Atmospheric Environment (v.42, #5)
Editorial board (i).
Accumulation histories of major and trace elements on pine needles in the Cologne Conurbation as function of air quality by E. Lehndorff; L. Schwark (833-845).
For a biomonitoring study in the greater Cologne area, we analyzed the accumulation of major and trace elements on Pinus nigra needles. At six sites, samples were collected separately in summer and winter 2004 from five needle generations (n=51). The elements Ba, Ca, Cd, Fe, Mo, Na, Pb, Sb, Ti, V, and Zr were determined by HR-ICP-MS and normalized to upper continental crust concentration using rare earth elements (REE). Inter-site variability was significantly higher than intra-site variability allowing for reliable source allocation. A systematic and steady increase in element loads with exposure was noted, with a seasonal trend superimposed on Pb, Cd, Na, and REE. Normalization onto lithogenic REE removes seasonal variability due to dust loadings. Enrichment factors for V, Fe, and Zr reveal the most pronounced summer/winter variability. The average enrichment factors were 967 for Sb, 620 for Cd, 176 for Mo, 33 for Pb and between 3 and 5 for Ba, Fe, Na, and V, wheras Ti and Zr gave enrichment factors <1. Most reliable as source indicators were REE for lithogenic dust, Sb, Fe, V for traffic, Mo and Pb for petrochemical emissions, and Cd for mining activity. Barium proved unsuitable as traffic indicator in the Cologne Conurbation area. Accumulation trends of major and trace elements on P. nigra needles confirm that these passive samplers are suitable for atmospheric quality analysis in areas with multiple emission sources.
Keywords: Pinus nigra; Biomonitoring; Atmospheric pollution; Enrichment factors; Cologne Conurbation;
Changes in rainwater composition in Wilmington, NC during tropical storm Ernesto by Carrie Miller; Joan D. Willey; Robert J. Kieber (846-855).
Tropical weather events can contribute large wet depositional fluxes of biogeochemically important rainwater constituents over relatively short time periods. One composite sample during these events does not capture the dynamic nature of rainwater composition and can lead to misinterpretation of the impact of tropical events on local aquatic systems. Eight sequential samples were collected at 2–3 h intervals in Wilmington, NC during the duration of tropical storm Ernesto to examine a suite of rainwater constituents influenced by gas phase, aerosol, or mixed sources in the atmosphere. Real time wind speed and air mass back trajectories were used to examine the progression of the storm. Hydrogen peroxide and nitrate displayed washout trends during the storm. Dissolved organic carbon (DOC), hydrogen ion (H+), and total mercury (HgT) displayed washout at the beginning of the storm but toward the end of the storm concentrations increased, which corresponded to a shift in air masses from marine to terrestrial, increased ground air mass influence, and increased wind speeds. Integrated fluorescence, a measure of the chromophoric properties of the DOC, was highest at the beginning of the storm and than decreased but unlike DOC, the fluorescence did not increase at the end of the storm, indicating a change in the DOC source and composition during the storm. Chloride and sulfate, which are strongly influenced by seasalt aerosols, increased with increasing wind speeds. Factors such as wind speed, storm trajectory, and rainwater volume influenced rainwater constituent concentrations; the relative importance of these factors was a function of the sources of these rainwater constituents in rainwater.
Keywords: Tropical storm; Hydrogen peroxide; Anions; Dissolved organic matter; Mercury;
Photooxidation of dicarboxylic acids—Part I: Effects of inorganic ions on degradation of azelaic acid by Liming Yang; Madhumita B. Ray; Liya E. Yu (856-867).
In this paper, the first of a two-part series, effects of chloride, sulfate, and nitrate ions and pH on photooxidation of azelaic acid were investigated in an aqueous system. Nitrate ions play the major role in accelerating photooxidation of azelaic acid by increasing •OH concentration, while chloride ions consume •OH concentration and retard photooxidation rates. In inorganic mixtures, a nitrate-to-chloride molar ratio of >1.5 accelerated photooxidation of azelaic acid indicating the dominant role of nitrate. Substantial inhibition effects of chloride on photooxidation of azelaic acid were demonstrated at a nitrate-to-chloride molar ratio <0.3. Nitrate and chloride are interrelated in affecting photooxidation of azelaic acid as photolysis of nitrate would significantly consume H+, retarding reaction of HOCl− with H+, and consequently decreasing •OH-chloride reaction. pH affects photooxidation of C2–C9 dicarboxylic acids (DCAs) in two ways: C2–C4 dicarboxylates exhibit substantially higher degradation rates than their parent DCAs, while C5–C9 dicarboxylates demonstrate degradation rates similar to their parent DCAs.
