Check out our New Publishers' Select for Free Articles

Atmospheric Environment (v.42, #9)

Editorial board (pp. i).

Quantification of crop residue burning in the field and its influence on ambient air quality in Suqian, China by Shijian Yang; Hongping He; Shangling Lu; Dong Chen; Jianxi Zhu (pp. 1961-1969).

In China, many pollutants are released because of crop residue burning in the field, resulting in serious pollution of ambient air. Suqian with 4523km² of total area under cultivation was selected as a case to be studied, where wheat–rice double cropping system is widely adopted. Based on the data of crop output from 2001 to 2005, the annual average amount of crop residue generated was estimated as 3.04×10⁶t. About 82% of wheat straw and 37% of rice straw were burned in the field, so the proportion of crop residue burned in the field was about 43%. In combination with emission factors proposed by some literatures, the total amounts, the amounts in summer harvest and in autumn harvest of TSP, PM₁₀, SO₂, NO _x, NH₃, CH₄, EC, OC, VOC, CO, and CO₂, emitted from crop residue burning in the field, were estimated. The total amounts of them were 11,051, 7572, 525, 3280, 1707, 3544, 905, 4331, 20,606, 120,747, and 1,988,376t, respectively, and about 78% of them were emitted in summer harvest. During the summer harvest from June 4 to 13 in 2006, influenced by crop residue burning in the field, the daily average concentrations of PM₁₀, NO₂, and SO₂ were 0.266, 0.051, and 0.063mgm⁻³, respectively. And the daily average concentration of PM₁₀ kept exceeding 0.250mgm⁻³, the Third Standard Level of National Ambient Air Quality (China). Based on hourly concentration changes of PM₁₀ and meteorological condition, crop residue burning in the field was characterized. According to the field survey, it is regarded that combine harvester acts as an important role in crop residue burning in the field.

Keywords: Crop residue; Field burning; Pollutant emissions; PM; ₁₀; Combine harvester

Direct contact cytotoxicity assays for filter-collected, carbonaceous (soot) nanoparticulate material and observations of lung cell response by K.F. Soto; K.M. Garza; Y. Shi; L.E. Murr (pp. 1970-1982).

A simple, direct contact, cytotoxicity (in vitro) assay has been developed where particulate matter (PM) collected on glass fiber filters was exposed to human epithelial (lung) cells. Carbonaceous (soot) PM included tire, wood, diesel, candle, and variously combusted natural gas PM from a kitchen stove range. Black carbon PM and a commercial multiwall carbon nanotube aggregate PM was also examined in vitro as surrogate materials, and all experimental PM was characterized by field emission scanning electron microscopy and transmission electron microscopy. Assay results for 48h cultures showed toxicity for all carbonaceous PM with various natural gas PM being the most toxic; this was comparable to the toxicity induced by the surrogate PM. Light microscopy examination of affected epithelial cells confirmed the semi-quantitative results. Comparison of polycyclic aromatic hydrocarbon (PAH) content and concentration for the carbonaceous PM showed no PAH correlation with relative cell viability (cell death) after 48h.

Keywords: Cytotoxicity; Direct contact assays; Nanoparticulate soots

Using environmental scanning electron microscopy to determine the hygroscopic properties of agricultural aerosols by Naruki Hiranuma; Sarah D. Brooks; Brent W. Auvermann; Rick Littleton (pp. 1983-1994).

A field study at a cattle feedlot in the Texas Panhandle was conducted to characterize the hygroscopic, morphological, and chemical properties of agricultural aerosols and to identify possible correlations between these properties. To explore the hygroscopic nature of the agricultural particles, we have collected size-resolved aerosol samples using a cascade impactor system and have used an environmental scanning electron microscope (ESEM) to determine the water uptake by individual particles in those samples as a function of relative humidity (RH). In addition, complementary determination of the elemental composition of single particles was performed using energy dispersive X-ray spectroscopy (EDS). Our results indicate that most of the agricultural particles do not take up significant amounts of water when exposed to up to 96% RH. However, a small fraction of particles in the coarse mode deliquesced at approximately 75% RH and reached twice their original sizes by 96% RH. The observed changes in particle size with increased RH may significantly impact total aerosol extinction, visibility, and human health.

Keywords: Agricultural aerosol; Visibility; Hygroscopicity; Environmental scanning electron microscope (ESEM); Energy dispersive X-ray spectroscope (EDS)

Nighttime measurements of ambient N₂O₅, NO₂, NO and O₃ in a sub-urban area, Toyokawa, Japan by Tomoki Nakayama; Tomoyuki Ide; Fumikazu Taketani; Megumi Kawai; Kenshi Takahashi; Yutaka Matsumi (pp. 1995-2006).

