Atmospheric Environment (v.41, #32)

Geostatistical characterization of nitrogen dioxide concentration in an urban area by Chantal de Fouquet; David Gallois; Gilles Perron (6691-6700).
The temporal component of the estimation error is usually neglected in calculation of the variance of the error associated with the mapping of annual nitrogen dioxide (NO2) concentration. However, under realistic hypotheses, adding a temporal term to the spatial estimation variance is convenient enough. In a survey using passive diffusion samplers, which was carried out in 2001 on the Mulhouse area, the two measurement phases do not allow calculation of variance of the temporal error. But this error is accessible by means of the few fixed analyzers that continuously measure NO2 concentrations. The statistics of the experimental temporal error are examined and the temporal variogram is calculated. Experimental quadratic error is then compared to the theoretical estimation variance, deduced from the temporal variogram.The fixed analyzers available in Alsace are then used to “optimize” empirically the duration and the date of the beginning of the temporary measurement phases.Without increasing the cost of the temporary survey, it is then possible to improve the precision of the maps of annual NO2 concentration, by combining the spatial optimization presented in Part I of the paper, and the temporal optimization presented here.
Keywords: Geostatistics; Spatial variability; Time variability; Estimation variance; Cartography; Sampling optimization; Nitrogen dioxide (NO2); Urban air pollution;

Geostatistical characterization of the nitrogen dioxide concentration in an urban area by Chantal de Fouquet; David Gallois; Gilles Perron (6701-6714).
Maps of the annual average of the NO2 concentration in an urban area are generally built from temporary seasonal measurements, as in 2001 at Mulhouse (France). To improve the precision of the estimation, auxiliary information about the environment can be used. Instead of kriging the average of the two seasonal measurements (in “winter” and in “summer”), cokriging these seasonal values guarantees the consistency of seasonal and annual estimations. Even more, cokriging allows the use of “incomplete series” at the sites measured during only one season. Based on cokriging, an optimization of the sampling is studied, while alternating the seasonal measurements on a part of the sites.Using the linear model of coregionalization, the fitting of simple and cross-variograms reveals a remarkable spatial decomposition of the seasonal concentrations. The different spatial components are interpreted in terms of physico-chemical processes of production, transformation or destruction of the NO2 in urban atmosphere.
Keywords: Geostatistics; Cokriging; Kriging analysis; Cartography; Sampling optimization; Nitrogen dioxide (NO2); Urban air pollution;

A chemical mass balance (CMB) receptor model was used for estimating the diurnal contributions of VOC emission sources to the ambient C2–C9 VOC concentration in Seoul, Korea. For this purpose, the VOC concentrations were measured in the morning, the afternoon, and the evening. The samples were collected using a 2-h integrated SUMMA canister. The source profiles were developed for the CMB calculation in the Seoul area. To investigate the effect of the chemical reaction loss of VOCs on the CMB calculation, the modified model employing a decay factor and the standard model that considers no loss were compared. The modified model estimated that the vehicle exhaust (52%) was the largest leading source of VOCs in the Seoul atmosphere, followed by the use of solvents (26%), gasoline evaporation (15%), the use of liquefied petroleum gas (LPG) (5%), and the use of liquefied natural gas (LNG) (2%). Relative source contribution for vehicle exhaust showed a clear diurnal variation with a high in the morning and evening and a low in the afternoon, while the contribution of evaporative emissions (gasoline evaporation and solvent usage) showed a different diurnal pattern from that of the vehicle exhaust, exhibiting a high in the afternoon and evening and a low in the morning. It was found that the difference between the total source contribution (μg m−3) estimated from these two models was not statistically significant. However, when the paired-sample t-test is applied to the individual sources, a significant difference was found for the vehicle exhaust and the solvent use. In addition, the modified model brought forth a better performance with high R 2 and low χ 2 as compared to those obtained from the standard model in the CMB calculation. The vehicle exhaust and solvent use were estimated to be the largest and the second largest contributors to ambient benzene as well as ozone formation potential (OFP), respectively. Based on above results we believe that incorporating the reaction loss in the CMB calculations helps to better fit the source profile to the ambient VOC concentrations. However, the reaction loss does not significantly affect the estimation of source contributions.
Keywords: Benzene; CMB; Diurnal source contribution; Ozone formation potential; Photochemical loss; VOCs;