Keywords: Dicarboxylic acid; Azelaic acid; Photooxidation; Inorganic species; Ionic strength;
Photooxidation of dicarboxylic acids—Part II: Kinetics, intermediates and field observations by Liming Yang; Madhumita B. Ray; Liya E. Yu (868-880).
Among C2–C9 dicarboxylic acids (DCAs), succinic acid (C4 DCA) exhibits the lowest photooxidation rate, while oxalic acid has the highest photooxidation rate in a liquid-phase reaction system. Twenty-seven identified intermediates are classified into six classes: secondary DCAs, oxo-DCAs, methyl-DCAs, hydroxy-DCAs, hydroxy-monocarboxylic acids (hydroxy-MCAs), and oxo-MCAs. Concentration profiles of the identified intermediates affirm two hypotheses: (1) longer DCAs can be the precursors of shorter DCAs and (2) succinic acid can be oxidized to malonic acid with malic acid as an intermediate. Ambient DCAs can also be precursors of substituted DCAs and MCAs; methyl-, oxo-, and hydroxy-substituents consistently position at the center carbon of the base DCA molecules, while hydroxy- and oxo-substituents favor the ω or (ω−1) position of the base MCAs. A comparison of field observations with the experimental data obtained in this study indicates that oxo-DCAs, having a higher concentration than methyl- and hydroxy-DCAs in ambient particulates, may characterize an atmosphere under prevailing photooxidation with little influence of anthropogenic pollution.
Keywords: Dicarboxylic acid; Photooxidation; Hydroxyl radical; Reaction pathway;
Comparison of two cluster analysis methods using single particle mass spectra by Weixiang Zhao; Philip K. Hopke; Kimberly A. Prather (881-892).
Cluster analysis of aerosol time-of-flight mass spectrometry (ATOFMS) data has been an effective tool for the identification of possible sources of ambient aerosols. In this study, the clustering results of two typical methods, adaptive resonance theory-based neural networks-2a (ART-2a) and density-based clustering of application with noise (DBSCAN), on ATOFMS data were investigated by employing a set of benchmark ATOFMS data. The advantages and disadvantages of these two methods are discussed and some feasible remedies proposed for problems encountered in the clustering process. The results of this study will provide promising directions for future work on ambient aerosol cluster analysis, suggesting a more effective and feasible clustering strategy based on the integration of ART-2a and DBSCAN.
Keywords: Aerosol time-of-flight mass spectrometer; Single particle; Density-based cluster analysis; Adaptive resonance theory neural networks; Source identification;
Volcanic dust characterization by EARLINET during Etna's eruptions in 2001–2002 by X. Wang; A. Boselli; L. D’Avino; G. Pisani; N. Spinelli; A. Amodeo; A. Chaikovsky; M. Wiegner; S. Nickovic; A. Papayannis; M.R. Perrone; V. Rizi; L. Sauvage; A. Stohl (893-905).
Lidar measurements were performed in the framework of the EARLINET project during the last eruptions (July–August 2001 and November 2002) of the Etna volcano. Both aerosol backscattering and extinction coefficients show the presence of remarkable aerosol layers in central and especially in southern Europe during the Etna eruptions periods. The aerosol layer altitudes ranged from 1 to 6 km. Back-trajectory, lidar ratio and backscatter related Angstrom coefficient analyses show that most of the aerosol layers originated from the Etna eruption and were made of sulfates and small absorbing volcanic ash. Thanks to the EARLINET network, the space and temporal distributions of volcanic aerosol have been studied over continental scale.
Keywords: Lidar; Mt. Etna; Lidar network; Volcanic aerosol; Aerosol transportation model;
Effects of the biodiesel blend fuel on aldehyde emissions from diesel engine exhaust by Chiung-Yu Peng; Hsi-Hsien Yang; Cheng-Hang Lan; Shu-Mei Chien (906-915).
