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Concentrations of 53 volatile organic compounds (VOCs) are reported from four locations near the World Trade Center (WTC) (New York, USA) complex for canister samples collected from September 2001 through January 2002. Across the four sampling sites, mean concentrations ranged from 94.5 to 219 μ g m - 3 for total VOCs. The highest mean concentrations for individual VOCs at any site were for ethane ( 18.7 μ g m - 3 ) , isopentane ( 17.1 μ g m - 3 ) , and m , p -xylenes ( 17.0 μ g m - 3 ) . VOC concentrations were generally highest for samples collected north and west of the WTC complex. Concentrations of total VOCs (and most individual VOCs) decreased from the period when fires were present at the WTC complex (before 19 December 2001) to the period after fires. The EPA Unmix Version 5.0 receptor model was used to assess the impact of WTC fires and recovery efforts on ambient VOC concentrations. Four factors were identified: burning of building debris, a mixed recovery/heating source, motor vehicle exhaust, and a mixed gasoline source.

The Florida Everglades Dry-Deposition Study (FEDDS) was designed to test the viability of using new and existing measurement techniques in the estimation of the dry-depositional loading of speciated mercury (elemental gaseous, reactive gaseous and particulate) to a mixed sawgrass (Cladium jamaicense) and cattail (Typha domingensis) stand within the Florida Everglades. Measurement intensives were performed during 24 February–04 March 1999 and 05–21 June 2000, which corresponded to the climatological dry and wet seasons in South Florida, respectively. During these intensives, direct measurements of mercury dry-deposition were made using a newly developed surrogate water surface technique. These direct measurements were compared with modeled estimates of mercury dry-deposition to the site that were obtained through the use of an inferential or “bigleaf” model that was modified for use with speciated mercury. On-site measurements of ambient speciated mercury concentrations and numerous micrometeorological variables were used as input to the model. The average mercury dry-deposition measured during the 1999 FEDDS measurement intensive was 13.3±4.0 ng m−2 day−1, while the modeled deposition for this period was 3.4±2.3 ng m−2 day−1. The average mercury dry-deposition measured during the 2000 FEDDS measurement intensive was lower, 5.9±2.8 ng m−2 day−1, while the average modeled deposition for this period was 1.8±0.6 ng m−2 day−1. A least-squares linear regression suggests that the model was able to explain 74% and 73% of the variability in the datasets for the 1999 and 2000 FEDDS intensives, respectively. While reported reductions in total mercury emissions across South Florida between study periods could explain the reductions in both the measured and predicted mercury dry-deposition estimates, the increased presence of cumulus convection during the summer-intensive could have also resulted in a removal of reactive and particulate mercury species within the atmosphere of South Florida.

In 2010, a dramatic increase in the levels of total trihalomethane (THM) and the relative proportion of brominated species was observed in finished water at several Pennsylvania water utilities (PDW) using the Allegheny River as their raw water supply. An increase in bromide (Br(-)) concentrations in the Allegheny River was implicated to be the cause of the elevated water disinfection byproducts. This study focused on quantifying the contribution of Br(-) from a commercial wastewater treatment facility (CWTF) that solely treats wastes from oil and gas producers and discharges into the upper reaches of the Allegheny River, and impacts on two downstream PDWs. In 2012, automated daily integrated samples were collected on the Allegheny River at six sites during three seasonal two-week sampling campaigns to characterize Br(-) concentrations and river dispersion characteristics during periods of high and low river discharges. The CWTF discharges resulted in significant increases in Br(-) compared to upstream baseline values in PDW raw drinking water intakes during periods of low river discharge. During high river discharge, the assimilative dilution capacity of the river resulted in lower absolute halide concentrations, but significant elevations Br(-) concentrations were still observed at the nearest downstream PDW intake over baseline river levels. On days with active CWTF effluent discharge the magnitude of bromide impact increased by 39 ppb (53%) and 7 ppb (22%) for low and high river discharge campaigns, respectively. Despite a declining trend in Allegheny River Br(-) (2009-2014), significant impacts from CWTF and coal-fired power plant discharges to Br(-) concentrations during the low river discharge regime at downstream PDW intakes was observed, resulting in small modeled increases in total THM (3%), and estimated positive shifts (41-47%) to more toxic brominated THM analogs. The lack of available coincident measurements of THM, precursors, and physical parameters limited the interpretation of historical trends.

Near-road exposure to air pollutants has been associated with decreased lung function and other adverse health effects in susceptible populations. This study was designed to investigate whether different types of near-road particulate matter (PM) contribute to exacerbation of allergic asthma. Samples of upwind and downwind coarse, fine, and ultrafine PM were collected using a wind direction-actuated ChemVol sampler at a single site 100 m from Interstate-96 in Detroit, MI during winter 2010/2011. Upwind PM was enriched in crustal and wood combustion sources while downwind PM was dominated by traffic sources. Control and ovalbumin (OVA)-sensitized BALB/cJ mice were exposed via oropharyngeal (OP) aspiration to 20 or 100 μg of each PM sample 2 h prior to OP challenge with OVA. In OVA-allergic mice, 100 μg of downwind coarse PM caused greater increases than downwind fine/ultrafine PM in bronchoalveolar lavage neutrophils, eosinophils, and lactate dehydrogenase. Upwind fine PM (100 μg) produced greater increases in neutrophils and eosinophils compared to other upwind size fractions. Cytokine (IL-5) levels in BAL fluid also increased markedly following 100 μg downwind coarse and downwind ultrafine PM exposures. These findings indicate coarse PM downwind and fine PM upwind of an interstate highway promote inflammation in allergic mice.

