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Atmospheric Environment (v.45, #21)

Editorial board (pp. i).

Size-fractionated PM10 monitoring in relation to the contribution of endotoxins in different polluted areas by D. Traversi; L. Alessandria; T. Schilirò; G. Gilli (pp. 3515-3521).

Particulate pollution is an environmental concern that is widespread and difficult to resolve. Recently various regulatory improvements around the world have been agreed upon to tackle this problem, especially as related to the fine fraction of particulates, which more closely correlates to human health effects than other fractions. The size-fractionation of inhalable particles and their organic composition represent a new area of research that has been poorly explored thus far. Endotoxins are a type of natural organic compound that can be found in particulate matter. They are correlated with Gram-negative bacterial contamination. Health outcomes associated with exposure to these toxins are not specific and often overlap with the health effects of PM (Particulate Matter) exposure, including asthma, bronchitis, acute respiratory distress syndrome and organic dust toxic syndrome. Very little information is available on the endotoxin distribution in different PM10 size fractions. This study examined PM10 size fractions and their endotoxin content. Sampling was conducted at five different locations: one urban, two rural and two rural sites that were highly influenced by large-scale farm animal production facilities. For each location, six different PM10 fractions were evaluated. PM10 sub-fractions were categorised as follows: PM_10–7.2 (1.15–31.30 μg m⁻³); PM_7.2–3.0 (1.86–30.73 μg m⁻³); PM_3.0–1.5 (1.74–13.90 μg m⁻³); PM_1.5–0.95 (0.24–10.57 μg m⁻³); PM_0.95–0.49 (1.22–14.33 μg m⁻³) and PM_<0.49 (13.15–85.49 μg m⁻³). The ranges of endotoxin levels determined were: PM_10–7.2 (0.051–5.401 endotoxin units (EU) m⁻³); PM_7.2–3.0 (0.123–7.801 EU m⁻³); PM_3.0–1.5 (0.057–1.635 EU m⁻³); PM_1.5–0.95 (0.040–2.477 EU m⁻³); PM_0.95–0.49 (0.007–3.159 EU m⁻³) and PM_<0.49 (0.039–3.975 EU m⁻³). Our results indicated consistency of the PM1 fraction at all of the sites and the predominant presence of endotoxins in the coarse fraction. The observed abatement of the PM10 and endotoxin levels was very high (above 1:10) as little as 50 m from the pollution source. This kind of model is useful to both improve our knowledge about PM10 endotoxin distribution and to evaluate the potential risks for the health of neighbouring populations.► This study examined PM10 size fractions and their endotoxin content. ► For each of the five locations, six different PM10 fractions were evaluated. ► Data indicated constancy of the PM1 and endotoxin prevalence in the coarse fraction. ► The abatement of the pollution was high already by 50 m from the pollution source.

Keywords: Endotoxin; Lipopolysaccharide; Particulate matter; PM10; Air pollution

Measurement of black carbon concentration as an indicator of air quality benefits of traffic restriction policies within the ecopass zone in Milan, Italy by Giovanni Invernizzi; Ario Ruprecht; Roberto Mazza; Cinzia De Marco; Griša Močnik; Costantinos Sioutas; Dane Westerdahl (pp. 3522-3527).

Traffic restrictions are an unpopular tool to mitigate urban air pollution, and a measurable improvement in air quality is needed to demonstrate the effectiveness of this measure. Previous attempts failed to detect measurable reductions of PM mass pollution within the areas subject to traffic restriction. However black carbon, which is emitted primarily by traffic sources, could be a PM metric more suitable than PM mass to demonstrate pollutant reductions. In this study we report the results of a black carbon monitoring campaign carried out in Milan, Italy, with the aim to detect - and demonstrate more suitably than PM mass - differences in local urban air quality among three zones located very closely with different traffic intensity. The study was carried out in three different days by measuring simultaneously black carbon and PM mass concentrations with fixed monitoring stations located in three main radial roads connecting the outskirts to the city center, each with three segments: 1) an outer one, with no traffic restrictions 2) an intermediate one, subject to the congestion traffic charge called “Ecopass”, where a ticket is required to enter for cars equipped with engines prior to Euro 4 standard; 3) the pedestrian zone (no cars admitted) of Duomo Square in the city center, where each of the three main roads ends. The results demonstrated a sharply declining gradient in black carbon levels from the outer zone, without traffic restrictions, to the more central areas, for all of the three radial main roads. The differences in mean black carbon levels in the same day in the different traffic scheme locations were highly significant for each comparison. In contrast to the Black carbon results, mean PM₁₀, PM_2.5, PM₁ concentrations did not show significant differences among the different traffic zones on the different campaign days. The ratio of black carbon to PM₁₀ decreased by 47% and 62% in the Ecopass zone and in the pedestrian zone, respectively, as compared to the no-restriction zone. To the best of our knowledge this is the first study showing that within-city proximal areas with different traffic intensity are associated with different black carbon levels. These data suggest that black carbon is a highly relevant metric of traffic pollution and should be taken into consideration in demonstrating the effectiveness of air quality mitigation measures.► The Ecopass zone is a traffic restriction zone for diesel vehicles in Milan. ► Black carbon concentrations were reduced in the Ecopass zone. ► In contrast, no difference in PM mass concentrations was observed. ► Black carbon is a powerful metric for evaluating traffic restriction impact.