Total element concentration and chemical fractionation in airborne particulate matter from Santiago, Chile by Pablo Richter; Paulina Griño; Inés Ahumada; Ady Giordano (6729-6738).
Total element determination and chemical fractionation were carried out in airborne particulate matter (PM10) from the Cerrillos monitoring station in Santiago, Chile, sampled in July (winter), 1997–2003.Element concentration in the period under study (1997–2003) was statistically analyzed through cluster analysis in order to identify groups of elements having similar behavior along time. Elements such as Cd, Cu, Pb, Ni, As and Mg show a clear decrease in concentration with time. On the contrary, chromium increases its concentration almost linearly during the period.In order to estimate whether the presence of a certain element in PM10 matrix is mainly due to anthropogenic or natural processes, the enrichment factor of each element was determined.According to their behavior in the sequential extraction procedure, the elements were grouped by multivariate analysis in three clusters: (a) those mobile elements (Pb, Cd, Zn, Mn, Cu and As) which are weakly bound to the matrix (fractions 1 and 2) (b) those elements (V, Ti, and Cr) mainly bound to carbonates and oxides (fraction 3) and (c) the most immobile elements (Ni, Mo, Ca, Mg, Ba and Al), mainly bound to silicates and organic matter (fraction 4). A source of great concern is the fact that elements of such high toxicity as Pb, Cd and As are highly concentrated in both mobile fractions, indicating that these elements have a direct impact on the environment and on the health of the exposed population.
Keywords: Total element concentration; Chemical fractionation; PM10; Santiago–Chile;

Scavenging of sea-salt aerosols by rain events over Arabian Sea during ARMEX by D.M. Chate; K. Ali; G.A. Momin; P.S.P. Rao; P.S. Praveen; P.D. Safai; P.C.S. Devara (6739-6744).
Scavenging coefficients are obtained for sea-salt particles at rainfall intensity of 5, 10, 15, 20 and 45 mm h−1. Evolutions of size distributions for sea-salt particles by precipitation scavenging are simulated using theoretically estimated scavenging coefficients. Results indicate that below-cloud scavenging affects mainly sea-salt particles in coarse mode. Observed concentrations of Na+ and Cl in rainwater increased with rainfall intensity and aerosol size. Comparison of predicted concentrations of Na+ and Cl in rainwater with observed ionic concentrations of short-timed wet-only samples collected during rain events on 2 August 2002 over Arabian Sea (ARMEX-2002) supports the model result.
Keywords: Ionic concentration; Wet removal; Below-cloud scavenging; Natural washout; Coagulation;

Development of the ClearSky smoke dispersion forecast system for agricultural field burning in the Pacific Northwest by Rahul Jain; Joseph Vaughan; Kyle Heitkamp; Charleston Ramos; Candis Claiborn; Maarten Schreuder; Mark Schaaf; Brian Lamb (6745-6761).
The post-harvest burning of agricultural fields is commonly used to dispose of crop residue and provide other desired services such as pest control. Despite careful regulation of burning, smoke plumes from field burning in the Pacific Northwest commonly degrade air quality, particularly for rural populations. In this paper, ClearSky, a numerical smoke dispersion forecast system for agricultural field burning that was developed to support smoke management in the Inland Pacific Northwest, is described. ClearSky began operation during the summer through fall burn season of 2002 and continues to the present. ClearSky utilizes Mesoscale Meteorological Model version 5 (MM5v3) forecasts from the University of Washington, data on agricultural fields, a web-based user interface for defining burn scenarios, the Lagrangian CALPUFF dispersion model and web-served animations of plume forecasts. The ClearSky system employs a unique hybrid source configuration, which treats the flaming portion of a field as a buoyant line source and the smoldering portion of the field as a buoyant area source. Limited field observations show that this hybrid approach yields reasonable plume rise estimates using source parameters derived from recent field burning emission field studies. The performance of this modeling system was evaluated for 2003 by comparing forecast meteorology against meteorological observations, and comparing model-predicted hourly averaged PM2.5 concentrations against observations. Examples from this evaluation illustrate that while the ClearSky system can accurately predict PM2.5 surface concentrations due to field burning, the overall model performance depends strongly on meteorological forecast error. Statistical evaluation of the meteorological forecast at seven surface stations indicates a strong relationship between topographical complexity near the station and absolute wind direction error with wind direction errors increasing from approximately 20° for sites in open areas to 70° or more for sites in very complex terrain. The analysis also showed some days with good forecast meteorology with absolute mean error in wind direction less than 30° when ClearSky correctly predicted PM2.5 surface concentrations at receptors affected by field burns. On several other days with similar levels of wind direction error the model did not predict apparent plume impacts. In most of these cases, there were no reported burns in the vicinity of the monitor and, thus, it appeared that other, non-reported burns were responsible for the apparent plume impact at the monitoring site. These cases do not provide information on the performance of the model, but rather indicate that further work is needed to identify all burns and to improve burn reports in an accurate and timely manner. There were also a number of days with wind direction errors exceeding 70° when the forecast system did not correctly predict plume behavior.
Keywords: CALPUFF; PM2.5; Biomass burning; Air quality model;

