigation application before plowing could mitigate N₂O emissions from soils. ► Combined application of compost and mineral fertilizer also reduced N₂O emission.

Keywords: Emission factor; Fertilizer type; Interannual variation; Irrigation; Long-term experiment; N; ₂; O

Indoor transfluthrin concentration levels during and after the application of electric vaporizers using a Proton-Transfer-Reaction Mass Spectrometer by Aude Vesin; Etienne Quivet; Brice Temime-Roussel; Henri Wortham (pp. 123-128).

Field measurements involving two different electric vaporizers emitting transfluthrin in a full-scale experimental room are realized under controlled air exchange rate conditions. Due to the high temporal variability of indoor air concentrations during household pesticide application, a High Sensitivity Proton-Transfer-Reaction Mass Spectrometer (HS-PTR-MS) providing high-time resolved measurements is used, in order to accurately follow the concentration profiles during and immediately after the spreading periods. Thanks to its high measurement frequency (>1 measurement per min), this analytical device provides key parameters such as peak concentrations and kinetic characteristics. Ventilation is found to be a minor but non-negligible loss mechanism, crucial to maintain an acceptable air quality since it definitively withdraws transfluthrin from the room volume. Adsorption on indoor surfaces also appears to be a significant elimination process of transfluthrin from the gaseous phase, however acting as a temporary sink due to the reversible nature of this mechanism.► Monitoring of household pesticides concentration profiles during spreading periods. ► Ventilation is found to be a major net elimination process. ► Adsorption on room surfaces is a significant but reversible loss mechanism.

Keywords: Pyrethroid pesticide; Kinetic behaviour; Indoor; HS-PTR-MS

Surface ozone at the Devils Postpile National Monument receptor site during low and high wildland fire years by Andrzej Bytnerowicz; Joel D. Burley; Ricardo Cisneros; Haiganoush K. Preisler; Susan Schilling; Donald Schweizer; John Ray; Deanna Dulen; Christopher Beck; Bianca Auble (pp. 129-141).

Surface ozone (O₃) was measured at the Devils Postpile National Monument (DEPO), eastern Sierra Nevada Mountains, California, during the 2007 (low-fire) and 2008 (high-fire) summer seasons. While mean and median values of O₃ concentrations for the 2007 and 2008 summer seasons were similar, maximum O₃ concentrations in June and August 2008 were higher than in any month of the 2007 summer season. This increase of maximum concentrations in the high-fire year is attributed to emissions of O₃ precursors from wildland fires upwind of DEPO in addition to transport of polluted air from the California Central Valley (CCV) and the San Francisco Bay Area (SFBA). Analysis of backward trajectories for high O₃ episodes in June 2007 and 2008 showed the lowest O₃ pollution at DEPO when air masses originated over the Pacific Ocean (PO) and passed from West to East over PO and CCV at high altitudes. The highest O₃ levels occurred when air masses originated in the vicinity of SFBA, swept through CCV in the NW–SE direction before reaching DEPO at low altitudes. Diurnal O₃ concentrations were characterized by a sharp increase early morning and maximum values in late afternoon, followed by gradual evening decreases with very low pre-dawn minima, a phenomenon explained by local generation of O₃ combined with the long range transport of polluted air masses from CCV, boundary layer destruction and surface deposition. Once in 2007, and 3 times in 2008, the 8-h average concentration exceeded 75 ppb, counting towards exceedance of the present primary Federal O₃ standard (4th highest 8 h concentration <75 ppb over 3 years). The California 8-h average standard (<70 ppb) was exceeded 5 times in 2007 and 6 times in 2008, and these instances counted towards exceedance of the newly proposed primary Federal primary standard (4th highest 8-h concentration <70 ppb over 3 years). In addition, in 2008, the California 1-h average standard (<90 ppb) was exceeded 3 times. The proposed Federal secondary O₃ standard of 13 ppm h was exceeded reaching 16 ppm h in 2007 and 15 ppm h in 2008 that indicates potentially phytotoxic effects on local flora.► Diurnal and seasonal O₃ concentrations were measured in remote Sierra Nevada location. ► Maximum hourly O₃ concentrations were higher in high-fire year than in low-fire year. ► Local O₃ generation and long range transport contributed to ambient O₃ status. ► Lowest O₃ was when air masses from above Pacific Ocean crossed California at high altitudes. ► Highest O₃ was when air masses from near San Francisco Bay crossed California Central Valley.

