Atmospheric Environment (v.38, #30)

Monitoring of atmospheric particulate matter around sources of secondary inorganic aerosol by A. Alastuey; X. Querol; S. Rodríguez; F. Plana; A. Lopez-Soler; C. Ruiz; E. Mantilla (4979-4992).
A physicochemical characterisation of airborne particulate matter (PM) was performed in a region affected by the emissions from a source of precursors of secondary inorganic aerosols (SIA, 1050 MW power plant). This characterisation sought to study the interferences of other possible natural and anthropogenic sources when monitoring PM10, PM2.5 and PM1 around this emission source. The study was performed in the semi-arid Ebro basin and Catalan and Iberian ranges (Eastern Spain) and consisted in (1) monitoring the transport and impacts on the ground of the SO 2 plume (fumigation), (2) chemically characterising (25 PM components) of TSP-size fractions, and diurnal and nocturnal PM10 and PM2.5 samples, and (3) in measuring the PM mass size distribution. This PM characterisation was undertaken in ambient air, during fumigations of the SO 2 plume on the ground and around other local PM sources. PM1 was found to be the best parameter for monitoring PM pollution derived from the SO 2 emissions owing to the formation of ammonium–sulphate in the finest PM fractions. Three PM1 & PM2.5 events were recorded during the field measurement campaign: two events were caused by ammonium–sulphate episodes, the third was due to an African dust outbreak. PM-mass size distribution and the high correlation of PM1 with SO 2 during the SO 2 fumigation events suggest that a significant fraction of sulphate is formed by means of `new particle formation' processes (nucleation). PM10 presents a much higher variability (noise) than PM1 & PM2.5 owing to the re-suspension of coarse (2.5– 10 μ m ) mineral dust particles. The PM1 load in PM10 undergoes significant variations: 60–80% during plume fumigations, 20–60% in ambient air, and down to 10% in areas affected by mineral dust re-suspension. The daily cycles observed in some PM components (sulphate, nitrate and mineral dust elements) and the chemical features of PM are also described in detail.
Keywords: PM1; PM2.5; PM10; Sulphate; SO 2 ; Mineral dust;

In Europe, air quality Limit Values have been established for PM 10 . In this study we determined the impact of PM 10 arising from a range building works and road works at over 80 monitoring sites in and around London during the period 1999 to 2001. Examination of PM 10 measurements suggests that these local fugitive sources may have been responsible for daily mean concentrations above 50 μ g m - 3 at 25% of the monitoring sites each year. PM 10 source apportionment was used to show that building works and road works close to monitoring sites can cause daily mean measurements of PM 10 to exceed 50 μ g m - 3 and may therefore contribute to a breach of the European Union (EU) Limit Value. In one case, building works close to the Marylebone Road monitoring site caused the daily mean PM 10 concentration to exceed 50 μ g m - 3 on 24 days between June and December 1999. In the future, such local fugitive sources will play a greater role in the attainment of the Limit Value as PM 10 from primary and secondary sources is reduced by control measures. Given that PM 10 from building works and road works have only a local impact it would be misleading to imply that a city, agglomeration or region has exceeded the EU Limit value on the basis of this type of local incident.
Keywords: PM 10 modelling; Fugitive sources of PM 10 ; Air pollution in London;

