The effects of the coastal environment on the atmospheric mercury cycle

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95186/1/jgrd10304.pd

Individual Particle Analysis of Ambient PM 2.5 Using Advanced Electron Microscopy Techniques

The overall goal of this project was to demonstrate a combination of advanced electron microscopy techniques that can be effectively used to identify and characterize individual particles and their sources. Specific techniques to be used include high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM), STEM energy dispersive X-ray spectrometry (EDX), and energy-filtered TEM (EFTEM). A series of ambient PM{sub 2.5} samples were collected in communities in southwestern Detroit, MI (close to multiple combustion sources) and Steubenville, OH (close to several coal fired utility boilers). High-resolution TEM (HRTEM) -imaging showed a series of nano-metal particles including transition metals and elemental composition of individual particles in detail. Submicron and nano-particles with Al, Fe, Ti, Ca, U, V, Cr, Si, Ba, Mn, Ni, K and S were observed and characterized from the samples. Among the identified nano-particles, combinations of Al, Fe, Si, Ca and Ti nano-particles embedded in carbonaceous particles were observed most frequently. These particles showed very similar characteristics of ultrafine coal fly ash particles that were previously reported. By utilizing HAADF-STEM, STEM-EDX, and EF-TEM, this investigation was able to gain information on the size, morphology, structure, and elemental composition of individual nano-particles collected in Detroit and Steubenville. The results showed that the contributions of local combustion sources - including coal fired utilities - to ultrafine particle levels were significant. Although this combination of advanced electron microscopy techniques by itself can not identify source categories, these techniques can be utilized as complementary analytical tools that are capable of providing detailed information on individual particles

Divergent effects of urban particulate air pollution on allergic airway responses in experimental asthma: a comparison of field exposure studies

Abstract Background Increases in ambient particulate matter of aerodynamic diameter of 2.5 μm (PM2.5) are associated with asthma morbidity and mortality. The overall objective of this study was to test the hypothesis that PM2.5 derived from two distinct urban U.S. communities would induce variable responses to aggravate airway symptoms during experimental asthma. Methods We used a mobile laboratory to conduct community-based inhalation exposures to laboratory rats with ovalbumin-induced allergic airways disease. In Grand Rapids exposures were conducted within 60 m of a major roadway, whereas the Detroit was located in an industrial area more than 400 m from roadways. Immediately after nasal allergen challenge, Brown Norway rats were exposed by whole body inhalation to either concentrated air particles (CAPs) or filtered air for 8 h (7:00 AM - 3:00 PM). Both ambient and concentrated PM2.5 was assessed for mass, size fractionation, and major component analyses, and trace element content. Sixteen hours after exposures, bronchoalveolar lavage fluid (BALF) and lung lobes were collected and evaluated for airway inflammatory and mucus responses. Results Similar CAPs mass concentrations were generated in Detroit (542 μg/m3) and Grand Rapids (519 μg/m3). Exposure to CAPs at either site had no effects in lungs of non-allergic rats. In contrast, asthmatic rats had 200% increases in airway mucus and had more BALF neutrophils (250% increase), eosinophils (90%), and total protein (300%) compared to controls. Exposure to Detroit CAPs enhanced all allergic inflammatory endpoints by 30-100%, whereas inhalation of Grand Rapids CAPs suppressed all allergic responses by 50%. Detroit CAPs were characterized by high sulfate, smaller sized particles and were derived from local combustion sources. Conversely Grand Rapids CAPs were derived primarily from motor vehicle sources. Conclusions Despite inhalation exposure to the same mass concentration of urban PM2.5, disparate health effects can be elicited in the airways of sensitive populations such as asthmatics. Modulation of airway inflammatory and immune responses is therefore dependent on specific chemical components and size distributions of urban PM2.5. Our results suggest that air quality standards based on particle speciation and sources may be more relevant than particle mass to protect human health from PM exposure.http://deepblue.lib.umich.edu/bitstream/2027.42/112357/1/12940_2012_Article_573.pd

Sources of mercury in the Arctic

Global and regional emission inventories of mercury are reviewed with special emphasis on the source regions with potential impact on the Arctic environment. These sources are located mostly in Eurasia and North America and emit almost 1300 t of Hg to the air annually. Combustion of fossil fuels to produce electricity and heat is the major source of Hg. Major portion of the element emissions from this source is in a gaseous phase. A small portion of Hg emissions in Eurasia and North America is deposited in the Arctic region, perhaps 60 to 80 t annually. Additional amounts of Hg in the Arctic air originate from natural sources, although it is very difficult to quantify them. A small decrease of anthropogenic Hg emissions is observed in Europe at present. These emissions are expected to increase again in the near future.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43916/1/11270_2005_Article_BF01189714.pd

