Atmospheric Environment (v.39, #36)

Characterization of non-methane volatile organic compounds at swine facilities in eastern North Carolina by Jessica Blunden; Viney P. Aneja; William A. Lonneman (6707-6718).
Samples were collected and analyzed in a field study to characterize C2–C12 volatile organic compounds (VOCs) emitted at five swine facilities in Eastern North Carolina between April 2002 and February 2003. Two sites employed conventional lagoon and field spray technologies, while three sites utilized various alternative waste treatment technologies in an effort to substantially reduce gaseous compound emissions, odor, and pathogens from these swine facilities. More than 100 compounds, including various paraffins, olefins, aromatics, ethers, alcohols, aldehydes, ketones, halogenated hydrocarbons, phenols, and sulfides were positively identified and quantified by Gas Chromatographic/Flame Ionization Detection (GC/FID) analysis and confirmed by Gas Chromatographic/Mass Spectrometry (GC/MS). GC/MS analysis of one particularly complex sample collected assisted in providing identification and retention times for 17 sulfur-type VOCs including dimethyl sulfide, dimethyl disulfide, and dimethyl trisulfide as well as many other VOCs. Highest VOC concentration levels measured at each of the facilities were near the hog barn ventilation fans. Total measured VOCs at the hog barns were typically dominated by oxygenated hydrocarbons (HCs), i.e., ethanol, methanol, acetaldehyde, and acetone. These compounds, in addition to other oxygenated VOCs measured at the various sites, generally represented ∼37–73% of net total measured VOCs that were emitted from the hog barns at the various sites. Dimethyl sulfide and dimethyl disulfide, both recognized as malodorous compounds, were determined to have higher concentration levels at the barns than the background at every farm sampled with the exception of one farm during the warm sampling season.
Keywords: CAFOs; Swine; VOCs; Odor; Dimethyl sulfide;

Fine particle emission profile for a large coke production facility based on highly time-resolved fence line measurements by Emily A. Weitkamp; Eric M. Lipsky; Patrick J. Pancras; John M. Ondov; Andrea Polidori; Barbara J. Turpin; Allen L. Robinson (6719-6733).
This paper presents a fine particle emission profile for a large metallurgical coke production facility. The profile is developed from highly time-resolved, ambient air quality measurements made at a fence line site adjacent to the plant. A fence line approach was employed because the coke plant has hundreds of stacks and other emission points, making it difficult to develop an integrated, facility-wide emission profile using stack sampling techniques. Continuous or semi-continuous measurements of PM2.5 mass, PM10 mass, SO2, NO x , organic and elemental carbon (OC and EC), particle size and number, 11 trace metals, wind direction and wind speed were made. Background pollutant levels were also measured. A combination of highly time-resolved meteorology and air quality data were used to determine when the coke facility emissions influenced the sampling site. Concentrations for most pollutants at the fence line site were one to two orders of magnitude higher than background levels when the facility plume heavily influenced the fence line site. Highly time-resolved measurements are essential to resolve these relatively short-duration, large spikes in pollutant concentrations. Simply measuring wind direction is insufficient. From these highly time-resolved measurements an average PM2.5 emission profile for the coke facility was developed. The profile is dominated by OC (40%±9% of PM2.5 mass emissions) and EC (25%±5% of PM2.5 mass emissions). Significant contributions of certain trace metals were also observed, including As, Zn, Se, and Pb. The particle emissions are dominated by the fine fraction, with PM2.5 estimated to contribute 84%±14% of the PM10 mass.
Keywords: Metallurgical coke production; Emission profile; PM2.5; Receptor modeling; Coal; Source sampling; Emission characterization; Emission inventory; Primary OC;