Characteristics of the major chemical constituents of PM2.5 and smog events in Seoul, Korea in 2003 and 2004 by Hyun-Sun Kim; Jong-Bae Huh; Philip K. Hopke; Thomas M. Holsen; Seung-Muk Yi (6762-6770).
One hundred ninety-five chemically speciated samples were collected from March 2003 to February 2005 in the Seoul Metropolitan area to investigate the characteristics of the major components in PM2.5 and to characterize the chemical variations between smog and non-smog events. The annual average PM2.5 concentration was 43 μg m−3 that is almost three times higher than the US NAAQS annual PM2.5 standard of 15 μg m−3. During this sampling period, smog and yellow sand events were observed on 27 and 10 days, respectively. The PM2.5 concentrations and its constituents during smog events were about two–three times higher than those during non-smog and yellow sand events. In particular, the mass fractions of secondary aerosols such as sulfate, nitrate, and ammonium during the smog events were higher than those of the other constituents. The mean concentration and mass fraction of secondary organic carbon (SOC) were highest during the winter smog events. Sulfate, nitrate and SOC that can have long residence times were important species during the smog events suggesting that regional scale sources rather than local sources were important. Five-day backward air trajectory analysis showed that the air parcels during smog events passed through the major industrial areas in China more often than those during non-smog events.
Keywords: Korea; PM2.5; Chemical variations; Smog events; Secondary aerosols; Regional scale sources;

The effect of the characteristics of the surface on the phototransformation of acridine, one of the most abundant azapolycyclic compounds encountered in urban atmospheres, and of one of its principal photoproducts, acridone, was studied when adsorbed onto models of the atmospheric particulate matter. For this purpose, relative photodegradation rates were determined from absorption or emission intensities as a function of irradiation times, and some products were isolated and characterized. The relative photodegradation rates of adsorbed acridine show the tendency (NH4)2SO4>MgO>Al2O3>SiO2. In general, the rates decrease as the fraction of protonated acridine species on the surface increases in MgO, Al2O3, and SiO2, except for (NH4)2SO4 where a fast surface reaction occurs. Oxygen reduces the photodestruction rates by as much as 40–60% when compared to an inert atmosphere, implying the participation of an acridine triplet state in the transformation processes on all surfaces except on (NH4)2SO4. Acridone, a major product, undergoes a photo-induced tautomerization to 9-hydroxy acridine. The formation of a dihydrodiol, another photoproduct of acridine, is suggested by comparison to reported spectral properties of these compounds. This is formed through a singlet oxygen reaction. Photoproducts showing the absence of the narrow absorption band of 250 nm, characteristic of the π→π* transition in tricyclic aromatics, were detected in small yields but not identified. These results suggest possible photochemical transformation pathways that could lead to the ultimate fate of these pollutants in the environment.
Keywords: Acridine; Acridone; Phototransformations; Models of atmospheric particulate matter;

