Organic volatile sulfur in lakes of the Canadian Shield and its loss to the atmosphere

Abstract

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.

Reviews and Syntheses: Carbonyl Sulfide as a Multi-scale Tracer for Carbon and Water Cycles

“…This might be due to more efficient mixing in the ocean surface waters compared to lakes. However, Richards et al (1991) found that the concentration remained at the same level throughout the water 20 column and observed a midsummer OCS concentration minima in 8 of the 11 studied lakes. This latter point was surprising because photochemical production should be highest during the summer months.…”

“…Richards et al (1991) calculated OCS flux from the different lakes in Ontario, Canada, based on concentration measurements and wind-speed-dependent gas transfer coefficient, resulting in fluxes of 2-5 pmol OCS m -2 s -1 . In another study, Richards et al (1994) found fluxes of 2-34 pmol OCS m -2 s -1 in salty lakes.…”

“…These fluxes are 5 to 75 times higher than those 5 measured in the oceans (Lennartz et al, 2017). In addition to direct emissions of OCS from freshwaters, there is also and indirect atmospheric OCS source from carbon disulfide (CS 2 ) production (Richards et al, 1991(Richards et al, , 1994, which can be oxidized into OCS (Wang et al, 2001).…”

Modeling natural emissions in the Community Multiscale Air Quality (CMAQ) Model–I: building an emissions data base

“…Emission factors applied here for H 2 S and DMS from freshwater lakes (see Appendix A) in Canada were selected by taking values from the lower range of freshwater sulfur flux estimates derived from several studies including Richards et al (1991), Bates et al (1992), Giblin and Wieder (1992), Gröne (1997), Bodenbender et al (1999), and . A representative day of H 2 S and DMS emissions was created from these emission factors and the SMOKE default temporal profile for natural sources.…”

“…b Approximate factor range for ocean DMS based on reallocation of annual sulfur values from Kloster et al (2006) to daily values. c Taken from values from the lower range of freshwater sulfur flux estimates derived from several studies including Richards et al (1991), Bates et al (1992), Giblin and Wieder (1992), Gröne (1997), Bodenbender et al (1999. d Given the lack of available information on natural emissions from the Great Salt Lake the H 2 S factor applied for freshwater lakes was conservatively applied.…”