We report on the development of a highly sensitive instrument for measuring ambient N₂O₅ molecules and its application to nighttime measurements of N₂O₅ in a sub-urban area, Toyokawa, Japan, during February 2006. The mixing ratio of N₂O₅ was quantified by cavity ring-down spectroscopy detection of NO₃ at 662nm, in which the NO₃ radicals were produced by thermal decomposition of the N₂O₅ molecules. The minimum detection limit (1 σ) for N₂O₅ was estimated to be 2.2pptv in a 100s averaging time. The mixing ratios of ambient NO₂, NO and O₃ were simultaneously measured along with N₂O₅. The ambient N₂O₅ mixing ratios range from below the detection limit (2.2pptv) to 20pptv during nighttime. By applying the steady-state approximation on the data of 27–28 February when the surface wind field was characterized by northerly wind associated with winter monsoon surges over Japan, the heterogeneous loss rate of N₂O₅ was estimated. Based on the mixing ratios and the loss rate of N₂O₅, the nocturnal loss rate of NO _x was evaluated as 0.5ppbv per night for that night. In addition, the temporal variation of N₂O₅ concentration during several hours after the local sunset on that night was calculated using the time-dependent box model. By comparing the results with the observed data, significant contributions of gas-phase loss processes of NO₃ were inferred.

Keywords: N; ₂; O; ₅; Nitrogen oxides; Nighttime measurement; Cavity ring-down spectroscopy

Estimating smoke emissions over the US Southern Great Plains using MODIS fire radiative power and aerosol observations by Nikisa S. Jordan; Charles Ichoku; Raymond M. Hoff (pp. 2007-2022).

A newly developed method, which involves the use of satellite measurements of energy released by fires, was used to estimate smoke emissions in the United States (US) Southern Great Plains (SGP). This SGP region was chosen because extensive agricultural and planned burning occurs there annually. Moderate resolution imaging spectroradiometer (MODIS) aerosol optical depth (AOD) and fire radiative energy (FRE) release rates (R_FRE), acquired in 2004 from the Terra and Aqua satellites, were used to derive a FRE-based smoke emission coefficient ( C_e kgMJ⁻¹), which when multiplied by R_FRE (MJs⁻¹) gives the rate of smoke emission (kgs⁻¹). Correlations between the smoke emission rates and the R_FRE were significant for Terra-MODIS ( R²=0.645, n=146, p<0.0001) and Aqua-MODIS ( R²=0.752, n=178, p<0.0001). Furthermore, the C_e values derived independently from Terra and Aqua were in close agreement, and the average C_e for this area is 0.049±0.024kgMJ⁻¹. A Monte Carlo (MC) probabilistic approach was used to approximate uncertainties from the smoke emission and resulting C_e. For the first time, smoke emission estimates have been derived for the US SGP using observations of energy released by fires. Although more work is necessary, the present study demonstrates the feasibility of using R_FRE for smoke emission estimation in that region. Burning peaked during the spring and fall seasons. Moreover, qualitative examination of smoke emission patterns side-by-side with local air-quality measurements indicated that the impact of smoke from local biomass burning activities was significant on the regional air-quality.

Keywords: Fire radiative energy (FRE); Smoke; MODIS; Emissions

Mechanism of formation of the heaviest pollution episode ever recorded in the Yangtze River Delta, China by Qingyan Fu; Guoshun Zhuang; Jing Wang; Chang Xu; Kan Huang; Juan Li; Bing Hou; Tao Lu; David G. Streets (pp. 2023-2036).

The heaviest aerosol pollution day in the historical record of the Yangtze River Delta occurred on 19 January 2007, in which the daily concentration of PM₁₀ reached 512μgm⁻³ in Shanghai, 463μgm⁻³ in Suzhou, 354μgm⁻³ in Hangzhou, and 282μgm⁻³ in Nanjing. The hourly concentrations of PM_2.5 and PM₁₀ reached peak values of 466 and 744μgm⁻³, respectively, in Shanghai. With visibility <0.6km, the regional haze covered nearly the entire Yangtze River Delta. High ratios of PM_2.5/PM₁₀ (61%), SO₂/PM₁₀ (0.38) and NO₂/PM₁₀ (0.24) were observed. The unusual stagnant dispersion conditions before a cold front played the predominant role in this high pollution episode, with relative humidity (RH) of 88%, both surface and upper-level inversions, as well as low wind speed (<1ms⁻¹). The sulfur oxidation rate (SOR) reached 0.67 and the nitrogen oxidation rate (NOR) reached 0.61, signifying that formation of sulfate and nitrate contributed significantly to the high secondary aerosol concentration of PM_2.5. The enrichment factors of As, Cd, and Pb reached 4058, 6971, and 3972, which were 4.45–6.68 times higher than those on good/moderate days. It was demonstrated that emissions from anthropogenic sources, especially stationary sources such as power plants, industrial boilers, and furnaces, were the major contributors to the heaviest aerosol pollution in the delta. More attention should be paid to the increases in emissions and the higher occurrence of haze days that have accompanied the rapid development of the economy in the Yangtze River Delta.

Keywords: Aerosol; Haze; Speciation; Shanghai; Yangtze River Delta

Concentrations, profiles and gas–particle partitioning of polychlorinated dibenzo- p-dioxins and dibenzofurans in the ambient air of Beijing, China by Yingming Li; Guibin Jiang; Yawei Wang; Zongwei Cai; Qinghua Zhang (pp. 2037-2047).