Marine aerosol size distributions in the springtime over China adjacent seas by Peng Lin; Min Hu; Zhijun Wu; Yuwen Niu; Tong Zhu (6784-6796).
Size distributions and particle number concentrations of atmospheric aerosols in the size (diameter) range from 15 nm to 10 μ m were measured on board of a research ship during three cruises in China adjacent seas. The total particle number concentrations were in average around 4000 cm - 3 in Yellow Sea, 2000 cm - 3 in East China Sea and 1000 cm - 3 in South China Sea. The observed size distributions were fitted with two or three log-normal modes and the data were classified according to time, regions and calculated air mass back-trajectories. The size distribution spectra of air masses of polluted continental origin as their back-trajectories showed were characterized by single mode with total number concentrations between 1000 and 10 000 cm - 3 . The size distributions in marine air masses showed dual mode characteristics, one maximum at 40–60 nm and the other at 160–190 nm with total number concentrations below 1000 cm - 3 . This type of dual mode was more pronounced at longer residence time of the air masses over the ocean. The burst of ultra-fine (UF) particles and the consequent growth processes were observed twice in Yellow Sea and possible reasons leading to these events are discussed. The particle growth rate (GR) was 3.4 ± 0.9 and 3.5 ± 1.6 nm h - 1 , respectively (95% confidence interval), indicating that the UF particles can grow to cloud condensation nuclei (CCN) within the next 1–2 days.
Keywords: Marine aerosol; Number concentration; Size distribution; China adjacent seas;

Fungi and bacteria in mould-damaged and non-damaged office environments in a subarctic climate by Heidi Salonen; Sanna Lappalainen; Outi Lindroos; Riitta Harju; Kari Reijula (6797-6807).
The fungi and bacterial levels of the indoor air environments of 77 office buildings were measured in winter and a comparison was made between the buildings with microbe sources in their structures and those without such sources. Penicillium, yeasts, Cladosporium and non-sporing isolates were the commonest fungi detected in the indoor air and in settled dust, in both the mould-damaged and control buildings. Aspergillus ochraceus, Aspergillus glaucus and Stachybotrys chartarium were found only in environmental samples from the mould-damaged buildings. Some other fungi, with growth requiring of water activity, a w, above 0.85, occurred in both the reference and mould-damaged buildings, but such fungi were commoner in the latter type of buildings. The airborne concentrations of Penicillium, Aspergillus versicolor and yeasts were the best indicators of mould damage in the buildings studied. Penicillium species and A. versicolor were also the most abundant fungi in the material samples. This study showed that the fungi concentrations were very low (2–45 cfu m−3 90% of the concentrations being <15 cfu m−3) in the indoor air of the normal office buildings. Although the concentration range of airborne fungi was wider for the mould-damaged buildings (2–2470 cfu m−3), only about 20% of the samples exceeded 100 cfu m−3. The concentrations of airborne bacteria ranged from 12 to 540 cfu m−3 in the control buildings and from 14 to 1550 cfu m−3 in the mould-damaged buildings. A statistical analysis of the results indicated that bacteria levels are generally <600 cfu m−3 in office buildings in winter and fungi levels are <50 cfu m−3. These normal levels are applicable to subarctic climates for urban, modern office buildings when measurements are made using a six-stage impactor. These levels should not be used in evaluations of health risks, but elevated levels may indicate the presence of abnormal microbe sources in indoor air and a need for additional environmental investigations.
Keywords: Fungi; Bacteria; Indoor air; Office building; Concentration;

Atmospheric aerosols are subject to below-cloud scavenging by precipitation. The scavenging coefficient depends on the aerosol size significantly. The traditional bulk parameterization represents the mean wet scavenging coefficient for the whole aerosol size range. This parameterization significantly overestimates the scavenging of aerosol mass by a heavy rain or a long-duration medium rain. In this study, we present a 3-mode parameterization of the mean scavenging coefficient for each aerosol mode instead of representation for the whole aerosol size range. The new parameterization takes into account the aerosol number size distribution, the rain droplet size distribution and the spectral collision efficiency between the aerosol particle and the rain droplet. Comparing the calculation of mass depletion due to below-cloud scavenging, the 3-mode parameterization agrees well with the size-resolved explicit method. The new parameterization can be easily implemented in atmospheric dispersion models.
Keywords: Aerosol; Wet scavenging; Atmospheric dispersion model;

Receptor modelling using Positive Matrix Factorisation, back trajectories and Radon-222 by Jagoda Crawford; Scott Chambers; David D. Cohen; Leisa Dyer; Tao Wang; Wlodek Zahorowski (6823-6837).
PM2.5 aerosols were sampled and atmospheric 222Rn (radon) was measured, at Hong Kong, China, over 3 years 2001–2003. The aerosol samples were analysed using accelerator-based Ion Beam Analysis (IBA) techniques to provide quantitative information on 21 of their major and minor elemental contributions. The radon concentration on aerosol sampling days was then used to classify the degree of land contact (high or low) experienced by air masses en route to the receptor site. It was found that elements known to originate from anthropogenic sources (e.g. Zn, K, Br, Pb and Black Carbon) were positively correlated with observed radon concentration. An eight-factor Positive Matrix Factorisation (PMF) analysis was performed on the data set, which resulted in elemental profiles (“fingerprints”) for eight potential sources and we identified source factors that were correlated with radon. The Potential Source Contribution Function technique was then used to identify the geographic regions most likely to have significantly contributed to the aerosol samples collected at the receptor site.
Keywords: Aerosol; Receptor modelling; Positive Matrix Factorisation; Potential Source Contribution Function; Radon;

