Browsing by Author "Vengosh, Avner"

Arsenic (As) exposure via groundwater consumption is a global health problem affecting millions. Monitoring exposure is a key step in understanding and predicating future health outcomes. This thesis explores the relationships between arsenic concentrations in toenails and arsenic in water. Three case studies were investigated, with residents from: North Carolina, USA (n=103); the Rift Valley, Ethiopia (n=60); and the Mekong Delta, Vietnam (n=65). Arsenic concentrations above the WHO's recommended 10ppb limit were found in groundwater from the three research sites.

Arsenic in toenails was analyzed by inductively coupled plasma mass spectrometry (ICP-MS).

In the Rift Valley of Ethiopia, 53% of the tested drinking wells (n=34) had As above the WHO's limit. Arsenic concentrations in toenails (n=60) were significantly correlated to As concentrations in groundwater (r=0.72; p<0.001), reflecting the direct exposure of rural communities to As in well water, which is their principle water source. Male minors (<18 years old) were found to have greater nail-As concentrations compared with adults consuming equal amounts of As (p<0.05). Estimated As dose specifically from drinking water sources was also associated with nail concentrations (p<0.01).

In the Mekong Delta of Vietnam (Dong Thap Province), 36 out of the 68 tested wells had As content above the WHO's recommended limit of 10ppb, with levels as high as 981 ppb. Arsenic contents in nails collected from local residents (n=62) were significantly correlated to As in drinking water (r=0.49, p<0.001). Demographic and survey data show that the ratio of As in nail to As in water varies among residents that reflects differential As accumulation in the exposed population. The data show that water filtration and diet, particularly increased consumption of animal protein and dairy and reduced consumption of seafood, were associated with lower ratios of As in nail to As in water and thus could play important roles in mitigating As exposure.

Sixty-one wells were tested from Union County, North Carolina, with 15 out of 61 wells exceeded the WHO's 10 ppb limit. Arsenic values ranged from below the limit of detection (0.07) to 130ppb, with a mean of 11ppb (median=1.5ppb). Nails were collected from county residents (n=103) and were statistically correlated with As-water concentrations (r=0.48, p<0.001).

Integration of the data from the three cases studies across different populations and ethnicities show high correlation between As concentrations in groundwater and As in nails in all the three locations (r(Union County)= 0.48, p<0.001; r(Ethiopia)=0.72 p<0.001; r(Vietnam)=0.49, p<0.001). For As-nail to As-water pairs in which As in water was above 1ppb, these three locations are statistically indistinguishable from one another (r=0.62, p<0.001, n=176). These results support the hypothesis that nails can be used as a biomarker of exposure regardless of geographic or ethnic differences in populations considered. Nutrition (meat, seafood, and milk consumption) rather than gender, ethnicity, or dose is suggested to be the major confounding issue affecting the magnitude of As exposure in the human body.

Groundwater is an increasingly important source of water for many parts of the world. Redox sensitive elements, like uranium, chromium, arsenic, and vanadium, are known to occur naturally in some groundwater systems, and may pose human health risks in populations that use groundwater as their major drinking water source. This dissertation characterizes factors affecting the occurrence of redox sensitive elements in different aquifer systems from different countries, including hydrogeology, geochemistry, and anthropogenic effects. It also addresses the co-occurrence of these elements in the groundwater resources, which may be associated with greater health risks than exposure to individual elements alone. The first three chapters of this dissertation focus on uranium occurrence in groundwater from different parts of India. Groundwater overexploitation has caused massive groundwater depletion and raised concerns for water and food security in India. Fieldwork in India combined with retrieving available data show that uranium is a widespread problem in groundwater across India, with concentrations greater than the World Health Organizations provisional guideline of 30 µg/L, mostly found in semiarid alluvial aquifers, as well as granitic and metamorphosed granitic crystalline aquifers. High concentrations of uranium in groundwater from the semiarid parts of Northwestern India is also associated with extensive agricultural activities. A detailed analysis, utilizing chemical (major and trace elements) and isotopic (δ18O, δ2H, δ11B, δ13C) data show that redox conditions, bicarbonate concentrations, and salinity have interconnected effects that control groundwater uranium concentrations, and that geochemical processes associated with irrigation under arid and semiarid conditions further intensify the groundwater uranium concentrations. An in-depth investigation of the groundwater chemistry from Rajasthan shows that in addition to uranium, groundwater used for drinking without any treatment contains multiple inorganic contaminants at levels that exceed both Indian and World Health Organization drinking water guidelines. The processes affecting Rajasthan's groundwater quality are common in many other groundwater resources from arid areas worldwide, and the lessons learned from evaluating the mechanisms that affect the groundwater quality in this study are universal and can be applied for other parts of the world. The last two chapters of this thesis address redox sensitive elements in groundwater form North Carolina, USA. Uranium, chromium, vanadium, and arsenic are all known to occur in North Carolina groundwater at health-relevant concentrations, with the highest concentrations of all elements occurring in fractured igneous and metamorphic formations from the Piedmont region. Arsenic occurs most frequently in suboxic to mixed redox character groundwater, whereas uranium, vanadium, and chromium occur mostly in oxic groundwater. Occurrences of arsenic, and to a lesser extent uranium, increase with pH, likely reflecting desorption from clay minerals on the aquifer rocks, while higher chromium and vanadium levels were measured in near-neutral pH and oxic groundwater, reflecting greater sensitivity to redox conditions. Due to similar geochemistry, vanadium and chromium co-occur most frequently. There is not enough health data to quantify the risks associated with such element co-occurrence, and there are large gaps between the current health recommendations and enforceable drinking water standards, especially for chromium given that hexavalent chromium, which is the predominant dissolved species of chromium in groundwater, is not regulated. The large complied dataset of measurments for chromium and hexavalent chromium in drinking water wells across North Carolina I demonstrate that most chromium in North Carolina occurs as the more toxic hexavalent chromium, presenting greater risks to human health. Several approaches to predicting chromium occurrence in NC groundwater are explored to help target future monitoring efforts and highlight areas of higher risks for occurrence and co-occurrence of these contaminants in groundwater resources of the Piedmont region of Eastern U.S.