Interest in use of biodiesel fuels derived from vegetable oils or animal fats as alternative fuels for petroleum-based diesels has increased due to biodiesels having similar properties of those of diesels, and characteristics of renewability, biodegradability and potential beneficial effects on exhaust emissions. Generally, exhaust emissions of regulated pollutants are widely studied and the results favor biodiesels on CO, HC and particulate emissions; however, limited and inconsistent data are showed for unregulated pollutants, such as carbonyl compounds, which are also important indicators for evaluating available vehicle fuels. For better understanding biodiesel, this study examines the effects of the biodiesel blend fuel on aldehyde chemical emissions from diesel engine exhausts in comparison with those from the diesel fuel. Test engines (Mitsubishi 4M40-2AT1) with four cylinders, a total displacement of 2.84 L, maximum horsepower of 80.9 kW at 3700 rpm, and maximum torque of 217.6 N m at 2000 rpm, were mounted and operated on a Schenck DyNAS 335 dynamometer. Exhaust emission tests were performed several times for each fuel under the US transient cycle protocol from mileages of 0–80,000 km with an interval of 20,000 km, and two additional measurements were carried out at 40,000 and 80,000 km after maintenance, respectively. Aldehyde samples were collected from diluted exhaust by using a constant volume sampling system. Samples were extracted and analyzed by the HPLC/UV system. Dominant aldehydes of both fuels’ exhausts are formaldehyde and acetaldehyde. These compounds together account for over 75% of total aldehyde emissions. Total aldehyde emissions for B20 (20% waste cooking oil biodiesel and 80% diesel) and diesel fuels are in the ranges of 15.4–26.9 mg bhp-h−1 and 21.3–28.6 mg bhp-h−1, respectively. The effects of increasing mileages and maintenance practice on aldehyde emissions are insignificant for both fuels. B20 generates slightly less emission than diesel does. Major difference in both fuels is formaldehyde emission which drops by 23% on the average. Lower aldehyde emissions found in B20 correspond to lower ozone formation potentials. As a result, use of biodiesel in diesel engines has the beneficial effect in terms of aldehyde emissions.
Keywords: Biodiesel; Aldehyde emissions; Durability test; Ozone formation potential;
Improved road traffic emission inventories by adding mean speed distributions by Robin Smit; Muriel Poelman; Jeroen Schrijver (916-926).
Does consideration of average speed distributions on roads—as compared to single mean speed—lead to different results in emission modelling of large road networks? To address this question, a post-processing method is developed to predict mean speed distributions using available traffic data from a dynamic macroscopic traffic model (Indy) that was run for an actual test network (Amsterdam). Two emission models are compared: a continuous (COPERT IV) and a discrete model (VERSIT+macro). Computations show that total network emissions of CO, HC, NO x , PM10 and CO2 are generally (but not always) increased after application of the mean speed distribution method up to +9%, and even up to +24% at sub-network level (urban, rural, motorway). Conventional computation methods thus appear to produce biased results (underestimation). The magnitude and direction of the effect is a function of emission model (type), shape of the composite emission factor curve and change in the joint distribution of (sub)-network VKT (vehicle kilometres travelled) and speed. Differences between the two emission models in predicted total network emissions are generally larger, which indicates that other issues (e.g., emission model validation, model choice) are more relevant.
Keywords: Emission inventory; Speed variability; Road traffic; Emission model; Road network; Accuracy;
Speciation of atmospheric mercury at two sites in northern Nevada, USA by Seth N. Lyman; Mae Sexauer Gustin (927-939).
Gaseous elemental mercury (Hg0), reactive gaseous mercury (RGM), and mercury bound to particles (Hgp) were measured during seasonal 1- or 2-week data collection campaigns at two Mercury Deposition Network sites (NV02 and NV99) in northern Nevada, USA. The sites are rural but are located in an area of diverse natural and anthropogenic mercury sources that include undisturbed and mining mercury-disturbed enriched substrates, coal-fired power plants, ore processing facilities, and industrial facilities. Concentrations of Hg0 averaged over all campaigns were 3.0±1.7 ng m−3 at NV02 and 2.5±3.1 ng m−3 at NV99, higher than has been reported for other rural sites. Hg0 concentrations at the sites were found to be influenced by both local substrate emission and transport from regional source areas. Concentrations of RGM and Hgp were within ranges reported for other rural sites (13±18 and 9±7 pg m−3 at NV02, 7±8 and 13±12 pg m−3 at NV99, respectively). Mercury wet deposition rates measured over 3 years (2003–2005) were similar to other sites in the arid West (3.0±0.7 μg m−2 yr−1 at NV02, 3.9±0.4 μg m−2 yr−1 at NV99).