Nucleation and growth of new particles in the rural atmosphere of Northern Italy—relationship to air quality monitoring by Sergio Rodríguez; Rita Van Dingenen; Jean-Philippe Putaud; Sebastiao Martins-Dos Santos; Davide Roselli (6734-6746).
This study investigates the relationship between aerosols number size distribution on the one hand, and air quality in terms of particulate matter (PM) mass concentrations (as usually monitored in the air quality networks) on the other hand. For this purpose, time series of trace gases levels, submicron aerosol size distributions, both recorded at a rural site in Northern Italy (ISPRA), and of trace gas levels and PM mass concentrations, recorded in the air quality network operating in this region, have been compared and interpreted. Because of the regional nature of the PM pollution events, the daily mean levels of the aerosol volume (V), surface area (S) and black carbon (BC) concentrations at ISPRA rural site are well correlated with the daily mean levels of PM mass concentrations recorded at the other air quality monitoring sites. At ISPRA, the submicron aerosol size distribution is strongly influenced by two main competing processes: nucleation of new particles and condensation of gas-phase components onto pre-existing particles (resulting in particles growth). These processes influence on the daily, seasonal and day-to-day variations of the submicron aerosol features. Because increasing aerosol S concentrations favour condensation and hinder nucleation (and vice versa) the ‘mean’ particle size D p N (mode of the dN/dlog  D size distribution) increases with increasing PM concentrations (e.g. 45 nm for V = 4 μ m 3 cm - 3 and 110 nm for V = 45 μ m 3 cm - 3 ). Owing to this, time series of aerosol D p N and V , S , mass and BC concentrations are strongly anti-correlated with those of the smallest ultrafine particle number concentration (N, 5–10 and 10–20 nm). Nucleation episodes occur under the clean air conditions prompted by the North-Föehn meteorology. This anti-correlation between submicron aerosol mass and N<20 nm concentrations (prompted by the low contribution of the ultrafine particles to the aerosol mass) has important implications for a proper air quality monitoring: the parameters classically used for the air quality assessing (e.g. PM2.5) are not suitable for monitoring of this ultrafine PM pollution and consequently a specific monitoring of the ultrafine PM number concentration should be performed. The significance of this specific ultrafine PM number concentration monitoring is supported by facts already proven: a significant fraction of the current urban PM emissions occurs in the ultrafine PM fraction and exposure to ultrafine PM is associated with adverse effects on human health.
Keywords: Aerosols size distribution; Number concentration; Air quality; Nucleation; Po valley;

Open burning of agricultural biomass: Physical and chemical properties of particle-phase emissions by Michael D. Hays; Philip M. Fine; Christopher D. Geron; Michael J. Kleeman; Brian K. Gullett (6747-6764).
We present the physical and chemical characterization of particulate matter (PM2.5) emissions from simulated agricultural fires (AFs) of surface residuals of two major grain crops, rice (Oryza sativa) and wheat (Triticum aestivum L.). The O2 levels and CO/CO2 ratios of the open burn simulations are typical of the field fires of agricultural residues. In the AF plumes, we observe predominantly accumulation mode (100–1000 nm) aerosols. The mean PM2.5 mass emission factors from replicate burns of the wheat and rice residuals are 4.7±0.04 and 13.0±0.3 g kg−1 of dry biomass, respectively. The combustion-derived PM emissions from wheat are enriched in K (31% weight/weight, w/w) and Cl (36% w/w), whereas the PM emissions from rice are largely carbonaceous (84% w/w). Molecular level gas chromatography/mass spectrometry analysis of PM2.5 solvent extracts identifies organic matter that accounts for as much as 18% of the PM mass emissions. A scarcity of detailed PM-phase chemical emissions data from AFs required that comparisons among other biomass combustion groups (wildfire, woodstove, and fireplace) be made. Statistical tests for equal variance among these groups indicate that the degree to which molecular emissions vary is compound dependent. Analysis of variance testing shows significant differences in the mean values of certain n-alkane, polycyclic aromatic hydrocarbon (PAH), oxy-PAH, and sugar marker compounds common to the biomass combustion types. Individual pairwise comparisons of means at the combustion group level confirm this result but suggest that apportioning airborne PM to these sources may require a more comprehensive use of the chemical emissions fingerprints. Hierarchical clustering of source test observations using molecular markers indicates agricultural fuels as distinct from other types of biomass combustion or biomass species. Rough approximations of the total potential PM2.5 emissions outputs from the combustion of the wheat and rice surface residues are given. This agricultural activity could significantly contribute to emissions inventories at regional, national, and global geographic levels.
Keywords: Agricultural fire; PM2.5; Chemical emissions characterization; Potassium; Chlorine; Organic speciation;