Regional trace element and sulfate transport

The goal of this paper was to investigate the transport of atmospheric sulfate and trace elements across the northeastern U.S.A. Data from a number of sites--Underhill (VT), Whiteface Mountain (NY), Mayville (NY), Laurel Hill and Allegheny Mountain (PA) and Deep Creek Lake (MD)--in August 1983 were considered. Sulfate was found to be regional in nature, displaying temporal variations which were similar at sites separated by large distances (several hundred kilometers) under certain meteorological conditions. Selenium was the only trace species investigated which displayed a regional character, though it too was influenced by local sources. Other elements, such as As and V displayed a somewhat regional nature but less than that observed for sulfate and selenium.The 5-day period 16-20 August, a period of elevated sulfate at all sites, was investigated as to the generality of regional signatures, utilizing trace element ratios. The inter-site variabilities in elemental ratios among the Allegheny, Laurel, Deep Creek and Mayville sites were generally small (a factor of 2 or less) and well within the variabilities at a given site from one day to another. But there were exceptions, probably reflecting influences of local sources. Comparison with earlier trace-element data from the same region suggests that temporal variations may be less than spatial ones. Together the data indicate that it is important to obtain data from multiple sites and periods within a region in any effort to construct a regional signature.An unusually clean period, 13-15 August, with steady air mass advection from the northeast to all sites, was investigated to evaluate the conservation of regional signatures into downwind regions. The inter-regional differences in trace element ratios proved to be far larger than the intea-regional ones--an order of magnitude in some cases, attributable mostly to addition of trace elements in the downwind region. The ability to identify in one region the signature from another region appears to be problematic. However, aerosol trace element ratios are found to be a powerful tool for investigating regional source influences when used in concert with meteorological information.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31952/1/0000905.pd

Air Pollution Exposure Assessment for Epidemiologic Studies of Pregnant Women and Children: Lessons Learned from the Centers for Children’s Environmental Health and Disease Prevention Research

The National Children’s Study is considering a wide spectrum of airborne pollutants that are hypothesized to potentially influence pregnancy outcomes, neurodevelopment, asthma, atopy, immune development, obesity, and pubertal development. In this article we summarize six applicable exposure assessment lessons learned from the Centers for Children’s Environmental Health and Disease Prevention Research that may enhance the National Children’s Study: a) Selecting individual study subjects with a wide range of pollution exposure profiles maximizes spatial-scale exposure contrasts for key pollutants of study interest. b) In studies with large sample sizes, long duration, and diverse outcomes and exposures, exposure assessment efforts should rely on modeling to provide estimates for the entire cohort, supported by subject-derived questionnaire data. c) Assessment of some exposures of interest requires individual measurements of exposures using snapshots of personal and microenvironmental exposures over short periods and/or in selected microenvironments. d) Understanding issues of spatial–temporal correlations of air pollutants, the surrogacy of specific pollutants for components of the complex mixture, and the exposure misclassification inherent in exposure estimates is critical in analysis and interpretation. e) “Usual” temporal, spatial, and physical patterns of activity can be used as modifiers of the exposure/outcome relationships. f) Biomarkers of exposure are useful for evaluation of specific exposures that have multiple routes of exposure. If these lessons are applied, the National Children’s Study offers a unique opportunity to assess the adverse effects of air pollution on interrelated health outcomes during the critical early life period

Wet deposition of mercury and ambient mercury concentrations at a site in the Lake Champlain basin

The “Great Waters” program, established in the 1990 Clean Air Act Amendments, mandated that atmospheric deposition of hazardous air pollutants to Lake Champlain (including Hg) be assessed. An assessment of the magnitude and seasonal variation of atmospheric Hg deposition in the Lake Champlain basin was initiated in December 1992 with one year of event precipitation collection, as well as collection of vapor and particle phase Hg in ambient air. Samples were collected at the Vermont Monitoring Cooperative air monitoring site at the Proctor Maple Research Center in Underhill Center, VT. The average volume-weighted concentration for Hg in precipitation was 8.3 ng/L for the sampling year and the average amount of Hg deposited with each precipitation event was 0.069 μg/m 2 . The total amount of Hg deposited through precipitation during 1993 was 9.26 μg/m 2 /yr. A seasonal pattern for Hg in precipitation was evident, with increased concentrations and deposition during spring and summer months. Meteorological analysis indicated the highest levels of Hg in precipitation were associated with regional transport from the south regardless of season, and with transport from the west, southwest and northwest during spring and summer months. Concentrations of ambient vapor phase Hg were typical of rural locations and consistent across seasons. Ambient particulate Hg concentrations averaged 11 pg/m 3 with highest concentrations during the winter months.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43913/1/11270_2005_Article_BF01189685.pd

