Geochemical controls on occurrence of arsenic in nearshore groundwater in the Great Lakes region

Session: Chemical Contaminants (1)

Sabina Rakhimbekova, University of Western Ontario, [email protected]
Clare Robinson, The University of Western Ontario, Civil & Environmental Eng., [email protected]
Denis O'Carroll, University of New South Wales, [email protected]

Abstract

Groundwater-lake interactions play an important role in the cycling of chemicals in nearshore environments. Recent studies have found elevated arsenic (As) concentrations (>20 ug/L) in shallow groundwater in beaches of the Great Lakes. It remains unclear if the elevated As concentrations are naturally occurring or whether they are associated with anthropogenic activities. The objective of this study was to identify the source of As and the effect of groundwater-lake interactions on the occurrence and behavior of As in nearshore environments. Pore water and sediment data from five beaches in the Great Lakes is analyzed to evaluate factors controlling As occurrence. Geochemical processes affecting the mobility of As are complex. Arsenic may be released from sediment to groundwater by dissolution of metal oxides or sulfide minerals, and desorption in the presence of competing anions. Understanding the ultimate source of As and factors controlling its occurrence is necessary to evaluate potential risks to water quality and receptors and thus develop appropriate management actions. The study findings also provide important insight into the processes controlling the fate of other inorganic pollutants such as mercury and phosphorus in nearshore environments.