Characterization and source identification of a fine particle episode in Finland by Jarkko V. Niemi; Heikki Tervahattu; Hanna Vehkamäki; Markku Kulmala; Tarja Koskentalo; Markus Sillanpää; Minna Rantamäki (5003-5012).
A strong long-range transported (LRT) fine particle (PM 2.5 ) episode occurred from March 17–22, 2002 over large areas of Finland. Most of the LRT particle mass was in the submicrometre size fraction. The number of concentrations of 90–500 nm particles increased by a factor of 5.6 during the episode, but the concentrations of particles smaller than 90 nm decreased. This reduction of the smallest particles was caused by suppressed gas-to-particle conversion due to the vapour uptake of LRT particles. Individual particle analyses using SEM/EDX showed that the proportion of sulphur-rich particles rose strongly during the episode and that the relative weight percentage of potassium was unusually high in these particles. The median S/K ratios of S-rich particles were 2.1 at the beginning of the episode, 5.2 at the peak stage of the episode and 8.9 during the reference days. The high proportion of K is a clear indication of emissions from biomass burning, because K is a good tracer of biomass-burning aerosols. Trajectories and satellite detections of fire areas indicated that the main source of biomass-burning aerosols was large-scale agricultural field burning in the Baltic countries, Belarus, Ukraine and Russia. The higher S/K ratio of S-rich particles during the peak stage was obviously due to the increased proportion of fossil fuel-burning emissions in the LRT particle mass, since air masses arrived from the more polluted areas of Europe at that time. The concentrations of sulphate, total nitrate and total ammonium increased during the episode. Our results suggest that large-scale agricultural field burning may substantially affect PM 2.5 concentrations under unfavourable meteorological conditions even at distances over 1000 km from the burning areas.
Keywords: Aerosol particles; Long-range transport; Size distributions; Chemical composition; Sources;

Organotin (OTC), organolead (OLC) and organomercury (OMC) compounds are highly toxic and exhibit a potential negative effect on terrestrial ecosystems. Individual ionic OTC, OLC and OMC compounds were identified and their concentrations determined in the gas phase, aerosol particles, and bulk precipitation at a rural (Waldstein) and an urban (Bayreuth city) site in NE-Bavaria. At both sites, butyltins, methyltins, octyltins, trimethyllead and monomethylmercury concentrations in the gas phase were < 100 pg m - 3 (determined as corresponding Sn, Pb and Hg concentrations, respectively) with the dominance of tri- and di-substituted OTC and octyltins. The same species were found in bulk precipitation with concentrations < 25 ng l - 1 (Sn, Pb, Hg) with the dominance of mono-substituted OTC. In aerosols, only butyltins, dimethyltin and monomethyltin ( < 500 pg Sn m - 3 ) were found and mono-substituted OTC predominated. No significant difference of concentrations of organometallic compounds in the atmosphere at the two sites was found. For OTC, the washout factors was in the order: mono- ⩾ di- > tri-substituted OTC, and the gas/particle partition coefficients were mono- ⪢ di- ⪢ tri-substituted OTC. The distribution spectrum of OTC in aerosols showed the strong linkage of OTC to the long-lived particles and high accumulation of OTC in the filter at the Waldstein site. The results indicate that long-range-transport of organometallic compounds in the atmosphere is an important source at our both sites. Aerosol particles may serve as a sink in the chemical cycles of OTC in the atmosphere, especially for monomethyltin and monobutyltin.
Keywords: Ionic organotin; Trimethyllead; Monomethylmercury; Gas; Aerosol; Bulk precipitation; Waldstein; Bayreuth;

Seasonal variability in the major soluble ion composition of atmospheric particulate matter in the principal sugar cane growing region of central São Paulo State indicates that pre-harvest burning of sugar cane plants is an important influence on the regional scale aerosol chemistry. Samples of particulate matter were collected between April 1999 and February 2001 in coarse ( > 3.5 μ m ) and fine ( < 3.5 μ m ) fractions, and analysed for HCOO - , CH 3 COO - , C 2 O 4 2 - , SO 4 2 - , NO 3 - , Cl - , Na + , K + , NH 4 + , Mg 2 + and Ca 2 + . Results indicated that the principal sources of the aerosols investigated were local or regional in nature (scale of tens to a few hundreds of km), and that differences between air masses of varying origins were small. Fine particles were typically acidic, containing secondary nitrates, sulphates and organic species. Coarse fraction concentrations were mainly influenced by physical parameters (wind speed, movement of vehicles and surface condition) affecting rates of re-suspension, although secondary nitrate and sulphate were also present in the larger particles.Concentrations of all measured species except sodium and chloride were higher during the burning season. Although concentrations were lower than often found in polluted urban environments, the massive increases during much of the year, due to a single anthropogenic activity (sugar cane burning) are indicative of a very large perturbation of the lower troposphere in the region relative to the natural condition. These aerosols are suspected of promoting respiratory disease. They also represent an important mechanism for the tropospheric transport of species relevant to surface acidification (sulphates, nitrates, ammonium and organic acids) and soil nutrient status (potassium, nitrogen, ammonium, calcium), so their impact on fragile natural ecosystems (following deposition) needs to be considered.
Keywords: Aerosols; Soluble ions; Brazil; Sugar cane; Biomass burning;