Local and transported pollution over San Diego, California by M. Luria; R.L. Tanner; R.J. Valente; S.T. Bairai; D. Koracin; A.W. Gertler (6765-6776).
Ten air-quality samplings flights were performed over the San Diego metropolitan area during July 2003. One of the objectives of these flights was to assess the contribution of the offshore pollution sources (civilian and military vessels) to the air quality in the region. The flights, which took place during the mid-day hours in the lower levels of the boundary layer, originated offshore and proceeded eastwards through a series of concentric arcs covering an area of approximately 600 km2. The data from the continuous gas analyzers were translated to image plots that enabled the determination of the impact of the various sources on air quality. The results revealed that the offshore sources could often be detected (at least during five of the 10 flights) from their SO2 plume. However, the area covered by these plumes and the concentrations were significantly lower than those measured over other parts of the domain due to sources south of the region. It was further observed that vehicular traffic contributed in a major source way to the formation of ozone. During most flights the pollution cloud, originating over the high traffic area in the vicinity of the downtown area, could be tracked ‘downwind’ until the completion of the photochemical processing. By then, most of the NO X had been converted to NO Z , and peak O3 levels caused by the local emissions had started to ebb. Also, during most flights boundary layer peak levels of O3 exceeded 100 ppbv, and in one case were above 140 ppbv.
Keywords: Airborne pollution measurements; Ozone; Sulfur dioxide; Carbon monoxide; Nitrogen oxides; Local sources; Transported pollution;

The mineralogy of atmospheric particles at the confluence of the Tinto and Odiel rivers, south of Huelva (a highly industrialized city in the SW Spain), was characterized in view to identify source origins. In spite of the small amount of sample collected, mineralogical characterization was performed by X-ray diffraction, polarized light microscopy and scanning electron microscopy with EDS analysis system, using an adequate sample preparation methodology. Sedimentable (SP) and aerosols particles were sampled an one-week basis every two months for one year. Quartz, calcite and feldspars were found to be the major minerals in both fractions, and phyllosilicates, dolomite and gypsum were also identified in lower content. Minor mineral particles included barite, apatite, sphalerite and pyrite. SEM studies revealed the additional presence of chalcopyrite in both SP and aerosols, and of chalcocite–covellite, halite and sylvite in the latter. Siderite, hematite and ankerite were only detected in the SP fraction. The concentrations of the previous minerals increased in summer by effect of the limited rain and the resulting scarcity of atmosphere washing. Non-mineral particles detected by SEM in SP and aerosol fractions included spherical, biological and compositionally complex particles. The main source of mineral particles was found to be the soil suspension in addition to the metallurgical and fertilizer production industries in the area.
Keywords: Mineralogy; Sedimentable particles; Aerosols; X-ray diffraction; Scanning electron microscopy;

Recent atmospheric Pb deposition at a rural site in southern Germany assessed using a peat core and snowpack, and comparison with other archives by Gaël Le Roux; Dominique Aubert; Peter Stille; Michael Krachler; Bernd Kober; Andriy Cheburkin; Georges Bonani; William Shotyk (6790-6801).
In a peat bog from Black Forest, Southern Germany, the rate of atmospheric Pb accumulation was quantified using a peat core dated by 210Pb and 14C. The most recent Pb accumulation rate (2.5 mg m−2  y−1) is similar to that obtained from a snowpack on the bog surface, which was sampled during the winter 2002 (1 to 4 mg m−2  y−1). The Pb accumulation rates recorded by the peat during the last 25 yr are also in agreement with published values of direct atmospheric fluxes in Black Forest. These values are 50 to 200 times greater than the “natural” average background rate of atmospheric Pb accumulation (20 μg m−2  y−1) obtained using peat samples from the same bog dating from 3300 to 1300 cal. yr B.C. The isotopic composition of Pb was measured in both the modern and ancient peat samples as well as in the snow samples, and clearly shows that recent inputs are dominated by anthropogenic Pb. The chronology and isotopic composition of atmospheric Pb accumulation recorded by the peat from the Black Forest is similar to the chronologies reported earlier using peat cores from various peat bogs as well as herbarium samples of Sphagnum and point to a common Pb source to the region for the past 150 years. In contrast, Pb contamination occurring before 1850 in southwestern Germany, differs from the record published for Switzerland mainly due to the mining activity in Black Forest. Taken together, the results show that peat cores from ombrotrophic bogs can yield accurate records of atmospheric Pb deposition, provided that the cores are carefully collected, handled, prepared, and analysed using appropriate methods.
Keywords: Pb flux; Peat bogs; Lead isotopes; Pollution; Snow cover;