Mercury Accumulation in Foliage over Time in Two Northern Mixed-Hardwood Forests

Concentrations of mercury (Hg) in live foliage increased ten-fold from spring bud break (mean ± std. dev. from bothsites: 3.5±1.3 ng g -1 ) to autumn litterfall(36±8 ng g -1 ). Mercury in foliage did not behavesimilarly to eight other elements with known soil or aerosolsources (Aluminum (Al), Vanadium (V), Strontium (Sr), Rubidium(Rb), Copper (Cu), Zinc (Zn), Barium (Ba), and lead (Pb)),suggesting that Hg originated from a distinct pathway. Based onmeasured and modeled data, uptake of only 25% of the availableambient dry deposited Hg 0 could explain all of the Hgmeasured in foliage throughout the growing season. Estimates ofgaseous elemental Hg (Hg 0 ) uptake from soil water accountedfor 3–14%% of the Hg in litterfall. Mercury deposition toforested sites in the Lake Champlain and Lake Huron basins washighest in litterfall (40%), followed by total throughfall(33%), and precipitation (27%). The Hg flux in litterfall was15.8±1.9~μg m -2 yr -1 to the Lake ChamplainWatershed in 1995 and was 11.4±2.8~μg m -2 yr -1 to the Lake Huron Watershed in 1996. In comparison, the Hg fluxes in precipitation and total throughfall were 9.0±0.6 and 11.6±0.7~μg m -2 yr -1 in the Lake Champlain Watershed (1995), and 8.7±0.5 and 10.5±1.0~μg m -2 yr -1 in the Lake Huron Watershed (1996).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43897/1/11270_2004_Article_323237.pd

Mercury Air/Surface Exchange Kinetics of Background Soils of the Tahquamenon River Watershed in the Michigan Upper Peninsula

Air/surface exchange of mercury was investigated over background soils at five sites in the Tahquamenon River watershed in the Michigan Upper Peninsula in the summer of 1998. Measurements of Hg fluxes were performed during middayperiods using the ORNL Teflon dynamic flux chamber. Mean Hg emission fluxes were 1.4±0.3–2.4±1.0 ng m -2 hr -1 for three shaded forest sites and 7.6±1.7 ng m -2 hr -1 for an open field site. Hg dry deposition was observed at a heavily shaded forest site overwet soils (mean = –0.3±0.2 ng m -2 hr -1 ). Theoverall mean Hg flux was 1.4±1.4 ng m -2 hr -1 for the four shaded forest sites. The Hg fluxes observed at these sites are similar to those found at other northern background sites. Significant, rapid response of Hg emission to solar radiation was observed over these background soils. Artificial irrigation over these soils induced immediate andmeasurable increases in Hg emission. Soil temperature was found to be less influential to Hg air/surface exchange over these heavily shaded forest background soils than we have seen elsewhere.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43896/1/11270_2004_Article_267454.pd

Historical trends of airborne trace metals in Detroit from 1971 to 1992

Ambient concentrations of particulate Fe, Zn, Ph, Ni, Cr, Cd and Hg were measured at nine sites located in the metropolitan area of Detroit from 1971 to 1992. The ambient concentrations of all the trace metals were found to be generally higher at industrial and commercial sites. The concentrations show significant variations between residential and commercial areas and between residential and industrial areas; however, no significant variation was found between the industrial and commercial settings. The spatial variation of trace metal levels within the urban area was influenced by the frequency distribution of the wind direction as well as type and location of emission sources. The ambient concentrations of the trace metals during the decade of 1971–1981 declined by 37–88%. In the 1980s many of the trace metals reversed this trend with the exception of Fe and Pb which continued to decline at annual rates of 2% and 9.8%, respectively. The sharp decrease in Pb concentrations during the 1980s, reflected the significant reduction of Pb content in gasoline from 0.28 g/liter in the 1982 to 0.026 g/liter in the 1989. The ambient concentrations of Zn, Ni, Cr, Cd and Hg showed an upward trend during the 1980s with an annual rate in the range of 0.6% to 10.6%. The long-term trends of selected U.S. market parameters, analyzed as potential long-term indicators of emission sources activityies, were consistent with the changes of ambient concentrations, the correlation coefficient being in the range of 0.58 to 0.84 for most of the trace metals.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43917/1/11270_2004_Article_BF00157419.pd