The Peace Bridge in Buffalo, New York, which spans the Niagara River at the east end of Lake Erie... more The Peace Bridge in Buffalo, New York, which spans the Niagara River at the east end of Lake Erie, is one of the busiest U.S. border crossings. The Peace Bridge plaza on the U.S. side is a complex of roads, customs inspection areas, passport control areas, and duty-free shops. On average 5000 heavy-duty diesel trucks and 20,000 passenger cars traverse the border daily, making the plaza area a potential "hot spot" for emissions from mobile sources. In a series of winter and summer field campaigns, we measured air pollutants, including many compounds considered by the U.S. Environmental Protection Agency (EPA*) as mobile-source air toxics (MSATs), at three fixed sampling sites: on the shore of Lake Erie, approximately 500 m upwind (under predominant wind conditions) of the Peace Bridge plaza; immediately downwind of (adjacent to) the plaza; and 500 m farther downwind, into the community of west Buffalo. Pollutants sampled were particulate matter (PM) < or = 10 microm (PM1...
ABSTRACT Arsenic and other trace metals commonly are released through the reductive dissolution o... more ABSTRACT Arsenic and other trace metals commonly are released through the reductive dissolution of iron and manganese oxides by microorganisms as part of energy metabolism. Both dissolved and sedimentary carbon substrates can be used by these microorganisms. Recent evidence implies that dissolved organic carbon (DOC) from the surface is efficiently transported to depth, where it stimulates in situ microbial communities. Other studies that correlate low aqueous As concentrations with older, recalcitrant organic carbon in older sediments. This work examines processes that affect which of these substrates contribute to reduction, and identifies potential characterizes how organic carbon moves through the subsurface to better understand this apparent contradiction. Based on laboratory experiments and field monitoring using soils and sediments from Vietnam, Cambodia and Bangladesh, we propose a conceptual model for DOC transport in which DOC transport is retarded by adsorption, and in which it re-equilibrates with sedimentary (particulate) organic carbon. In many cases, desorbed sedimentary organic forms a distinct DOC carbon pool with properties and reactivity that are similar to that of young DOC and much higher than predicted based on its age. Under conditions in which this sedimentary DOC is efficiently mobilized, the associated reducing conditions can stimulate arsenic release and in some cases, down-gradient transport.
Arsenic is a contaminant found at more than 500 US Superfund sites. Since pump and treat technolo... more Arsenic is a contaminant found at more than 500 US Superfund sites. Since pump and treat technologies are widely used for remediation of contaminated groundwater, increasing the efficiency of contaminant removal at such sites should allow limited financial resources to clean up more sites. The Vineland Chemical Company Superfund site is extensively contaminated with arsenic after waste arsenic salts were stored and disposed of improperly for much of the company's 44 year manufacturing lifetime. Despite approximately eight years of pump and treat remediation, arsenic concentrations in the recovery wells can still be greater than 1000 ppb. The arsenic concentrations in the groundwater remain high because of slow desorption of arsenic from contaminated aquifer solids. Extrapolation of laboratory column experiments suggest that continuing the current groundwater remediation practice based on flushing ambient groundwater through the system may require on the order of hundreds of years to clean the site. However, chemical additions of phosphate or oxalic acid into the aquifer could decrease the remediation time scale substantially. Laboratory results from a soil column experiment using input of 10 mM oxalic acid suggest that site clean up of groundwater could be decreased to as little as four years. Pilot scale forced gradient field experiments will help establish whether chemical additions can be effective for increasing arsenic mobilization from aquifer solids and thus substantially decrease pump and treat clean up time.
Atmospheric environment (Oxford, England : 1994), 2015
Particulate matter (PM) varies in chemical composition and mass concentration based on location, ... more Particulate matter (PM) varies in chemical composition and mass concentration based on location, source, and particle size. This study sought to evaluate the in vitro and in vivo toxicity of coarse (PM10-2.5) and fine (PM25) PM samples collected at 5 diverse sites within California. Coarse and fine PM samples were collected simultaneously at 2 rural and 3 urban sites within California during the summer. A human pulmonary microvascular endothelial cell line (HPMEC-ST1.6R) was exposed to PM suspensions (50 μg/mL) and analyzed for reactive oxygen species (ROS) after 5 hours of treatment. In addition, FVB/N mice were exposed by oropharyngeal aspiration to 50 μg PM, and lavage fluid was collected 24 hrs post-exposure and analyzed for total protein and %PMNs. Correlations between trace metal concentrations, endotoxin, and biological endpoints were calculated, and the effect of particle size range, locale (urban vs. rural), and location was determined. Absolute principal factor analysis wa...