Aerosol slurry samples were collected at 30-min intervals for sequential 1-month periods at each of two sites (Sydney and “Dairy”) in the Tampa Bay area during the 2002 Bay Regional Atmospheric Chemistry Experiment using the University of Maryland Semicontinuous Elements in Aerosol Sampler-II (SEAS-II). More than 500 samples, believed to be affected by plumes from local utility and industrial sources, were selected for electrothermal atomic absorption spectrophotometric analyses for elemental markers (Al, Fe, Cr, Cu, Mn, Pb, Se, As, Ni, Zn and Cd) based on excursions in SO2 and NOx measurements. Correlation of short-term excursions in metals and SO2, and surface wind directions observed between May 23 and 26th, 2002, revealed the influence of an animal feed supplements production facility (AFS), 17 km upwind at a station angle of 81°, for which emissions had not previously been detected by standard monitoring methods. Emission “profiles” for this source were developed, separately, from the time series data and by using principle components analysis (PCA) and positive matrix factorization (PMF). In addition, a local dust component was evident in Al and Fe concentration profiles during periods of elevated wind speeds and was resolved by PCA/PMF. Similarly, large but brief 1.5-h excursions in Zn (maximum, 403 ng m−3), Cd, and Pb on May 17th were correlated with winds from the direction of an incinerator (station angle, 250°) 17 km from Sydney. Lastly, large excursions in As concentrations (maximum, 86 ng m−3) observed (May 4th and 5th at Sydney and November 2nd and 3rd at the Dairy) were used to locate previously unrecognized sources, tentatively associated with combustion/production of pressure-treated lumber. Profiles developed directly from the time series data were in the range of those derived from PCA-PMF (AFS); and those for the incinerator, with previously published values.

Intensive field measurements of atmospheric mercury and related species were carried out in Ny Alesund, Spitsbergen, during the spring of 2003 at two altitudes. Measurements were made at the Italian research station Dirigibile Italia (12 m a.s.l.) and on the top of Zeppelin Mountain at the Norwegian Research Station (474 m a.s.l.). Ambient concentrations of gaseous elemental mercury, divalent reactive gaseous mercury and particulate phase mercury were semi-continuously measured at both sites using an integrated Tekran system. Atmospheric elemental gaseous mercury depletion events (AMDEs) were observed at both locations, the lowest observed Hg0 concentration was 0.3 ng m−3. At sea level, mercury species concentrations following AMDEs were found to be higher and to exhibit larger variability in comparison to those observed at Zeppelin station.

Concentrations of elemental carbon (EC), organic carbon matter (OM), particulate matter less than 2.5 microm (PM2.5), reconstructed soil, trace element oxides, and sulfate are reported from four locations near the World Trade Center (WTC) complex for airborne particulate matter (PM) samples collected from September 2001 through January 2002. Across the four sampling sites, daily mean concentrations ranged from 1.5 to 6.8 microg/m3 for EC, from 10.2 to 31.4 microg/m3 for OM, and from 22.6 to 66.2 microg/m3 for PM2.5. Highest concentrations of PM species were generally measured north and west of the WTC complex. Total carbon matter and sulfate constituted the largest fraction of reconstructed PM2.5 concentrations. Concentrations of PM species across all sites decreased from the period when fires were present at the WTC complex (before December 19, 2001) to the period after the fires. Averaged over all sites, concentrations decreased by 25.6 microg/m3 for PM2.5, 2.7 microg/m3 for EC, and 9.2 microg/m3 for OM from the fire period to after fire period.

The U.S. Environmental Protection Agency (EPA), the Florida Department of Environmental Protection (FLDEP), and Texas A&M University collaborated in the design, construction, and testing of a unique, highly crosslinked, Teflon-coated inlet and manifold gas and aerosol sampling system that is being used in EPA aircraft atmospheric pollution characterization studies. The aircraft-borne ambient sampling system, which consists of a Teflon-coated shrouded probe coupled to a Teflon-coated aluminum manifold, is designed to collect reactive gases (e.g., mercury and halide species) and aerosols for subsequent analysis and characterization. The shrouded inlet probe was tested for particle transmission ratios in a high-speed aerosol wind tunnel. An existing wind tunnel was upgraded from a maximum wind speed of 13.4 m/s (48 km/h or 30 miles/h) to 50.5 m/s (182 km/h or 113 miles/h) to test this probe. The wind tunnel was evaluated for compliance with the criteria of ANSI 13.1 to establish the acceptability of its use ...

An assessment of trace metal quantification capabilities for indoor (123±53 μg; mean±standard deviation of particle mass) and personal exposure (PE) (32±12 μg) PM2.5 samples from Baltimore, MD was undertaken as part of an EPA study investigating health effects associated with particulate matter. This study included determination of total PM2.5 metal concentrations by energy dispersive X-ray fluorescence and instrumental neutron activation analysis, as well as method development to quantify amounts of water and acid-extractable metals from PM2.5 using inductively coupled plasma-mass spectrometry (ICP-MS). Analytical uncertainties, filter blank contributions, and sample preparation were all found to significantly impact quantification limits. The ICP-MS leaching procedure resulted in partial extraction of metals from the PM2.5. Most of the extractable components of the metals were in a water-soluble form suggesting a high potential for bioavailability of elements from respiratory exposure to PM2.5. A comparison of PM2.5 trace metal concentrations from indoor air samples collected from a central indoor site versus concurrently collected PE samples indicates that resident activities result in exposure to higher concentrations of soluble trace metals.

