Factors
Controlling the Risks of Co-occurrence of
the Redox-Sensitive Elements of Arsenic, Chromium, Vanadium, and Uranium
in Groundwater from the Eastern United States
posted on 2020-03-23, 17:07authored byRachel
M. Coyte, Avner Vengosh
The co-occurrence
of contaminants in drinking water may pose enhanced
risks to health beyond the effects of single contaminants. Here, we
investigated the co-occurrence of four health-relevant redox-sensitive
elements (U, As, V, and Cr) in 1494 groundwater wells across North
Carolina. The highest concentrations of these elements were measured
mostly in groundwater from fractured igneous and metamorphic formations
throughout the Piedmont region. Arsenic occurred most frequently in
suboxic to mixed redox character groundwater, whereas U, V, and Cr
occurred mostly in oxic groundwater. Occurrences of As, and to a lesser
extent U, increased with pH, likely reflecting desorption, while higher
Cr and V levels were measured in near-neutral pH and oxic groundwater,
reflecting greater sensitivity to redox conditions. Due to similar
geochemistry, V and Cr co-occurred most frequently. Concentrations
of V and Cr(VI) co-exceeded health recommendations from the NC Department
of Health and Human Services in up to 84% of wells from the King’s
Mountain Belt and the Charlotte and Milton Belts of the Piedmont region.
This study highlights the large gap between health recommendations
and enforceable regulations and demonstrates a degree of co-occurrence
between redox-sensitive elements, which may pose additional risks
to groundwater-reliant individuals.