Magnetite strongly retains As, and is relatively stable under Fe(III)-reducing conditions common ... more Magnetite strongly retains As, and is relatively stable under Fe(III)-reducing conditions common in aquifers that release As. Here, laboratory microcosm experiments were conducted to investigate a potential As remediation method involving magnetite formation, using groundwater and sediments from the Vineland Superfund site. The microcosms were amended with various combinations of nitrate, Fe(II) (aq) (as ferrous sulfate) and lactate, and were incubated for more than 5 weeks. In the microcosms enriched with 10 mM nitrate and 5 mM Fe(II) (aq), black magnetic particles were produced, and As removal from solution was observed even under sustained Fe(III) reduction stimulated by the addition of 10 mM lactate. The enhanced As retention was mainly attributed to co-precipitation within magnetite and adsorption on a mixture of magnetite and ferrihydrite. Sequential chemical extraction, X-ray absorption spectroscopy and magnetic susceptibility measurements showed that these minerals formed at...
Stockport Flats (41.3N, 73.8W) and Tivoli North Bay (42.0N, 73.9W) are the two northernmost Hudso... more Stockport Flats (41.3N, 73.8W) and Tivoli North Bay (42.0N, 73.9W) are the two northernmost Hudson River National Estuarine Research Reserve freshwater tidal marshes in New York. Our paleoecological records based on pollen, spores, macrofossils, and loss-on-ignition (LOI) of marsh sediment cores at these two sites suggest significant local and regional anthropogenic changes and climatic variability, including the Medieval Warming Period. We implement the use of a field portable X-Ray Fluorescence Spectroscopy (Innov-X, USA) as an independent proxy to provide more information about chronology, watershed land-use changes, and estuarine processes. Over the last 200 years, there is a pronounced decrease in organic matter, a shift in vegetation, and an increase in invasive species such as Phragmites australis, Lythrum salicaria, and Typha angustifolia. Coupling of more traditional chronological measurements, such as Ambrosia pollen rise and radiometric dating (C-14, Cs-137, and Pb-210), ...
At a former landfill site in southern Maine approximately 300 ppb arsenic has been observed in gr... more At a former landfill site in southern Maine approximately 300 ppb arsenic has been observed in groundwater over the last two decades. Laboratory and field measurements support the hypothesis that this arsenic originates within the underlying glaciofluvial sediments containing natural arsenic at concentrations of approximately 6 ppm. Arsenic is mobilized under the landfill by reducing conditions induced by decomposition of
Few studies examine urban air pollution in sub-Saharan Africa (SSA), yet urbanization rates there... more Few studies examine urban air pollution in sub-Saharan Africa (SSA), yet urbanization rates there are among the highest in the world. In this study, we measured 8-hr average occupational exposure levels of fine particulate matter (PM2.5), black carbon (BC), ultra violet active-particulate matter (UV-PM), and trace elements for individuals who worked along roadways in Nairobi, specifically bus drivers, garage workers, street vendors, and women who worked inside informal settlements. We found BC and re-suspended dust were important contributors to PM2.5 levels for all study populations, particularly among bus drivers, while PM2.5 exposure levels for garage workers, street vendors, and informal settlement residents were not statistically different from each other. We also found a strong signal for biomass emissions and trash burning, which is common in Nairobi&amp;amp;amp;amp;amp;amp;#39;s low-income areas and open-air garages. These results suggest that the large portion of urban residents in SSA who walk along roadways would benefit from air quality regulations targeting roadway emissions from diesel vehicles, dust, and trash burning. This is the first study to measure occupational exposure to urban air pollution in SSA and results imply that roadway emissions are a serious public health concern.