Keywords: California; Fires; Ozone; Backward trajectories; Air pollution standards

Short-term climatology of PM10 at a high altitude background station in southern Europe by L. Tositti; A. Riccio; S. Sandrini; E. Brattich; D. Baldacci; S. Parmeggiani; P. Cristofanelli; P. Bonasoni (pp. 142-152).

The paper analyzes PM10 data from Mt. Cimone observatory (44°11′ N, 10°42′ E) in the period 1998–2011. Mt. Cimone is the highest peak of the Italian northern Apennines (2165 m asl) which hosts a high altitude background station in Southern Europe. The dataset is discussed in the framework of the main atmospheric meteorological and territorial features, representative of the central Mediterranean free troposphere. The overall geometric mean of PM10 mass concentration in the period investigated is 6.0 μg m⁻³ (arithmetic mean 8.8 ± 8.0 μg m⁻³), with large variability at the synoptic time-scale. At Mt. Cimone station the PM10 mass load features a strong seasonal fluctuation with a winter minimum (0.1 μg m⁻³, average winter value: 4.1 ± 4.8 μg m⁻³) and a summer maximum (45.7 μg m⁻³, average summer value: 13.7 ± 7.2 μg m⁻³). Influence of surface source areas upon PM10 is discussed by comparison of simultaneous PM10 data collected at ground stations to the north and south of the Northern Apennine range in order to investigate transport connections at the regional scale. PM10 data collected from the Environmental Protection Agencies networks of Emilia Romagna and Tuscany mostly cover urban stations and a few rural and semirural stations usually at ground level. In general PM10 mass load exhibits a vertical negative gradient with altitude, with Mt. Cimone displaying the least average value. Nevertheless exceptions can be observed on an event basis, while direct comparison of concentration data is not advisable due to the remoteness of Mt. Cimone as compared even to rural or semirural stations. Analysis of PM10 time series in conjunction with fine and coarse particle number densities reveals the influence of transports from source regions such as the Northern African desert, the Po valley and the European continent including the Balkan area. Source apportionment of PM10 is achieved applying a methodology based on Hysplit back-trajectories calculation.► PM10 time series collected over the years 1998–2011. ► Mt. Cimone, high altitude station representative of the European continental background conditions. ► Analysis of PM10 data in connection with fine and coarse particle number densities. ► Conditional probability analysis during high level pollution episodes by back-trajectories clustering technique.

Keywords: Particulate matter; Source apportionment; Back-trajectories clustering technique; Mediterranean basin “crossroads” of pollution transport

Influence of large changes in public transportation (Transantiago) on the black carbon pollution near streets by E. Gramsch; G. Le Nir; M. Araya; M.A. Rubio; F. Moreno; P. Oyola (pp. 153-163).