Keywords: Air pollution; Particulate matter; Aerosols; Traffic pollution; Black carbon; Spatial variability

Black Smoke and Black Carbon: Further investigation of the relationship between these ambient air metrics by Paul Quincey; David Butterfield; David Green; Gary W. Fuller (pp. 3528-3534).

A previous paper () described a simple quadratic relationship between OECD Black Smoke Index ( I_BS) and Black Carbon (aethalometry) measurements of ambient particulate samples ( C_BC):CBC=4.18IBS+59.6−7.72, based on their common link to optical absorption coefficient, supported by a single dataset. Further parallel datasets are presented here that support the general validity of the relationship, while highlighting limitations to the traditional Black Smoke method at kerbside sites, and variations between sites. The opportunity is taken to clarify some confusing aspects concerning published standard methods for Black Smoke.► Modified relationship between Black Smoke and Black Carbon parameters derived. ► New parallel measurements of Black Smoke and Black Carbon at five sites presented. ► Derived relationship holds experimentally within ∼25% except at kerbside site. ► Kerbside anomaly attributed to failure of Black Smoke method with high diesel soot.

Keywords: Black Smoke; Black Carbon; Soot; Air pollution; Air quality

Seasonal and rainfall-type variations in inorganic ions and dicarboxylic acids and acidity of wet deposition samples collected from subtropical East Asia by Ying I. Tsai; Li-Ying Hsieh; Su-Ching Kuo; Chien-Lung Chen; Pei-Ling Wu (pp. 3535-3547).

Rainfall samples were collected over a period of 3 years and 8 months in subtropical East Asia. They are categorized into different rainfall types and analyzed to assess the ionic composition and its effect on the acidity of wet deposition in southern Taiwan. Only 4% of samples had a pH of <5.0, indicating that the study area is not impacted significantly by acid rain. The volume-weighted mean (VWM) pH by rainfall type was Spring Rain 5.74, Typhoon Rain 5.56, Summer Rain 5.46, Typhoon Outer Circulation (TOC) Rain 5.45, Plum Rain 5.32 and Autumn–Winter Rain 5.29. Dilution effects were important to the equivalent ionic concentration of different rainfall types. HCO₃⁻, SO₄²⁻ and Cl⁻ were detected as major anions whereas NH₄⁺, Na⁺ and Ca²⁺ were major cations. CO₂-derived HCO₃⁻ was the major ionic species in all but Typhoon Rain and Spring Rain, in which the major species were Na⁺ and Cl⁻ and Ca²⁺, respectively. Excluding HCO₃⁻, the major species were NH₄⁺, Na⁺ and Ca²⁺ in Plum Rain, the secondary photochemical products SO₄²⁻, NO₃⁻ and NH₄⁺ in TOC Rain and Summer Rain, and Na⁺ and Ca²⁺ in Autumn–Winter Rain. Calculation of arithmetic means showed that dicarboxylic acids contributed between 0.25% and 0.53% of the total ionic concentration and of these, oxalic acid contributed the least (81.3% of the dicarboxylic acid) to TOC Rain and the most (96.1% of the dicarboxylic acid) to Spring Rain, suggestive of long-range transport in the latter. Differences in wet deposition composition were shown to be a result of differences in local emissions and long-range transport (hence of prevailing wind direction) during the period of rainfall and of the frequency and volume of rain that typifies each rainfall type. Principal component analysis (PCA) further revealed that traffic-related and industrial organic and inorganic pollutants, their secondary photochemical products, sea salts, and dust are important contributors to wet deposition. Moreover, the ratio of malonic acid to succinic acid (M:S ratio) indicated that both traffic and secondary photochemical reactions are major contributors to all but TOC Rain, for which the M:S ratio of 4.54 indicates a relative abundance of pollutants from secondary photochemical reactions. An ion balance (IB) ratio analysis demonstrated the validity of the results in this research.► The wet deposition in southern Taiwan was analyzed and categorized. ► Not impacted significantly by acid rain. ► Inorganic ions the vast majority of the total ionic concentration. ► Dicarboxylic acids between 0.25% and 0.53% of the total ionic concentration. ► Important contributors traffic, industrial plus secondary products, sea salts, dust.

