Concentrations of dimethyl sulfide in the Strait of Georgia and its impact on the atmospheric sulfur budget of the Canadian West Coast

Abstract

A study was conducted in the Strait of Georgia to determine the seasonal variation of the biogenic sulfur budget, mainly dimethyl sulfide (DMS), during the three seasons, autumn (November 1999), spring (April 2000) and summer (August 2000). During autumn, surface DMS concentrations were low, 0.02–0.3 nmol l−1. They were highest during spring, 2–30 nmol l−1 and moderately high during summer, 0.2–14 nmol l−1. Related parameters such as chlorophyll a (chl a) and particulate or dissolved dimethyl sulphonioproprionate (DMSPp and DMSPd) were also measured. DMSPp levels were highest during spring coincident with the highest chl a concentrations. In contrast, DMSPd concentrations were highest during summer. Using the Liss‐Merlivat model for sea‐air gas exchange DMS fluxes to the atmosphere was calculated. The areal average DMS flux from the Strait of Georgia decreased from a maximum of 6.4 μmol m−2 d−1 during the spring to 2.2 μmol m−2 d−1 during the summer to 0.15 μmol m−2 d−1 during the autumn. DMS emissions from the Georgia Basin can contribute as much as 26% to the total sulfur emissions (natural and anthropogenic) from the region. Our results also indicate that biogenic sulfur emissions from the Pacific Ocean are also an important source of sulfur to the total regional sulfur budget for the Lower Fraser Valley and they will become more important as anthropogenic S emissions become better controlled.