Speciation and toxicity of arsenic in mining-affected lake sediments in the Quinsam watershed, British Columbia

Anthropogenic arsenic inputs into fresh water lakes in the Quinsam watershed, British Columbia, were probed by using multiple methods of inquiry including sediment coring combined with 210Pb dating, a principal components analysis of elemental composition of sediments, arsenic speciation, bioaccessibility, and toxicity testing. The quantification of arsenic inputs from anthropogenic sources was not trivial because a variety of processes redistribute the element throughout lakes. However, elevated arsenic and sulfate concentrations in Long Lake, a lake that receives arsenic from a seep, suggest that this lake is influenced by mine operations. X-ray absorption near edge structure (XANES) spectra reveal similar arsenic speciation for all sediments within the studied lakes. Bioaccessibility tests, which in this study were used to approximate the solubility and availability of arsenic to benthic organisms, indicate moderate bioaccessibility of arsenic in sediments (7.9–35%). Toxicity testing indicates that not all benthic organisms should be used for evaluating arsenic toxicity, and suggests that the amphipod, Corophium volutator, shows promise as a candidate for widespread use for arsenic sediment toxicity testing. •The quantification of anthropogenic arsenic inputs into freshwater lakes must be done using multiple lines of evidence.•Freshwater lakes within and outside of mine property show similar arsenic speciation, regardless of the total arsenic load.•The amphipod C. volutator responds in a predictable manner to lake sediments and shows promise for arsenic toxicity testing.