Keywords: Rainwater; Wet precipitation; Typhoon; Chemical composition; Dicarboxylic acids; Oxalic acid; Southern Taiwan

Distribution and variability of the 24-h average air exchange rates and interzonal flow rates in 26 Japanese residences in 5 seasons by Naohide Shinohara; Toshiyuki Kataoka; Koichi Takamine; Masashi Gamo (pp. 3548-3552).

In this study, to evaluate the distribution of air exchange rates in Japan, daily, seasonal, and inter-residence variabilities were determined as well as the air exchange rate itself. In addition, airflows among multiple zones were also evaluated. For this purpose, the 24 h average air exchange rates and interzonal air flow rates were measured using a passive perfluorocarbon tracer (PFT) method with three kinds of tracer gases for 1 week in three rooms of 26 Japanese residences over five seasons: summer and autumn of 2005, and winter, spring, and summer of 2006. During these seasons, the weekly average air exchange rates were found to be 1.6 ± 1.7, 0.58 ± 0.94, 0.61 ± 0.93, 1.2 ± 2.5, and 1.7 ± 1.8 h⁻¹, respectively. Two-way repeated measure analysis of variance (ANOVA) revealed that the air exchange rates differed significantly with respect to the seasons, residences, and interaction of seasons and residences ( p < 0.01). In addition, the air exchange rates in both summers and spring were statistically higher than those in autumn and winter (Sheffe test, p < 0.01). According to the ANOVA, the percentage contribution of inter-residence variability, seasonal variability, interaction of seasonal and inter-residence variabilities, and daily variability to the total variability of the 24 h average air exchange rates in the present survey was 51%, 44%, 3.7%, and 1.0%, respectively.► The 24 h ave. air exchange rates were measured in 26 residences over 5 seasons. ► Air exchange rates were statistically higher in summer than in autumn and winter. ► Inter-residence and seasonal variabilities were 51% and 44% contributed to the total variance. ► The air exchange rate was significantly affected by the windows opening duration.

Keywords: Air exchange rate; Interzonal air flow rates; PFT method; Daily variability; Seasonal variability; Inter-residence variability

Long-range atmospheric transport of terrestrial biomarkers by the Asian winter monsoon: Evidence from fresh snow from Sapporo, northern Japan by Shinya Yamamoto; Kimitaka Kawamura; Osamu Seki (pp. 3553-3560).

Molecular distributions of terrestrial biomarkers were investigated in fresh snow samples from Sapporo, northern Japan, to better understand the long-range atmospheric transport of terrestrial organic matter by the Asian winter monsoon. Stable carbon (δ¹³C) and hydrogen (δD) isotope ratios of C₂₂–C₂₈ n-alkanoic acids were also measured to decipher their source regions. The snow samples are found to contain higher plant-derived n-alkanes, n-alkanols and n-alkanoic acids as major components. Relative abundances of these three biomarker classes suggest that they are likely derived from higher plants in the Asian continent. The C₂₇/C₃₁ ratios of terrestrial n-alkanes in the snow samples range from 1.3 to 5.5, being similar to those of the plants growing in the latitudes >40°N of East Asia. The δ¹³C values of the n-alkanoic acids in the snow samples (−33.4 to −27.6‰) are similar to those of typical C₃ gymnosperm from Sapporo (−34.9 to −29.3‰). However, the δD values of the n-alkanoic acids (−208 to −148‰) are found to be significantly depleted with deuterium (by ∼72‰) than those of plant leaves from Sapporo. Such depletion can be most likely interpreted by the long-range atmospheric transport of the n-alkanoic acids from vegetation in the latitudes further north of Sapporo because the δD values of terrestrial higher plants tend to decrease northward in East Asia reflecting the δD of precipitation. Together with the results of backward trajectory analyses, this study suggests that the terrestrial biomarkers in the Sapporo snow samples are likely transported from Siberia, Russian Far East and northeast China to northern Japan by the Asian winter monsoon.► Fresh snow from Sapporo contains abundant terrestrial biomarkers. ► These biomarkers originate from the higher latitudes of the Asian continent. ► The Asian winter monsoon transports terrestrial biomarkers to northern Japan.