Polychlorinated dibenzo- p-dioxins (PCDDs) and furans (PCDFs) were monitored in the ambient air of Beijing, China, from February to December 2006 to evaluate their concentrations, congener profiles and gas–particle partitioning. The PCDD/F concentrations for three different districts ranged from 275 to 10,780fgm⁻³, with an average of 4355fgm⁻³. The I-TEQs were 18–644fgI-TEQm⁻³, with an average of 268fgI-TEQm⁻³, which was comparable or slightly higher than other urban locations around the world. Severe dust event occurred during the sampling period, on 17–19 April 2006. The levels of PCDD/Fs did not increase during the dust event (average 2489fgm⁻³) compared to non-dust events (average 3671fgm⁻³) although the total suspended particulates (1109μgm⁻³) presented a 2.8-fold increase compared to non-dust events (392μgm⁻³). The PCDD/Fs were found exclusively in the particle phase. Significant linear correlations for PCDD/Fs were observed ( R²: 0.57–0.64) between the gas–particle partition coefficient ( K_p) and the subcooled liquid vapor pressure (PL0). The Junge–Pankow model and the K_oa absorption model were employed to predict the gas–particle partitioning of PCDD/F congeners. The K_oa absorption model fitted well with the measurement results. However, the Junge–Pankow model slightly underestimated the particulate sorption of PCDD/Fs, which was contradicted with previous studies reported in the literature.

Keywords: PCDD/Fs; Ambient air; Beijing; Gas–particle partitioning; Dust event

Fog chemistry in the Texas–Louisiana Gulf Coast corridor by Suresh Raja; Ravikrishna Raghunathan; X.-Y. Xiao-Ying Yu; Taehyoung Lee; Jing Chen; Raghava R. Kommalapati; Karthik Murugesan; Xinhua Shen; Yuan Qingzhong; Kalliat T. Valsaraj; Jeffrey L. Collett Jr. (pp. 2048-2061).

Fog samples were collected in two population centers of the US Gulf Coast (Houston, Texas and Baton Rouge, Louisiana) using Caltech active strand cloud collectors. A total of 32 fogwater samples were collected in Baton Rouge (November 2004–February 2005) and Houston (February 2006). These samples were analyzed for pH, total and dissolved organic carbon, major inorganic ions, and a variety of organic compounds including organic acids, aromatics, carbonyls, and linear alkanes. Fogs in both environments were of moderate density, with typical fog liquid water contents <100mgm⁻³. Fog samples collected in Houston reflect a clear influence of marine and anthropogenic inputs, while Baton Rouge samples also reflect agricultural inputs. The volume-weighted mean fog pH was somewhat more acidic (∼4.3) in Houston than in Baton Rouge (∼5.0). A wide pH range was observed in fog at both locations. Houston fog had higher concentrations of Cl⁻, NO₃⁻, Na⁺, Mg²⁺, and Ca²⁺. Sulfate to nitrate ratios were high in fogs at both locations, typical of many clouds in the eastern US. Total organic carbon concentrations were much higher in Houston fogs than in Baton Rouge fogs. Efforts to speciate dissolved organic carbon (DOC) reveal large contributions from organic acids and carbonyls, with smaller contributions from other organic compound families including aromatics, alkanes, amides, and alcohols. Approximately 40% of the fog DOC was unspeciated in samples from both study locations.

Keywords: Gulf Coast; Fog; Organics; Sulfate; Air pollution; Aerosol

Comparison of particulate sulfate and nitrate at collocated CASTNET and IMPROVE sites in the eastern US by Joseph E. Sickles II; Douglas S. Shadwick (pp. 2062-2073).

Airborne concentration measurements of particulate SO₄²⁻ and NO₃⁻ from two networks, the Clean Air Status and Trends Network (CASTNET) and Interagency Monitoring of PROtected Visual Environments (IMPROVE) Network, are compared at 10 collocated sites in the eastern US for the period 1990 through fall of 2006. CASTNET samples are comprised one nominal 168-h sample per week versus 24-h IMPROVE samples collected twice a week or every third day. To permit comparison, CASTNET and IMPROVE concentration data are matched by week and composed into paired seasonal mean concentration values. CASTNET and IMPROVE seasonal mean SO₄²⁻ and NO₃⁻ concentrations are highly correlated, with respective correlation coefficients of 0.97 and 0.91. Two sites with marine influence display large median relative biases (MRBs) for NO₃⁻ (−42% and −102%) and smaller MRBs for SO₄²⁻ (−14% and −17%), indicating seasonal mean CASTNET concentrations to be biased higher than corresponding collocated values from IMPROVE at these two sites. Statistically significant median biases (MBs) and MRBs are present for comparisons of seasonal mean CASTNET and IMPROVE SO₄²⁻ concentrations, indicating seasonal mean CASTNET SO₄²⁻ concentrations to be biased 4–7% higher than collocated values from IMPROVE. Larger and more variable MRBs are present for comparisons of seasonal mean CASTNET and IMPROVE NO₃⁻ concentrations. For the 10 collocated sites considered in the current study, MRBs between site-specific seasonal mean CASTNET and IMPROVE NO₃⁻ concentrations range between 39% and −102%, and between 39% and −25% when marine sites are excluded. For the ensemble of all paired sites, the summertime MRB of 44% indicates that CASTNET NO₃⁻ concentrations are biased low, consistent with volatilization losses of particulate NO₃⁻ in the CASTNET sampler at high temperatures and low ambient NO₃⁻ concentrations that are typical during summer. These results should be considered prior to combining data from the CASTNET and IMPROVE (and possibly Chemical Speciation Network, CSN) networks for obtaining more aerially comprehensive representations of the atmosphere or for comparison with air quality model predictions. Biases in particulate SO₄²⁻ and NO₃⁻ concentrations from collocated CASTNET and IMPROVE sites are likely due in part to differences in the configurations of the samplers employed by the two networks (e.g., presence or absence of size-selective inlets).