In the last few decades, fire and smoke-haze occurrence increased in Indonesia by intentionally set land clearing fires and higher fire susceptibility of disturbed forests. Particularly, during El Niño years with prolonged droughts in Indonesia, land clearing fires become uncontrolled wildfires and produce large amounts of gaseous and particulate emissions. This paper investigates the influence of smoke-haze aerosols from such fires on clouds and precipitation over Indonesia during the El Niño event 1997/1998 by numerical modelling. Warm precipitation formation in both layered and convective clouds is calculated dependent on the atmospheric aerosol concentration. In the smoke-haze affected regions of Indonesia, aerosol–cloud interactions induce events with both precipitation suppression and increase compared to a reference simulation without aerosol–cloud interactions. The effect of precipitation suppression is found to dominate with about 2/3 of all precipitation modification events pointing to a prolongation of smoke-haze episodes. The corresponding convective cloud top height of shallow clouds is increased whereas distinct lower deep convective cloud top heights are found. The remaining about 1/3 events are characterised by increased precipitation and cloud liquid water content, accompanied by lower convective cloud top heights of shallow clouds and higher deep convective clouds.
Keywords: Second indirect aerosol effect; Regional climate modelling; Aerosol–cloud interactions;

Decomposition of low-concentration gas-phase toluene using plasma-driven photocatalyst reactor by Ru-Bao Sun; Zhu-Ge Xi; Fu-Huan Chao; Wei Zhang; Hua-Shan Zhang; Dan-Feng Yang (6853-6859).
Plasma-driven photocatalysis system was prepared and performed. To overcome the treatment difficulty of volatile organic compounds, non-thermal plasma was used as a light source of photocatalysis. The removal of low-concentration toluene was investigated and secondary products were analyzed by gas chromatograph–mass spectroscopy. The plasma-driven photocatalyst reactor using direct current as a light source and titanium dioxide catalyst loaded on activated carbon fiber (TiO2/ACF) as photocatalyst was studied. It was found that plasma-driven photocatalysis system could significantly increase the removal effect of toluene. The number of secondary products was largely decreased. It means that plasma-driven photocatalysis hybrid system was an effective method for the removal of volatile organic compounds.
Keywords: Non-thermal plasma; TiO2; Toluene; Plasma-driven photocatalysis; Indoor air;

To improve our understanding of the mechanisms of particulate sulfur formation (non sea-salt sulfate, nss-SO4 2−) and methanesulfonate (MS x used here to represent the sum of gaseous methanesulfonic acid, MSA, and particulate methanesulfonate, MS) in the eastern Mediterranean and to evaluate the relative contribution of biogenic and anthropogenic sources to the S budget, a chemical box model coupled offline with an aerosol–cloud model has been used.Based on the measurements of gaseous dimethyl sulfide (DMS) and methanesulfonic acid (MSA) and the MSA sticking coefficient determined during the Mediterranean Intensive Oxidant Study (MINOS) experiment, the yield of gaseous MSA from the OH-initiated oxidation of DMS was calculated to be about 0.3%. Consequently, MSA production from gas-phase oxidation of DMS is too small to explain the observed levels of MS. On the other hand, heterogeneous reactions of dimethyl sulfoxide (DMSO) and its gas-phase oxidation product methanesulfinic acid (MSIA) can account for most of the observed MS levels. The modelling results indicate that about 80% of the production of MS can be attributed to heterogeneous reactions.Observed submicron nss-SO4 2− levels can be fully explained by homogeneous (photochemical) gas-phase oxidation of sulfur dioxide (SO2) to sulfuric acid (H2SO4), which is subsequently scavenged by (mainly submicron) aerosol particles. The predominant oxidant during daytime is hydroxyl radical (OH) showing very high peak levels in the area during summer mostly under cloudless conditions. Therefore, during summer in the east Mediterranean, heterogeneous sulfate production appears to be negligible. This result is of particular interest for sulfur abatement strategy. On the other hand only about 10% of the supermicron nss-SO4 2− can be explained by condensation of gas-phase H2SO4, the rest must be formed via heterogeneous pathways.Marine biogenic sulfur emissions contribute up to 20% to the total oxidized sulfur production (SO2 and H2SO4) in good agreement with earlier estimates for the area.
Keywords: Sulfate; Methanesulfonate; Summer time; Eastern Mediterranean; Modelling;