Keywords: Stable carbon isotopes; Stable hydrogen isotopes; Terrestrial biomarker; Snow; Asian monsoon

Secondary pollutants from ozone reactions with ventilation filters and degradation of filter media additives by Hugo Destaillats; Wenhao Chen; Michael G. Apte; Nuan Li; Michael Spears; Jérémie Almosni; Gregory Brunner; Jianshun (Jensen) Zhang; William J. Fisk (pp. 3561-3568).

Prior research suggests that chemical processes taking place on the surface of particle filters employed in buildings may lead to the formation of harmful secondary byproducts. We investigated ozone reactions with fiberglass, polyester, cotton/polyester and polyolefin filter media, as well as hydrolysis of filter media additives. Studies were carried out on unused media, and on filters that were installed for 3 months in buildings at two different locations in the San Francisco Bay Area. Specimens from each filter media were exposed to ∼150 ppbv ozone in a flow tube under a constant flow of dry or humidified air (50% RH). Ozone breakthrough was recorded for each sample over periods of ∼1000 min; the ozone uptake rate was calculated for an initial transient period and for steady-state conditions. While ozone uptake was observed in all cases, we did not observe significant differences in the uptake rate and capacity for the various types of filter media tested. Most experiments were performed at an airflow rate of 1.3 L min⁻¹ (face velocity = 0.013 m s⁻¹), and a few tests were also run at higher rates (8–10 L min⁻¹). Formaldehyde and acetaldehyde, two oxidation byproducts, were quantified downstream of each sample. Those aldehydes ( m/ z 31 and 45) and other volatile byproducts ( m/ z 57, 59, 61 and 101) were also detected in real-time using Proton-Transfer Reaction-Mass Spectrometry (PTR-MS). Low-ppbv byproduct emissions were consistently higher under humidified air than under dry conditions, and were higher when the filters were loaded with particles, as compared with unused filters. No significant differences were observed when ozone reacted over various types of filter media. Fiberglass filters heavily coated with impaction oil (tackifier) showed higher formaldehyde emissions than other samples. Those emissions were particularly high in the case of used filters, and were observed even in the absence of ozone, suggesting that hydrolysis of additives, rather than ozonolysis, is the main formaldehyde source in those filters. Emission rates of formaldehyde and acetaldehyde were not found to be large enough to substantially increase indoor concentrations in typical building scenarios. Nevertheless, ozone reactions on HVAC filters cannot be ignored as a source of low levels of indoor irritants.► Ozone reactions with fiberglass, polyester, cotton/polyester and polyolefin filter media. ► Unused media, and filters installed for 3 months at 2 locations in SF Bay Area. ► Ozone uptake observed in all cases; higher with used filters and 50% relative humidity. ► Byproducts: formaldehyde, acetaldehyde, other byproducts ( m/ z 57, 59, 61 and 101). ► Impaction oil led to higher formaldehyde emissions due to hydrolysis at high RH.

Keywords: Ozone; HVAC; Ventilation; Indoor pollutants; Filters

Heterogeneous reaction of formaldehyde on the surface of γ-Al₂O₃ particles by Bingye Xu; Jing Shang; Tong Zhu; Xiaoyan Tang (pp. 3569-3575).