In 2006 a large transformation was carried out on the public transportation system in Santiago de Chile. The original system (before 2006) had hundreds of bus owners with about 7000 diesel buses. The new system has only 13 firms with about 5900 buses which operate in different parts of the city with little overlap between them. In this work we evaluate the impact of the Transantiago system on the black carbon pollution along four roads directly affected by the modification to the transport system. Measurements were carried out during May–July of 2005 (before Transantiago) and June–July of 2007 (after Transantiago).We have used the Wilcoxon rank-sum test to evaluate black carbon concentration in four streets in year 2005 and 2007. The results show that a statistically significant reduction between year 2005 (before Transantiago) and year 2007 (after Transantiago) in Alameda street, which changed from a mean of 18.8 μg m⁻³ in 2005 to 11.9 μg m⁻³ in 2007. In this street there was a decrease in the number of buses as well as the number of private vehicles and an improvement in the technology of public transportation between those years. Other two streets (Usach and Departamental) did not change or experienced a small increase in the black carbon concentration in spite of having less flux of buses in 2007. Eliodoro Yañez Street, which did not have public transportation in 2005 or 2007 experienced a 15% increase in the black carbon concentration between those years. Analysis of the data indicates that the change is related to a decrease in the total number of vehicles or the number of other diesel vehicles in the street rather than a decrease in the number of buses only. These results are an indication that in order to decrease pollution near a street is not enough to reduce the number of buses or improve its quality, but to reduce the total number of vehicles.► Black carbon (BC) has been studied in relation to public transportation. ► Lower black carbon concentration was observed in only one street. ► The street with less BC had a large decrease in the total number of vehicles. ► Streets with reduction in number of buses only did not show a decrease BC. ► The decrease seems to be related to a reduction in the total number of vehicles.

Keywords: Black carbon; Public transportation; Santiago de Chile; Diesel; Buses

Atmospheric chemistry of CF₃O₂: A theoretical study on mechanisms and pathways of the CF₃O₂ + I reaction by Yizhen Tang; Haofen Sun; Jing Zhao; Jinhu Liu; Rongshun Wang (pp. 164-170).

Mechanisms and reaction channels of the CF₃O₂ with atomic iodine reaction were studied using quantum chemistry methods. The result indicates that the title reaction can take place on either the singlet or triplet potential energy surfaces (PES). On the singlet PES, addition and substitution mechanisms were located, and the former one is dominant. The most favorable channel involves the association of CF₃O₂ and I to form CF₃OOI via a barrierless process. CF₂O + FOI or CF₃O + IO and other products could be formed as well, but they can be neglected because of highly energy barriers and unstable products. On the triplet PES, the most feasible product should be CF₃O + IO via a modest barrier in the atmospheric condition, especially at higher temperature and lower pressure condition. However it is unfavorable thermodynamically to the overall reaction. Time-dependent DFT (TD-DFT) calculations indicate that CF₃OOI takes photolysis easily in the sunlight at the wavelength of 548 and 427 nm.► The mechanisms and reaction pathways of the CF₃O₂ + I reaction was studied theoretically. ► The reaction can take place on the singlet and triplet potential energy surfaces. ► Substitution and addition mechanisms were located. ► CF₃OOI is the dominant product for the title reaction. ► CF₃OOI does photolyze in the sunlight.

Keywords: CF; ₃; O; ₂; Atmospheric reaction; Iodine; Mechanisms; Photolysis

Which metric of ambient ozone to predict daily mortality? by Hanns Moshammer; Hans-Peter Hutter; Michael Kundi (pp. 171-176).

It is well known that ozone concentration is associated with daily cause specific mortality. But which ozone metric is the best predictor of the daily variability in mortality?We performed a time series analysis on daily deaths (all causes, respiratory and cardiovascular causes as well as death in elderly 65+) in Vienna for the years 1991–2009. We controlled for seasonal and long term trend, day of the week, temperature and humidity using the same basic model for all pollutant metrics. We found model fit was best for same day variability of ozone concentration (calculated as the difference between daily hourly maximum and minimum) and hourly maximum. Of these the variability displayed a more linear dose–response function. Maximum 8 h moving average and daily mean value performed not so well. Nitrogen dioxide (daily mean) in comparison performed better when previous day values were assessed. Same day ozone and previous day nitrogen dioxide effect estimates did not confound each other.Variability in daily ozone levels or peak ozone levels seem to be a better proxy of a complex reactive secondary pollutant mixture than daily average ozone levels in the Middle European setting. If this finding is confirmed this would have implications for the setting of legally binding limit values.► We performed a time-series analysis over 19 years of ozone and daily mortality. ► Within-day variability of ozone was the best predictors of same day mortality. ► Previous day nitrogen dioxide did not confound the results.