Characterization of carbonaceous aerosols in urban air by Liaquat Husain; Vincent A. Dutkiewicz; A.J. Khan; Badar M. Ghauri (6872-6883).
Concentrations of black carbon, [BC], were determined with an Aethalometer every 5 min at Lahore, a city of about 10 million in Pakistan, from 22 November 2005 to 31 January 2006. [BC] were very high, ranging from about 5 to 110 μ g m - 3 , with a mean of 21.7 μ g m - 3 . A distinct diurnal variation was observed: concentrations were lowest from about 10 a.m. to 4 p.m. local time (LT), and highest around 5–9 p.m. No clear relationship was observed between surface wind directions and [BC], although some of the highest concentrations were observed when the airflow was from southwest to northwest. The daily variations in concentrations were strongly affected by the diurnal variations in the mixing height; BC concentrations were low during the day when the mixing heights were high, ∼ 1000 m , and very high at night when the mixing heights were low < 250 m . Periods of light to dense fog occurred from 22 December through 4 January. [BC] were generally lower than average when fog occurred during the night and early morning, but they were not necessarily lower during daytime fogs. We also collected aerosols on quartz filters every 3, 6, or 12 h and determined the concentrations of elemental, [EC], and organic carbon, [OC], using the thermal–optical method. The [BC] were highly correlated with EC ( r 2 = 0.71 ) , but on average 25% higher than [EC]. The [EC] and [OC] concentrations were moderately correlated ( r 2 = 0.65 ) . The [OC]/[EC] ratios varied from 2.8 to 12, with a mean of 5.6. Although a large component of the carbonaceous aerosols in Lahore originated from fossil fuel combustion, a significant fraction was derived from biomass burning.
Keywords: Black carbon; Elemental carbon; Organic carbon; Carbonaceous aerosols; PM 2.5 mass; Urban aerosols; Fog; Asia;

Fugitive metal in PM2.5 at the blast furnace (S 1), reverberatory furnace (S 2), and surrounding environment (S 0) of a secondary aluminum smelter (a secondary ALS) was studied. PM2.5 mass concentration at the blast furnace exceeded that at the reverberatory furnace and this was especially apparent during operation, giving an early indication that the blast furnace is more important as a pollutant source. Further, PM2.5 mass concentration levels and patterns at S 0 indicated that emissions from the blast furnace and reverberatory furnace were the major source of the observed fine particle pollution in the surrounding environment. Si and K were the main components and hence pollutants by mass in the PM2.5 at S 1, S 2 and S 0 during both operation and non-operation. Hg was not detected in the PM2.5 aerosol during smelter operation but was present at all three sampling locations during non-operation. This is due to the falling blast furnace and reverberatory furnace temperatures during non-operation which cause Hg vapor formed during operation to condense to form detectable Hg particles, and hence Hg contributes to the pollutant load during non-operation. Average S 1/S 0 and S 2/S 0 mass concentration ratios of 40.32 and 18.53, respectively, for all measured metals during operation and 7.83 and 5.73 for all measured metals during non-operation indicate that metal particulate pollution at the workplaces of secondary ALSs, particularly at the blast furnace during operation, is a serious issue. S 1/S 0 mass concentration ratios were higher still for Pb (62.22), Ti (113.40) and Ba (248.64), while the S 2/S 0 mass concentration ratio for Mo was 138.20. Principal component analyses produced a PC1 that explained 32.36–48.16% of the total variance during operation of the smelter and 47.86–69.Ten percent during non-operation. Their strong component loadings were mainly related to the fugitive PM2.5 mass. Compared to atmospheric metal concentrations reported for other regions of the world, the toxic metals that have relatively higher concentrations in the secondary ALS emissions are Cr, Cd, Cu, As, Pb, Se, Al and Zn, especially during smelter operation. Concentrations of these toxic heavy metals are approximately 2–4 orders of magnitude higher than those reported for various industrial regions and metropolises with heavy traffic across the world.
Keywords: Aluminum smelter; Blast furnace; Reverberatory furnace; Metallic profiles;