Formaldehyde is one of the most important carbonyl organic compounds. Heterogeneous reactions of formaldehyde on the surface of oxides of crustal elements could be an important sink for formaldehyde in the atmosphere. In this study, the kinetics of the heterogeneous reaction of formaldehyde on the surface of γ-Al₂O₃ was investigated in situ by diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) combined with ion chromatography (IC), X-ray diffraction (XRD), and field emission environmental scanning electron microscope (ESEM). The adsorbed species, formate, dioxymethylene, polyoxymethylene, and formaldehyde, on γ-Al₂O₃ particles, were identified by infrared spectroscopy. On the surface of γ-Al₂O₃ particles, formaldehyde is first oxidized to dioxymethylene, which is further oxidized to formate. The reaction order was determined as 0.74 ± 0.05, and the initial reactive uptake coefficients at room temperature were calculated with the geometric and Brunauer–Emmett–Teller specific surface areas as (3.6 ± 0.8) × 10⁻⁴ and (1.4 ± 0.31) × 10⁻⁸, respectively. The influences of oxygen concentration, humidity, and temperature on the reaction products and reactive uptake coefficients were studied. The results indicated the reaction is independent of the O₂ concentration within the range used in this experiment, and humidity is negatively correlated with the uptake of formaldehyde by the particles. Temperature not only plays a role on the heterogeneous reaction products but also is positively correlated with the uptake rate of formaldehyde by γ-Al₂O₃ particles in the troposphere. The apparent activation energy of the reaction was determined.► Main products of HCHO on γ-Al₂O₃ were identified qualitatively and quantitatively. ► The reaction order and the reactive uptake coefficients were determined. ► The reaction is independent of the O₂ concentration. ► Humidity is negatively correlated with the uptake of HCHO by γ-Al₂O₃. ► Temperature is positively correlated with the uptake of HCHO by γ-Al₂O₃.

Keywords: Formaldehyde; γ-Al; ₂; O; ₃; DRIFTS; Heterogeneous reaction; Reactive uptake coefficient

Comparison of land-use regression models for predicting spatial NO_x contrasts over a three year period in Oslo, Norway by Christian Madsen; Ulrike Gehring; Siri Eldevik Håberg; Per Nafstad; Kees Meliefste; Wenche Nystad; Karin C. Lødrup Carlsen; Bert Brunekreef (pp. 3576-3583).

Spatial modelling of traffic-related air pollution through land-use regression (LUR) is increasingly applied in epidemiological studies. These models provide highly spatially resolved data, but assume that the spatial contrasts are stable over long periods of time. It is not known to which extent these models can be used to predict concentrations in earlier or later periods. We aimed at testing the stability of measured and modelled spatial contrasts over a three year period in order to assess the relevance for future assessments of individual exposure to traffic-related air pollutants in epidemiological studies.A land-use regression model was previously developed to estimate address-level outdoor concentrations of traffic-related air pollution based on samples of nitrogen oxides (NO_x) at 80 locations during the winter of 2005. In the winter of 2008, we measured NO_x again at 69 of these 80 locations and developed a new LUR model. This enabled us to compare short-term measurements and model predictions with three years apart in the same area.Measurements conducted in 2008 agreed well with measurements sampled in 2005 at the same locations ( r = 0.91–0.95). The LUR models from 2005 and 2008 explained 66–77% and 60–74% of the variability of the measured concentrations, respectively. The 2008 LUR models explained 55–68% of the spatial variability of the 2005 measurements, while the 2005 LUR models explained 53–66% of the spatial variability of the 2008 measurements. The models performed better for NO_x and NO₂ compared to NO, and were shown to be equally valid when using leave-one-out cross-validation and validation of models based on independent training sets.We found a good agreement between short-term measured spatial contrasts in outdoor NO_x over a three year period. LUR models for this area performed equally well using two different validation methods. These models predicted the spatial variation well for this area both forward and backward in time.► Good agreement between measured spatial contrasts in NO_x over a three year period. ► Good predicted spatial variation both forward and backward in time. ► LUR models performed equally well using different validation methods.

Keywords: Exposure; Air pollution; Geographic information system; Traffic; Land-use regression modelling; Spatial variability

Road traffic emission inventory for air quality modelling and to evaluate the abatement strategies: A case of Ho Chi Minh City, Vietnam by Bang Quoc Ho; Alain Clappier (pp. 3584-3593).

A road traffic Emission Inventory (EI) is generated for Ho Chi Minh City (HCMC), Vietnam. For generating the EI for road traffic sources, we used the new EMISENS model, which combines the top-down and bottom-up approaches. The bulk emission factors of traffic stem from another study that estimated the emission factors for HCMC by using an inverse air quality model method. The results show that the motorcycles are responsible for the bulk of traffic emissions (contributing 94% of CO, 68% of NMVOC, 61% of SO2 and 99% of CH4). Four scenarios for reducing of the traffic emissions are designed using the HCMC’s plan for reduction of emissions. Two scenarios are the reduction scenarios for the year of 2015 and 2020. In addition, two scenarios are the Business as Usual scenario for the year of 2015 and 2020. If the local government does not have any plan for reduction of emissions (scenario of Business as Usual) the emissions will increase rapidly. If the government follows the planning as set out by the local managers, the emissions of the city will decrease.► We combined the top-down and bottom-up approaches for generating Emission Inventory. ► Motorcycles are responsible for the bulk of traffic emission (99%) in Ho Chi Minh City. ► Emission in 2015 will reduce 15% than 2006, If HCMC follows the planning for reduction. ► Emission in 2015 increases 30% than 2006, If HCMC does not have any plan for reduction.