Keywords: Collocated sampling intercomparison; Filter pack; CASTNET; IMPROVE; Particulate; Sulfate; Nitrate

Simulated effects of climate change on summertime nitrogen deposition in the eastern US by Kevin L. Civerolo; Christian Hogrefe; Barry Lynn; Cynthia Rosenzweig; Richard Goldberg; Joyce Rosenthal; Kim Knowlton; Patrick L. Kinney (pp. 2074-2082).

It is anticipated that climate change may impact regional-scale air quality and atmospheric deposition in the coming decades. To simulate the effects of climate change on nitrogen (N) deposition across numerous watersheds in the eastern US, we applied the NASA Goddard Institute for Space Studies General Circulation Model (GISS-GCM), Fifth Generation Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model (MM5), Sparse Matrix Operator Kernel Emissions (SMOKE) modeling system, and the US Environmental Protection Agency Community Multiscale Air Quality (CMAQ) Model. Keeping chemical initial and boundary conditions, land use, and anthropogenic area and point source emissions fixed, this modeling system was applied over five summers (June–August) from 1993 to 1997 and five summers from 2053 to 2057. Over these eastern US watersheds, the modeling system estimated 3–14% increases in summertime N deposition as a result of climate change. This increase is primarily due to the direct effects of climate change on atmospheric conditions and chemistry. Wet N deposition is predicted to increase as a result of increased precipitation, while dry N deposition is predicted to increase as higher surface temperatures favor gas-phase nitric acid to particulate nitrate. The simulated increase suggests that additional reductions in N oxides and/or ammonia may be needed to fully realize the anticipated benefits of planned reduction strategies, including the Clean Air Interstate Rule (CAIR).

Keywords: Atmospheric deposition; Climate change; CMAQ; MM5; Nitrogen

VOCs in industrial, urban and suburban neighborhoods, Part 1: Indoor and outdoor concentrations, variation, and risk drivers by Chunrong Jia; Stuart Batterman; Christopher Godwin (pp. 2083-2100).

Information regarding indoor and ambient concentrations and exposures of volatile organic compounds (VOCs) is limited in terms of the number and types of compounds measured, the spatial and temporal variation of concentrations, and the significance of indoor and outdoor emission sources. This study characterizes a wide range of VOCs across three communities that represent a gradient of population density and industrial activity. Monitoring was conducted in two seasons inside and outside of 159 residences in industrial, urban and suburban cities located in southeast Michigan, USA. Passive samplers were deployed at each location, and analyzed for 98 compounds. Outdoors, 46 different VOCs were detected. Benzene, toluene, p, m-xylene and carbon tetrachloride had the highest concentrations (medians from 1 to 2μgm⁻³). Concentrations were elevated in winter in the suburban community, and levels were the highest in the industrial community. Indoors, 53 VOCs were detected, and benzene, toluene, p, m-xylene, n-heptane, α-pinene and d-limonene had the highest concentrations (medians from 1 to 17μgm⁻³). Seasonal changes were small or inconsistent. Median indoor levels among the three communities generally followed outdoor rankings. Indoor/outdoor ratios varied from 1 to 10 for most compounds, but up to 100 for several compounds, e.g., d-limonene. Over a quarter of residences had benzene, naphthalene, chloroform and carbon tetrachloride at levels giving a chronic lifetime cancer risk above 10⁻⁵ and sometimes much higher; outdoors, these compounds gave risks exceeding 10⁻⁶. The study identifies a number of indoor emission sources associated with specific and sometimes very high VOC exposures, reports on several VOCs that have not been measured in previous indoor and outdoor studies, and shows the importance of both indoor and outdoor sources. Measured concentrations were at an intermediate level with respect to recent measurements elsewhere in the US, suggesting that study results are broadly representative.

Keywords: Indoor air; Ambient air; Benzene; Exposure; Emissions; Risk; Naphthalene; Seasonality; Volatile organic compounds

VOCs in industrial, urban and suburban neighborhoods—Part 2: Factors affecting indoor and outdoor concentrations by Chunrong Jia; Stuart Batterman; Christopher Godwin (pp. 2101-2116).

