Atmospheric occurrence and socioeconomic drivers of cyclic volatile methyl siloxanes across China

<p>Cyclic volatile methyl siloxanes (cVMS) are high-production volume chemicals, and their release into the atmosphere has raised increasing concerns regarding potential adverse effects on human health and the environment. China dominates global cVMS production, particularly octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5); but their atmospheric occurrence and socio-economic drivers are largely unknown. Here, we report initial findings from mobile and in situ measurements of atmospheric D4 and D5 across China using the Vocus proton-transfer-reaction time-of-flight mass spectrometer. We observed high concentrations of D4 (up to 139 pptv) and D5 (up to 176 pptv), induced by strong chemical factory emissions. The ambient mixing ratios of both chemicals increased from north to south and west to east, and D4 was one order of magnitude higher than D5. Moreover, we found that residential income better explained the domestic and global heterogeneity of cVMS compared to population density. These findings pave the way for exploring large-scale emission inventories and environmental impacts of atmospheric cVMS, highlighting China’s substantial contribution to global atmospheric D4 levels primarily from industrial production and underscoring the need to consider regional economic factors in global D5 emission models.</p>