In situ measurement of N2O5 in the urban atmosphere by thermal decomposition/laser-induced fluorescence technique by Jun Matsumoto; Hidekazu Imai; Naohiro Kosugi; Yoshizumi Kajii (6802-6811).
The laser-induced fluorescence (LIF) detector with a thermal converter has been developed for measuring atmospheric N2O5. The detection limit for N2O5 was 11 pptv for 10-min averaging ( S / N = 2 , [NO2]=0). The field measurements of N2O5 were conducted in the urban atmosphere in winter. N2O5 was successfully monitored during four nights. Typically, observed N2O5 level was in the range of 0–200 pptv. Note that N2O5 reached 800 pptv at one night, when NO x level was extremely high and the temperature was low. After the data were selected by the stability of NO x , N2O5 chemistry was discussed for a representative case of the urban night. Observed trend of N2O5 was compared with the theoretically predicted one. The heterogeneous loss rate of N2O5 on the aerosol surfaces was estimated as 5.2×10−4  s−1. Consequently, it was confirmed that N2O5 loss was critical for NO x budget in the urban atmosphere in winter, in comparison with NO x loss via NO3. The LIF instrument proved to be useful for studying nocturnal chemistry of N2O5 in the source region.
Keywords: Dinitrogen pentoxide; Laser-induced fluorescence; Urban atmosphere; Heterogeneous reaction; NO x sink;

In this paper, we have analysed the particle number and CO2 concentration data from four previous dynamometer studies, each consisting of a number of heavy-duty vehicles of different age and operating on different diesel fuel blends. Emission rates were calculated for four operational modes corresponding to 0%, 25%, 50% and 100% of the maximum rated engine power. In a given mode the calculated CO2 emission rates were approximately the same for all vehicles, but the calculated particle number emission rates varied considerably between vehicles. Using concentrations measured directly from the dilution tunnel, we found that the ratio of diluted particle number concentration, to diluted CO2 concentration (P/C ratio) was directly proportional to the calculated undiluted particle number emission concentration, with a high degree of correlation. These observations suggest that the P/C ratio within the diluted sample is a good indicator of the particle number emission concentration for the undiluted exhaust. This was confirmed by grouping the vehicles according to age whence the newest age group, expected to have the cleanest emissions, always showed the lowest P/C ratio. An additional series of experiments were conducted on-road with a light duty diesel vehicle, at speeds ranging from 40 to 100 km h−1. The diluted exhaust emissions were collected in a large bag housed in a trailer attached to the back of the vehicle. Various dilution ratios were achieved by sampling over a range of distances directly behind the vehicle tail-pipe outlet. As expected, the particle number concentration in the bag, for different distances and therefore different dilution ratios, showed a definite relationship to the dilution ratio, however the P/C ratio was independent of dilution for dilution ratios in the range 20–110.Based on the results of the dynamometer and on-road studies, it is suggested that the P/C ratio may be used as a viable method for the rapid identification of high particle number emitting vehicles as they drive past on a road. The technique has the added advantage that it is independent of the position of the sampling point in relation to the emission plume.
Keywords: Diesel emissions; Ultrafine particles; Dilution ratio; On-road studies; Dynamometer studies;