Emission of polycyclic aromatic hydrocarbons from diesel engine in a bus station, Londrina, Brazil by Moacir Tavares; Jurandir P. Pinto; Alexandre L. Souza; Ieda S. Scarmínio; Maria Cristina Solci (5039-5044).
The concentrations of vapor phase polycyclic aromatic hydrocarbons (PAHs) were measured at the Central Bus Station of Londrina, where only diesel-powered vehicles circulate. The samples were collected within a period of 24 h for 14 consecutive days in January 2002. The semi-volatile PAHs were collected using a cartridge packed with XAD-2 resin, extracted under sonication and subsequently analyzed by gas chromatograph equipped with the flame ionization and mass spectrometer detectors (GC-FID and GC/MS). Ten PAH compounds were found (naphthalene, acenapthylene, acenapthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthracene and chrysene). The average concentrations ranged from 1.4±0.3 ng m−3 for benzo(a)anthracene to 348.0±32.7 ng m−3 for phenanthrene. The species that presented higher concentration were phenanthrene (348.0±32.7 ng m−3), fluorene (140.2±17.3 ng m−3) and naphthalene (97.7±10.3 ng m−3). The PAHs with two and three rings were responsible by 90.2% of the total concentration among 10 PAHs. The concentrations of PAHs were lower on Sunday in comparison with the workdays, due to the reduction of bus traffic in the station. Correlations and principal component analysis with Varimax rotation were used to estimate the local PAH emission source profile originating from the diesel exhaust. The ratio PHEN/FLU of 2.5 calculated from the results is suggested as indication from diesel combustion exhaust.
Keywords: Vapor-phase PAHs; Diesel engines; Mobile source; Diagnostic ratio; Profile; Multivariate analysis;

Atmospheric concentrations of NO 2 , HNO 3 , NH 3 , aerosol NH 4 + and NO 3 - , and the bulk deposition of NH 4 + and NO 3 - were measured for two years at ten sites around the West Midlands, UK. Eight of these sites were spread across the 125 km 2 Lichfield nitrate vulnerable zone (NVZ). The measured data were interpolated across the area, and by applying land-use specific deposition velocities to the airborne concentrations, seasonal N deposition fluxes to the NVZ were estimated. There was a large spatial variation in deposition flux, driven mainly by land-use, but also by measured concentration gradients. Spatially averaged total flux exhibited a seasonal pattern; peaking in spring-summer. Each measured component contributed a substantial fraction of the total flux, but the importance of each varied seasonally. Oxidised-N and reduced-N fluxes were relatively equal. Annual average flux was approximately 20 kg N ha - 1 yr - 1 .
Keywords: Nitrogen deposition; Nitrate vulnerable zone; Deposition flux; Reduced nitrogen; Oxidised nitrogen;

The use of MODIS data and aerosol products for air quality prediction by Keith D. Hutchison; Solar Smith; Shazia Faruqui (5057-5070).
The Center for Space Research (CSR) is exploring new approaches to integrate data collected by the MODerate resolution Imaging Spectroradiometer (MODIS) sensor, flown on NASA's Earth Observing System (EOS) satellites, into a real-time prediction methodology to support operational air quality forecasts issued by the Monitoring Operations Division (MOD) of the Texas Commission on Environmental Quality (TCEQ). Air pollution is a widespread problem in the United States, with over 130 million individuals exposed to levels of air pollution that exceed one or more health-based standards. Texas air quality is under assault by a variety of anthropogenic sources associated with a rapidly growing population along with increases in emissions from the diesel engines that drive international trade between the US and Central America. The challenges of meeting air quality standards established by the Environmental Protection Agency are further impacted by the transport of pollution into Texas that originates from outside its borders and are cumulative with those generated by local sources. In an earlier study, CSR demonstrated the value of MODIS imagery and aerosol products for monitoring ozone-laden pollution that originated in the central US before migrating into Texas and causing TCEQ to issue a health alert for 150 counties. Now, data from this same event are re-analyzed in an attempt to predict air quality from MODIS aerosol optical thickness (AOT) observations. The results demonstrate a method to forecast air quality from remotely sensed satellite observations when the transient pollution can be isolated from local sources. These pollution sources can be separated using TCEQ's network of ground-based Continuous Air quality Monitoring (CAM) stations.
Keywords: Remote sensing; Modis; Pollution; Air quality; Forecasting; Continental haze;

