ORGANIC VOLATILE SULFUR IN LAKES RANGING IN SULFATE AND DISSOLVED SALT CONCENTRATION OVER 5 ORDERS OF MAGNITUDE

Organic volatile sulfur compounds (VSCs) were studied in six hypersaline lakes (southern Saskatchewan) and in dilute wetland ponds (Hudson Bay Lowlands, HBL). [SO42-] (0.0002-64 g liter-1) and salt concentration (0.003-370 g liter-1) ranged over 5 orders of magnitude. Organic VSC concentrations in ponds and lakes with [SO42-] < 7 g liter-1 were similar to those measured previously in freshwater lakes. Lakes with > 20 g SO42- liter-1, however, had VSC concentrations several orders of magnitude higher. Dimethyl sulfide (DMS) was the dominant species, reaching a concentration of 3,050 nM in one salt lake-the highest concentration yet recorded. Carbonyl sulfide (COS), methanethiol (MSH), dimethyl disulfide (DMDS), and carbon disulfide (CS2) were also detected. In the salt lakes, [DMS], [MSH], and [total VSC] were positively correlated (P < 0.05) to [SO42-] but not to dissolved salt concentration (P < 0.05). The estimated mean atmospheric flux from the salt lakes ranged from 2 to 590 mumol S m-2 d-1. The low end of this range is similar to fluxes from Canadian Shield lakes and the ocean; the high end is 500 x higher. Fluxes from the HBL ponds (0.4-4 mumol S m-2 d-1) were similar to fluxes from Canadian Shield lakes.