Keywords: Ozone; Mortality; Causal interpretation; Diurnal variation

Analysis of ammonia variation in the urban atmosphere by Nhu-Thuc Phan; Ki-Hyun Kim; Zang-Ho Shon; Eui-Chan Jeon; Kweon Jung; Nam-Jin Kim (pp. 177-185).

Long-term monitoring of ammonia concentration and other trace gases was made at hourly intervals along with meteorological parameters in Seoul, Korea for a one-year period (1 September 2010–23 August 2011). The mean ammonia concentrations measured at two sites (Gwang-Jin (GJ) and Gang-Seo (GS) districts) were 10.9 ± 4.25 and 12.3 ± 4.23 ppb, respectively. A comparison of the seasonal data shows its relative dominance at both GJ and GS sites during the warm period (summer and spring) over the cool period (winter and fall). Likewise, over the diurnal scale, relative dominance during daytime was also apparent ( p < 0.05). A comparison between different studies suggests that the long-term trend of ammonia levels should be tightly affected by an increasing number of vehicles. As such, the results of our statistical analysis also point to the potentially significant role of traffic activities in the elevation of ammonia levels in urban areas.► The on-line analysis of ammonia is conducted at two urban monitoring sites. ► Sources affecting its temporal variation are evaluated in a number of respects. ► Ammonia levels in the urban air exhibit unique temporal trends over seasonal cycle. ► The results indicate a potential linkage between ammonia levels and traffic activities.

Keywords: Ammonia; Vehicle exhaust; Urban atmosphere; Pseudo-first-order loss; Partitioning

Characteristics and health impacts of particulate matter pollution in China (2001–2011) by Zhen Cheng; Jingkun Jiang; Oscar Fajardo; Shuxiao Wang; Jiming Hao (pp. 186-194).

In this study, a systematic overview of inhalable particulate matter (PM₁₀) pollution in China was conducted based on the dataset from national monitoring network from 2001 to 2011. The long-term trend, spatial and temporal distributions, and health impacts of PM₁₀ pollution were evaluated. It was found that the annual PM₁₀ concentration decreased from 116.0 μg m⁻³ in 2001 to 85.3 μg m⁻³ in 2011. The days with PM₁₀ concentration above the new Chinese ambient air quality standard dropped from 66 (18%) in 2001 to 28 (7.8%) in 2011, while the days exceeding the World Health Organization (WHO) guideline decreased from 294 (80.5%) in 2001 to 250 (68.5%) in 2011. PM₁₀ pollution in northern China is much worse than that in southern China. Six of nine most polluted cities (>110 μg m⁻³) are in the north, while six cleanest cities (<50 μg m⁻³) are all in the south. The seasonal average PM₁₀ concentrations in 2001–2011 for all cities are 104.4 μg m⁻³ (spring), 75.3 μg m⁻³ (summer), 94.7 μg m⁻³ (autumn), and 118.4 μg m⁻³ (winter), respectively, indicating that winter and spring are the most polluted seasons. Different health endpoints due to PM₁₀ pollution show similar trends. Taking premature mortality between 2001 and 2011 as an example, the ratio of deaths due to PM₁₀ pollution to all causes of deaths dropped from 13.5% to 11.6% and 511,000 deaths are avoided due to the concentration reduction, though the absolute damage number due to PM₁₀ pollution increased from 418,000 to 514,000 because of increasing urban population. These results indicate that PM₁₀ pollution in China has been eased significantly over the last decade, mainly due to the application of emission control measures. However, the PM₁₀ concentration remains at a high level comparing with the WHO guideline and its health impacts are still significant.► Characteristics and health impacts of PM₁₀ pollution in China were evaluated. ► PM₁₀ pollution in China has been reduced during the last decade. ► PM pollution (especially fine particles) is still a severe environmental problem. ► Great health benefit is achieved due to PM₁₀ reduction. ► The absolute damage cases are increasing due to the increase in urban population.