In this study, gas-phase elemental mercury (Hg0) and related species (including inorganic reactive gaseous mercury (RGM) and particulate mercury (PHg)) were measured at Cheeka Peak Observatory (CPO), Washington State, in the marine boundary layer during 2001-2002. Air of continental origin containing anthropogenic pollutants from the urban areas to the east contained on average 5.3% lower Hg0 levels as compared to the marine background. This result is difficult to reconcile since it is known that industrial emissions in our region are sources of Hg0. The rate of removal of Hg0 from a pollution plume necessary to account for our observations is inconsistent with the accepted view of Hg0 as a stable atmospheric pollutant. The largest and most frequent Hg0 loss events occurred in the presence of increased ozone (O3) during the summer. Hg0 and O3 also display diurnal cycles that are out-of-phase with one another. In other seasons Hg0 behavior is less consistent, as we observe weak positive correlations with O3 and occasional Hg0 enhancements in local pollution. RGM and PHg concentrations are enhanced only slightly during Hg0 loss events, comprising a small fraction of the mercury pool (approximately 3%). Long-range transported pollution of Asian origin was also detected at CPO, and this contains both higher and lower levels of Hg0 as compared to the background with maximum changes being20%. Here, the more photochemically processed the air mass, as determined by propane/ethane ratios, the more likely we are to observe Hg0 loss. Air from the marine background in summer displays a significant diurnal cycle with a phase that matches the diurnal cycles seen in polluted air masses. A Junge lifetime for Hg0 in the clean marine boundary layer is calculated to be 7.1 months, which is on the low end of previous estimates (0.5-2 yr).

Gaseous elemental mercury (Hg0) is a globally distributed air toxin with a long atmospheric residence time. Any process that reduces its atmospheric lifetime increases its potential accumulation in the biosphere. Our data from Barrow, AK, at 71 degrees N show that rapid, photochemically driven oxidation of boundary-layer Hg0 after polar sunrise, probably by reactive halogens, creates a rapidly depositing species of oxidized gaseous mercury in the remote Arctic troposphere at concentrations in excess of 900 pg m(-3). This mercury accumulates in the snowpack during polar spring at an accelerated rate in a form that is bioavailable to bacteria and is released with snowmelt during the summer emergence of the Arctic ecosystem. Evidence suggests that this is a recent phenomenon that may be occurring throughout the earth's polar regions. Udgivelsesdato: 2002-Mar-15

The reduction of divalent gaseous mercury (Hg(II)) to elemental gaseous mercury (Hg(0)) in a commercial coal-fired power plant (CFPP) exhaust plume was investigated by simultaneous measurement in-stack and in-plume as part of a collaborative study among the U.S. EPA, EPRI, EERC, and Southern Company. In-stack continuous emission monitoring data were used to establish the CFPP's real-time mercury speciation and plume dilution tracer species (SO2, NOX) emission rates, and an airship was utilized as an airborne sampling platform to maintain static position with respect to the exhaust plume centerline for semicontinuous measurement of target species. Varying levels of Hg(II) concentration (2.39-3.90 μg m(-3)) and percent abundance (∼ 87-99%) in flue gas and in-plume reduction were observed. The existence and magnitude of Hg(II) reduction to Hg(0) (0-55%) observed varied with respect to the types and relative amounts of coals combusted, suggesting that exhaust plume reduction occurring downwind of the CFPP is influenced by coal chemical composition and characteristics.

In a recent study, EPA found a significant relationship between PM2.5 mass measurements at a community site and personal exposure samples in a Towson, MD retirement facility. This manuscript builds upon the mass concentration results by evaluating the exposure relationships with the elemental composition of the PM2.5 mass. Daily community, outdoor, and indoor PM2.5 were measured with a URG Versatile Air Pollutant Sampler (VAPS). Daily personal and apartment PM2.5 samples were collected with a Marple Personal Exposure Monitor (PEM). Only subjects with the most complete data records (n=10) were used in this analysis. Significant differences were found between the VAPS and PEM samplers for PM2.5 elemental composition, so all subsequent analyses were conducted independently for each of the data sets. Both the VAPS and PEM samples were analyzed with energy dispersive X-ray fluorescence (XRF). In addition, the VAPS samples were analyzed for pH, major ions, and elemental/organic carbon. The spatial correlation coefficients between the community and outdoor monitor, and the indoor infiltration rates were calculated for several PM2.5 constituents calculated from the VAPS samples including sulfate, nitrate, trace element oxides, soil, and NaCl. The spatial correlations for most PM2.5 constituents were good (e.g. sulfate (r2=0.99)), with the exception of soil (r2=0.40). Infiltration rates of the PM2.5 constituents were determined by linear regression analysis and varied according to particle size. Infiltration rates ranged from 0.41 (r2=0.98) for sulfate to 0.09 (r2=0.83) for nitrate. Outdoor, central indoor, apartment, and personal exposures PEM samples were also evaluated using a linear mixed effects model and median Pearson correlation coefficients. The modeling results indicate that personal exposures to PM2.5 and sulfate were strongly associated with outdoor concentrations. Conversely, personal exposures to soil and trace element oxides were not significantly correlated to outdoor concentrations.