Coal fired power plants are ubiquitous in the United States and most developed countries around the world, providing affordable electricity to consumers. In the US, approximately six hundred power plants generate 136 million tons of Coal Combustion Residuals (CCRs) annually, encompassing fly ash, bottom ash, and flue gas desulfurization materials. The range and blends of CCRs varies substantially across coal-fired plants and depends on a unique set of circumstances for each plant and coal source. Current U.S. regulations mandate the installation of advanced capture technologies to reduce atmospheric pollution, but do not address the transfer and storage, or the potential impacts to water resources. Thus improved air quality is traded for significant enrichments of contaminants in the solid waste and effluent discharged from power plants.

This work examines the geochemical and isotopic characteristics of CCRs, as well as potential environmental impacts from CCRs. This investigation looks at several different aspects of CCR and environmental interactions from 1) the immediate impacts of the 2008 TVA coal ash spill in Kingston, TN, 2) the long-term (18-month) exposure of the spilled ash in the Emory and Clinch rivers, 3) impacts on waterways in North Carolina that receive CCR effluent from coal fired power plants, and 4) examination of boron and strontium isotopes of CCRs from leaching experiments and their application as tracers in the environment of the TVA spill and NC waterways. These investigations have illuminated several conclusions, including contact of surface water with CCRs leach high concentrations of leachable CCR contaminants, such as As, Se, B, Sr, Mo, and V in the surface waters; the dilution effect is critical in determining the concentration of contaminants from the CCRs in surface water (both at the spill and in waterways receiving CCR effluent); recycling of trace elements (such as As) through adsorption/desorption can impact water quality; and elevated boron and strontium concentrations, in addition to their isotopes, can trace CCR effluent in the environment. Combining the geochemical behavior and isotopic characteristics provides a novel tool for the identification CCR effluents in the environment.

Fossil fuels continue to be a major component of the energy economies in North America, accounting for 60% of electricity generation in the U.S. Recent incidences (i.e. spills) and limited regulation of the fossil fuel industry has generated public concern about the risks fossil fuel development pose to water resources. Previous studies have identified negative impacts on water quality associated with the storage and disposal of coal combustion residuals, oil sands process-affected water, and oil and gas wastewater, as well as leaking of methane to groundwater in areas of hydraulic fracturing. In addition, contamination of water resources from natural (geogenic) sources has also been observed in many of the areas associated with fossil fuel development. Since naturally occurring saline water is common in some regions associated with fossil fuel explorations, delineating the effects of anthropogenic contamination sources is a major challenge for evaluating the impact of fossil fuel development on water quality.

This thesis investigates the geochemical and isotopic characteristics of wastewater from coal combustion residual storage ponds, unconventional oil and gas exploration, and oil sands mining, in an attempt to evaluate the use of geochemical and isotopic tracers to identify fossil fuel-associated wastewaters in the environment. This includes the investigation of (1) halogen (Br, I) and ammonium contents of oil and gas wastewater (OGW);(2) the lithium isotope ratios in OGW and coal combustion residuals; and (3) the inorganic geochemistry and boron, strontium and lithium isotope ratios of oil sands processed-affected water (OSPW). In three case studies, these geochemical and isotopic tools were integrated into comprehensive geochemical frameworks that investigated the (1) leaking of coal ash ponds to surface and groundwater in the southeastern United Sates; (2) geochemistry of groundwater in an area of shale gas development in West Virginia through time and space; and (3) evaluation of the sources of molybdenum in contaminated groundwater in southeastern

Wisconsin and possible links to coal ash surface disposal. These investigations illustrate a range of situations in which isotopic fingerprinting provided a unique geochemical tool that can successfully identify fossil fuel-related wastewater in the environment. These studies have also demonstrated the environmental impact upon releasing of fossil fuels wastewater to the environment. The case studies support the use of geochemical and isotope tools as robust methods to not only identify contamination of water resources by fossil fuel-related activities, but also to distinguish wastewater contamination from naturally occurring contamination in areas of fossil fuel development. These studies highlight the benefit of using a suite of geochemical tools when investigating water quality impacts.