A meteorological and chemical modeling system is used to determine the effect of ethene and propene point source emission rates on the magnitude and distribution of ozone in the vicinity of Houston. The model performance is evaluated using surface and airborne meteorological and chemical measurements made as part of the 2000 Texas Air Quality Study. A simulation that employed the reported mobile, area, biogenic, and point source emissions produced ozone mixing ratios as high as 120 ppb and distributions of nitrogen oxides that were similar to measurements at most locations, but the model underestimated ozone mixing ratios greater than 140 ppb that were located just downwind of petrochemical facilities. When the point source emission rates of ethene and propene were increased by a factor of 10, the simulated peak ozone levels were in better agreement with surface, aircraft, and lidar observations. The magnitude of the simulated ethene and olefin concentrations were in better agreement with canister samples aloft as well; however, there was still a large amount of scatter in the results. While the highest ozone mixing ratios were produced just downwind of large point source emissions of VOCs, sensitivity simulations also showed that reductions in anthropogenic emissions of NO x would be needed to reduce ozone mixing ratios over a larger area.
Keywords: Regional photochemical modeling; Emission inventories; Air quality; Ethene and propene; Houtson; Tx;

Iodine in the atmosphere, identified largely by the presence of IO, is a ubiquitous component of the troposphere in coastal and oceanic areas. The role, if any, that iodine chemistry plays in the polar ozone depletion episodes is not known. These events are rationalized today largely in terms of Br2- and BrCl-initiated reactions. The potential for enhancement of ozone depletions through the presence of iodine-containing molecules (I2, IBr, ICl, CH2I2, CH2IBr, CH2ICl, and CH3I) is investigated in this study. Computer simulations of the homogeneous chemistry are made using a reasonably complete reaction mechanism for Br-, Cl- and I-containing species together with representative chemistry of trace gases in the clean troposphere. The extent of uncertain alternative pathways and efficiencies for OIO and I2O2 photolyses are varied over a range of possible values to establish the sensitivity of the depletion events to these variables. The study shows that significant enhancements of the polar ozone depletion are expected when small amounts of iodine-containing compounds such as CH2I2, IBr, or ICl are present in a polar air mass containing representative Br2–BrCl-trace gas mixtures. The synergistic effect of the iodine compounds results from additional halogen-atom formation from IO–IO, IO–BrO, and IO–ClO reactions. Measurements of IO and precursor iodine-containing compounds are encouraged for future polar spring studies, as well as currently acknowledged important trace species (O3, CH2O, BrO, Br2, and BrCl).
Keywords: Arctic O3 depletion; Computer simulations; Atmospheric chemistry; Iodine-containing compounds;