The United States Environmental Protection Agency (US EPA) recently conducted the 1998 Baltimore Particulate Matter (PM) Epidemiology-Exposure Study of the Elderly. The primary goal of that study was to establish the relationship between outdoor PM concentrations and actual human PM exposures within a susceptible (elderly) sub-population. Personal, indoor, and outdoor sampling of particulate matter was conducted at a retirement center in the Towson area of northern Baltimore County. Concurrent sampling was conducted at a central community site. The main objective of this work was to use computer-controlled scanning electron microscopy (CCSEM) with individual-particle X-ray analysis to measure the chemical and physical characteristics of geological and trace element particles collected at the various sampling locations in and around the retirement facility. The CCSEM results show that the relative abundances of some geological and trace element particle classes identified at the outdoor and community locations differ from each other and from the indoor location. Particle images acquired during the computer-controlled analyses played a key role in the identification of certain particle types. Review of these images was particularly useful in distinguishing spherical particles (usually indicative of combustion) from non-spherical particles of similar chemical composition. Pollens and spores were also identified through a manual review of the particle images.

We have measured total gaseous mercury concentrations(Hg°) at Point Barrow, Alaska since September 1998 in aneffort to determine the geographic extent and reaction mechanismof the so-called mercury depletion events (MDE) previouslyreported in the high Arctic at Alert, Canada. Hg° has beensampled now for nearly 2 years at Barrow. In September, 1999, webegan making the first automated measurements of reactive gaseousmercury (RGM) attempted in the Arctic, along with measurements ofHg accumulation in snowpack to determine the fate of the ‘depleted’ Hg°. During the fall and early winter, Hg°and RGM exhibit only minor variation, Hg° remaining within∼10% of global background, near 1.6–1.8 ng m-3. The MDEperiods are quite different, however; within days of Arcticsunrise in January, Hg° exhibits major variations from themean, rapidly dropping as low as 0.05 ng m-3 and then cyclingback to typical levels, sometimes exceeding global background. These events continue throughout Arctic spring, then end abruptlyfollowing snowmelt, in early June. Prior to Arctic sunrise, RGMremains near detection (

In 1993, the University of Michigan Air Quality Laboratory (UMAQL) designed a new wet-only precipitation collection system that was utilized in the Lake Michigan Loading Study. The collection system was designed to collect discrete mercury (Hg) and trace element samples on either an event or weekly basis. Performance characteristics such as collector opening efficiency, collocated precision, spike recovery, field blanks, and bottle blanks were rigorously evaluated from October 1994 through October 1995 at a semi-rural site near Dexter, MI. Comparisons for Hg were made between HCl preserved versus unpreserved event collection, wet-only event versus manual event collection, and weekly volume-weighted wet-only event versus weekly bulk collection. Results of this investigation indicated that with proper preparation and ultra-clean collection techniques, wet-only precipitation collection utilizing the UMAQL modified MIC-B collector can provide virtually contamina tion-free Hg and trace element samples. On aver...

Twelve hours integrated PM2.5 samples collected with a Weekly Air Particulate Sampler (URG Model 2000-01J) from September 2008 to November 2008 in Guiyang, China, were analyzed on the Kevex energy dispersive x-ray spectrometer (XRF) for elements. Monitoring results found elevated concentrations of heavy metals (Ti, Mn, Fe, Zn, and Pb) in PM2.5 in Guiyang. The average concentrations were 30±22 ng m -3 for Ti, 250±400 ng m -3 for Mn, 340±280 ng m -3 for Fe, 290±330 ng m -3 for Zn, and 130±130 ng m -3 for Pb, respectively. Temporal variation patterns in the resulting data were also obtained. It is hypothesized that local anthropogenic sources and the seasonal variability result in the temporal variability.

Two modified passive samplers were evaluated at multiple field locations. The sampling rate (SR) of the modified polyurethane foam (PUF)-disk passive sampler for total gaseous mercury (TGM) using gold-coated quartz fiber filters (GcQFF) and gaseous oxidized mercury (GOM) using ion-exchange membranes (IEM) were 6.4 ± 1.4 and 15.3 ± 0.3 m(3) day(-1), respectively. The relative percent difference between TGM and GOM concentrations measured by a Tekran system and the passive samplers averaged 19 ± 14 and 13 ± 12% and ranged between 4-44 and 1.5-41%, respectively. The GcQFF and IEM substrates were also evaluated as collection media for surrogate surface dry deposition measurements. Mercury (Hg) concentration and dry deposition gradients were observed using these samplers at an urban/industrial site and compared to a rural/remote site. The Hg dry deposition rates measured by the surrogate surfaces were always higher than those calculated by a widely used inferential modeling method (1.3-50 fold). The Hg dry deposition measured at urban and suburban sites were comparable to those calculated from model. However, they were very different at a rural site, probably due to the low concentrations. Both methods are relatively low cost and will aid in understanding spatial distributions of Hg ambient air concentrations and dry deposition.