The Peace Bridge in Buffalo, New York, which spans the Niagara River at the east end of Lake Erie... more The Peace Bridge in Buffalo, New York, which spans the Niagara River at the east end of Lake Erie, is one of the busiest U.S. border crossings. The Peace Bridge plaza on the U.S. side is a complex of roads, customs inspection areas, passport control areas, and duty-free shops. On average 5000 heavy-duty diesel trucks and 20,000 passenger cars traverse the border daily, making the plaza area a potential "hot spot" for emissions from mobile sources. In a series of winter and summer field campaigns, we measured air pollutants, including many compounds considered by the U.S. Environmental Protection Agency (EPA*) as mobile-source air toxics (MSATs), at three fixed sampling sites: on the shore of Lake Erie, approximately 500 m upwind (under predominant wind conditions) of the Peace Bridge plaza; immediately downwind of (adjacent to) the plaza; and 500 m farther downwind, into the community of west Buffalo. Pollutants sampled were particulate matter (PM) < or = 10 microm (PM1...
ABSTRACT Arsenic and other trace metals commonly are released through the reductive dissolution o... more ABSTRACT Arsenic and other trace metals commonly are released through the reductive dissolution of iron and manganese oxides by microorganisms as part of energy metabolism. Both dissolved and sedimentary carbon substrates can be used by these microorganisms. Recent evidence implies that dissolved organic carbon (DOC) from the surface is efficiently transported to depth, where it stimulates in situ microbial communities. Other studies that correlate low aqueous As concentrations with older, recalcitrant organic carbon in older sediments. This work examines processes that affect which of these substrates contribute to reduction, and identifies potential characterizes how organic carbon moves through the subsurface to better understand this apparent contradiction. Based on laboratory experiments and field monitoring using soils and sediments from Vietnam, Cambodia and Bangladesh, we propose a conceptual model for DOC transport in which DOC transport is retarded by adsorption, and in which it re-equilibrates with sedimentary (particulate) organic carbon. In many cases, desorbed sedimentary organic forms a distinct DOC carbon pool with properties and reactivity that are similar to that of young DOC and much higher than predicted based on its age. Under conditions in which this sedimentary DOC is efficiently mobilized, the associated reducing conditions can stimulate arsenic release and in some cases, down-gradient transport.
Arsenic is a contaminant found at more than 500 US Superfund sites. Since pump and treat technolo... more Arsenic is a contaminant found at more than 500 US Superfund sites. Since pump and treat technologies are widely used for remediation of contaminated groundwater, increasing the efficiency of contaminant removal at such sites should allow limited financial resources to clean up more sites. The Vineland Chemical Company Superfund site is extensively contaminated with arsenic after waste arsenic salts were stored and disposed of improperly for much of the company's 44 year manufacturing lifetime. Despite approximately eight years of pump and treat remediation, arsenic concentrations in the recovery wells can still be greater than 1000 ppb. The arsenic concentrations in the groundwater remain high because of slow desorption of arsenic from contaminated aquifer solids. Extrapolation of laboratory column experiments suggest that continuing the current groundwater remediation practice based on flushing ambient groundwater through the system may require on the order of hundreds of years to clean the site. However, chemical additions of phosphate or oxalic acid into the aquifer could decrease the remediation time scale substantially. Laboratory results from a soil column experiment using input of 10 mM oxalic acid suggest that site clean up of groundwater could be decreased to as little as four years. Pilot scale forced gradient field experiments will help establish whether chemical additions can be effective for increasing arsenic mobilization from aquifer solids and thus substantially decrease pump and treat clean up time.
Atmospheric environment (Oxford, England : 1994), 2015
Particulate matter (PM) varies in chemical composition and mass concentration based on location, ... more Particulate matter (PM) varies in chemical composition and mass concentration based on location, source, and particle size. This study sought to evaluate the in vitro and in vivo toxicity of coarse (PM10-2.5) and fine (PM25) PM samples collected at 5 diverse sites within California. Coarse and fine PM samples were collected simultaneously at 2 rural and 3 urban sites within California during the summer. A human pulmonary microvascular endothelial cell line (HPMEC-ST1.6R) was exposed to PM suspensions (50 μg/mL) and analyzed for reactive oxygen species (ROS) after 5 hours of treatment. In addition, FVB/N mice were exposed by oropharyngeal aspiration to 50 μg PM, and lavage fluid was collected 24 hrs post-exposure and analyzed for total protein and %PMNs. Correlations between trace metal concentrations, endotoxin, and biological endpoints were calculated, and the effect of particle size range, locale (urban vs. rural), and location was determined. Absolute principal factor analysis wa...