Particle nucleation from the reaction of α-pinene and O3 by Sangdon Lee; Richard M. Kamens (6822-6832).
Nucleation precursors from α-pinene+O3 reactions were investigated with a flow reactor combined with a Teflon bag reactor. Initial particle formation exponentially increased with the reacted amount of α-pinene with O3, and this, given certain assumptions, is consistent with classical nucleation theory. Initial reaction products indicated products such as cis-pinonaldehyde, cis-pinonic acid, cis-norpinonic acid, and pinalic-4-acid did not initiate particle self-nucleation because of their low concentrations compared to their theoretically estimated saturation concentrations. Although particle formation was observed on the time scale of the flow reactor (⩾0.4–6 s), cis-pinic and cis-norpinic acid were not detected as products, and hence are also not candidates for initiating self-nucleation. Thermally stabilized Criegee intermediates (SCI) were implicated in the nucleation process. Evidence for this comes from the observation of significant reductions in particle formation by scavenging SCIs with low-molecular-weight compounds. On a molecule reaction basis, nucleation was suppressed with SCI scavengers in the following order: water ≪acetaldehyde≈methanol<formic acid. Teflon bag experiments showed that decreased initial particle number concentrations by SCI scavenger (formic acid and acetic acid) did not affect the final total particle mass concentration. Possible nucleation precursors are discussed in the context of estimated vapor pressures and initial concentrations.
Keywords: Criegee; α-pinene; Nucleation; SOA; Ozonolysis;

Predicting ammonia and carbon dioxide emissions from carbon and nitrogen biodegradability during animal waste composting by Jean-Marie Paillat; Paul Robin; Mélynda Hassouna; Philippe Leterme (6833-6842).
During composting of livestock manure, transformations of organic matter result in gaseous emissions, which can harm the environment. Two experiments were done in enclosures to measure the fluxes of NH3, N2O, CO2, CH4 and H2O emitted by 8 heaps of compost representing the range of biodegradability of nitrogen and carbon in the livestock manure. The heaps were monitored for the first 2 months, corresponding to the thermophilic phase during which nearly all-mass losses occur. Four parameters describe the NH3 emission kinetics and the main influential factors were noted: (1) the response time to reach maximum intensity is affected mainly by the initial micro-flora; (2) the amplitude depends mainly on C biodegradability and also on micro-flora; (3) the emission duration depends mainly on N biodegradability; and (4) the cumulative emission, which varied from 16.5 to 48.9% of the nitrogen initially present in the heap, depends both on C and N biodegradability. A predictive model for NH3 and CO2 emissions for the thermophilic phase of the composting of livestock manure is proposed. The variability in cumulative emissions of CO2 and of NH3 is well explained by the contents of soluble elements and hemicellulose in the dry matter (Van Soest fractioning), and soluble nitrogen (12 h extraction at 4 °C in water). In our conditions of favourable aeration and humidity, N2O and CH4 emissions were low. The role of the biodegradable carbon in reducing NH3 emission is highlighted.
Keywords: Ammonia; Carbon dioxide; Greenhouse gases; Compost; Animal manure;

In the present study, the real world on-road diesel vehicle emissions of carbon monoxide (CO), hydrocarbons (HC) and nitric oxide (NO) were investigated at nine sites in Hong Kong. A regression analysis approach based on the measured vehicle emission data was used to estimate the on-road diesel vehicle emission factors of CO, HC and NO with respect to the effects of instantaneous vehicle speed and acceleration/deceleration profiles for local urban driving patterns. The results show that the diesel vehicle model years, engine sizes, vehicle types and driving patterns have a strong correlation with their emission factors. A comparison was made between the average diesel and petrol vehicle emissions factors in Hong Kong. The deviation of the average emission factors of aggregate diesel vehicles reflects the variability of local road condition, vehicle traffic fleet and volume, driving pattern, fuel composition and ambient condition etc. Finally, a unique database of the correlation of diesel vehicle emission factors (i.e., g km−1 and g l−1) on different model years and vehicle types for urban driving patterns in Hong Kong was established.
Keywords: On-road vehicle emissions; Remote sensing measurement technique; Emission factors; Regression analysis;

Estimating measurement uncertainty in an ambient sulfate trend by W.H. White; L.L. Ashbaugh; N.P. Hyslop; C.E. McDade (6857-6867).
This paper examines the effects of sampling and analytical error on time trends derived from routine monitoring. Our analysis is based on actual concentration differences observed among three long sulfate series recorded by collocated and independent measurements at Shenandoah National Park. Five-year sulfate trends at this location are shown to include a one-sigma uncertainty of about 1% year–1 from measurement error alone. This is significantly more than would be estimated under naïve statistical assumptions from the demonstrated precision of the measurements. The excess uncertainty arises from subtle trends in the errors themselves.
Keywords: IMPROVE; CASTNet; Shenandoah; Sulfate; Trend; Error; Uncertainty;

