HOW TECTONIC HISTORY AND GEOCHEMICAL PROCESSES COULD INFLUENCE ARSENIC IN DRINKING WATER

Accreted terranes once associated with convergent margins carry a heterogeneous mixture of minerals, some containing trace amounts of arsenic. Rift basins provide ample accumulation space for deposition of eroded sediments, and contain groundwater currently used as drinking water sources. Groundwater, surface water, and rocks from the Southern Appalachian Mountain basins are collected to assess the relationship between tectonic history and geochemical processes related to arsenic. Water samples are analyzed as both unfiltered and filtered (0.45 μm) samples to examine the role of particulates in the mobility of arsenic. Concentrations are determined using ICP-MS (detection limit < 0.01 μg/L) by oxidizing the arsenic to As⁵⁺ using ultraviolet light followed by the production of arsine gas by hydride generation. Preliminary results of groundwater and surface water from the Gettysburg Basin show no significant difference between arsenic concentrations of filtered and unfiltered samples. Arsenic concentrations in all samples are below the EPA MCL of 10 μg/L. The mean groundwater concentration is 1.3 μg/L with a minimum of 0.36 μg/L and a maximum of 3.4 μg/L. The mean surface water concentration is 1.0 μg/L with a minimum of 0.30 μg/L and a maximum of 2.8 μg/L. Continued study of the geochemical parameters in these basins will ultimately lead to a predictive model of natural arsenic contributions to groundwater.