High time-resolution aerosol sampling was conducted for one month during July-August 2007 in Dearborn, MI, a non-attainment area for fine particulate matter (PM2.5) National Ambient Air Quality Standards (NAAQS). Measurements of more than 30 PM2.5 species were made using a suite of semi-continuous sampling and monitoring instruments. Dynamic variations in the sub-hourly concentrations of source 'marker' elements were observed when discrete plumes from local sources impacted the sampling site. Hourly averaged PM2.5 composition data for 639 samples were used to identify and apportion PM2.5 emission sources using the multivariate receptor modeling techniques EPA Positive Matrix Factorization (PMF) v4.2 and EPA Unmix v6.0. Source contribution estimates from PMF and Unmix were then evaluated using the Sustained Wind Instance Method (SWIM), which identified plausible source origins. Ten sources were identified by both PMF and Unmix: (1) secondary sulfate, (2) secondary nitrate characterized by a significant diurnal trend, (3) iron and steel production, (4) a potassium-rich factor attributable to iron/steel slag waste processing, (5) a cadmium-rich factor attributable to incineration, (6) an oil refinery characterized by La/Ce>1 specific to south wind, (7) oil combustion, (8) coal combustion, (9) motor vehicles, and (10) road dust enriched with organic carbon. While both models apportioned secondary sulfate, oil refinery, and oil combustion PM2.5 masses closely, the mobile and industrial source apportionments differed. Analyses were also carried out to help infer time-of-day variations in the contributions of local sources.

Intra-storm variability and soluble fractionation was explored for summer-time rain events in Steubenville, Ohio to evaluate the physical processes controlling mercury (Hg) in wet deposition in this industrialized region. Comprehensive precipitation sample collection was conducted from July through September 2006 using three different methods to evaluate both soluble and insoluble fractions as well as scavenging and washout properties of Hg and a suite of trace elements. Real-time filtration of event total precipitation revealed that 61 ± 17% (mean ± standard deviation) of Hg in wet deposition was in a soluble form. Comparison of total and dissolved element concentrations (solubility fractionation) showed the following order of decreasing solubility: S > Na > Se > Ca > Mg > Hg > As > Mn > V > Cr > Fe > La ≈ Ce ranging from 95% (S) to 4% (Ce). To examine removal mechanisms occurring during the course of a precipitation event, discrete, sequential sub-event precipitation samples were collected. Results indicated that Hg had lower “scavenging coefficients” (the rate of Hg concentration decrease throughout the events) than the majority of elements analyzed, indicating that either (i) Hg is incorporated into rain via gas phase inclusion or particulate nucleation within cloud, or (ii) Hg is available in the boundary layer for scavenging, even in the latter stages of precipitation. The Hg scavenging coefficient (− 0.39) was low compared to S (− 0.73), a co-pollutant of Hg. When compared to an upwind, regionally representative site, the scavenging coefficient of Hg for the locally influenced precipitation was 25% lower. This observation suggests that a continuous feed of soluble Hg was the reason for the low scavenging coefficient. Overall, this investigation of Hg wet deposition in Steubenville indicates that the physical and chemical properties of Hg emissions are driving the elevated deposition rates observed near point sources.

The Near-Road Exposures and Effects of Urban Air Pollutants Study (NEXUS) was designed to examine the relationship between near-roadway exposures to air pollutants and respiratory outcomes in a cohort of asthmatic children who live close to major roadways in Detroit, Michigan USA. From September 2010 to December 2012 a total of 139 children with asthma, ages 6–14, were enrolled in the study on the basis of the proximity of their home to major roadways that carried different amounts of diesel traffic. The goal of the study was to investigate the effects of traffic-associated exposures on adverse respiratory outcomes, biomolecular markers of inflammatory and oxidative stress, and how these exposures affect the frequency and severity of respiratory viral infections in a cohort of children with asthma. An integrated measurement and modeling approach was used to quantitatively estimate the contribution of traffic sources to near-roadway air pollution and evaluate predictive models for assessing the impact of near-roadway pollution on children's exposures. Two intensive field campaigns were conducted in Fall 2010 and Spring 2011 to measure a suite of air pollutants including PM 2.5 mass and composition, oxides of nitrogen (NO and NO 2 ), carbon monoxide, and black carbon indoors and outdoors of 25 participants' homes, at two area schools, and along a spatial transect adjacent to I-96, a major highway in Detroit. These data were used to evaluate and refine models to estimate air quality and exposures for each child on a daily basis for the health analyses. The study design and methods are described, and selected measurement results from the Fall 2010 field intensive are presented to illustrate the design and successful implementation of the study. These data provide evidence of roadway impacts and exposure variability between study participants that will be further explored for associations with the health measures.

Mercury (Hg) is a toxic heavy metal that is found associated with fossil fuel deposits and that can be released to the atmosphere during fossil fuel combustion and/or processing. Hg emitted to the atmosphere can be deposited to aquatic and terrestrial ecosystems where it can be methylated by bacteria. Methylmercury is strongly biomagnified in food webs and this leads to toxic levels in high trophic level fish, the consumption of which is a major human exposure pathway. Epiphytic tree lichens have been widely used to investigate the relationship between atmospheric point sources of Hg and regional Hg deposition patterns. An intensive study of Hg concentration and stable isotopic composition of the epiphytic tree lichen Hypogymnia physodes was carried out in the area within 150 km of the Athabasca oil sands region (AOSR) industrial developments. Concentrations of Hg were comparable to background values measured in previous studies from remote areas and were far below the values observed near significant atmospheric industrial sources of Hg. Spatial patterns provide no evidence for a significant atmospheric point source of Hg from the oil sands developments, and Hg accumulation actually decreases in lichens within 25 km of the northern AOSR development, presumably due to physiological responses of H. physodes to enhanced SO2 deposition. Stable Hg isotope ratios show an increase in Δ199Hg and Δ201Hg within 25 km of the AOSR, and we speculate that this is due to a change in the proportion of the various ligands to which Hg is bonded in the lichens, and a resulting change in the isotope fractionation during partial photochemical reduction and loss of Hg from lichen surfaces.

