Stability of organic selenium species in waters receiving industrial discharges

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Several different types of mining operations in Canada inadvertently mobilize selenium (Se) from the naturalresources they're processing. In some cases, selenium may cause adverse effects on aquatic organisms, somining operations affected by Se issues remove most of the mobilized Se from their process waters prior todischarge. However, as a result of historic emissions and/or current low level emissions, some receivingenvironments have elevated Se concentrations in their sediments. It is known that microbes in sediments mayconvert some of the deposited Se into more bioavailable organic forms ("species"), but it is unknown whetherthese organic Se species are released from the sediments back into the overlying waters, where they might thenbe available to organisms in the water column. We have recently developed analytical methods to measurediscrete organic Se species in waters at the ng/L concentration level, and are now able to study suchcompounds in environmental waters.If such organic Se species occur in mining-impacted aquatic systems, one primary open research question istheir stability in these waters. In laboratory experiments, it has been shown previously that these organic Sespecies are susceptible to oxidation, e.g. by oxygen or UV-radiation, but there are to date no field data thatquantify the rates of these degradation processes in actual receiving waters. In this project, we will collectwater samples from several sites within a Se-impacted ecosystem, and follow the degradation of organic Sespecies (native or spiked) in these waters under controlled laboratory conditions over time. The goal of thisproject is to determine the degradation rates of discrete organic Se species in environmental waters, in order toassess for how long they might be available for bioaccumulation. As a useful side aspect, this study will alsodetermine the short term stability of the studied organic Se species in these waters, to check if significantdegradation occurs during transport from sampling site to analytical laboratory.