Simulations of atomic mercury depletion episodes in the polar spring are now based largely on Br2 and Br-atom initiated chemistry. Chlorine is believed to contribute little to the observed depletion. The role, if any, that the presence of iodine compounds play in Hg-atom depletion is unknown at present. The theoretically predicted instability of the HgI species suggests that I-atom reactions with mercury may be an unimportant loss process. However, iodine atoms react rapidly with ozone to develop IO radicals that interact with BrO radicals to enhance Br- and I-atom concentrations, so an indirect influence of iodine compounds on Hg removal might be expected. Computer simulations are described in this study that test this hypothesis using the homogeneous portion of the chemistry of the mercury depletion in the troposphere. Conditions are chosen equivalent to the 1300–1400 h on a clear day (17 March) at the location of Barrow, Alaska (Atmos. Environ. 37 (2003) 4467). Small amounts of reactive trace gases, representative of the Arctic spring, are present initially with typical background levels of Hg (0.24 ppt) and 50 ppb of O3. The simulations show that gaseous atomic mercury depletion in typical Br2 and BrCl mixtures can be enhanced significantly by the presence of small amounts of iodine-containing compounds (I2, CH2I2, CH2IBr, CH2ICl, IBr, and ICl). The major initial product of the possible mercury reactions is HgBr. The subsequent coupling reactions of this species with Br, BrO, Cl, ClO, I, IO, and OH radicals are expected to lead to a variety of reactive gaseous mercury-containing products.
Keywords: AMDE; RGM; Computer simulations; Polar Hg chemistry; Halogen chemistry;

A description of the NO X -dependence of annual mean concentrations of nitrogen dioxide ( NO 2 ) is an important component of empirical policy models used to investigate the impacts of NO X emissions control measures. Consideration of nitric oxide (NO), NO 2 and ozone ( O 3 ) as a set of chemically coupled species, rather than NO and NO 2 alone, is used to gain additional insights into the factors controlling ambient levels of NO 2 (and O 3 ), and how they vary with NO X concentration. Monitoring data from 66 urban roadside, urban centre, urban background, suburban, urban industrial and rural sites in the UK are used in this analysis. Annual mean [ NO 2 ] vs. [ NO X ] and [ O 3 ] vs. [ NO X ] relationships are defined by establishing, first, how the concentration of `oxidant' ([OX], defined as [ O 3 ] + [ NO 2 ] ) varies with [ NO X ] and, secondly, how the fractional contributions of NO 2 and O 3 to OX (i.e., [ NO 2 ] / [ OX ] and [ O 3 ] / [ OX ] ) vary with [ NO X ] . This allows site-specific relationships describing the NO X -dependence of annual mean NO 2 and O 3 concentrations to be recommended for 56 non-rural sites. The results are also used to derive representative expressions for different regions of the UK, and these are compared with those currently employed in national empirical modelling activities to calculate future annual mean NO 2 concentrations. Because the present methodology decouples factors which relate to chemical partitioning from those which relate to sources of oxidant, the expressions presented here have the flexibility to enable predictions that take account of modest future changes in regional oxidant (i.e. the background ozone level), or changes in local oxidant inputs (e.g., primary NO 2 emissions) which might arise, for example, from modifications in vehicle emissions control technologies or vehicle fleet composition.
Keywords: Ozone; Nitrogen dioxide; NO X ; Oxidant; Regional pollution; Local pollution; Monitoring networks; Air quality; Policy models;

Hourly mean concentration data for nitric oxide (NO), nitrogen dioxide (NO2) and ozone (O3) at Marylebone Rd (an urban kerbside site in London) are used to investigate the diurnal and seasonal dependence of sources of oxidant, and their origins. The observed concentrations of oxidant ([OX], defined as [NO2]+[O3]) are interpreted in terms of a the sum of a NO X -independent ‘regional’ contribution, and a linearly NO X -dependent ‘local’ contribution. The former is believed to equate to the background O3 concentration, whereas the latter is likely to be dominated by emissions of NO2 from road transport at the studied location. The derived regional OX concentrations display a significant seasonal variation, with a springtime maximum value of ca. 43 ppb in April, the results being broadly similar to those reported for background ozone at low altitude sites in northwest Europe. A strong diurnal variation in the local OX contribution is observed throughout the year, with the highest values (typically ca. 0.11 ppb ppb−1 NO X ) during the daytime. Diurnal profiles averaged over the periods of the year when the UK operates under GMT and BST demonstrate a clear temporal shift, consistent with the local OX contribution being due to primary NO2 emissions from road transport. In conjunction with traffic flow statistics and associated NO X emissions estimates, the results suggest that primary NO2 from diesel-fuelled vehicles accounts for 0.996 v −0.6 of diesel NO X emissions, by volume, where v is the mean vehicle speed in km h−1 (valid range, 30–60 km h−1). This corresponds to (11.8±1.2)% of NO X emissions integrated over the average diurnal cycle for the conditions at Marylebone Rd. The results also suggest that primary NO2 emissions from petrol-fuelled vehicles are far less important, with an upper limit NO2/NO X emission ratio of <3%.
Keywords: Ozone; Nitrogen dioxide; NO X ; Oxidant; Regional pollution; Local pollution; Monitoring networks; Air quality; Policy models;