A study was conducted that coupled use of element concentrations and lead (Pb) isotope ratios in the lichen Hypogymnia physodes collected during 2002 and 2008, to assess the impacts of air emissions from the Athabasca Oil Sands Region (AOSR, Canada) mining and processing operations. The lichens selected from the 2002 data set were from 15 samples sites collected on an N–S and E–W grid centered between the oil sands processing sites. The lichens selected for analysis in 2008 were collected using a stratified, nested circular grid approach radiating away from the oil sands processing sites, and included 121 sampling sites as far as 150 km from the mining and processing operations. Spatial analysis indicates three main element groupings including a geogenic source (aluminum and others) related to oil sands mining, an oil processing source (vanadium and others), and a grouping that is likely related to biogeochemical processes (manganese and others). An exponential decrease in concentration of the geogenic grouping of elements versus distance from the mining sites was found, whereas near source concentrations of elements typically associated with oil processing are more homogeneous spatially than the geogenic elements. The mining and oil processing related element groupings are superimposed over the elemental signature that reflects lichen biogeochemical processes. The ranges in Pb isotope ratios were similar in 2002 and 2008, suggesting that sources of Pb accumulated by the lichens did not change substantially between 2002 and 2008. The Pb isotope ratios from lichens collected beyond 50 km from the mining and processing sites cluster into a grouping with a 207 Pb/ 206 Pb ratio of 0.8650 and a 208 Pb/ 206 Pb ratio near 2.095. This grouping likely reflects the regional background Pb isotope ratio signature. The lowering of the 207 Pb/ 206 Pb and 208 Pb/ 206 Pb ratios near the mining and processing operations indicates that other Pb sources, likely related to the oil sands mining and processing, are contributing to the Pb source signature. This assessment was confirmed through the analysis of source and stack samples. The Pb isotope ratios were a better predictor of the extent of the source contribution than the element concentrations because the Pb isotope ratios are not affected by either the metabolic processing of elements by the lichens or by moisture related controls on atmospheric deposition processes at the collection sites. The main goals for this project to determine (i) the efficacy of using Pb isotopes to assist in identifying the sources of atmospherically deposited air pollutants in the AOSR and (ii) whether coupling Pb isotopes with elemental concentrations can help to elucidate the causes for spatial differences in the accumulation of elements by epiphytic lichens in relation to emission sources were successful. An approach that couples Pb isotopes, spatial analysis, and element concentrations is recommended for future source attribution studies in the AOSR.

The contribution of inorganic air pollutant emissions to atmospheric deposition in the Athabasca Oil Sands Region (AOSR) of Alberta, Canada, was investigated in the surrounding boreal forests, using a common epiphytic lichen bioindicator species ( Hypogymnia physodes ) and applying multiple receptor models. Source materials from anthropogenic and natural emitters of air pollution in the AOSR were obtained and chemically characterized to aid in the assessment. The lichens selected for analysis were collected in 2008 using a stratified, nested grid approach radiating away from the central area of oil sands production at 121 sampling sites extending as far as 150 km. Source and lichen samples were extracted and analyzed for 43 elements using dynamic reaction cell quadrupole inductively coupled plasma mass spectroscopy (DRC-ICPMS). Source apportionment of the lichen tissue analytical results was conducted using principal component analysis (PCA), chemical mass balance (CMB), positive matrix factorization (PMF), and Unmix models. Initial Varimax-rotated PCA screening analysis indicated that there were five principal components that could explain 89% of the variance contained in the lichen data set, with the majority of the variance lumped into a fugitive dust factor. This fugitive dust source could be separated into tailing sand, haul road, and overburden components using CMB on lichen samples collected near the mining and oil processing facilities. However, the CMB model performance was limited by the similarity of sources and the lack of total nitrogen measurements in the emission source profiles. The PMF and Unmix models were found to perform best with this unique AOSR lichen data set, providing very similar results at near-source as well as remote lichen collection sites. The PMF results showed that sources significantly contributing to concentrations of elements in the lichen tissue include combustion processes (∼ 23%), tailing sand (∼ 19%), haul roads and limestone (∼ 15%), oil sand and processed materials (∼ 15%), and a general anthropogenic urban source (∼ 15%). The spatial patterns of CMB, PMF, and Unmix receptor models estimated that source impacts on the H. physodes tissue elemental concentrations from the oil sand processing and fugitive dust sources had a significant association with the distance from the primary oil sands surface mining operations and related production facilities. The spatial extent of the fugitive dust impact was limited to a radius of approximately 20 km around the major mining and oil production facilities, which is indicative of ground-level coarse particulate fugitive emissions from these sources. The impact of the general urban source was found to be enhanced in the southern portion of the sampling domain in the vicinity of the Fort McMurray urban area. The receptor model results showed lower Mn concentrations in lichen tissues near oil sands production operations suggesting a biogeochemical response. Overall, the largest impact on elemental concentrations of H. physodes tissue in the AOSR was related to fugitive dust, suggesting that implementation of a fugitive dust abatement strategy could minimize the near-field atmospheric deposition of any future mining-related production activities.

