Geochemical and isotopic constraints on the sources of arsenic in groundwater from Coastal Maine, New England

摘要

Anomalously high contents of arsenic are found in groundwater of Coastal Maine. Major and trace element compositional variations of sulfidic bedrock, sediments, soils, and arsenic-bearing minerals from mines and disseminated in rocks were studied to identify the source of arsenic in groundwater. Our inventory identifies possible arsenic sources and establishes pathways by which arsenic is transported from arsenic-bearing minerals (arsenian pyrite, arsenopyrite, orpiment, arsenolite, etc.), via sulfide oxidation or carbonation reactions, into various generations of secondary minerals (goethite, jarosite, and natrojarosite, etc.). Pb isotopic compositions of sulfides and secondary minerals produced by weathering are similar. Isotopic variations help to establish the compositions of fluids in which the secondary minerals precipitated and point to predominant control from the natural environment. A local contribution as a result of anthropogenic activities is also possible.