Magnetite strongly retains As, and is relatively stable under Fe(III)-reducing conditions common ... more Magnetite strongly retains As, and is relatively stable under Fe(III)-reducing conditions common in aquifers that release As. Here, laboratory microcosm experiments were conducted to investigate a potential As remediation method involving magnetite formation, using groundwater and sediments from the Vineland Superfund site. The microcosms were amended with various combinations of nitrate, Fe(II) (aq) (as ferrous sulfate) and lactate, and were incubated for more than 5 weeks. In the microcosms enriched with 10 mM nitrate and 5 mM Fe(II) (aq), black magnetic particles were produced, and As removal from solution was observed even under sustained Fe(III) reduction stimulated by the addition of 10 mM lactate. The enhanced As retention was mainly attributed to co-precipitation within magnetite and adsorption on a mixture of magnetite and ferrihydrite. Sequential chemical extraction, X-ray absorption spectroscopy and magnetic susceptibility measurements showed that these minerals formed at...
Stockport Flats (41.3N, 73.8W) and Tivoli North Bay (42.0N, 73.9W) are the two northernmost Hudso... more Stockport Flats (41.3N, 73.8W) and Tivoli North Bay (42.0N, 73.9W) are the two northernmost Hudson River National Estuarine Research Reserve freshwater tidal marshes in New York. Our paleoecological records based on pollen, spores, macrofossils, and loss-on-ignition (LOI) of marsh sediment cores at these two sites suggest significant local and regional anthropogenic changes and climatic variability, including the Medieval Warming Period. We implement the use of a field portable X-Ray Fluorescence Spectroscopy (Innov-X, USA) as an independent proxy to provide more information about chronology, watershed land-use changes, and estuarine processes. Over the last 200 years, there is a pronounced decrease in organic matter, a shift in vegetation, and an increase in invasive species such as Phragmites australis, Lythrum salicaria, and Typha angustifolia. Coupling of more traditional chronological measurements, such as Ambrosia pollen rise and radiometric dating (C-14, Cs-137, and Pb-210), ...
At a former landfill site in southern Maine approximately 300 ppb arsenic has been observed in gr... more At a former landfill site in southern Maine approximately 300 ppb arsenic has been observed in groundwater over the last two decades. Laboratory and field measurements support the hypothesis that this arsenic originates within the underlying glaciofluvial sediments containing natural arsenic at concentrations of approximately 6 ppm. Arsenic is mobilized under the landfill by reducing conditions induced by decomposition of
Few studies examine urban air pollution in sub-Saharan Africa (SSA), yet urbanization rates there... more Few studies examine urban air pollution in sub-Saharan Africa (SSA), yet urbanization rates there are among the highest in the world. In this study, we measured 8-hr average occupational exposure levels of fine particulate matter (PM2.5), black carbon (BC), ultra violet active-particulate matter (UV-PM), and trace elements for individuals who worked along roadways in Nairobi, specifically bus drivers, garage workers, street vendors, and women who worked inside informal settlements. We found BC and re-suspended dust were important contributors to PM2.5 levels for all study populations, particularly among bus drivers, while PM2.5 exposure levels for garage workers, street vendors, and informal settlement residents were not statistically different from each other. We also found a strong signal for biomass emissions and trash burning, which is common in Nairobi&amp;amp;amp;amp;amp;amp;#39;s low-income areas and open-air garages. These results suggest that the large portion of urban residents in SSA who walk along roadways would benefit from air quality regulations targeting roadway emissions from diesel vehicles, dust, and trash burning. This is the first study to measure occupational exposure to urban air pollution in SSA and results imply that roadway emissions are a serious public health concern.
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