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Geologic Controls on Arsenic Distribution and Mobilization in Pennsylvania Groundwater

EPA Grant Number: F5B20305
Title: Geologic Controls on Arsenic Distribution and Mobilization in Pennsylvania Groundwater
Investigators: Burkert, Lori A.
Institution: Lehigh University
EPA Project Officer: Thompson, Delores
Project Period: September 1, 2005 through August 1, 2006
Project Amount: $62,872
RFA: STAR Graduate Fellowships (2005)
Research Category: Academic Fellowships

Description:

Objective:

Arsenic is a ubiquitous element found throughout the environment, however environmental materials show wide ranges of arsenic concentrations due to varying inputs (Cullen and Reimer, 1989). High concentrations are typically found in groundwaters more often than surface waters (Smedley and Kinniburgh, 2002). Characterizing the speciation and mobility of natural sources of arsenic contamination in the groundwater is necessary to understand the triggers of elevated concentrations of arsenic (>10 ppb) in natural waters. This issue is socially significant because of more stringent revisions to the U.S. drinking water quality standard for arsenic to be implemented in January 2006. Moreover, major aqueous arsenic species As (III) and As (V) have different toxicological effects on human health. The objectives of this research are to determine the geologic source, possible mechanisms of release, and dominant species of arsenic in various lithological formations of the north-central Appalachian orogeny having elevated concentrations of arsenic in the groundwater. I plan to look at how natural variations in redox potential, pH, and solid-phase arsenic concentration ultimately effect the arsenic concentration of a groundwater. Biological interactions affecting arsenic cycling will be considered should geologic controls be inadequate in describing controls on speciation and mobilization.

Approach:

My experimental approach consists of three parts:

  1. a GIS based survey and analysis of the distribution of arsenic in groundwater throughout Pennsylvania and the relationship to geology;
  2. a field program to collect representative rock samples from local lithologies and water samples from domestic wells in areas with elevated concentrations of arsenic in the groundwater;
  3. and lab analysis of the rock and water samples for As concentration and As speciation using coupled Ion Chromatography (IC) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS).

Major element chemistry, redox potential, and pH will also be determined.

The GIS study compares bedrock geology to groundwater chemistry using data collected from the PA Department of Environmental Protection (PA DEP) Drinking Water and Sampling Information System databases (1993-2004), the United States Geological Survey National Water Information System Arsenic Data database, and the PA DEP Ambient and Fixed Station Network Groundwater Monitoring Point Data database to characterize the distribution of arsenic in Pennsylvania groundwater. Focus will be placed on geographic areas of Pennsylvania with elevated concentrations of arsenic in the groundwater. These areas were delineated with the GIS and suggest strong individual links between regional coal-bearing, shale, sandstone, and mudstone lithologies and groundwater arsenic concentration.

Expected Results:

I expect that lithology will be deterministic in characterizing concentrations of arsenic in the groundwater at both the regional and local level. I hypothesize that iron-sulfide reactions will dominate in the coal-bearing regions with oxidative dissolution of arsenopyrite acting as the chief mechanism of release. Differences in initial solid-state arsenic concentrations may attribute to the variation in arsenic concentrations in the groundwater both within and between coal-bearing regions. Analysis of groundwater and rock samples from shale, sandstone, and mudstone formations will determine whether dissolution or desorption processes dominate these groundwater systems.

Supplemental Keywords:

Arsenic, As, arsenic speciation, arsenic mobilization, arsenic cycling, groundwater, geochemistry, environmental chemistry, Pennsylvania, geologic control, redox potential, oxidation state, ion chromatography, IC, Inductively Coupled Plasma-Mass Spectrometry, ICP-MS, Geographic Information System, GIS, drinking water, coal, sandstone, mudstone, shale, iron, sulfide, , POLLUTANTS/TOXICS, Water, Geographic Area, Scientific Discipline, RFA, Arsenic, Water Pollutants, Environmental Chemistry, State, arsenic exposure, fate and transport, Pennsylvania, speciation, groundwater, arsenic cycling, mobilization, contaminant transport, biogeochemistry, well water

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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