Health risks of NO2, SPM and SO2 in Delhi (India) by Jai Shanker Pandey; Rakesh Kumar; Sukumar Devotta (6868-6874).
There is increasingly growing evidence linking urban air pollution to acute and chronic illnesses amongst all age groups. Therefore, monitoring of ambient concentrations of various air pollutants as well as quantification of the dose inhaled becomes quite important, specially in view of the fact that in many countries, policy decisions for reducing pollutant concentrations are mainly taken on the basis of their health impacts. The dose when gets combined with the likely responses, indicates the ultimate health risk (HR). Thus, as an extension of our earlier studies, HR has been estimated for three pollutants, namely, suspended particulate matter (SPM), nitrogen dioxide (NO2) and sulfur dioxide (SO2) for Delhi City in India. For estimation and analyses, three zones have been considered, namely, residential, industrial and commercial. The total population has been divided into three age classes (infants, children and adults) with different body weights and breathing rates. The exercise takes into account age-specific breathing rates, body weights for different age categories and occupancy factors for different zones. Results indicate that health risks due to air pollution in Delhi are highest for children. For all age categories, health risks due to SO2 (HR_SO2) are the lowest. Hence, HR_SO2 has been taken as the reference with respect to which HR values due to SPM and NO2 have been compared. Taking into account all the age categories and their occupancy in different zones, average HR values for NO2 and SPM turn out to be respectively 22.11 and 16.13 times more than that for SO2. The present study can be useful in generating public awareness as well as in averting and mitigating the health risks.
Keywords: Air pollution; Exposure; Health risks; Dose–response; Population classes;

Previous analysis of London's congestion charging scheme (CCS) has shown that changes in vehicle speed are an important factor in reducing vehicle emissions. Therefore, a detailed investigation of network average vehicle speed in both central and inner London has been undertaken using a combination of the non-parametric Wilcoxon sign ranks test and a method for calculating the cumulative difference between mean speeds pre- and post-CCS, or cumulative sum (CUSUM) analysis. Within the charging zone (CZ), the Wilcoxon test has shown that the difference in speed between pre- and post-CCS periods has increased on average by 2.1 km h−1 and that these changes are significant at the p = 0.05 level. The CUSUM analysis has provided evidence of the timing of this change in mean speed in the CZ and this agrees well with the introduction of the CCS on the 17 February 2003. In combination, these results provide compelling evidence that the introduction of congestion charging has significantly increased vehicle speed in the CZ and by comparison with the results in inner London, that these changes are not part of a wider trend. To examine one impact of this change we used an instantaneous emissions model, the Vehicle Transient Emissions Simulation Software, to undertake a comparison between the change in vehicle emissions associated with changing driving characteristics, between pre- and post-charging periods, and those associated with a change in average speed. The analysis was limited to three vehicle types: a Euro II LGV, a Euro III diesel car and a Euro IV petrol car, but showed that driving characteristics in central London have a relatively small effect on emissions of NO X and CO2 compared with the average vehicle speed. However, for PM10 emissions from the Euro II LGV the opposite was found and for this vehicle the driving characteristics were more important than the average speed in estimating exhaust emissions. For this vehicle, emissions increased between pre- and post-CCS periods by 4%. For the Euro IV petrol car NO X emissions also increased by 6% between pre- and post-CCS periods. These findings will help to further understand the extent to which congestion charging reduces vehicle emissions in London.
Keywords: Environment and transport planning; Road user pricing; Emissions modelling; CUSUM; Congestion charging;

