Sulfur (32S, 33S, 34S, 36S) and oxygen (16O,17O,18O) isotopic ratios of primary sulfate produced from combustion processes

The recent discovery of an anomalous enrichment in ¹⁷O isotope in atmospheric sulfate has opened a new way to investigate the oxidation pathways of sulfur in the atmosphere. From laboratory investigations, it has been suggested that the wet oxidation of sulfur in rain droplets was responsible for the excess ¹⁷O. In order to confirm this theory, sulfur and oxygen isotope ratios of different primary sulfates produced during fossil fuel combustion have been investigated and are reported. None of these samples exhibits any anomalous oxygen or sulfur isotopic content, as compared to urban sulfate aerosols. These results, in agreement with the laboratory investigations, reinforce the idea of an aqueous origin for the oxygen-17 anomaly found in tropospheric sulfates.