| 1. |
- Aeppli, Christoph, et al.
(författare)
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Direct compound-specific stable chlorine isotope analysis of organic compounds with quadrupole GC/MS using standard isotope bracketing
- 2010
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Ingår i: Analytical Chemistry. - Columbus, OH : American Chemical Society. - 0003-2700 .- 1520-6882. ; 82:1, s. 420-426
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Tidskriftsartikel (refereegranskat)abstract
- A method has been developed for the direct determination of the stable chlorine isotope composition (delta(37)Cl) of organochlorines that eliminates sample preparation, achieves precision comparable to earlier techniques while improving the sensitivity, and makes use of benchtop gas chromatography-quadrupole mass spectrometry instruments (GCqMS). The method is based on the use of multiple injections (n = 8-10) of the sample, bracketed by a molecularly identical isotopic standard with known delta(37)Cl, determined using off-line thermal ionization mass spectrometry (TIMS). Mass traces of two isotopologues differing by one chlorine isotope were used to calculate delta(37)Cl values. Optimization of mass spectrometry and peak integration parameters as well as method validation was achieved using tetrachloroethene (PCE), p,p'-dichlorodiphenyltrichloroethane (DDT), and pentachlorophenol (PCP), spanning a delta(37)Cl range of -5.5 to +3.2 per thousand vs SMOC. Injecting 1.6-1100 pmol resulted in standard deviations (1sigma) of 0.6-1.3 per thousand, and the delta(37)Cl results agreed with values independently measured with TIMS. The method was tested by determining the Rayleigh fractionation during evaporation of pure liquid PCE, resulting in a chlorine isotopic enrichment factor of epsilon(Cl) = -1.1 +/- 0.4 per thousand. Furthermore, position-specific delta(37)Cl analysis based on analysis of DDT mass fragments was evaluated. The GCqMS-delta(37)Cl method offers a simplified yet sensitive approach for compound-specific chlorine isotope analysis.
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| 2. |
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| 3. |
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| 4. |
- Aeppli, Christoph, et al.
(författare)
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Use of Cl and C Isotopic Fractionation to Identify Degradation and Sources of Polychlorinated Phenols : Mechanistic Study and Field Application
- 2013
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 47:2, s. 790-797
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Tidskriftsartikel (refereegranskat)abstract
- The widespread use of chlorinated phenols (CPs) as a wood preservative has led to numerous contaminated sawmill sites. However, it remains challenging to assess the extent of in situ degradation of CPs. We evaluated the use of compound-specific chlorine and carbon isotope analysis (Cl- and C-CSLA) to assess CP biotransformation. In a laboratory system, we measured isotopic fractionation during oxidative 2,4,6-trichlorophenol dechlorination by representative soil enzymes (C. fumago chloroperoxidase, horseradish peroxidase, and laccase from T. versicolor). Using a mathematical model, the validity of the Rayleigh approach to evaluate apparent kinetic isotope effects (AKIE) was confirmed. A small but significant Cl-AKIE of 1.0022 +/- 0.0006 was observed for all three enzymes, consistent with a reaction pathway via a cationic radical species. For carbon, a slight inverse isotope effect was observed (C-AKIE = 0.9945 +/- 0.0019). This fractionation behavior is clearly distinguishable from reported reductive dechlorination mechanisms. Based on these results we then assessed degradation and apportioned different types of technical CP mixtures used at two former sawmill sites. To our knowledge, this is the first study that makes use of two-element CSIA to study sources and transformation of CPs in the environment.
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| 5. |
- Bikkina, Srinivas, et al.
(författare)
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Air quality in megacity Delhi affected by countryside biomass burning
- 2019
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Ingår i: Nature Sustainability. - : Springer Science and Business Media LLC. - 2398-9629. ; 2:3, s. 200-205
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Tidskriftsartikel (refereegranskat)abstract
- South Asian megacities are strong sources of regional air pollution. Delhi is a key hotspot of health-and climate-impacting black carbon (BC) emissions, affecting environmental sustainability in densely populated northern India. Effective mitigation of BC impact is hampered by highly uncertain emission source estimates. Here, we use dual-carbon isotope fingerprints (delta C-13/Delta C-14) of BC to constrain the seasonal source variability in Delhi. These measurements show that lower BC concentrations in summer are predominantly from fossil fuel sources (similar to 83%). However, large-scale open burning of post-harvest crop residue/wood in nearby rural regions is contributing to severe haze pollution in Delhi during winter and autumn (similar to 42 +/- 17%). Hence, the common conception that megacities affect their surroundings is here amended or seasonally reversed. Therefore, to combat the severe air pollution problems in Delhi and the environmental quality of northern India, current urban efforts need to be complemented with countryside regional mitigation.