Received 7 November 2006; revised 22 June 2007; accepted 13 August 2007; published 11 December 2007. [1] We describe the development of a model for transport and photochemistry of atmospheric mercury at the regional scale, along with an application to the eastern United States and adjacent Atlantic Ocean and Gulf of Mexico, and comparison with aircraftbased measurements in Florida. The model is the Community Multiscale Air Quality model (CMAQ) with modifications to include an integrated solution for gas phase and aqueous photochemistry. The expanded chemistry includes O3 ,N Ox, organics, sulfur, halogens and mercury. Divalent reactive gaseous mercury (RGM) is formed slowly through gas phase reactions and removed rapidly by aqueous reactions in cloud water. Model results show that elevated RGM (up to 260 pg m � 3 ) forms intermittently over the Atlantic Ocean in air masses that have a cloud-free history. Aircraft measurements in Florida show RGM varying between 10 and 250 pg m � 3 and increasing with altitude, a pattern that is consistent with model results. Ambient RGM would increase by 50% if aqueous reduction reactions were omitted. The model predicts that ambient elemental mercury and RGM anticorrelate in regions where RGM is produced photochemically and correlate in regions dominated by direct emissions. Model results also suggest positive correlations between RGM and SO2, reactive nitrogen and H2O2, which may be used to identify photochemically produced versus directly emitted RGM. RGM in the model is strongly correlated with O3 during pollution events, and ozone formation from anthropogenic precursors is predicted to cause a significant increase in RGM.

A field evaluation between two annular denuder configurations was conducted during the spring of 2003 in the marine Arctic at Ny-Alesund, Svalbard. The IIA annular denuder system (ADS) employed a series of five single-channel annular denuders, a cyclone and a filter pack to discriminate between gas and aerosol species, while the EPA-Versatile Air Pollution Sampler (VAPS) configuration used a single multi-channel annular denuder to protect the integrity of PM2.5 sample filters by collecting acidic gases. We compared the concentrations of gaseous nitric acid (HNO3), nitrous acid (HONO), sulfur dioxide (SO2) and hydrochloric acid (HCl) measured by the two systems. Results for HNO3 and SO2 suggested losses of gas phase species within the EPA-VAPS inlet surfaces due to low temperatures, high relative humidities, and coarse particle sea-salt deposition to the VAPS inlet during sampling. The difference in HNO3 concentrations (55%) between the two data sets might also be due to the reaction between HNO3 and NaCl on inlet surfaces within the EPA-VAPS system. Furthermore, we detected the release of HCl from marine aerosol particles in the EPA-VAPS inlet during sampling contributing to higher observed concentrations. Based on this work we present recommendations on the application of denuder sampling techniques for low-concentration gaseous species in Arctic and remote marine locations to minimize sampling biases. We suggest an annular denuder technique without a large surface area inlet device in order to minimize retention and/or production of gaseous atmospheric pollutants during sampling.

In the fall of 2002, an enhanced air monitoring site was established in Steubenville, Ohio as part of a multi-year comprehensive mercury monitoring and source apportionment study to investigate the impact of local and regional coal combustion sources on atmospheric mercury deposition in the Ohio River Valley. This study deployed advanced monitoring instrumentation, utilized innovative analytical techniques, and applied state-of-the-art statistical receptor models. This paper presents wet deposition data and source apportionment modeling results from daily event precipitation samples collected during the calendar years 2003-2004. The volume-weighted mean mercury concentrations for 2003 and 2004 were 14.0 and 13.5 ng L(-1), respectively, and total annual mercury wet deposition was 13.5 and 19.7 microg m(-2), respectively. Two new EPA-implemented multivariate statistical models, positive matrix factorization (PMF) and Unmix, were applied to the data set and six sources were identified. The dominant contributor to the mercury wet deposition was found by both models to be coal combustion (approximately 70%). Meteorological analysis also indicated that a majority of the mercury deposition found at the Steubenville site was due to local and regional sources.

There is a qualitative understanding that gaseous elemental mercury (GEM) is oxidized during Arctic spring to reactive gaseous mercury (RGM) that afterwards is removed by fast deposition to snow surfaces. The conditional sampling or relaxed eddy accumulation (REA), technique represents the first opportunity to directly measure fluxes of reactive gaseous mercury (RGM) to the snow pack in the Arctic. Using a micrometeorological method REA system, with a heated sampling system specifically designed for Arctic use, the dry deposition of RGM is measured after polar sunrise, in Barrow, Alaska. Heated KCl-coated manual RGM annular denuders were used as the accumulators with an inlet allowing only fine particles to pass (Cut off diameter 2.5mm). At 3 m above the snow pack significant RGM fluxes were measured each spring in 2001–2004. Both depositions and emissions were observed. The emissions were attributed to chemical formation of RGM at or near the snow surface. The surface resistance, Rc, for RGM was found to be very small and set to zero as a first estimate. r 2006 Elsevier Ltd. All rights reserved.

