Atmospheric methanethiol emitted from a pulp and paper plant on the shore of Lake Baikal

On-site measurement of methanethiol (CH 3 SH) was performed for three years on ships and cars near a pulp and paper plant standing on the shore of Lake Baikal in Siberia, Russia, to investigate the behavior and impact of atmospheric CH 3 SH emitted from a point source. Despite its strong odor, there are few reports on atmospheric CH 3 SH, while many investigations have been carried out on dimethyl sulfide (DMS). In this work, CH 3 SH and DMS were measured every 15 min by a recently developed automated instrument based on single column trapping/separation and chemiluminescence measurement. Hydrogen sulfide, sulfur dioxide and ozone were also measured simultaneously by individual instruments. Of these sulfur compounds, CH 3 SH was dominant and its concentration sometimes reached several tens of ppbv. The concentration of CH 3 SH was high at night, because of the lack of photodecomposition and local winds from the mountain to the lake. Such time variation was marked in the summer. The CH 3 SH level decreased significantly downwind, while decreases in concentrations of other compounds such as DMS and SO 2 were relatively small. From these temporal and spatial variations, the behavior of CH 3 SH is described in this paper. The impact of CH 3 SH near the Siberian big sources is discussed with the presented data.