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| 6. |
- Budhavant, Krishnakant, et al.
(författare)
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Black carbon aerosols over Indian Ocean have unique source fingerprint and optical characteristics during monsoon season
- 2023
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 120:8
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Tidskriftsartikel (refereegranskat)abstract
- Effects of aerosols such as black carbon (BC) on climate and buildup of the monsoon over the Indian Ocean are insufficiently quantified. Uncertain contributions from various natural and anthropogenic sources impede our understanding. Here, we use observations over 5 y of BC and its isotopes at a remote island observatory in northern Indian Ocean to constrain loadings and sources during little-studied monsoon season. Carbon-14 data show a highly variable yet largely fossil (65 ± 15%) source mixture. Combining carbon-14 with carbon-13 reveals the impact of African savanna burning, which occasionally approach 50% (48 ± 9%) of the total BC loadings. The BC mass-absorption cross-section for this regime is 7.6 ± 2.6 m2/g, with higher values during savanna fire input. Taken together, the combustion sources, longevity, and optical properties of BC aerosols over summertime Indian Ocean are different than the more-studied winter aerosol, with implications for chemical transport and climate model simulations of the Indian monsoon.
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| 7. |
- Budhavant, Krishnakant, et al.
(författare)
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Changing optical properties of Black Carbon and Brown Carbon aerosols during long-range transport from the Indo-Gangetic Plain to the equatorial Indian Ocean
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Atmospheric aerosols strongly influence the global climate by their light absorption (e.g., black carbon, BC, brown carbon, BrC) and scattering (e.g., sulfate) properties. This study presents simultaneous measurements of ambient aerosol light absorption properties and chemical composition from three large-footprint South Asian receptor sites during the South Asian Pollution Experiment (SAPOEX) in December 2017 - March 2018. The BC mass absorption cross-section (BC-MAC678) values increased from 3.5 ± 1.3 at the Bhola Climate Observatory-Bangladesh (i.e., located at exit outflow of Indo-Gangetic Plain) to 6.4 ± 1.3 at the two regional receptor observatories at Maldives Climate Observatory-Hanimaadhoo (MCOH) and Maldives Climate Observatory-Gan (MCOG), an increase of 80%. This likely reflects a scavenging fractionation resulting in a population of finer BC with higher MAC678 having higher longevity. At the same time, the BrC-MAC365 decreased by a factor of three from the IGP exit to the equatorial Indian Ocean, likely due to photochemical bleaching of organic chromophores. The high chlorine-to-sodium ratio at the near-source-region BCOB suggests a significant contribution of chlorine from anthropogenic activities. This particulate Cl- has the potential to convert into Cl-radicals that can affect the oxidation capacity of the polluted air. Moreover, Cl- is shown to be near-fully consumed during the long-range transport. The results of this synoptic study over the large South Asian scale contribute rare observational constraints on optical properties of ambient BC (and BrC) aerosols over regional scales away from emission sources. It also contributes significantly to understanding the ageing effect of the optical and chemical properties of aerosols as the pollution from the Indo-Gangetic Plain disperses over the tropical ocean.
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| 8. |
- Budhavant, Krishnakant, et al.