Characteristics and sources of PM2.5 and carbonaceous species during winter in Taiyuan, China by Z.Y. Meng; X.M. Jiang; P. Yan; W.L. Lin; H.D. Zhang; Y. Wang (6901-6908).
Continuous observation of PM2.5 was conducted in Taiyuan, a heavily polluted city in China, during high pollution season from December 2005 to February 2006. The results of this study showed that PM2.5 and carbonaceous species pollution were serious during winter in Taiyuan. The organic carbon (OC) and element carbon (EC) were accounted for 18.6±11.2% and 2.9±1.6% of PM2.5, respectively, which indicated that carbonaceous aerosols were key components for control fine particles pollution in Taiyuan. Coal combustion was a dominant source of OC and EC of PM2.5 in the urban area of Taiyuan during winter. The impact of local and remote particle sources on urban air quality was assessed using PM2.5 concentration rose and 3-day back trajectories of air masses arriving at Taiyuan. The meteorological conditions were found to affect the ambient concentrations of PM2.5, OC, EC and OC/EC ratio.
Keywords: PM2.5; Organic carbon; Element carbon; Emission sources;

The vertical profile of atmospheric heating rate of black carbon aerosols at Kanpur in northern India by S.N. Tripathi; Atul K. Srivastava; Sagnik Dey; S.K. Satheesh; K. Krishnamoorthy (6909-6915).
Altitude profiles of the mass concentrations of aerosol black carbon (BC) and composite aerosols were obtained from the collocated measurements of these quantities onboard an aircraft, over the urban area of Kanpur, in the Ganga basin of northern India during summer, for the first time in India. The enhancement in the mean BC concentration was observed at ∼1200 m in the summer, but the vertical gradient of BC concentration is less than the standard deviation at that altitude. The difference in the BC altitude profile and columnar concentration in the winter and summer is attributed to the enhanced turbulent mixing within the boundary layer in summer. This effect is more conspicuous with BC than the composite aerosols, resulting in an increase in the BC mass fraction (F BC) at higher levels in summer. This high BC fraction results in an increase in the lower atmospheric heating rate in both the forenoon, FN and afternoon, AN, but with contrasting altitude profile. The FN profile shows fluctuating trend with highest value (2.1 K day−1) at 300 m and a secondary peak at 1200 m altitudes, whereas the AN profile shows increasing trend with highest value (1.82 K day−1) at 1200 m altitude.
Keywords: Black carbon profile; Heating rate; Pollution; Northern India;

The aerosol scattering properties were investigated at two continental sites in northern China in 2004. Aerosol light scattering coefficient (σ sp) at 525 nm, PM10, and aerosol mass scattering efficiencies (α) at Dunhuang had a mean value of 165.1±148.8 M m−1, 157.6±270.0 μg m−3, and 2.30±3.41 m2  g−1, respectively, while these values at Dongsheng were, respectively, 180.2±151.9 M m−1, 119.0±112.9 μg m−3, and 1.87±1.41 m2  g−1. There existed a seasonal variability of aerosol scattering properties. In spring, at Dunhuang PM10, σ sp, and α were 184.1±211.548 μg m−3, 126.3±89.6 M m−1, and 1.05±0.97 m2  g−1, respectively, and these values at Dongsheng were 146.4±142.1 μg m−3, 183.4±81.7 M m−1, and 1.98±1.52 m2  g−1, respectively. However, in winter at Dunhuang PM10, σ sp, and α were 158.1±261.4 μg m−3, 303.3±165.2 M m−1, and 3.17±1.93 m2  g−1, respectively, and these values at Dongsheng were 155.7±170.1 μg m−3, 304.4±158.1 M m−1, and 2.90±1.72 m2  g−1, respectively. σ sp and α in winter were higher than that in spring at both the sites, which coincides with the characteristics of dust aerosol and pollution aerosol. Overall, the dominant aerosol types in spring and winter at both sites in northern China are dust aerosol and pollution aerosol, respectively.
Keywords: Dust and pollution aerosol; Integrating nephelometer; Scattering coefficient; PM10;