Increased primary and secondary H2SO4 showing the opposing roles in secondary organic aerosol formation from ethyl methacrylate ozonolysis

Abstract

Abstract. Stressed plants and polymer production can emit many unsaturated volatile organic esters (UVOEs). However, secondary organic aerosol (SOA) formation\nof UVOEs remains unclear, especially under complex ambient conditions. In this study, we mainly investigated ethyl methacrylate (EM) ozonolysis.\nResults showed that a substantial increase in secondary H2SO4 particles promoted SOA formation with increasing SO2 . An\nimportant reason was that the homogeneous nucleation of more H2SO4 at high SO2 level provided greater surface area and volume\nfor SOA condensation. However, increased primary H2SO4 with seed acidity enhanced EM uptake but reduced SOA formation. This was\nascribed to the fact that the ozonolysis of more adsorbed EM was hampered with the formation of surface H2SO4 at higher particle\nacidity. Moreover, the increase in secondary H2SO4 particle via homogeneous nucleation favored to the oligomerization of oxidation\nproducts, whereas the increasing of primary H2SO4 with acidity in the presence of seed tended to promote the functionalization\nconversion products. This study indicated that the role of increased H2SO4 to EM-derived SOA may not be the same under different ambient\nconditions, which helps to advance our understanding of the complicated roles of H2SO4 in the formation of EM-derived SOA.