Fine-particle Mn and other metals linked to the introduction of MMT into gasoline in Sydney, Australia: Results of a natural experiment by D.D. Cohen; B.L. Gulson; J.M. Davis; E. Stelcer; D. Garton; O. Hawas; A. Taylor (6885-6896).
Using a combination of accelerator-based ion beam methods we have analysed PM2.5 particulates for a suite of 21 species (H, C, Na, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Br, Pb) to evaluate the contribution to Sydney (New South Wales, Australia) air associated with the introduction of MMT as a replacement for lead. MMT was discontinued in 2004. Teflon filters representing continuous sampling for a 7 year period from 1998 to 2004 were analysed from two sites: one from Mascot, a suburb close to the Central Business District [CBD ( n = 718 )] and a high trafficked area, and the other, a relatively rural (background) setting at Richmond, ∼20 km west of the CBD ( n = 730 ). Manganese concentrations in air at the background site increased from a mean of 1.5–1.6 ng m−3 to less than 2 ng m−3 at the time of greatest MMT use whereas those at Mascot increased from about 2 to 5 ng m−3. From the maximum values, the Mn showed a steady decrease at both sites concomitant with the decreasing use of MMT. Lead concentrations in air at both sites decreased from 1998 onwards, concomitant with the phase out of leaded gasoline, attained in 2002. Employing previously determined elemental signatures it was possible to adjust effects from season along with auto emissions and soil. A high correlation was obtained for the relationship between Mn in air and lead replacement gasoline use (R 2 0.83) and an improved correlation for Mn/ Al+Si+K and lead replacement gasoline use (R 2 0.93). In addition, using Mn concentrations normalized to background values of Al+Si+K or Ti to account for the lithogenically derived Mn, the proportion of anthropogenic Mn was approximately 70%. The changes for Mn and Pb detected in the particulates are attributed to the before-during-after use of MMT and decreasing use of lead in gasoline. The values measured in Sydney air are well below the reference concentration of 50 ng Mn m−3. The incremental increases in air, however, are larger than expected given the limited use of MMT only in lead replacement gasoline and high quality monitoring should be undertaken in countries where MMT is used in all gasoline.
Keywords: Mn; Pb; Automobiles; Air; Soil; Ion beam methods; Sources;

Deposition velocities and washout ratios on a coastal site (southeastern Spain) calculated from 7Be and 210Pb measurements by C. Dueñas; M.C. Fernández; J. Carretero; E. Liger; S. Cañete (6897-6908).
The activity concentrations of 7Be and 210Pb were measured in Málaga, Southeastern Spain (36°43′40″N; 4°28′8″W) in aerosols, precipitation and dry fallout continuously and systematically for 8 years. At the same sampling point, aerosols were collected weekly on filters and monthly precipitation sampling was carried out to study deposition. The air concentration of 7Be showed a seasonal increase during the spring and summer months while the air concentration of 210Pb was greater in summer. The concentration data of 7Be and 210Pb together with meteorological variables were used for a comprehensive analysis of variations. The specific activities of 7Be and 210Pb in bulk deposition samples showed a similar seasonal trend variation to that of the aerosols concentrations. Using the concentrations of 7Be and 210Pb in air and their depositional fluxes, the deposition velocities of aerosols and washout ratios were calculated. The mean deposition velocity of 7Be and 210Pb over the 8-year period is 0.4 and 1.5 cm s−1, respectively, and the corresponding washout ratios are 477 and 1908, respectively. The results showed a prevailing influence of amount of rainfall for deposition velocities and other factors such as TSP, the number of rainy days and the number of dry days for washout ratios. A comparison of our measurements and other data obtained at different locations in the world was also made.
Keywords: 7Be; 210Pb; Deposition velocity; Washout ratio;

Single particle characterization of spring and summer aerosols in Beijing: Formation of composite sulfate of calcium and potassium by Xiande Liu; Jia Zhu; P. Van Espen; F. Adams; Rui Xiao; Shuping Dong; Yuwu Li (6909-6918).
Scanning electron microscopy–energy dispersive X-ray analysis (SEM–EDX) was used for the analysis of 2500 single particles in five atmospheric aerosol samples collected during the spring and summer of 2000 in Beijing, China. Mineral dust appeared to be the dominant particles during an Asian dust episode, while in other circumstances mineral dust and S-containing particles constituted the major particle components. During anthropogenic pollution episodes in the summer, a large abundance of S-containing particles featured the atmospheric aerosol. Chemical and size distribution characteristics are discussed for Ca–S, K–S and Ca–K–S particle classes. Formation of Ca–K–S and other S-containing particle classes with high abundance was closely related to meteorological conditions such as relative humidity and cloud coverage. Simple and composite sulfate particles with an elongated crystalline morphology were detected which appear to be indicative of aqueous phase oxidation, such as in-cloud processing for sulfate formation pathway.
Keywords: Atmospheric aerosol; Single-particle analysis; Scanning electron microscopy–energy dispersive X-ray analysis; Sulfate formation; In-cloud processing; Beijing;