Many microenvironmental and behavioral factors can affect concentrations of and exposures to volatile organic compounds (VOCs). Identifying these determinants is important to understand exposures and risks, and also to design policies and strategies that minimize concentrations. This study is aimed at determining factors associated with VOC concentrations found indoors in residences and outdoors in ambient air. It utilizes results from a comprehensive field study in which 98 VOCs were measured both inside and outside of 159 residences in three communities in southeast Michigan, USA. Additional measurements included indoor CO₂ concentrations, temperature, relative humidity, building and neighborhood characteristics, and occupant activities, assessed using a questionnaire and comprehensive walkthrough investigation. Factors potentially affecting concentrations were identified using bivariate and multivariate analyses. Outdoors, seasonal and community effects were observed. Indoors, seasonal effects were limited to the urban and industrial communities, largely due to changes in ambient levels. Elevated indoor VOC concentrations were associated with eight sources or activities: the presence of an attached garage; recent renovations; older residences; indoor smoking; less frequent window or door opening; higher CO₂ concentrations; and lower ventilation rates. VOC levels were uninfluenced by building materials (wood vs. brick), flooring type (carpeting vs. wood), stove type (gas or electric), number of occupants, air freshener use, and hobbies involving arts and crafts. Factor analyses identified up to five factors for the ambient VOC measurements, and up to 10 factors for the indoor measurements, which further helped to explain the variability of concentrations and associations between VOCs.

Keywords: Ambient air; Apportionment; Factor analysis; Garage; Indoor air quality; Smoking; Ventilation; Risk; Seasonality; Volatile organic compound; VOC

Use of REMPI–TOFMS for real-time measurement of trace aromatics during operation of aircraft ground equipment by Brian Gullett; Abderrahmane Touati; Lukas Oudejans (pp. 2117-2128).

Emissions of aromatic air toxics from aircraft ground equipment (AGE) were measured with a resonance enhanced multiphoton ionization–time of flight mass spectrometry (REMPI–TOFMS) system consisting of a pulsed solid state laser for photoionization and a TOFMS for mass discrimination. This instrument was capable of characterizing turbine emissions and the effect of varying load operations on pollutant production. REMPI–TOFMS is capable of high selectivity and low detection limits (part per trillion to part per billion) in real time (1s resolution). Hazardous air pollutants and criteria pollutants were measured during startups and idle and full load operations. Measurements of compounds such as benzene, toluene, ethylbenzene, xylenes, styrene, and polycyclic aromatic hydrocarbons compared well with standard methods. Startup emissions from the AGE data showed persistent concentrations of pollutants, unlike those from a diesel generator, where a sharp spike in emissions rapidly declined to steady state levels. The time-resolved responses of air toxics concentrations varied significantly by source, complicating efforts to minimize these emissions with common operating prescriptions. The time-resolved measurements showed that pollutant concentrations decline (up to 5×) in a species-specific manner over the course of multiple hours of operation, complicating determination of accurate and precise emission factors via standard extractive sampling. Correlations of air toxic concentrations with more commonly measured pollutants such as CO or PM were poor due to the relatively greater changes in the measured toxics’ concentrations.

Keywords: Aircraft ground equipment; Emissions; Auxiliary power unit; REMPI; Aromatic air toxics; Hazardous air pollutants; Measurement; REMPI–TOFMS; Real time; Diesel generator

Particulate emissions by a small non-road diesel engine: Biodiesel and diesel characterization and mass measurements using the extended idealized aggregates theory by A. Chung; A.A. Lall; S.E. Paulson (pp. 2129-2140).

Particulate emissions from a 4.8-kW diesel generator running on ultra-low sulfur diesel and biodiesel fuels are characterized as a function of engine load. Number distributions measured by a scanning mobility particle sizer (SMPS) show that particle mobility diameters rise with increasing engine loads. The elemental carbon (EC) to organic carbon (OC) ratio, measured by thermo-optical transmission evolved gas analysis, with careful attention to avoid OC sampling artifacts, increases from about 0.5 at idle load to 3.8 at 100% load when using diesel fuel. Transmission electron microscopy (TEM) images of the particles showed that at idle, the particles were liquid droplets together with a few aggregates. When a load was applied, the droplets were replaced by chain aggregates, which had a mean primary particle size of 29±9nm at 100% load. Fractal dimension averaged 1.63±0.13, consistent with much larger diesel engines emissions reported in the literature. The use of biofuel (B100) results in emissions of particles that are compact, irregular, and lack the clearly defined primary particles of diesel aggregates, and yet at maximum load they have similar EC and OC content as diesel particles. The accuracy of the idealized aggregate (IA) theory correction and its extension to the transition regime [Lall, A.A., Friedlander, S.K., 2006. On-line measurement of ultrafine aggregate surface area and volume distributions by electrical mobility analysis: 1. Theoretical analysis. Journal of Aerosol Science 37, 260–271] was tested as a method to obtain mass distributions for diesel aggregates using and SMPS. The total mass concentrations calculated from the SMPS measurements using the extended IA theory are in good agreement with the mass concentrations obtained from gravimetric and EC/OC measurements. The loss of aggregates in the TSI SMPS inlet impactor is also discussed.