Keywords: Mercury; RGM; Source; Deposition; Nevada;
Emissions of PCDDs/DFs and dioxin-like PCBs from small waste incinerators in Korea by Ki-In Choi; Suk-Hui Lee; Dong-Hoon Lee (940-948).
This study investigated dioxins in gasses emitted from 50 small waste incinerators in Korea. The concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/DFs) ranged from 0.05 to 609.27 ng TEQ N m−3, and those of dioxin-like polychlorinated biphenyls (PCBs) ranged from 0.02 to 188.46 ng TEQ N m−3. The incineration of 1 ton of waste emitted, on average, 1302.4 μg of PCDDs/DFs and 26.4 μg of dioxin-like PCBs from small municipal waste incinerators and 830.8 μg of PCDDs/DFs and 27.3 μg of dioxin-like PCBs from small hazardous waste incinerators. These values are much higher than those for large incinerators, probably reflecting factors such as poor performance by air pollution control devices, discontinuous operation, and irregular waste feeding. Principal component analysis classified the congener distribution of dioxins from small incinerators into several patterns. In particular, a pattern consisting of a high proportion of dioxin-like PCBs and low proportion of PCDDs/DFs was common for small incinerators but not typical of large incinerators.
Keywords: Small incinerator; PCDDs/DFs; Dioxin-like PCBs;
Atmospheric fate of nuclei-mode particles estimated from the number concentrations and chemical composition of particles measured at roadside and background sites by Akihiro Fushimi; Shuichi Hasegawa; Katsuyuki Takahashi; Yuji Fujitani; Kiyoshi Tanabe; Shinji Kobayashi (949-959).
Number concentrations and size-resolved chemical compositions of atmospheric particles at a roadside site in Kawasaki City, Japan, and a background site 200 m away were measured in winter to estimate the atmospheric fate of nuclei-mode particles emitted from vehicles. Measurements with a scanning mobility particle sizer showed a sharp peak in nuclei-mode particles with a modal diameter of around 0.020 μm at the roadside site; in contrast, no peak for nuclei-mode particles was observed at the background site. For chemical analysis, size-resolved particles were sampled by low-pressure impactors. Carbon analysis suggested that diesel exhaust particles contributed to both the roadside and background Stage 1 (S1; 0.030–0.060 μm) particles. The ratios of organic carbon (OC) to total carbon (TC) increased for smaller particles, and were 28% and 51% for the roadside and the background S1 particles, respectively. It is likely that the OC/TC ratio for nuclei-mode particles was larger than for the S1 particles, and that OC was one of the major constituents of the nuclei-mode particles at the roadside site. From this result and the greater Kelvin effect for smaller particles, it is likely that nuclei-mode particles in the roadside atmosphere are more volatile than the S1 particles. Organic analysis of the size-resolved particles suggested that lubricating oil from vehicles affected the organic composition of both the roadside and background S1 particles, and that C33 n-alkane and more volatile organic compounds in the S1 particles partially evaporated in the atmosphere following the emission of the particles from diesel vehicles. It is likely that evaporation of the constituents (or possibly coagulation with pre-existing particles after shrinking by partial evaporation) of the nuclei-mode particles in the atmosphere was responsible for the absence of nuclei-mode particles in the background atmosphere.
Keywords: Nanoparticles; Diesel exhaust particles (DEP); Carbonaceous compounds; Organic compounds; TD–GC/MS;
Heterogeneous reactivity of carbonyl sulfide on α-Al2O3 and γ-Al2O3 by Yongchun Liu; Hong He; Yujing Mu (960-969).
The heterogeneous reactions of trace gases in the atmosphere on atmospheric particles could greatly affect the nitrogen, sulfur, ozone, and photochemical oxidant cycles. The uptake coefficient is an important kinetic parameter for atmospheric models to assess the role of heterogeneous reaction in the global cycles of trace gases. In this study, the heterogeneous uptake coefficients of carbonyl sulfide (OCS) on Al2O3 have been measured using a Knudsen cell reactor at 300 K. Hydrogen sulfide (H2S) and carbon dioxide (CO2) were found to be the gaseous products. The reaction mechanism of OCS on Al2O3 was confirmed based on previous work and this study. The true initial uptake coefficient and steady-state uptake coefficient of OCS on α-Al2O3 were (3.8±0.8)×10−7 and (6.5±2.49)×10−8, and the corresponding uptake coefficients on γ-Al2O3 were (7.0±0.7)×10−8 and (1.8±0.4)×10−8, respectively. The annual flux of OCS due to heterogeneous reaction on α-Al2O3 was calculated to be 0.11–0.63 Tg yr−1 based on the initial uptake coefficient and the steady-state uptake coefficient. When the fraction of Al2O3 in authentic atmospheric particles is taken into account, the annual flux of OCS due to heterogeneous reaction on atmospheric particles in the troposphere should be 0.02–0.10 Tg yr−1.