Keywords: Emission inventory; Uncertainty analysis; Monte Carlo; EMISENS model; Ho Chi Minh City; Road traffic; Emission abatement strategies

Impact of time–activity patterns on personal exposure to black carbon by Evi Dons; Luc Int Panis; Martine Van Poppel; Jan Theunis; Hanny Willems; Rudi Torfs; Geert Wets (pp. 3594-3602).

Time–activity patterns are an important determinant of personal exposure to air pollution. This is demonstrated by measuring personal exposure of 16 participants for 7 consecutive days: 8 couples of which one person was a full-time worker and the other was a homemaker; both had a very different time–activity pattern. We used portable aethalometers to measure black carbon levels with a high temporal resolution and a PDA with GPS-logger and electronic diary. The exposure to black carbon differs between partners by up to 30%, although they live at the same location. The activity contributing most to this difference is transport: Average exposure in transport is 6445 ng m⁻³, followed by exposure during shopping (2584 ng m⁻³). Average exposure is lowest while sleeping (1153 ng m⁻³) and when doing home-based activities (1223 ng m⁻³). Full-time workers spend almost twice as much time in transport as the homemakers. As a result of the study design we measured in several different homes, shops, cars, etc. enabling a better insight in true overall exposure in those microenvironments. Other factors influencing personal exposure are: background concentrations and location of residence in an urban, suburban or rural environment.► Personal exposure monitoring with a high temporal resolution. ► Time–activity patterns are a key determinant of personal exposure to air pollution. ► Exposure between partners, living at the same address, can differ by up to 30%. ► Exposure while in transport far exceeds exposure in other microenvironments. ► This research underlines the importance of personal monitoring for health purposes.

Keywords: Air pollution; Black carbon; Personal monitoring; Exposure; Time–activity pattern; Traffic

Fine particle and organic vapor emissions from staged tests of an in-use aircraft engine by Albert A. Presto; Ngoc T. Nguyen; Manish Ranjan; Aaron J. Reeder; Eric M. Lipsky; Christopher J. Hennigan; Marissa A. Miracolo; Daniel D. Riemer; Allen L. Robinson (pp. 3603-3612).

Staged tests were conducted to measure the particle and vapor emissions from a CFM56-2B1 gas-turbine engine mounted on a KC-135T Stratotanker airframe at different engine loads. Exhaust was sampled using a rake inlet installed 1-m downstream of the engine exit plane of a parked and chocked aircraft and a dilution sampler and portable smog chamber were used to investigate the particulate matter (PM) emissions. Total fine PM mass emissions were highest at low (4%) and high (85%) load and lower at intermediate loads (7% and 30%). PM mass emissions at 4% load are dominated by organics, while at 85% load elemental carbon is dominant. Quantifying the primary organic aerosol (POA) emissions is complicated by substantial filter sampling artifacts. Partitioning experiments reveal that the majority of the POA is semivolatile; for example, the POA emission factor changed by a factor of two when the background organic aerosol concentration was increased from 0.7 to 4μgm⁻³. Therefore, one cannot define a single non-volatile PM emission factor for aircraft exhaust. The gas- and particle-phase organic emissions were comprehensively characterized by analyzing canister, sorbent and filter samples with gas-chromatography/mass-spectrometry. Vapor-phase organic emissions are highest at 4% load and decrease with increasing load. Low-volatility organics (less volatile than a C₁₂ n-alkane) contributed 10–20% of the total organic emissions. The low-volatility organic emissions contain signatures of unburned fuel and aircraft lubricating oil but are dominated by an unresolved complex mixture (UCM) of presumably branched and cyclic alkanes. Emissions at all loads contain more low-volatility organic vapors than POA; thus secondary organic aerosol formation in the aging plume will likely exceed POA emissions.► In this study we quantify organic emissions from an in-use aircraft engine. ► Organic emissions cover a wide range of volatility, from volatile to non-volatile. ► The organic emissions at all loads are dominated by the volatile component. ► Low-volatility organic species comprise 10–20% of the total organic emissions.