Keywords: Air pollution; Particulate matter; Public health; China

Fluorescence spectra and elastic scattering characteristics of atmospheric aerosol in Las Cruces, New Mexico, USA: Variability of concentrations and possible constituents and sources of particles in various spectral clusters by R.G. Pinnick; E. Fernandez; J.M. Rosen; S.C. Hill; Y. Wang; Y.L. Pan (pp. 195-204).

The UV-excited laser-induced-fluorescence (UV-LIF) spectra of single atmospheric particles and the three-band integrating-nephelometer elastic scattering of atmospheric aerosol were measured during four approximately 24-h periods on May 2007 in Las Cruces, New Mexico, USA. Aerosol scattering measurements in the nephelometer red channel (50-nm band centered at 700-nm) ranged from around 3–10 times the molecular (Rayleigh) scattering background. On average 22.8% of particles with size greater than about 1 μm diameter have fluorescence above a preset fluorescence threshold. A hierarchical cluster analysis indicates that most of the single-particle UV-LIF spectra fall into about 10 categories (spectral clusters) as found previously at other geographic sites (Pinnick et al., 2004; Pan et al., 2007). The clusters include spectra characteristic of various humic/fulvic acids, humic-like-substances (HULIS), chemically aged terpenes, fungal spores, polycyclic aromatic hydrocarbons, bacteria, cellulose/pollens, and mixtures of various organic carbon compounds. By far the most populated cluster category is similar to those of chemically aged terpenes/humic-materials; on average this population comprises about 62% of fluorescent particles. Clusters with spectra similar to that of some HULIS aerosol contain on average 10.0% of particles; those characteristic of some fungal spores (or perhaps mixtures of aromatic organic compounds) 8.4% of particles; bacteria-like spectra 1.6% of particles; and cellulose/pollen-like spectra 0.8% of particles. Measurements of fluorescent particles over relatively short (24 min) periods reveal that the concentrations of particles in the most populated clusters are highly correlated, suggesting that the particles populating them derive from the same region; these particles might be composed of crustal material coated with secondary organic carbon. On the other hand, concentrations of particles having cellulose-like spectra are generally uncorrelated with those in any other cluster. No clear distinction in fluorescent aerosol characteristics can be seen for different air mass trajectories arriving at the sampling site, suggesting that fluorescent aerosol particles are primarily of local origin. Integrations of the single-particle UV-LIF spectra over approximate 24 h time intervals reveal two broad peaks around 350 nm and 450 nm (for 263 nm excitation); the 450 nm peak is somewhat similar to that measured previously for water soluble organic carbon derived from aerosol collections. The 350 nm peak apparently has not been seen before in measurements of aerosol collections and may derive from non-soluble primary biological aerosol particles such as fungal spores. Further measurements are needed to investigate in more detail the generality of these results.► Possible sources of fluorescent atmospheric aerosol particle. ► Time series of atmospheric aerosol concentration in various spectral clusters. ► UV-LIF spectra and nephelometer scattering of atmospheric aerosol particles. ► Integrated fluorescence spectral profiles vary with time.

Keywords: Atmospheric aerosol particles; Fluorescence spectra; Elastic scattering; Clustered spectra; Integrated spectra; Time resolved

Indoor airborne particle sources and semi-volatile partitioning effect of outdoor fine PM in offices by G. Sangiorgi; L. Ferrero; B.S. Ferrini; C. Lo Porto; M.G. Perrone; R. Zangrando; A. Gambaro; Z. Lazzati; E. Bolzacchini (pp. 205-214).