On-line alkali analysis of individual aerosol particles in urban air by Maria Svane; Sara Janhäll; Magnus Hagström; Mattias Hallquist; J.B.C. Pettersson (6919-6930).
On-line measurements of individual alkali-containing submicron particles in ambient air have been performed at two urban sites in Göteborg, on the west coast of Sweden. Results obtained with a recently developed particle beam mass spectrometer are presented. This instrument combines an optimized particle inlet with mass spectrometric techniques and detection of particle-bound alkali metal is based on surface ionization technique. The concentrations of Na and K in submicron particles were followed over periods of a few weeks. Mass concentrations of alkali in ambient air varied in the range 0.02–100 ng m−3 during the measurement periods depending on air mass history, wind direction, season, and contributions from local sources. The number of alkali-containing particles varied between 0.1 and 100 cm−3. Most detected individual particles contained a relatively small amount of Na, and few particles had sufficient Na content to be identified as pure sea-salt particles. The detected aerosol was concluded to be dominated by emissions from combustion of biomass and fossil fuels, with a significant contribution from sea-salt particles only during intrusion of marine air. This conclusion was supported by backward air mass trajectories and calculated K/Na weight ratios that generally agreed well with earlier measurements in urban environments.
Keywords: Surface ionization; Mass spectrometry; Individual aerosol particles; Sea salt particles; Urban aerosol;

Lack of spatial variation of endotoxin in ambient particulate matter across a German metropolitan area by Verena Morgenstern; Cara L. Carty; Ulrike Gehring; Josef Cyrys; Wolfgang Bischof; Joachim Heinrich (6931-6941).
In this study, we describe the spatial variation of endotoxin across an urban setting using Geographic Information Systems (GIS) methods. We also identify potential sources of endotoxin that account for between-site variability and compare endotoxin levels in particulate matter with a 50% aerodynamic cut-off diameter of 2.5 μm (PM2.5) and of 10 μm (PM10). In 1999–2000, we collected PM2.5 and PM10 in Munich urban air and measured soluble endotoxin concentrations in both particle fractions. Using Teflon filters and Harvard impactors, PM2.5 was collected at 40 outdoor monitoring sites across Munich and PM10 at a subset of these sites ( n = 12 ). Approximately four samples were collected at each site for a total of 158 PM2.5 samples and 48 PM10 samples. We visited and characterized the surrounding 100 m of each site for potential endotoxin sources. The geometric mean endotoxin concentration for all sites was 1.46 EU mg−1 PM2.5 (95% confidence intervals (CI): 1.21–1.77) and at the subset of the sites was 1.30 EU mg−1 PM2.5 (95% CI: 1.01–1.67 EU mg−1 PM2.5). Endotoxin levels in PM10 were higher, 3.91 EU mg−1 PM10 (95% CI: 3.03–5.03 EU mg−1 PM10), than in PM2.5 and were moderately correlated, r = 0.51 .All endotoxin concentrations measured in this study were <5.5 EU m−3 and thus lower than the accepted thresholds for acute adverse health effects for occupational exposures. Sites with more potential sources ( n ⩾ 3 ) had slightly higher mean endotoxin levels (MR: 1.30 for EU mg−1 PM2.5 and 1.13 for EU m−3 PM2.5) than sites with no identified sources. Based on the ranges of endotoxin levels at the different sites, we found very little spatial variation in ambient endotoxin concentrations across the metropolitan area of Munich using inverse distance weighting method (IDW) methods ( R 2 = 0.013 for EU mg−1 PM2.5 and R 2 = 0.020 for EU m−3 PM2.5). Potential sources of endotoxin surrounding the sites only partly explained the variation seen.
Keywords: Airborne endotoxin; Outdoor; Bacteria; Particulate matter; GIS;