Keywords: Aircraft emissions; Particulate matter; Hydrocarbon emissions

Sampling design for air quality measurement surveys: An optimization approach by Thomas Romary; Chantal de Fouquet; Laure Malherbe (pp. 3613-3620).

Measurement surveys using passive diffusion tubes are regularly carried out to elaborate atmospheric concentration maps over various areas. Sampling schemes must be designed to characterize both contaminant concentrations (of benzene or nitrogen dioxide for example) and their relations to environmental variables so as to obtain pollution maps as precise as possible. The concentration variable is interpolated by external drift kriging, with the help of exhaustively known covariates. The quality of a sampling scheme is quantified by the spatially averaged external drift kriging variance, which incorporates the drift estimation error as well as the spatial interpolation error. A weighted criterion is also introduced. Optimizing this criterion by simulated annealing provides an optimal sampling scheme. A preliminary study is performed on concentration data available from previous surveys on two different agglomerations so as to determine the covariance model and the relevant covariates to be used on a third agglomeration. It does not reveal a single model but a whole parametrized family of relevant models. The method is then applied to the third agglomeration with different values of the model parameters. The results are discussed and finally compared to those obtained with a pragmatic approach, described in a previous paper.► A methodology to produce optimal design for air quality surveys is provided. ► An efficient modelling of benzene concentration is carried out by universal kriging. ► A design quality criterion accounting for the aims of the survey is introduced. ► Efficient minimization of the quality criterion is performed by simulated annealing. ► A new solution generator is proposed.

Keywords: Optimal design; Geostatistics; External drift kriging; Simulated annealing; Sampling scheme

Characterization and morphological analysis of airborne PM_2.5 and PM₁₀ in Agra located in north central India by Atar Singh Pipal; Aditi Kulshrestha; Ajay Taneja (pp. 3621-3630).

PM_2.5 and PM₁₀ samples were collected from road and semirural sites of Agra, the north central part of India. The average mass concentration of PM₁₀ was 278.67 ± 106.58 μg/m³ and of PM_2.5 was 90.16 ± 7.21 μg/m³ at roadside while at semirural site it was 234.54 ± 128.27 μg/m³ for PM₁₀ and 89.12 ± 37.94 μg/m³ for PM_2.5. Scanning electron microscopy coupled with energy dispersive spectrometer (SEM-EDS) was used to understand the difference in terms of shapes, morphology, and elemental composition of aerosols in PM₁₀ and PM_2.5 and to further link them to the potential source as well as emission and transport of pollutants from different polluted areas. The SEM micrograph of PM₁₀ was different from PM_2.5 size range particles at both sites. EDS spectra indicates the three main groups of particles i.e., C, O rich particles, Si, Na and Al rich particles and Mg, Ca, Fe, K, S, Co rich particles on the basis of their percentage contribution in PM₁₀ and PM_2.5. PM_2.5 constituted C, O (95.93%), Si, Al, Na (2.63%), S, Fe, K, (1.41%) and PM₁₀ constituted O, C (72.16%), Si, Al, Na (24.58%), S, K, Fe, Co (3.24%) respectively at roadside whereas at semirural site, PM_2.5 and PM₁₀ constituted O, C (92.8%), Si, Al, Na (4.86%), Mg, K, Ca, Fe (2.32%), and O, C, (72.14%), Si, Na, Al (23.11%) and Mg, K, Ca, Fe (4.73%) respectively. Crustal elements such as Si, Na and Al rich particles are dominant excluding C and O in PM₁₀ and PM_2.5 at roadside as well as semirural site. Correlation between element and particulate matter indicates two groups in which one group is highly significant ( r > 0.90) and another group shows positive correlation ( r > 0.53 to 0.90). Soot, tarballs, carbonaceous and mineral type particles were observed at roadside while aluminosilicates, quartz, fly ash and soil dust particles were observed at semirural site in PM_2.5 and PM₁₀ respectively. It was concluded that SEM-EDS is a convenient method to identify the source of emission of particulate air pollution.► PM_2.5 and PM₁₀ concentration at two sites of North central region of India. ► Morphological analysis of PM_2.5 and PM₁₀ by Scanning Electron Microscopy. ► Characterization of chemical constituents by Energy Dispersive Spectrometer. ► Correlations between analyzed species determined to identify their relationships. ► PM concentration, shape and characteristics are used to see the sources of origin.