The springtime phenomenon, termed as the mercury depletion event (MDE), during which elemental gaseous mercury (Hg-0) may be converted to a reactive form that accumulates in polar ecosystems, first noted in the Arctic, has now been observed at both poles and results in an important removal pathway for atmospheric mercury. An intensive international springtime mercury experiment was performed at Ny-Alesund, Spitsbergen, from 19 April to 13 May 2003 to study the atmospheric mercury chemistry in the Arctic environment and, in particular, the MDEs which occurred in the arctic boundary layer after polar sunrise. Automated ambient measurements of Hg-0, divalent reactive gaseous mercury (RGM) and fine particulate mercury (< 2.5 mu m) (Hg(p)) were made at the Zeppelin Mountain Station (ZMS). During the experiment mercury concentrations in the lower atmosphere varied in synchrony with ozone levels throughout the Spring. Hg-0 concentrations ranged from background levels (similar to 1.6 ng m(-3)) to undetectable values (< 0.1 ng m(-3)) during the first and major MDE, while RGM data showed an opposite trend during the sampling period with concentrations increasing dramatically to a peak of 230 pg m(-3), synchronous with the depletion of Hg-0. The results of a meteorological transport analysis indicate the MDEs observed at ZMS were primarily due to air masses being transported in from open water areas in the Arctic Ocean that were already depleted of Hg-0 when they arrived and not due to in-situ oxidation mechanisms.

[1] Atmospheric mercury (Hg) species were investigated on the east coast of Florida during June 2000. The site was impacted by air mass transport from the Atlantic Ocean and south Florida. Periods with atmospheric transport from the Atlantic were characterized by low concentrations of elemental gaseous Hg and inorganic divalent reactive gaseous mercury (RGM), demonstrating that the marine boundary layer was not a significant source of RGM to this coastal site as previous researchers have hypothesized. When anthropogenic impacts were observed at the site, indicated by elevated concentrations of gases including HNO3 and SO2, RGM concentrations had higher daytime maximums. Particulate phase Hg concentrations were higher than can be explained by sea spray alone, as determined by chemical analysis of the seawater, suggesting that gaseous Hg is diffusing into the sea-salt aerosol. Although atmospheric Hg concentrations were not elevated, the observed scavenging of Hg gases by sea-salt aerosols indicates that Hg may be rapidly cycled at the atmosphere-ocean interface between gaseous, aerosol, and oceanic forms. Deposition of aerosol enriched in Hg via this process may constitute a significant global mercury flux to the oceans.

[1] In the paper by Steding and Flegal [2002] the authors claim to identify Hg in rain from trans-Pacific sources. Specifically, Steding and Flegal (paragraph [1]) state that ‘‘the Asian fluxes appear to enhance Hg concentrations both directly, through the emission of particle-bound Hg and reactive Hg, and indirectly, by increasing the rate of oxidation of Hg in the atmosphere.’’ They arrive at this conclusion by analysis of 46 event-based precipitation measurements of total Hg from two sites in California, combined with isentropic back-trajectories to identify the source region for the sampled air masses. [2] While this paper provides some potentially useful new data on Hg in rain, we found the arguments less then convincing. It is important to note that while the authors’ conclusion is plausible, the evidence presented by Steding and Flegal [2002] is insufficient to support this conclusion. Our concern with their analysis is based on three key points.

Atmospheric mercury is predominantly present in the gaseous elemental form (Hg0). However, anthropogenic emissions (e.g., incineration, fossil fuel combustion) emit and natural processes create particulate-phase mercury(Hg(p)) and divalent reactive gas-phase mercury (RGM). RGM species (e.g., HgCl2, HgBr2) are water-soluble and have much shorter residence times in the atmosphere than Hg0 due to their higher removal rates through wet and dry deposition mechanisms. Manual and automated annular denuder methodologies, to provide high-resolution (1-2 h) ambient RGM measurements, were developed and evaluated. Following collection of RGM onto KCl-coated quartz annular denuders, RGM was thermally decomposed and quantified as Hg0. Laboratory and field evaluations of the denuders found the RGM collection efficiency to be94% and mean collocated precision to be15%. Method detection limits for sampling durations ranging from 1 to 12 h were 6.2-0.5 pg m(-3), respectively. As part of this research, the authors observed that methods to measure Hg(p) had a significant positive artifact when RGM coexists with Hg(p). This artifact was eliminated if a KCl-coated annular denuder preceded the filter. This new atmospheric mercury speciation methodology has dramatically enhanced our ability to investigate the mechanisms of transformation and deposition of mercury in the atmosphere.

[1] It is well known that due to its long atmospheric residence time, mercury is distributed on a global scale and aeolian transport is believed to be the major contributor to mercury in polar environments. No measurements of reactive gaseous mercury (RGM) at all have ever been performed in the Antarctic before. Hg0(g) concentrations were in the range 0.29 to 2.3 ng m−3, with an average value of 0.9 ± 0.3 ng m−3. RGM was measured using KCl-coated annular denuders and a speciation unit coupled to a TGM analyzer; concentrations ranged from 10.5 to 334 pg m−3, with an average of 116.2 ± 77.8 pg m−3. The Hg0(g) measurements are in good agreement with the few data available for such southerly latitudes. The RGM concentrations are as high as those found in some industrial environments; the high concentrations in the absence of local sources (anthropogenic or natural) show that in situ gas phase oxidation of Hg0 is the most important factor influencing RGM production and therefore also Hg deposition. The toxicity of Hg means that the consequences of high concentrations of oxidized and soluble Hg species depositing in the fragile Antarctic environment could be serious indeed.