Keywords: Heterogeneous reactivity; Carbonyl sulfide; Al2O3; Global flux; Knudsen cell;
Total gaseous mercury concentrations in ambient air in the eastern slope of Mt. Gongga, South-Eastern fringe of the Tibetan plateau, China by Xuewu Fu; Xinbin Feng; Wanze Zhu; Shaofeng Wang; Julia Lu (970-979).
During May 2005–June 2006, measurements of total gaseous mercury (TGM) concentrations were carried out by using a set of automatic atmospheric mercury vapor analyzer (Tekran 2537A) at Moxi base station (102°07′E, 29°40′N, 1640 m a.s.l.) of the Gongga alpine ecosystem observation and experiment station of Chinese academy of sciences (CAS) which belongs to the Chinese ecosystem research network (CERN). A seasonal distribution pattern of TGM in ambient air was observed on the descending order of winter, fall, spring, and summer. Geometric mean TGM concentration over the sampling periods was 3.98 ng m−3 with a range from 0.52 to 21.03 ng m−3. The measurements showed a noticeable diurnal TGM distribution pattern with high concentration during daytime compared to nighttime; the maximum and the minimum concentration appeared near solar noon and immediately before sunrise, respectively. TGM concentrations were regulated by the wind directions, and wind from the southeastern direction carried more mercury than any other direction suggesting that anthropogenic sources, such as local zinc smelting activities and fuel combustion, played a predominant role in the elevation of TGM concentrations in this area.
Keywords: Total gaseous mercury (TGM); Atmosphere; Mt. Gongga; Southwest of China;
Pragmatic mass closure study for PM1.0, PM2.5 and PM10 at roadside, urban background and rural sites by Jianxin Yin; Roy M. Harrison (980-988).
Airborne particulate matter in the PM10, PM2.5 and PM1.0 size ranges has been sampled at three sites within 20 km of one another, representing urban background, urban roadside and rural locations. The samples have been subject to chemical analysis for major constituents and the gravimetrically measured mass reconstructed using the pragmatic mass closure model of Harrison et al. [2003. A pragmatic mass closure model for airborne particulate matter at urban background and roadside sites. Atmospheric Environment 37, 4927–4933]. Despite the separation in both time and space and the inclusion of a rural site, the coefficients determined in the earlier mass closure study provide an equally good mass closure on the current dataset. This extends also to the PM1.0 fraction when the coefficients determined for PM2.5 are applied. The mass and composition data for PM2.5 and PM1.0 are intercompared and perhaps surprisingly the differences are accounted for more by components typical of fine fraction particles such as ammonium sulphate and ammonium nitrate than those residing primarily in the coarse fraction such as sea salt, calcium- and iron-rich dusts. A comparison of the composition of 24-h samples collected on days when average PM10 exceeded 50 μg m−3 with data for all days demonstrates the immense importance of nitrates, which together with their strongly bound water, account for on average 39% of PM10 and 46% of PM2.5 during episode conditions, which is more than double their contribution to the overall dataset.
Keywords: PM10; PM2.5; PM1.0; Mass closure; Episodes; PM standards;
Relationship of visibility, aerosol optical thickness and aerosol size distribution in an ageing air mass over South-West Germany by D. Bäumer; B. Vogel; S. Versick; R. Rinke; O. Möhler; M. Schnaiter (989-998).
