| 1. |
- 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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| 2. |
- 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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| 3. |
- Ren, Hong, et al.
(författare)
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Measurement report: Vertical distribution of biogenic and anthropogenic secondary organic aerosols in the urban boundary layer over Beijing during late summer
- 2021
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Ingår i: ATMOSPHERIC CHEMISTRY AND PHYSICS. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 21:17, s. 12949-12963
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Tidskriftsartikel (refereegranskat)abstract
- Secondary organic aerosol (SOA) plays a significant role in atmospheric chemistry. However, little is known about the vertical profiles of SOA in the urban boundary layer (UBL). This knowledge gap constrains the SOA simulation in chemical transport models. Here, the aerosol samples were synchronously collected at 8, 120, and 260m based on a 325m meteorological tower in Beijing from 15 August to 10 September 2015. Strict emission controls were implemented during this period for the 2015 China Victory Day parade. Here, we observed that the total concentration of biogenic SOA tracers increased with height. The fraction of SOA from isoprene oxidation increased with height, whereas the fractions of SOA from monoterpenes and sesquiterpenes decreased, and 2,3-dihydroxy-4-oxopentanoic acid (DHOPA), a tracer of anthropogenic SOA from toluene oxidation, also increased with height. The complicated vertical profiles of SOA tracers highlighted the need to characterize SOA within the UBL. The mass concentration of estimated secondary organic carbon (SOC) ranged from 341 to 673 ngC m(-3). The increase in the estimated SOC fractions from isoprene and toluene with height was found to be more related to regional transport, whereas the decrease in the estimated SOC from monoterpenes and sesquiterpene with height was more subject to local emissions. Emission controls during the parade reduced SOC by 4 %-35 %, with toluene SOC decreasing more than the other SOC. This study demonstrates that vertical distributions of SOA within the UBL are complex, and the vertical profiles of SOA concentrations and sources should be considered in field and modeling studies in the future.
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| 4. |
- 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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| 5. |
- 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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| 6. |
- Xu, Buqing, et al.
(författare)
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Compound-Specific Radiocarbon Analysis of Low Molecular Weight Dicarboxylic Acids in Ambient Aerosols Using Preparative Gas Chromatography : Method Development
- 2021
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Ingår i: Environmental Science and Technology Letters. - : American Chemical Society (ACS). - 2328-8930. ; 8:2, s. 135-141
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Tidskriftsartikel (refereegranskat)abstract
- Low molecular weight dicarboxylic acids constitute a large fraction of atmospheric organic aerosols, which impact atmospheric radiative forcing and hence Earth's climate. Radiocarbon (C-14) is a unique approach to unambiguously distinguishing the relative contributions of biomass-derived and fossil sources. Here, we developed a compound-specific radiocarbon analysis (CSRA) method for individual dicarboxylic acids in atmospheric particulates. Specifically, the method starts with a dibutyl ester derivatization technique, followed by separation and harvesting of single compounds employing AIMS a preparative capillary gas chromatography in sufficient amounts for offline C-14 measurement with accelerator mass spectrometry. The optimized preparative steps yielded recoveries of >60% and purities of >99% for target molecules. The radiocarbon isotope compositions determined for reference standards taken through the entire method agree well with the original composition of each standard (R-2 = 0.9998). The applicability of the approach was demonstrated with ambient aerosol samples representing contrasting air mass regimes. This yielded two radically different yet system-consistent precursor sources. A minimum size of 50 mu g of C of ambient dicarboxylic acids is needed for credible C-14 measurement. The established method for CSRA of dicarboxylic acids demonstrates a new analytical dimension for studies of the source and evolution of atmospheric secondary organic aerosols.
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| 7. |
- Xu, Buqing, et al.
(författare)
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Large contribution of fossil-derived components to aqueous secondary organic aerosols in China
- 2022
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Incomplete understanding of the sources of secondary organic aerosol (SOA) leads to large uncertainty in both air quality management and in climate change assessment. Chemical reactions occurring in the atmospheric aqueous phase represent an important source of SOA mass, yet, the effects of anthropogenic emissions on the aqueous SOA (aqSOA) are not well constrained. Here we use compound-specific dual-carbon isotopic fingerprints (δ13C and Δ14C) of dominant aqSOA molecules, such as oxalic acid, to track the precursor sources and formation mechanisms of aqSOA. Substantial stable carbon isotope fractionation of aqSOA molecules provides robust evidence for extensive aqueous-phase processing. Contrary to the paradigm that these aqSOA compounds are largely biogenic, radiocarbon-based source apportionments show that fossil precursors produced over one-half of the aqSOA molecules. Large fractions of fossil-derived aqSOA contribute substantially to the total water-soluble organic aerosol load and hence impact projections of both air quality and anthropogenic radiative forcing. Our findings reveal the importance of fossil emissions for aqSOA with effects on climate and air quality.
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| 8. |
- Yue, Siyao, et al.
(författare)
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Sources and Radiative Absorption of Water-Soluble Brown Carbon in the High Arctic Atmosphere
- 2019
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 46:24, s. 14881-14891
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Tidskriftsartikel (refereegranskat)abstract
- Brown carbon (BrC) is a source of light-absorbing aerosols. The Arctic is more sensitive to emissions of light-absorbing aerosols than lower latitudes. Knowledge of BrC in a historical period is beneficial to understand its role in a changing climate. Here, we present measurement of water-soluble BrC (WS-BrC) for the Arctic aerosols during late winter-late spring in 1991. Mass absorption coefficient (0.07 +/- 0.04 M/m) and efficiency (0.41 +/- 0.21 m(2)/g) at 365 nm of WS-BrC were lower than those in polluted urban and rural regions. WS-BrC was mainly from biomass burning/combustion (dark winter to mid-March) and marine sources connected with photochemical gas to particle conversion (after polar sunrise to June). Solar radiative absorption of WS-BrC relative to elemental carbon was 5% on average in February to April and surged to 34% after mid-May. This study helps in understanding the role of BrC in the Arctic climate.
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