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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 ’ 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 µmol 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× higher. Fluxes from the HBL ponds (0.4–4 µmol S m−2 d−1) were similar to fluxes from Canadian Shield lakes.

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Identities, concentrations, and fluxes of volatile sulfur compounds (VSCs) were determined in 11 lakes in northwestern Ontario. Carbonyl sulfide (COS: up to 1.1 nM) and dimethyl sulfide (DMS: up to 11 nM) were present in surface waters during most of the ice-free season. Depth profiles showed accumulations below the mixed layer of methane thiol (MSH), DMS, and dimethyl disulfide (DMDS). There was no effect of low pH or increased [SOd2-] (from 2.4 to 12.3 mg liter-') on the concentrations and identities of surface-water VSCs. Accumulation of DMS below the mixed layer was 9 x higher in an acidified system, however, when compared to an unacidified reference lake. Estimates of flux from two stratified lakes indicated that volatilization was not an important sulfur loss mechanism compared to others such as sedimentary S0,2-. reduction.Concentrations of MSH, DMS, and DMDS in shallow Lakes 114 and 303 were often 5-30 X higher than in any other lake studied, and the flux from Lake 114 was -0.96-l .6 x the estimated oceanic DMS flux per unit of area. On a regional basis, in areas where SOd2-in precipitation is low, export of VSCs to the atmosphere from shallow lakes and bog pools may be significant compared to sulfur inputs through precipitation.