Polybrominated diphenyl ethers (PBDES) at a solid waste incineration plant I: Atmospheric concentrations by Cecilia Agrell; Arnout F.H. ter Schure; Jeanette Sveder; Alma Bokenstrand; Per Larsson; Bart N. Zegers (5139-5148).
In the first of two papers, the atmospheric poly brominated diphenyl ether (PBDE) concentrations at a municipal solid waste incineration (MSW) plant with electronic recycling is compared with that at an industrial urban reference site producing asphalt and concrete. In the second paper, atmospheric deposition and washout behaviour is presented (Atmos. Environ. (2004a)). PBDEs (BDE28, −47, −66, −100, −154, −153, −183, −209) in the gaseous and particulate phase were measured with high resolution in time during the colder parts of the year to minimise the influence of potential historical pollution at the sites through volatilisation. This also means that reported levels are lower compared to other reported data. Results of BDE47 (TetraBDE) and BDE209 (DecaBDE) as representatives of “old” vs. “new” PBDEs as well as ∑PBDE, excluding BDE209, are presented. Median ∑PBDE, BDE47 and BDE209 concentration were 6.3, 2.1 and 10.4 pg m−3 at the MSW and 3.5, 1.7 and 6.5 pg m−3 at the reference site. The total concentrations (gaseous and particulate phase) were significantly higher at the MSW compared to the reference site for ∑PBDE and BDE47 but not for BDE209. The same results were obtained regarding concentrations in the gaseous phase. Particle concentrations were significantly higher at the MSW for ∑PBDE, BDE47 and BDE209. Within each site, the gaseous-phase concentration was significantly higher than the particulate-phase concentration except for BDE209 at the MSW. Thus, the proportion of BDE209 detected in the particulate phase was higher at the MSW compared to the reference site. Together with the results of the second paper, we suggest that treatment of waste is presently a source of “old” PBDEs to the environment, whereas the rather similar BDE209 concentrations at the two sites are more a result of proximity to potential diffuse sources.
Keywords: PBDE; Partitioning; Waste treatment; Sources;

Polybrominated diphenyl ethers at a solid waste incineration plant II: atmospheric deposition by Arnout F.H. ter Schure; Cecilia Agrell; Alma Bokenstrand; Jeanette Sveder; Per Larsson; Bart N. Zegers (5149-5155).
In the second of two papers, the atmospheric polybrominated diphenyl ethers (PBDE) deposition (wet and dry) at a municipal solid waste incineration (MSW) plant with electronics recycling is compared with that at an industrial urban reference site (URS) producing asphalt and concrete. Results of BDE209 and ΣPBDE excluding BDE209 as representatives of “new” vs. “old” PBDEs are presented. Volume weighted mean ΣPBDE and BDE209 concentrations at the MSW were 6.2 and 14.4 ng l−1, and at the URS were 2.5 and 14.1 ng l−1. Median ΣPBDE and BDE209 deposition fluxes were 21.3, 63.8 and 7.0, 14.7 ng m−2  day−1 at the MSW and URS, respectively. The concentrations in precipitation and the deposition fluxes were significantly higher at the MSW compared to the URS. Measured total washout- ratios (W T) were dependent on particle scavenging and the median W T for all congeners was 5.4×105. Median dry particle deposition velocities ranged from 0.4 to 49 cm s−1, depending on congener, showing that PBDEs are effectively removed from the atmosphere by particle deposition. PBDE fluxes increased at the reference site when winds were blowing from west–south–west, i.e. from the direction of the MSW. PBDE deposition and washout ratios were not influenced by temperature or rain volume, suggesting a constant emission from the MSW regardless of weather conditions. Together with the results of paper I (Agrell et al., 2004, Atmospheric Environment, this issue) we therefore suggest that treatment of waste, e.g. electronics recycling, is more a source of “old” PBDEs to the environment, whereas the rather similar BDE209 concentrations at the two urban sites are more a result of proximity to potential diffuse sources.
Keywords: PBDE; Deposition; Partitioning; Washout; Waste treatment;