(författare)
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Enhanced Light-Absorption of Black Carbon in Rainwater Compared With Aerosols Over the Northern Indian Ocean
- 2020
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Ingår i: Journal of Geophysical Research - Atmospheres. - 2169-897X .- 2169-8996. ; 125:2
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Tidskriftsartikel (refereegranskat)abstract
- Black carbon (BC) aerosols affect climate, especially in high aerosol loading regions such as South Asia. A key uncertainty for the climate effects of BC is the evolution of light-absorbing properties in the atmosphere. Here, we present a year-round comparison of the mass absorption cross section (MAC; 678 nm) of BC in air (PM10) and rain, for samples collected at the Maldives Climate Observatory at Hanimaadhoo. We develop a filter-loading correction scheme for estimating BC absorption on filters used in high-volume samplers. The year-round average MAC(678) of BC in the rain is almost twice (13.3 +/- 4.2 m(2)/g) compared to the PM10 aerosol (7.2 +/- 2.6 m(2)/g). A possible explanation is the elevated ratio of organic carbon (OC) to BC observed in rain particulate matter (9.4 +/- 6.3) compared to in the aerosols (OC/BC 2.6 +/- 1.4 and water-insoluble organic carbon/BC 1.2 +/- 0.8), indicating a coating-enhancement effect. In addition to BC, we also investigated the MAC(365) of water-soluble brown carbon in PM10 (0.4 +/- 0.4 m(2)/g, at 365 nm). In contrast to BC, MAC(365)brown carbon relates to air mass history, showing higher values for samples from air originating over the South Asian landmass. Furthermore, calculated washout ratios are much lower for BC compared to OC and inorganic ions such as sulfate, implying a longer atmospheric lifetime for BC. The wet deposition flux for BC during the high loading winter was 3 times higher than during the wet summer, despite much less precipitation in the winter.
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| 9. |
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| 10. |
- Carrizo, Daniel, et al.
(författare)
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Compound-specific bromine isotope compositions of one natural and six = dustrially synthesised organobromine substances
- 2011
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Ingår i: Environmental Chemistry. - 1448-2517 .- 1449-8979. ; 8:2, s. 127-132
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Tidskriftsartikel (refereegranskat)abstract
- AB The stable bromine isotopic composition (delta(81)Br) was determined for six industrially synthesised brominated organic compounds (BOCs) and one natural BOC by gas-chromatography multi-collector inductively coupled plasma mass spectrometry (GC-mcICP-MS). The delta(81)Br compositions of brominated benzenes, phenols (both natural and industrial), anisoles, and naphthalenes were constrained with the standard differential measurement approach using as reference a monobromobenzene sample with an independently determined delta(81)Br value (-0.39 parts per thousand v. Standard Mean Ocean Bromide, SMOB). The delta(81)Br values for the industrial BOCs ranged from -4.3 to -0.4 parts per thousand. The average delta(81)Br value for the natural compound (2,4-dibromophenol) was 0.2 +/- 1.6% (1 s.d.), and for the identical industrial compound (2,4-dibromophenol) -1.1 +/- 0.9 parts per thousand (1 s.d.), with a statistically significant difference of similar to 1.4 (P<0.05). The delta(81)Br of four out of six industrial compounds was found to be significantly different from that of the natural sample. These novel results establish the bromine isotopic variability among the industrially produced BOCs in relation to a natural sample.
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| 11. |
- Dasari, Sanjeev, et al.
(författare)
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Observation-constrained atmospheric lifetime and emission fluxes of black carbon aerosols over South Asia
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Black carbon (BC) aerosols cause climate perturbation and affect air quality/human health. In densely populated South Asia—where the warming effect of BC is estimated to be ~ orders of magnitude higher than the global average—model simulations underestimate the wintertime atmospheric abundance of BC relative to surface observations. Two possible explanations for this model-observation offset are ill-constrained regional emission fluxes and atmospheric BC lifetime (τBC). Here, we combine hourly-resolved BC and carbon monoxide (CO) measurements for three successive winters from a South Asian receptor site—the Maldives Climate Observatory at Hanimaadhoo (MCOH)—in inverse frameworks, to assess the impact of emissions fluxes and lifetimes on ambient BC concentrations. The average ΔBC/ΔCO ratio (background corrected) at MCOH of 14±5 ng m-3 ppb-1 is found to be 2-3 times higher than in the East Asian outflow (range: 2 to 8 ng m-3 ppb-1). A BC transport efficiency of ~86% suggests low influence of wet scavenging processes during the dry South Asian winter period. Using statistical time series analysis, the τBC for dry wintertime South Asia is estimated to be 8±0.5 days, which is higher than commonly used in models. By coupling air mass back trajectories, lifetimes, and the ΔBC/ΔCO time-series data within an inverse modelling framework, we provide an observation-based “top-down” BC emission flux for South Asia estimated to be ~2.4±1 Tg/year. This is significantly higher than estimates from current “bottom-up” emission inventories (EIs). Taken together, this study suggests that to reconcile long-standing BC model-observation offsets in South Asia, existing emission estimates may need to be more than doubled in magnitude.