The ageing process of an air mass over South-West Germany during 5 consecutive days has been examined. In-situ measurements of the visibility, aerosol size distributions, aerosol scattering coefficients and meteorological variables as relative humidity were measured during that situation. Additionally, we measured column aerosol properties, and PM10 mass concentrations of a nearby station of the local environmental protection agency were available. A distinct decrease in the visibility from 45 to 25 km, which was directly measured by two independent methods, a significant increase in PM10, and an increase in the aerosol optical thickness from 0.1 to 0.6 have been detected. The visibility decrease is associated with distinct changes in the aerosol number–size distribution. The number of particles with diameters larger than 300 nm increased considerably during the period, whereas smaller particles did not show such a clear trend. A comparison with meteorological ranges derived from nephelometer scattering coefficients using the Koschmieder formula and a humidity correction is presented. The quality of the nephelometer measurements is verified by a comparison with meteorological ranges calculated from scanning mobility particle sizer (SMPS)/aerodynamic particle sizer (APS) aerosol size distributions applying Mie theory. The calculated meteorological ranges are too high in comparison with the measured visibilities in the beginning, whereas this overestimation decreases at the end of the period when more relatively large particles were abundant. Our results demonstrate the general lack of representativeness of an in-situ measurement for a horizontally averaged parameter as the observed visibility. However, this representativeness was improved when the visibility decreased. In addition, a clear reciprocal behaviour of the visibility and the aerosol optical thickness has been found.
Keywords: Visibility; Extinction coefficient; PM10; Aerosol optical properties; Aerosol measurement;
Geochemical records of limestone façades exposed to urban atmospheric contamination as monitoring tools? by F. Monna; A. Puertas; F. Lévêque; R. Losno; G. Fronteau; B. Marin; J. Dominik; C. Petit; B. Forel; C. Chateau (999-1011).
Magnetic susceptibility, surface rock soiling, elemental composition and lead isotope ratios were measured in surface stone samples collected at different heights of a late 19th century building in Dijon, France. We targeted four limestone façades that differ in orientation and proximity to car traffic. It seems that zinc, copper, sulphur and cadmium are present as diffuse pollutants in urban atmosphere, at least at the scale of the building studied. In contrast, lead and arsenic exhibit point sources: automotive traffic and past coal-burning fly-ash emissions; both coherent with lead isotopic composition measurements. Parameter variations primarily result from exposition to rain washing or micro-scale runoff, and from the closeness, magnitude and origin of anthropogenic sources. Both anthropogenic particles and natural dust tend to be similarly affected by deposition/soiling and rain washing, which act dynamically as competitive processes. Examination of archival photographs suggests that soiling predominated in the past, when the air was rich in black dust, whereas equilibrium or even weathering may occur nowadays due to recent improvements or at least changes in air quality. Using the chemical composition of building façades to provide insights into the magnitude and dispersion of urban atmospheric pollutants may not always be straightforward because of uncertainties related to the period of accumulation.
Keywords: Pollution; Heavy metals; Magnetic susceptibility; Soiling; Lead isotopes;
Long-term measurements of CO, NO, NO2, benzene, toluene and PM10 at a motorway location in an Austrian valley by R. Schnitzhofer; J. Beauchamp; J. Dunkl; A. Wisthaler; A. Weber; A. Hansel (1012-1024).
Continuous measurements of CO, NO, NO2, PM10, benzene and toluene were conducted over a one-year period at a motorway location in the alpine Inn valley. Diurnal changes in concentrations of detected compounds were observed to vary according to traffic type and frequency, and meteorological conditions of the valley atmosphere, which were both additionally recorded at this location. Seasonal variations were also clearly seen, with lowest levels of compound abundances present in summer and highest levels in winter. Annual mean abundances of compounds were assessed with respect to guideline limits and it was found that NO2 and PM10 exceeded their legislation thresholds. This investigation also included the first continuous year-long measurements of benzene at this location, yielding an annual mean volume mixing ratio of 0.6 ppbV, which is well within the EU guideline limit of 1.5 ppbV. Additionally, benzene abundances were found to correlate well with CO concentrations. A significant correlation was also found between toluene and benzene. However, the ratio toluene:benzene shifted from about 2:1 in summer to approximately 1:1 in winter. This may be explained by a strong evaporative and therefore temperature dependent toluene source, while benzene concentrations mainly result from non-ambient temperature dependent exhaust pipe emissions. This seasonal variation must be taken into account whenever this ratio is used to determine the chemical age of an air mass.
Keywords: Automobile emissions; Alpine valley meteorology; PTR-MS; Toluene/Benzene; NO x ;
Morphological characterization of carbonaceous aggregates in soot and free fall aerosol samples by Kamna Sachdeva; Arun K. Attri (1025-1034).
