Photochemical Processing of Inorganic and Organic Species in the Canadian High Arctic Aerosols: Impact of Ammonium Cation, Transition Metals, and Dicarboxylic Acids before and after Polar Sunrise at Alert

Abstract

Temporal variations and correlation statistics of major inorganic and organic species and carbonaceous components of the total suspended particulate matter (TSPM) at Alert were concurrently studied. Organic carbon (OC) and water-soluble organic carbon (WSOC) declined from February to mid-March together with elemental carbon (EC), but OC and WSOC increased in April while EC stayed low, suggesting photochemical production of organic aerosols. WSOC/OC ratios peaked in mid-April (89%). The ammonium availability index (AAI) increases from 31% (before sunrise) to 58% (after sunrise). Strong correlations of NH4 + with WSOC and dicarboxylic acids (DCAs) were found, implying the formation of organic salts at polar sunrise. K+ is substantially correlated (R 2 = 0.96; p = 0.03) with levoglucosan before sunrise; however, the correlation decreases after. Significant correlations were found for 5 cations (NH4 +, Na+, K+, Mg2+, and Ca2+), 2-alkaline earth metals (Ca and Mg), and 3 transition metals (Fe, Cu, and Mn) with DCAs and WSOC during both periods. Fe and Cu are strongly correlated (up to R 2 = 0.80; p < 0.05) with DCAs before and after polar sunrise, implying the Fenton reaction both in dark and light periods. On the basis of the significant correlation, we found the plausibility of Fenton chemistry of Fe and Cu with oxalic acid. In the multiple linear regression model, Mn is the most significant predictor of WSOC followed by Cu and Fe after sunrise. This study demonstrates the importance of the photochemical processing of Arctic aerosols that are carried by long-range transport to the Arctic at Alert, and bridges and answers the research gap and some questions raised in our previous study (regarding, for example, the impacts of inorganic species, primarily NH4 + and transition metals on organic aerosols).

Virtual Issue on Atmospheric Aerosol Research

“…These observations provide insights into the sources of organic constituents in real urban aerosol − and the relationship between these species and the climate-relevant aerosol properties . Studies from more remote regions show signatures of Fenton chemistry, halogen-mediated chemistry, and bacterial metabolism of organic material …”

“…The fundamental concepts put forth by idealized laboratory and theoretical studies are put to the test by observations of atmospheric aerosols in the field. Our authors have contributed observations from Antarctica to the Canadian High Arctic, with Singapore, Nepal, India, , and the Pacific Ocean in between, including the first-ever characterization of particulate matter in Lomé, Togo, using advanced low-cost sensor field calibration techniques . These observations provide insights into the sources of organic constituents in real urban aerosol − and the relationship between these species and the climate-relevant aerosol properties .…”

“…31 These observations provide insights into the sources of organic constituents in real urban aerosol 27−29 and the relationship between these species and the climate-relevant aerosol properties. 26 Studies from more remote regions show signatures of Fenton chemistry, 25 halogenmediated chemistry, 30 and bacterial metabolism of organic material. 24 This brief survey of recent articles illustrates that atmospheric aerosol research is a rapidly evolving and expanding field of physical and environmental science.…”