To date, few studies have focused on PM air quality in offices, despite the fact that a lot of people spend many working hours a day in such offices. The aim of the present study is to investigate PM1 and PM2.5 in offices in Milan (Northern Italy) and in the air outside those offices. The PM samples were analyzed to determine the entity of certain compounds with possible direct or indirect adverse effects on human health: PAHs, BpA, and water soluble inorganic ions.A good correlation between outdoor and indoor PM mass concentrations emerged ( R² ∼0.87). The maximum I/ O concentration ratio was 0.92, suggesting that the indoor PM level was always lower than the outdoor level. The average infiltration factor, F_INF, was 0.55, showing that about a half of the outdoor PM had come indoors. The indoor-generated particles, C_ig, had values ranging from 0 to 4.4 μg m⁻³ (<25% of the indoor PM), showing that PM indoor sources had only made a limited contribution to total indoor PM.The results of the indoor-to-outdoor comparisons for the aforementioned chemical compounds demonstrate that the offices were characterized by the absence of effective indoor sources of particulate-bound PAHs and inorganic ions, whereas C_ig was around 58% of the indoor concentration for BpA. Our analysis of the F_INF data pointed to the presence of a volatilization effect from PM for semi-volatile compounds like ammonium nitrate and 4- or 5-ring PAHs, which affected the measurement of their F_INF. We propose the introduction of a new and simple parameter, called volatilization correction, to take account of this effect.Display Omitted► Indoor-to-outdoor relationship for PM1 and PM2.5 ( I/ O, F_INF and C_ig). ► Chemical characterization of inorganic ions, PAHs and BpA in fine PM. ► More than 50% of urban (Milan) fine PM enters the indoor office environments. ► Office indoor sources generate about 60% of indoor particulate-bound BpA. ► Semi-volatile loss from outdoor PM when entering a warmer indoor environment.

Keywords: Indoor air quality; Polycyclic Aromatic Hydrocarbons; Inorganic ions; Bisphenol A; Indoor-to-outdoor ratio; Particulate matter

The concentrations of culturable microorganisms in relation to particulate matter in urban air by D. Haas; H. Galler; J. Luxner; G. Zarfel; W. Buzina; H. Friedl; E. Marth; J. Habib; F.F. Reinthaler (pp. 215-222).

The ambient air consists not only of gases but also of bioaerosols and particulate matter. The concentrations of particulate matter in relation to the culturable microorganisms in the urban ambient air and their dependence on air temperature and relative humidity were investigated. The seasonal distribution of particles sizes, the concentrations of aerobic mesophilic bacteria and xerophilic fungi in the air were evaluated. Moreover, the identification of the fungal genera Cladosporium, Aspergillus and Penicillium were conducted.Within one year at 177 days particle and microorganism concentrations in the ambient air were recorded in the city centre of Graz/Austria.The results show that the concentrations of fine particles and coarse particles were the highest in winter and decreased continuously to a minimum in the summer months depending on temperature and air humidity. The concentrations of xerophilic fungi showed no correlation to the different particle concentrations. The spore concentrations of Cladosporium spp. showed the same results of xerophilic fungi whereas the genera Penicillium and Aspergillus increased with the increase of fine particles. The concentrations of mesophilic bacteria were positively correlated with all particle counts. The maximum mesophilic bacteria concentrations were found in the winter months.Further studies are required to evaluate the concentrations of specific microorganisms in the natural environment in relation to the particulate matter.► Relation between the concentrations of particles, fungi and bacteria in the air. ► Xerophilic fungi did not correlate with particle counts. ► Penicillium and Aspergillus genera increased with the increase of fine particles. ► Cladosporium spp. did not correlate with particle counts. ► Bacteria correlated with particle counts, especially with the coarse particles.

Keywords: Particles; Bioaerosols; Bacteria; Fungi; Spores

Corrigendum to “Penetration of fine particles through rough cracks” [Atmos. Environ. 60C (2012) 436–443] by Alvin C.K. Lai; Joanna L.S. Fung; M. Li; K.Y. Leung (pp. 223-223).

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