Keywords: Crustal elements; SEM-EDS; Particulate concentration; Particulate morphology

Compost spreading in Mediterranean shrubland indirectly increases biogenic emissions by promoting growth of VOC-emitting plant parts by Romain Olivier; Anne-Violette Lavoir; Elena Ormeño; Florent Mouillot; Stéphane Greff; Caroline Lecareux; Michael Staudt; Catherine Fernandez (pp. 3631-3639).

We investigated the effect of sewage sludge compost spreading on plant growth and leaf terpene emissions and content of Quercus coccifera, Rosmarinus officinalis and Cistus albidus in a Mediterranean shrubland. Measurements were performed during 3 consecutive summers on 2 different plots treated in 2002 or 2007 with 50 or 100 tons of compost per hectare, corresponding to observations carried out 2 months to 7 years after spreading. A slight nutrient enrichment of soil and leaves ( R. officinalis and C. albidus) was observed, especially for phosphorous. Terpene emissions were not affected by compost spreading, although they tended to increase on treated plots after 6 and 7 years for R. officinalis and C. albidus respectively. Terpene content was not affected by any compost treatment. Leaf and stem growth were significantly enhanced by compost spreading after 2 and/or 7 years in all species with little difference between doses. Total leaf biomass on the last growth units was increased by more than 50% in C. albidus and more than 90% in Q. coccifera. The results suggest that compost spreading in Meditteranean shrublands has no or little direct effect on leaf terpene emissions, but indirectly leads to their increase through leaf biomass enhancement. Simulation of terpene emissions at stand level revealed an increase of terpene fluxes ranging between 6 and 13%, depending on the plant species. Overall, compost spreading was assessed to result in an emission rate of 1.1 kg ha⁻¹ y⁻¹ for a typical Q. coccifera shrubland, but can reach 2.6 kg ha⁻¹ y⁻¹ for a typical R. officinalis shrubland.► Compost spreading has a effects on leaf terpene emissions in three Mediterranean shrubs. ► Compost spreading increases leaf biomass of three Mediterranean shrubs. ► Compost spreading indirectly increases biogenic emissions from Mediterranean shrubs.

Keywords: Monoterpenes; Compost; Quercus coccifera; Rosmarinus officinalis; Cistus albidus; Growth

Study of aerosol behavior on the basis of morphological characteristics during festival events in India by Anubha Agrawal; Vinay K. Upadhyay; Kamna Sachdeva (pp. 3640-3644).

Two important festival events were selected to assess their impacts on atmospheric chemistry by understanding settling velocity and emission time of aerosols. Using high volume sampler, aerosols were collected in a sequential manner to understand settling velocity and emission time of aerosols on a particular day. Composition and total suspended particulate load of the aerosols collected during the festivals were used as markers for strengthening the assessment. Terminal settling velocity of the aerosols were calculated using morphological and elemental compositional data, obtained from scanning electron microcopy (SEM) and energy dispersive X-ray (EDX) study. Aerosol load, black carbon, aromatic carbon and terminal velocity calculations were correlated to obtain conclusion that aerosols collected on the festival day might have been emitted prior to the festival. Settling time of aerosols collected on 17th and 19th October’09 during Diwali were found to be 36.5 (1.5 days) and 12.8 h, respectively. Carbon concentration estimated using EDX was found to be almost double in the sample collected after 2 days of the festival event. This strengthens our inference of time calculation where carbon with high concentration of load must have settled approximately after two days of the event. Settling time of aerosols collected on Holi morning and afternoon was found to be 1.7 and 24.8 h, respectively. Further, because of the small distance of 5.4 km between the meteorological station and sampling site, observed TSP values were compared with theoretical load values, calculated by using visibility values taken from the meteorological data. And it was found that both experimental and calculated values are close to each other about 50% of the times, which proves the assumption that experimental and meteorological data are comparable.► Concept of setting velocity was used to assess impact of festival events on the atmosphere chemistry. ► SEM-EDX analysis was used to determine terminal setting velocity. ► Correlation between BC, AOC and aerosol load was used to determine the settling time of the aerosols. ► Role of morphology of aerosols in altering the atmospheric chemistry was also highlighted in the study.

Keywords: Aerosol; Settling velocity; Indian festivals; Black carbon; Scanning electron microscopy

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Atmospheric Environment (v.45, #21)

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Atmospheric Environment (v.45, #21)