环境地球化学国家重点实验室知识库

Recently air pollution is seriously threatening the health of millions of people in China. The multiple sulfur isotopic composition of sulfate in PM2.5 samples collected in Beijing is used to better constrain potential sources and formation processes of sulfate aerosol. The Delta S-33 values of sulfate in PM2.5 show a pronounced seasonality with positive values in spring, summer and autumn and negative values in winter. Positive Delta S-33 anomalies are interpreted to result from SO2 photolysis with self-shielding, and may reflect air mass transport between the troposphere and the stratosphere. The negative Delta S-33 signature (-0.300 parts per thousand < Delta S-33 < 0 parts per thousand) in winter is possibly related to incomplete combustion of coal in residential stoves during the heating season, implying that sulfur dioxide released from residential stoves in more rural areas is an important contributor to atmospheric sulfate. However, negative Delta S-33 anomalies (-0.664 parts per thousand < Delta S-33 <- 0.300 parts per thousand) in winter and positive Delta S-33 anomalies (0.300 parts per thousand < Delta S-33 < 0.480 parts per thousand) in spring, summer, and autumn suggest sulfur isotopic equilibrium on an annual time frame, which may provide an implication for the absence of mass-independent fractionation of sulfur isotopes (S-MIF) in younger sediments. Results obtained here reveal that reducing the usage of coal and improving the heating system in rural areas will be important for efficiently decreasing the emissions of sulfur in China and beyond.