Bioaccumulation and transfer of mercury and arsenic in aquatic invertebrates and emergent insects at historical gold mine tailing sites of Nova Scotia

Abstract

Historical gold mining in Nova Scotia resulted in over 3,000,000 tonnes of mine tailings deposited into aquatic habitats and low-lying areas, where they remain today. Legacy tailings are typically elevated in mercury (Hg) and arsenic (As), however, aquatic ecological effects remain largely unquantified to date. An initial literature review revealed only three studies mentioning contaminants in aquatic invertebrates at tailing sites. My objective was to assess [Hg] and [As] in aquatic invertebrates living on tailings-affected wetlands, and the role of emergent insects as biovectors of these contaminants. Samples showed that sediment and water at tailings sites were elevated in Hg and As, often surpassing CCME guidelines. Aquatic invertebrates from tailings sites had elevated [Hg] (up to 4.20 ppm). Invertebrate [As] frequently exceeded CCME guidelines for fish. Adult emergent insects were shown to be likely biovectors of Hg, while As was largely shed with casings during hatching.