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- Singh, Dharmendra Kumar, et al.
(författare)
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Distributions of Polycyclic Aromatic Hydrocarbons, Aromatic Ketones, Carboxylic Acids, and Trace Metals in Arctic Aerosols : Long-Range Atmospheric Transport, Photochemical Degradation/Production at Polar Sunrise
- 2017
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 51:16, s. 8992-9004
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Tidskriftsartikel (refereegranskat)abstract
- The distributions, correlations, and source apportionment of aromatic acids, aromatic ketones, polycyclic aromatic hydrocarbons (PAHs), and trace metals were studied in Canadian high Arctic aerosols. Nineteen PAHs including minor sulfur-containing heterocyclic PAH (dibenzothiophene) and major 6 carcinogenic PAHs were detected with a high proportion of fluoranthene followed by benzo[k]fluoranthene, pyrene, and chrysene. However, in the sunlit period of spring, their concentrations significantly declined likely due to photochemical decomposition. During the polar sunrise from mid-March to mid-April, benzo[a]pyrene to benzo[e]pyrene ratios significantly dropped, and the ratios diminished further from late April to May onward. These results suggest that PAHs transported over the Arctic are subjected to strong photochemical degradation at polar sunrise. Although aromatic ketones decreased in spring, concentrations of some aromatic acids such as benzoic and phthalic acids increased during the course of polar sunrise, suggesting that aromatic hydrocarbons are oxidized to result in aromatic acids. However, PAHs do not act as the major source for low molecular weight (LMW) diacids such as oxalic acid that are largely formed at polar sunrise in the arctic atmosphere because PAHs are 1 to 2 orders of magnitude less abundant than LMW diacids. Correlations of trace metals with organics, their sources, and the possible role of trace transition metals are explained.
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- Singh, Dharmendra Kumar, et al.
(författare)
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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
- 2021
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Ingår i: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 5:10, s. 2865-2877
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Tidskriftsartikel (refereegranskat)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 (R2 = 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 R2 = 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).
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