Selenium occurrence in mine effluents in Canada
Mining activities are the main contributor to selenium mobilization and distribution throughout the environment through mine effluent runoff. Selenium-rich mine effluents may contaminate downstream water and soil-plant systems and consequently induce major impacts on aquatic and wildlife. Due to selenium impacts at excessive levels and the emergence of more strict guidelines for selenium monitoring in mine discharges, total selenium and selenium speciation control become an urgent issue. The current work aimed to assess the total selenium concentration and selenium speciation in different mine effluents in the region of Abitibi-Temiscamingue in Canada. Total selenium registered the highest values for Mine 1 and Mine 2 (179,25 and 108,43 µg/L respectively in November and 100,8 and 206,75 µg/L respectively in February) and for Mine 5 in November (37,77 µg/L) while the lowest values were registered for Mine 3 and Mine 4 (0,79 and 0,45 µg/L respectively in November and 2,3 and 0,98 µg/L respectively in February). Total Se is mainly composed of dissolved species for all the effluents. Selenate has totally composed Mine 4 effluent in November and it was predominant in Mine 2 and Mine 5 (92,56% and 97,92% respectively in november). Selenite predominated only in Mine 3 by 68,62% in February. Equal proportions of selenate and selenite were identified in Mine 1 effluent. Minor proportions of methyl selenenic acid and unknown species appeared in Mine 5 effluent in february next to equal proportions of selenate and selenite. Selenium speciation will govern the effluent mobility, bioavailability and toxicity as well as the determination of the most convenient treatment technology for each mine effluent.