The morphological characteristics of BC aggregates present in the soot and carbonaceous aerosol (CA) samples were investigated. The process of soot formation under laboratory conditions took into account the commonly used practice of burning fuel in the households in India. The fractal morphology was determined by using box counting algorithm and maximum projected area of the aggregates by using their digital electron microscopic images. Former provided the estimates of perimeter fractal dimension (PDf) of each aggregate, and later estimated the average density fractal dimension (DDf) of aggregate groups. Numbers of particles constituting the aggregates, using projected area approach, were significantly higher than the estimates based on pixel counting. The measured average diameter of the primary particles in aggregates, ranged between 24 and 57 nm. The fractal dimensions, PDf, for the laboratory-generated soot aggregates varied from 1.36 to 1.88. The PDf for aggregates derived from diesel-vehicles and biomass burning showed significant variation: biomass, 1.27; diesel vehicle, 1.82 and 1.7. The size and the dimensions estimated for the free fall CA samples showed large deviation. The ratio L/R g (length/radius of gyration) for soot aggregates (gasoline, kerosene, diesel, mustard oil and hexane) ranged from 3.5 to 4.8. Surface morphology of these aggregates, using scanning electron microscope (SEM), showed the presence of spherical “charred cenosphere” like particles in gasoline and free fall aerosol aggregates. FTIR investigations revealed the presence of a large number of organic groups (OC) associated with carbonaceous aggregates present in soot and free fall aerosol samples.
Keywords: Carbonaceous aerosol; Black carbon; Fractal dimension; Electron microscopy; Morphology;
Evidence for organic N deposition and its anthropogenic sources in China by Ying Zhang; Lixia Zheng; Xuejun Liu; Tim Jickells; John Neil Cape; Keith Goulding; Andreas Fangmeier; Fusuo Zhang (1035-1041).
Organic nitrogen (N) is an important component of the atmospheric deposition of reactive N, but its sources are essentially unknown. Assessing whether this dissolved organic N (DON) is of natural, anthropogenic or mixed origin is critically important in attempting to determine the scale of human perturbation of the global N cycle. Here we report evidence for atmospheric organic N deposition and its anthropogenic sources in China. Precipitation samples were collected and analyzed from 15 rural, suburban and urban sites during 2005 and 2006. The average deposition of DON was 8.6 kg ha−1 yr−1 with a volume-weighted concentration of 111 μmol L−1, which was much higher than in other regions of the world. The contribution of DON to total dissolved N (TDN) was approximately 30% on average, agreeing well with other reported data in the literature. Parallel collections of wet-only and bulk deposition showed wet deposition to be 68% on average, indicating a significant dry deposition component. Combining data from the Chinese sites with those from elsewhere in the world, significant (p<0.0001) correlations between DON and NH4–N, NO3–N and TDN suggest that atmospheric organic N originates from similar sources to dissolved inorganic N (DIN) (NH4–N and NO3–N), which are largely attributed to anthropogenic emissions from both agricultural and industrial sources.
Keywords: Atmospheric deposition; Organic N; Inorganic N; Anthropogenic sources;
Seasonal chemical composition variations of wet deposition in Urumchi, Northwestern China by Ming Xu; Aihua Lü; Feng Xu; Bin Wang (1042-1048).
Urumchi suffered serious air quality problem in recent years. Although the main air pollutants and wet deposition monitoring have been undertaken by Urumchi Environmental Monitoring Center for many years, researches on chemical composition and variations of wet deposition were not there till now. In this paper, wet deposition monitoring data in Urumchi from 2000 and 2005 were selected to perform this evaluation based on data quality and data integrity. The volume-weighted mean (VWM) concentrations of parameters of wet deposition, namely pH, conductivity, SO4 2−, NO3 −, F−, Cl−, NH4 +,Ca2+, Mg2+, Na+ and K+ concentrations, were 6.86 and 91.04 μs cm−1, 14.3, 1.63, 0.37, 3.78, 1.22, 4.79, 0.59, 1.05, 0.74 mg L−1, respectively. Acid precipitation appeared only in wintertime in few cases, and its extreme value was 4.96; the maximum emerged during sand storm event in the non-winter season with the value of 9.35. Wet deposition and air pollution characteristics varied with seasons. In order to make a certainty of possible sources of ions in different seasons, principal component analysis was applied, and conclusions were drawn that in wintertime, the predominant contributor to the wet deposition was coal combustion for residential heating; however, in the non-winter season, the situation was more complicated, dust and soil from outside the urban, dust re-suspension, local industries process, motor vehicle emissions all played their roles.
