Automotive tire wear as a source for atmospheric OCS and CS2

The emission of CS₂, OCS and traces of SO₂ from mixtures of fifteen different ground tire treads has been detected in laboratory experiments using gas chromatography/flame photometric detection (GC/FPD) and gas chromatography/mass spectrometry (GC/MS). Samples of ground tire particles (60-100 mesh) were flushed at different temperatures using either clean nitrogen gas or a mixture of 100 ppb O₃ in N₂. CS₂ was the dominant sulfur gas detected in all of the experiments. OCS and CS₂ emissions increased strongly with temperature and were independent of the presence of O₃. In contrast, SO₂ was observed only at high ozone levels. It is roughly estimated that tire wear may produce as much as 0.04 ± 0.004 Tg S (OCS) yr^-1 or about 6.7% of the total OCS flux into the atmosphere. Therefore, this as yet undescribed automotive source may make a small but significant contribution to the atmospheric OCS budget.