Keywords: SMPS; Organic carbon artifact; EC/OC ratio; Biodiesel; Chain aggregates; Impactor losses

Mixing of mineral with pollution aerosols in dust season in Beijing: Revealed by source apportionment study by Hui Yuan; Guoshun Zhuang; Juan Li; Zifa Wang; Jie Li (pp. 2141-2157).

A detailed systematic aerosol source apportionment study was performed with two intensive sampling campaigns in the spring dust storm seasons of 2001 and 2002 in Beijing, China. The concentrations of 23 elements and 15 ions and the total mass in 115 total suspended particulate (TSP) samples were measured. Combining enrichment factors, elemental signatures, back trajectory analysis, bilinear positive matrix factorization (PMF2) analysis with the meteorological pattern, the mixing of mineral aerosol with pollution aerosol and their apportionments in different dust episodes were elucidated. Ca/Al was proved to be a good signature to trace different dust origin areas. Soil dust, road dust, secondary, industrial/coal combustion, salts, phosphates, nitrites, and oil combustion were identified by PMF to be the eight main sources. Soil dust (from outside) increased sharply when cold front intruded Beijing in dust events (∼80–95% of total dust), which neutralized local acidic aerosol. Road dust (from local by re-suspension) contributed 15–30% of the total TSP. Intruded dusts brought lots of sulfate (from soil containing high-S or from pollutants introduced on the pathway) but little nitrate. The secondary sulfate/nitrate and the total pollutants contributed 25% and 40–50%, respectively, of the TSP in those dust episodes, which were transported in lower layer and mixed strongly with local re-suspended pollution aerosols. Sulfur/Nitrogen oxidation ratios in dust storms and in non-dust storms were <2% and 10–40%, respectively, and had a little jumps just after dust peaks, which indicated that dust provided a good basic surface for the heterogeneous reactions.

Keywords: Source apportionment; Dust; Aerosol; TSP; PMF; Beijing

Nighttime residential wood burning evidenced from an indirect method for estimating real-time concentration of particulate organic matter (POM) by J. Sciare; Sarda-Esteve R. Sarda-Estève; O. Favez; H. Cachier; G. Aymoz; P. Laj (pp. 2158-2172).

Real-time analyzers of selected chemical components (sulfate, nitrate, Black Carbon) and integrative aerosol parameters (particulate matter and light scattering coefficient) were implemented for a 2-week campaign (November–December 2005) in a suburban area of Clermont-Ferrand (France) in order to document fast changes in the chemical composition of submicron aerosols. Measurements of particulate organic matter (POM) were not available in the field but were indirectly estimated from time-resolved (3-min) reconstruction of the light scattering coefficient. This methodology offered the opportunity to investigate almost real-time and artifact-free POM concentrations even at low concentrations (typically below 0.1μgm⁻³). The overall uncertainties associated with this POM calculation were of the order of 20%, which are comparable to those commonly referred in literature for POM calculation or measurements. A chemical mass balance (CMB) of PM₁ was performed using the derived POM concentrations and showed a very good correlation (slope=0.93; r²=0.91, N=663) with real-time PM₁ measurements obtained from R&P TEOM-FDMS, demonstrating the consistency of our approach. Important diurnal variations were observed in POM concentrations, with a dominant contribution of POM from fossil fuel origin during daytime and a dominant contribution of POM from residential wood burning at night. POM was calculated to contribute as much as 70% of PM₁ during our study, pointing out the major role of carbonaceous aerosols at this period of the year at our residential area.

Keywords: Organic aerosols; Light scattering; Chemical mass balance; Artifact; PM; ₁; Combustion aerosols

Size and composition of particulate emissions from motor vehicles in the Kaisermühlen-Tunnel, Vienna by Markus Handler; Christoph Puls; Johannes Zbiral; Iain Marr; Hans Puxbaum; Andreas Limbeck (pp. 2173-2186).

Size segregated emissions of particle-phase species from on-road motor vehicles were investigated in the Kaisermühlen Tunnel (Vienna, Austria) during April and May 2005. Emission factors were calculated from concentration differences between tunnel inside and tunnel outside samples, the distance between tunnel entrance and sampling location, the ventilation rate and the number of vehicles passing the tunnel. For a mixed car fleet with an average contribution of 9.6% heavy duty vehicles (HDVs) mean particle mass emissions of 26±10mgveh⁻¹km⁻¹ in PM2.5, 62±18mgveh⁻¹km⁻¹ in PM10 and 129±45mgveh⁻¹km⁻¹ for total suspended particulates (TSPs) were observed. The released particles mainly consisted of elemental carbon (EC), organic carbon (OC) and the mineral components (MC=Si, Fe, Ca, Al, Mg). They accounted for 34.4% (EC), 30.3% (OC) and 18.2% (MC) of total PM10 emissions and 68.5%, 8.7% and 14.9% of PM2.5 emissions, respectively. Trace metal emissions (As, Ba, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sb, Sn, Sr, Ti, V, Zn) contributed for less than 1% of total emissions in all size fractions. Emissions of coarse particles were found to be dominated by resuspended matter as well as by brake wear, whereas fine particles were mainly derived from combustion processes. On weekends for some components distinctly reduced emissions were observed which could be explained with changes in the driving conditions and/or fleet composition.