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| 12. |
- Dasari, Sanjeev, 1989-, et al.
(författare)
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Observational Evidence of Large Contribution from Primary Sources for Carbon Monoxide in the South Asian Outflow
- 2022
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 56:1, s. 165-174
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Tidskriftsartikel (refereegranskat)abstract
- South Asian air is among the most polluted in the world, causing premature death of millions and asserting a strong perturbation of the regional climate. A central component is carbon monoxide (CO), which is a key modulator of the oxidizing capacity of the atmosphere and a potent indirect greenhouse gas. While CO concentrations are declining elsewhere, South Asia exhibits an increasing trend for unresolved reasons. In this paper, we use dual-isotope (δ13C and δ18O) fingerprinting of CO intercepted in the South Asian outflow to constrain the relative contributions from primary and secondary CO sources. Results show that combustion-derived primary sources dominate the wintertime continental CO fingerprint (fprimary ∼ 79 ± 4%), significantly higher than the global estimate (fprimary ∼ 55 ± 5%). Satellite-based inventory estimates match isotope-constrained fprimary-CO, suggesting observational convergence in source characterization and a prospect for model–observation reconciliation. This “ground-truthing” emphasizes the pressing need to mitigate incomplete combustion activities for climate/air quality benefits in South Asia.
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| 13. |
- Dasari, Sanjeev, et al.
(författare)
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Photochemical degradation affects the light absorption of water-soluble brown carbon in the South Asian outflow
- 2019
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- Light-absorbing organic aerosols, known as brown carbon (BrC), counteract the overall cooling effect of aerosols on Earth's climate. The spatial and temporal dynamics of their light-absorbing properties are poorly constrained and unaccounted for in climate models, because of limited ambient observations. We combine carbon isotope forensics (delta C-13) with measurements of light absorption in a conceptual aging model to constrain the loss of light absorptivity (i.e., bleaching) of water-soluble BrC (WS-BrC) aerosols in one of the world's largest BrC emission regions-South Asia. On this regional scale, we find that atmospheric photochemical oxidation reduces the light absorption of WS-BrC by similar to 84% during transport over 6000 km in the Indo-Gangetic Plain, with an ambient first-order bleaching rate of 0.20 +/- 0.05 day(-1) during over-ocean transit across Bay of Bengal to an Indian Ocean receptor site. This study facilitates dynamic parameterization of WS-BrC absorption properties, thereby constraining BrC climate impact over South Asia.
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| 14. |
- Dasari, Sanjeev, et al.
(författare)
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Source Quantification of South Asian Black Carbon Aerosols with Isotopes and Modeling
- 2020
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 54:19, s. 11771-11779
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Tidskriftsartikel (refereegranskat)abstract
- Black carbon (BC) aerosols perturb climate and impoverish air quality/ human health-affecting similar to 1.5 billion people in South Asia. However, the lack of source-diagnostic observations of BC is hindering the evaluation of uncertain bottom-up emission inventories (EIs) and thereby also models/policies. Here, we present dual-isotope-based (Delta C-14/delta C-13) fingerprinting of wintertime BC at two receptor sites of the continental outflow. Our results show a remarkable similarity in contributions of biomass and fossil combustion, both from the site capturing the highly populated highly polluted Indo-Gangetic Plain footprint (IGP; Delta C-14-f(biomass) = 50 +/- 3%) and the second site in the N. Indian Ocean representing a wider South Asian footprint (52 +/- 6%). Yet, both sites reflect distinct delta C-13-fingerprints, indicating a distinguishable contribution of C-4-biomass burning from peninsular India (PI). Tailored-model-predicted seasonaveraged BC concentrations (700 +/- 440 ng m(-3)) match observations (740 +/- 250 ng m(-3)), however, unveiling a systematically increasing model-observation bias (+19% to -53%) through winter. Inclusion of BC from open burning alone does not reconcile predictions (f(biomass) = 44 +/- 8%) with observations. Direct source-segregated comparison reveals regional offsets in anthropogenic emission fluxes in EIs, overestimated fossil-BC in the IGP, and underestimated biomass-BC in PI, which contributes to the model-observation bias. This ground-truthing pinpoints uncertainties in BC emission sources, which benefit both climate/air-quality modeling and mitigation policies in South Asia.
