Secondary organic aerosols from OH oxidation of cyclic volatile methyl siloxanes as an important Si source in the atmosphere

Abstract. Cyclic volatile methyl siloxanes (cVMSs), which can volatilize into the atmosphere, are active ingredients in widely used consumer products, thus attracting much attention due to their potential environmental risks. While atmosphere cVMSs undergo oxidation, yielding both gaseous and particulate products. The aerosol yields compositions from OH oxidation of four (D3–D6) were determined under low- high-NOx conditions an flow reactor. increased progressively D3 D6, consistent with volatilities molecule weights these cVMSs. NOx restrict formation secondary organic aerosols (SOAs), leading lower SOA than low-NOx conditions, a yield decrease between 0.05–0.30 depending on Ammonium sulfate seeds exhibited minor impacts but significantly D3–D5 at short photochemical ages conditions. mass spectra SOAs showed dependence its chemical exposure. At high exposures equivalent >4 d D4–D6 mainly consisted CxHy CxHyOzSin whereas they primarily contained NmOz, CxHy, CxHyO1, CxHyO>1 contributions evaluated using reported annual production obtained present study. A global cVMS-derived (D4–D6) source strength is estimated be 0.01 Tg yr−1, distributed over major urban centers.