Evidencing lead deposition at the urban scale using “short-lived” isotopic signatures of the source term (Pb–Zn refinery) by Matthias Franssens; Pascal Flament; Karine Deboudt; Dominique Weis; Espéranza Perdrix (5157-5168).
To demonstrate the ability of the lead isotope signature technique to evidence the spatial extent of an industrial Pb deposition plume at a local scale, dry deposition of lead in the urban environment of a Pb–Zn refinery was investigated, as a study case, using transient (“short-lived”) isotopic signatures of the industrial source. Sampling campaigns were achieved in representative weather conditions, on an 8-h basis. Dry deposition rates measured downwind from refinery emissions (≈102–103  μg Pb m−2  h−1), cross-sectionally in a 3–5 km radius area around the plant, represent 10–100 times the urban background dry fallout, measured upwind, as well as fallout measured near other potential sources of anthropogenic Pb. The Pb–Zn refinery isotopic signature (approx. 1.100<206Pb/207Pb<1.135) is made identifiable, using the same set of Pb and Zn ores for 2 days before sampling and during field experiments, by agreement with the executive staff of the plant. This source signature is less radiogenic than signatures of urban background Pb aerosols (1.155<206Pb/207Pb<1.165) and minor sources of Pb aerosols (1.147<206Pb/207Pb<1.165). By a simple binary mixing model calculation, we established the extension of the industrial Pb deposition plume. Fifty to eighty percents of total lead settled by the dry deposition mode, 3–4 km away from the refinery, still have an industrial origin. That represents from 40 to 80 μg Pb m−2  h−1, in an area where the blood lead level exceeds 100 μg Pb l−1 for 30% of men and 12% of women living there. We demonstrate here that stable Pb isotope analysis is able to evidence the Pb dry deposition plume in stabilised aerodynamic conditions, using a short-lived source term, suggesting that this methodology is able to furnish valuable data to validate industrial Pb aerosols dispersion models, at the urban scale.
Keywords: Lead isotopes; Pb–Zn refinery; Urban area; Aerosol measurements; MC-ICP-MS;

The field measurement program of the Central California Ozone Study (CCOS) was conducted during the summer of 2000 with an overall goal of improving the understanding of ozone formation over central and northern California. Measurements of actinic flux were made as part of the study using spectroradiometers located at University of California, Davis; Sunol, California, and the Desert Research Institute in Reno, Nevada. The measured actinic flux was compared with the standard Peterson flux for a high ozone episode that occurred at the end of July. The standard Peterson flux was found to be greater than the measured flux across the spectral range. The measured actinic flux was used, along with standard quantum yields and absorption cross-section data to calculate the photolysis rate parameters for nitrogen dioxide, ozone and formaldehyde, and a radiative transfer model was used to simulate these same photolysis rate parameters. The simulated photolysis rate parameters for nitrogen dioxide could be up to 56% greater than the photolysis rate parameters derived from the measured actinic flux; for ozone the difference was as great as 160%; for the molecular reaction of formaldehyde the difference was as great as 89%; and for the radical producing channel the difference was as great as 126%. A simple atmospheric chemistry box-model was used to estimate the significance of these differences for air quality assessment. For a typical high ozone episode day 31 July, differences between modeled ozone concentrations based on photolysis rate parameters versus those derived from measured actinic flux were less than 7% change in concentration, while differences in HO concentrations were as high as 15%.
Keywords: Actinic flux; Photolysis rates; Ozone; Hydroxyl;