Keywords: Particulate motor vehicle emissions; Size segregated emission rates; Trace metals; Tunnel study; HDV; LDV

Evaluation of MODIS aerosol optical thickness over Europe using sun photometer observations by M. Schaap; R.M.A. Timmermans; R.B.A. Koelemeijer; G. de Leeuw; P.J.H. Builtjes (pp. 2187-2197).

Satellite retrieved aerosol optical thickness (AOT) may be useful to improve the insight in PM distributions in Europe in combination with models and ground-based measurements. To use AOT in mapping or assimilation experiments, it requires well-validated satellite data. We have compared the AOT retrieved by MODIS (collection 4) to sun photometer data from the AERONET network in Europe and found a good temporal correlation between MODIS and AERONET. However, we also found a large positive bias of about 50% in the MODIS AOT data, which is in accordance with earlier findings. We highlight the strong seasonal signature in the overestimation of AOT by MODIS with a maximum during summer. After correction for the bias, the accuracy of MODIS AOT retrievals agrees with reported uncertainties and the residuals show a normal distribution. We have introduced a simple method for the evaluation of the possible extent of cloud contamination and hypothesise that on average, up to one-third of the MODIS retrievals may be cloud contaminated. For some stations in central Europe, this percentage was found to be larger than >50%. The consequences of a bias between satellite and in situ data for their use in the mapping of aerosol levels are discussed.

Keywords: Aerosol optical thickness; Europe; Remote sensing; Verification

Magnetic properties of urban dustfall in Lanzhou, China, and its environmental implications by D.S. Xia; F.H. Chen; J. Bloemendal; X.M. Liu; Y. Yu; L.P. Yang (pp. 2198-2207).

Lanzhou has been one of the most seriously polluted cities in the world due to its special geographical location, weather conditions and large amount of emissions from coal-fired factories. These factors make it an ideal place for urban particulate pollution study. In this study, a set of environmental magnetic parameters ( χ_lf, χ_fd%, χ_ARM, saturation isothermal remanent magnetization (SIRM), HIRM, SOFT and backfield IRM) were measured on dustfall samples collected monthly during April 1997–May 2000 and November 2004–October 2005 at the Lanzhou University campus (KLD). Results show that the magnetic assemblage in the dustfall is dominated by pseudo-single domain (PSD) magnetite associated with maghaemite and haematite. Anthropogenic activities (mainly from coal burning) are the main sources for urban particulate pollutants in Lanzhou. The great efforts of the government and local authority in reducing local industrial and domestic emissions during the past several decades has led to improved air quality in winter in Lanzhou; however, the air quality in summer has not been significantly improved.

Keywords: Environmental magnetism; Dustfall; Amend pollution; Lanzhou

Seasonal characteristics of lidar ratios measured with a Raman lidar at Gwangju, Korea in spring and autumn by Young M. Noh; Young J. Kim; Muller Detlef Müller (pp. 2208-2224).

Vertical profiles of aerosol lidar ratios at wavelengths of 355 and 532nm were measured with the GIST/ADEMRC (Gwangju Institute of Science & Technology/ADvanced Environmental Monitoring Research Center) multi-wavelength Raman lidar system at Gwangju, Korea (35.10°N, 126.53°E) during several observation periods between February 2004 and May 2005. The total number of observed aerosol layers was 63, of which 38 and 25 were observed in spring and autumn, respectively. Average values of the lidar ratio, S_a, were 55±10sr and 56±9sr at 355 and 532nm, respectively, in spring and 61.4±7.5sr and 63.1±12.8sr at 355 and 532nm, respectively, in autumn. Cases of high lidar ratio values (>65sr) were observed more frequently in autumn than in spring for 28% and 46% of the time at 355 and 532nm, respectively. Mean lidar ratio value of 51±6sr at 532nm was obtained for Asian dust particles in spring which was lower than those for non-dust (60±10sr) and smoke (65±8sr) particles. Very high lidar ratios of 75.3±15.8sr at 532nm were observed above the planetary boundary layer (PBL) in autumn. These high values are believed to have largely resulted from an increased amount of light-absorbing particles mostly in the fine mode of the particle size distribution, generated by coal combustion and agricultural biomass burning. Lidar ratios, Ångström exponents and effective radii values retrieved from collocated sunphotometer data were similar to those obtained from Raman lidar measurements.

Keywords: Lidar ratio; Ångström exponent; Raman lidar; Sunphotometer

Indoor air quality and its determinants in tropical child care centers by M.S. Zuraimi; K.W. Tham (pp. 2225-2239).

