Lakes in the Yellowknife area (NWT) were exposed to atmospheric deposition of arsenic emissions from ore roasting at local gold mines.

Legacy arsenic contamination remains an environmental concern due to its mobility within sediments after initial deposition. Warmer water and sediment temperatures associated with climate change may impact arsenic diffusion rates from lake sediments either by the direct effect on diffusion rate or indirect effects such as on microbial metabolism and sediment redox conditions influenced by warmer temperatures. 

This study assessed the influence of warmer temperatures on arsenic diffusion from contaminated sediment of two lakes with different composition using an experimental incubation approach. Sediments from Yellowknife Bay consisted of clay material with low organic content, whereas sediments from Lower Martin Lake had high organic content. Duplicate sediment batches from each lake were incubated for four weekly temperature treatments (5℃ to 20℃ at 5℃ intervals) under well-oxygenated conditions. 

Surface water was sampled regularly to measure arsenic concentrations and diffusion rates. Arsenic diffused from sediments to overlying water in all treatments, and the flux was greater from Yellowknife Bay sediments than from Lower Martin Lake sediments. 

The results suggest temperature had no measurable influence on arsenic flux from the two different sediment types, and other factors must be considered.