| 1. |
- Winiger, Patrik, et al.
(författare)
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Source apportionment of circum-Arctic atmospheric black carbon from isotopes and modeling
- 2019
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 5:2
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Tidskriftsartikel (refereegranskat)abstract
- Black carbon (BC) contributes to Arctic climate warming, yet source attributions are inaccurate due to lacking observational constraints and uncertainties in emission inventories. Year-round, isotope-constrained observations reveal strong seasonal variations in BC sources with a consistent and synchronous pattern at all Arctic sites. These sources were dominated by emissions from fossil fuel combustion in the winter and by biomass burning in the summer. The annual mean source of BC to the circum-Arctic was 39 +/- 10% from biomass burning. Comparison of transport-model predictions with the observations showed good agreement for BC concentrations, with larger discrepancies for (fossil/biomass burning) sources. The accuracy of simulated BC concentration, but not of origin, points to misallocations of emissions in the emission inventories. The consistency in seasonal source contributions of BC throughout the Arctic provides strong justification for targeted emission reductions to limit the impact of BC on climate warming in the Arctic and beyond.
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| 2. |
- Sharma, S., et al.
(författare)
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A Factor and Trends Analysis of Multidecadal Lower Tropospheric Observations of Arctic Aerosol Composition, Black Carbon, Ozone, and Mercury at Alert, Canada
- 2019
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Ingår i: Journal of Geophysical Research - Atmospheres. - 2169-897X .- 2169-8996. ; 124:24, s. 14133-14161
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Tidskriftsartikel (refereegranskat)abstract
- Observations from 1980 to 2013 of 20 aerosol constituents, ozone and mercury at Alert, Canada (82.50 degrees N, 62.35 degrees W), were analyzed for trends and dominant factors of the Arctic haze during winter and spring. Trends reflect changing emissions in Eurasia, the main source region for surface pollution in the high Arctic. SO42-, H+, NH4,+ K+, Cu, Ni, Pb, Zn, nonsoil V, nonsoil Mn, and equivalent black carbon decreased between 23% and 80% as emissions declined rapidly in northern Eurasia during the early 1990s. NO3- increased by 20% as aerosol acidity declined. Metals were linked to emissions from smelting and fossil fuel combustion. In winter, ozone increased by 5% over 23 years, consistent with other observations and global modeling. Twelve PMF factors emerged for the dark period (November to February) and 13 for the light period (March to May). Eleven PMF factors are common to both dark and light, a twelfth factor was associated with sulfate in the dark and nitrate in the light, and the thirteenth (light period) was related to ozone and gaseous mercury depletion near Alert. IODINE and NITRATE factors, important for Arctic chemistry, changed with sunlight. In the light, 50% of all NO3- was on the NITRATE factor, while in the dark, most was associated with MODIFIED SEA SALT and equivalent black carbon. In the dark (light), 90% (28%) of iodine were found on the factor IODINE and 58% associated with SEA-SALT and MODIFIED SEA-SALT. These results help in understanding the role of atmospheric chemistry in weather and climate processes.
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| 3. |
- Fu, Pingqing, et al.
(författare)
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Fluorescent water-soluble organic aerosols in the High Arctic atmosphere
- 2015
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Organic aerosols are ubiquitous in the earth's atmosphere. They have been extensively studied in urban, rural and marine environments. However, little is known about the fluorescence properties of water-soluble organic carbon (WSOC) or their transport to and distribution in the polar regions. Here, we present evidence that fluorescent WSOC is a substantial component of High Arctic aerosols. The ratios of fluorescence intensity of protein-like peak to humic-like peak generally increased from dark winter to early summer, indicating an enhanced contribution of protein-like organics from the ocean to Arctic aerosols after the polar sunrise. Such a seasonal pattern is in agreement with an increase of stable carbon isotope ratios of total carbon (delta C-13(TC)) from -26.8 parts per thousand to -22.5 parts per thousand. Our results suggest that Arctic aerosols are derived from a combination of the long-range transport of terrestrial organics and local sea-to-air emission of marine organics, with an estimated contribution from the latter of 8.7-77% (mean 45%).
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| 4. |
- Kawana, Kaori, et al.
(författare)
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Hygroscopicity and CCN Activity of Water-Soluble Extracts From the Arctic Aerosols in Winter to Early Summer
- 2022
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Ingår i: Journal of Geophysical Research - Atmospheres. - 2169-897X .- 2169-8996. ; 127:19
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Tidskriftsartikel (refereegranskat)abstract
- The hygroscopicity and cloud condensation nuclei (CCN) activity of water-soluble extracts from Arctic lower tropospheric aerosols during winter to summer were investigated under sub- and super-saturated conditions, with chemical composition and air mass origin. The κ values from the hygroscopic growth factor at 80%–90% relative humidity (κHTDMA) during winter, spring, and summer were 0.34 ± 0.06, 0.41 ± 0.05, and 0.25 ± 0.02, respectively, whereas those derived from CCN activation diameter at 0.29%–0.59% supersaturation (κCCNC) were 0.42 ± 0.03, 0.43 ± 0.05, and 0.34 ± 0.11, respectively. The hygroscopicity and CCN activity showed clear seasonal variations following changes in composition that are linked to natural, anthropogenic, and biogenic sources. During winter and spring, κ was high when highly hygroscopic components such as sea salts, sulfate, and highly-oxidized/aged particles were dominant due to long-range atmospheric transport and photochemical reactions. In contrast, κ was significantly lower in summer when water-insoluble (22%) and water-soluble organic matter (OM) (17%) were dominated with high biogenic activity associated with ice-edge zones. The κCCNC and κHTDMA values agreed well within 8% and the surface tension agreed with that of pure water within 10%. The κ for OM (κOM) estimated from chemical composition during spring and summer was on average 0.04 ± 0.06 (up to ∼0.17). This result suggests that highly hygroscopic components such as sea salt and sulfate mainly controlled particle hygroscopicity and CCN activity in winter, but water-soluble OM could also contribute in spring and summer.
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| 5. |
- 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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| 6. |
- 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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