Keywords: Arid area; Sand-dust; Emission; Variation; Contribution; Principal component analysis;
Determination of 14C/12C of acetaldehyde in indoor air by compound specific radiocarbon analysis by Yoshimi Kato; Naohide Shinohara; Jun Yoshinaga; Masao Uchida; Ayuri Matsuda; Minoru Yoneda; Yasuyuki Shibata (1049-1056).
A method of compound-specific radiocarbon analysis (CSRA) for acetaldehyde in indoor air was established for the source apportionment purpose and the methodology was applied to indoor air samples. Acetaldehyde in indoor air samples was collected using the conventional 2,4-dinitrophenylhydrazine (DNPH) derivatization method. Typically 24-h air sampling at 5–10 L min−1 allowed collection of adequate amount of acetaldehyde for radiocarbon analysis by accelerator mass spectrometry (AMS). The 14C abundance of acetaldehyde in indoor air was measured by AMS after solvent extraction of derivatized acetaldehyde and sequential purification by a preparative liquid chromatography system and a preparative capillary gas chromatography system. The recovery and purity of the derivatized acetaldehyde was satisfactory for 14C analysis by AMS. 14C abundance of acetaldehyde was calculated by considering that of derivatizing agent DNPH. Our preliminary survey showed that percent modern carbon (pMC) values of acetaldehyde isolated from indoor air sampled in newly built, unoccupied housings (n=5) in the suburb of Tokyo ranged from 49.4 to 67.0. This result indicated that contribution of anthropogenic source was greater than previously expected.
Keywords: Acetaldehyde; Indoor air; Radiocarbon; Preparative chromatography;
Observation of difference in the size distribution of carbon and major inorganic compounds of atmospheric aerosols after the long-range transport between the selected days of winter and summer by Kyu-Won Hwang; Joo-Ho Lee; Dae-Young Jeong; Chi-Hun Lee; Amit Bhatnagar; Ju-Myon Park; Seong-Heon Kim (1057-1063).
This paper presents the results from a study conducted in two urban areas in Korea to compare the size distributions of atmospheric aerosols, focusing on carbonaceous and certain major inorganic compounds, after long-range transport between selected days in winter and summer. Size segregated aerosols were sampled for 3 consecutive days each in February and July, 2004, and were analyzed to obtain the 24-h averaged concentrations of total mass, elemental carbon, organic carbon, nitrate, and sulfate. Backward trajectories from the receptor site on the sampling days were calculated to estimate the elapsed time for the air parcel to travel between Wonju and the Seoul metropolitan area. The averaged elapsed time on the sampling days was 3–12 h in the winter and 10–19 h in the summer. The enrichment of fine particles as expressed in particulate matter (PM)2/(PM10–PM2) was higher in the summer as compared to that in the winter. Size-fractionized concentration ratios of the organic to the elemental carbon at Wonju were two times as high as those at Seoul except for the particles with size <0.5 μm. This increasing trend was in proportional to the length of the elapsed time during the summer. Ultrafine particles in the summer were further enriched in carbon compounds, particularly in organic carbons and those in winter more enriched in the sulfates and nitrates. The mass fractions of organic carbon, elemental carbon, sulfate and nitrate became more significant with the decrease in the particle size.
Keywords: Transport; Inorganic compounds; Carbon compounds; Size distribution;
City-wide sweeping a source for respirable particulate matter in the atmosphere by Ankit Tandon; Sudesh Yadav; Arun K. Attri (1064-1069).
Most of the cities located in Northern India are afflicted with the presence of unusually high concentration of PM10 in the ambient environment posing a serious risk to human health. To understand the reasons underlying the persistence of the high levels of PM10 in the Delhi region, a novel experiment was designed by appropriating a well-known tracer-source—Diwali fireworks—emitting a large amount of particulate matter (PM) in the atmosphere. Sequential eight hourly PM10 samples were collected and analyzed for the elemental signatures associated with the tracer and other sources. Principal component analysis was used to resolve the sources; their respective mass contribution to PM10 load, in time sequence, was estimated using absolute principal component score method. The results suggest that the well-established practice of city-wide street-cleaning, resuspends the surface deposited PM10 back to the atmosphere. We suspect that this practice resuspends about 25% of the sedimented PM10 back into the atmosphere.
Keywords: PM10; APCS; Tracer source; Resuspension;
New Directions: Future needs for global monitoring and research of aerosol chemical composition by Willy Maenhaut (1070-1072).