Seasonal Comparison of Particulate Matter Chemical Composition in Riverside, California

ALEXANDER B. MACDONALD, Xuanlin Du, Ningjin Xu, Ying Zhou, Cesunica E. Ivey, Don Collins, Roya Bahreini, University of California, Riverside

     Abstract Number: 448
     Working Group: Aerosol Chemistry

Abstract
Elevated concentrations of fine particulate matter (PM) with diameter ≤ 2.5 μm (PM_2.5) pose a serious threat to human health, as PM_2.5 is linked to respiratory diseases and mortality. Even though vehicular emissions of polluting precursor gases have decreased in California thanks to regulations implemented in recent decades, underappreciated sources such as industrial operation emissions and volatile chemical products contribute significant precursor gases. Several regions across California still exceed 24-hour PM_2.5 National Ambient Air Quality Standards (NAAQS), with some regions being disproportionately more affected than others. This study is a comparison between two 4-week campaigns in late winter and summer 2022 in Riverside, California, a region which is influenced by fresh, local urban pollution sources and aged emissions from the greater Los Angeles Basin. Size-resolved chemical composition of the ambient PM was measured using an Aerodyne compact time-of-flight mini aerosol mass spectrometer (CToF mAMS). Results suggest that the photochemical production of secondary aerosol was greater during the summer campaign, as approximated by more pronounced changes in mass concentration with the diurnal cycle. Higher ratios of nitrate to organic during summer highlight the periodic importance of inorganic aerosol components in Riverside even during the summer months.