This cross-sectional study aims to investigate indoor pollutants concentrations in child care centers (CCCs) and evaluate their determinants involving representative samples in Singapore. Measurements were performed for air temperature, relative humidity, air velocity, ventilation rates, carbon dioxide, carbon monoxide, ozone, fine particle mass, bacteria and fungi while information on CCC characteristics and maintenance activities were collected via a combination of inspection and interviews. It was found that due to higher ventilation rates, indoor CO₂ concentration levels were lower in Singapore CCCs compared to those in the cold climates. Determinants of indoor pollutant levels from outdoor and indoor sources and maintenance activities were evaluated with regression analyses based on mass balance principles. Indoor carbon dioxide was positively associated with outdoor concentrations and occupant density while only outdoor levels significantly determined indoor carbon monoxide concentrations. For PM_2.5, outdoor concentration, carpeted floor, presence of curtains and soft toys, recent renovation, shelf area and fan cleaning frequencies were positively associated with indoor levels while determinants of indoor ozone include outdoor concentration, shelf area and table cleaning. Increased human related bacteria levels were associated with high occupant densities and irregular floor but regular table cleaning frequencies. Outdoor concentration, curtain types and floor cleaning were significant determinants for environmental bacteria. Outdoor concentrations, presence of dampness, irregular floor and fan cleaning were associated with increased indoor mesophilic fungi levels. For indoor xerophilic fungi, levels were associated with outdoor concentrations, curtain types, dampness, occupant density and floor cleaning. We conclude that our findings confirm the important influence of indoor sources and maintenance activities on indoor concentrations of pollutants in Singapore CCCs. Future epidemiological analyses in CCCs should consider these determinants in classifying exposures as surrogate indicators of sources and cleaning activities.

Keywords: Indoor air quality (IAQ); Determinants; Child care centers (CCC); Tropics; Sources; Cleaning

A mass closure and PMF source apportionment study on the sub-micron sized aerosol fraction at urban sites in Italy by R. Vecchi; M. Chiari; A. D’Alessandro; P. Fermo; F. Lucarelli; F. Mazzei; S. Nava; A. Piazzalunga; P. Prati; F. Silvani; G. Valli (pp. 2240-2253).

Sub-micron sized particles are of increasing concern owing to their effects on human health and on the environment. Up to now there are still very few studies on PM1 (i.e. particulate matter with aerodynamic diameter smaller than 1μm) chemical characterisation; the sub-micron sized fraction is not under regulations although it is of interest because it is almost exclusively associated to anthropogenic sources. To perform the first large-scale assessment of sub-micron sized aerosol concentrations, composition and sources, two monitoring campaigns at three urban sites in Italy were carried out during the wintertime and summertime of 2004.Chemical characterisation (elements, soluble ionic fraction, elemental and organic carbon) was carried out on PM1 samples: major contributions were due to organic matter (about 30% in summer and 50% in winter) and ammonium sulphate (about 10% in winter and 40% in summer). During the cold season, nitrates also contributed up to 30% in Milan (lower contributions were registered at the other two urban sites). Chemical mass closure was achieved with an unaccounted mass in the range 14–22%. Positive Matrix Factorisation (PMF) was applied to identify the major sub-micron sized particles’ sources.

Keywords: PM1; Mass closure; Source apportionment; Urban sites; PMF

Natural radioactivity in common building construction and radiation shielding materials by R.G. Sonkawade; K. Kant; S. Muralithar; R. Kumar; R.C. Ramola (pp. 2254-2259).

Commonly used building construction materials, radiation shielding bricks, hematite aggregate and other materials have been analyzed for the activity concentration of the natural radionuclides, namely²³⁸U,²³²Th and⁴⁰K, besides the radon exhalation rates. The activity concentration for²³⁸U,²³²Th and⁴⁰K varies from 29±1 to 98±4Bqkg⁻¹, 20±2 to 112±2.8Bqkg⁻¹, and 200±8 to 1908±15.6Bqkg⁻¹, respectively, in various materials studied in the present work. Radon activity in the various samples varies from 190±11 to 313±14Bqm⁻³, the mass exhalation rate for radon varies from 1.05±0.07 to 1.92±0.09mBqkg⁻¹h⁻¹ and surface exhalation rate varies from 9.0±0.30 to 19.8±22mBqm⁻²h⁻¹ for materials under investigation. The activity concentrations of uranium, thorium and potassium and radon exhalation rates vary from material to material. Thorium and potassium activity in the granite materials is higher, followed by radiation shielding material compared to other common construction materials. Uranium activity concentration is higher in cement as compared to radiation shielding material and other common construction materials. The absorbed dose varies from 23 to 185nGyh⁻¹ and the indoor annual effective dose varies from 0.11 to 0.91mSv. The outdoor annual effective dose varies from 0.03 to 0.23mSv. The absorbed dose and the effective dose equivalent are found to be higher in the granite, followed by radiation shielding material and other common construction materials. In all the samples, the activity concentration of²³⁸U,²³²Th and⁴⁰K is found below the permissible levels. A strong correlation coefficient has been observed between radon activity and surface exhalation rate (correlation coefficient=0.899).

Keywords: Radon; Thoron; Uranium; Radium; Thorium; Potassium; Exhalation rate; Health

Sections

Personal tools

Atmospheric Environment (v.42, #9)

Sections

Personal tools

Local resources

Atmospheric Environment (v.42, #9)