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| 15. |
- Ek, Caroline, et al.
(författare)
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Using Compound-Specific and Bulk Stable Isotope Analysis for Trophic Positioning of Bivalves in Contaminated Baltic Sea Sediments
- 2018
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 52:8, s. 4861-4868
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Tidskriftsartikel (refereegranskat)abstract
- Stable nitrogen isotopes (delta N-15) are used as indicators of trophic position (TP) of consumers. Deriving TP from delta N-15 of individual amino acids (AAs) is becoming popular in ecological studies, because of lower uncertainty than TP based on bulk delta N-15 (TPbulk). This method would also facilitate biomagnification studies provided that isotope fractionation is unaffected by toxic exposure. We compared TPAA and TPbulk estimates for a sediment-dwelling bivalve from two coastal sites, a pristine and a contaminated. Chemical analysis of PCB levels in mussels, sediments, and pore water confirmed the expected difference between sites. Both methods, but in particular the TPAA underestimated the actual TP of bivalves. Using error propagation, the total uncertainty related to the analytical precision and assumptions in the TP calculations was found to be similar between the two methods. Interestingly, the significantly higher intercept for the regression between T-AA, and TPbulk in the contaminated site compared to the pristine site indicates a higher deamination rate due to detoxification as a result of chronic exposure and a higher N-15 fractionation. Hence, there is a need for controlled experiments on assumptions underlying amino acid-specific stable isotope methods in food web and bimagnification studies.
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| 16. |
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| 17. |
- Fang, Wenzheng, et al.
(författare)
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Combined influences of sources and atmospheric bleaching on light absorption of water-soluble brown carbon aerosols
- 2023
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Ingår i: npj Climate and Atmospheric Science. - 2397-3722. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- Light-absorbing Brown Carbon (BrC) aerosols partially offset the overall climate-cooling of aerosols. However, the evolution of BrC light-absorption during atmospheric transport is poorly constrained. Here, we utilize optical properties, ageing-diagnostic delta C-13-BrC and transport time to deduce that the mass absorption cross-section (MACWS-BrC) is decreasing by similar to 50% during long-range oversea transport, resulting in a first-order bleaching rate of 0.24 day(-1) during the 3-day transit from continental East Asia to a south-east Yellow Sea receptor. A modern C-14 signal points to a strong inverse correlation between BrC light-absorption and age of the source material. Combining this with results for South Asia reveals a striking agreement between these two major-emission regions of rapid photobleaching of BrC with a higher intrinsic absorptivity for BrC stemming from biomass burning. The consistency of bleaching parameters constrained independently for the outflows of both East and South Asia indicates that the weakening of BrC light absorption, thus primarily related to photochemical processes rather than sources, is likely a ubiquitous phenomenon.
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| 18. |
- Fang, Wenzheng, et al.
(författare)
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Divergent Evolution of Carbonaceous Aerosols during Dispersal of East Asian Haze
- 2017
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Wintertime East Asia is plagued by severe haze episodes, characterized by large contributions of carbonaceous aerosols. However, the sources and atmospheric transformations of these major components are poorly constrained, hindering development of efficient mitigation strategies and detailed modelling of effects. Here we present dual carbon isotope (delta C-13 and Delta C-14) signatures for black carbon (BC), organic carbon (OC) and water-soluble organic carbon (WSOC) aerosols collected in urban (Beijing and BC for Shanghai) and regional receptors (e.g., Korea Climate Observatory at Gosan) during January 2014. Fossil sources (>50%) dominate BC at all sites with most stemming from coal combustion, except for Shanghai, where liquid fossil source is largest. During source-to-receptor transport, the delta C-13 fingerprint becomes enriched for WSOC but depleted for water-insoluble OC (WIOC). This reveals that the atmospheric processing of these two major pools are fundamentally different. The photochemical aging (e.g., photodissociation, photooxidation) during formation and transport can release CO2/CO or short-chain VOCs with lighter carbon, whereas the remaining WSOC becomes increasingly enriched in delta C-13. On the other hand, several processes, e.g., secondary formation, rearrangement reaction in the particle phase, and photooxidation can influence WIOC. Taken together, this study highlights high fossil contributions for all carbonaceous aerosol sub-compartments in East Asia, and suggests different transformation pathways for different classes of carbonaceous aerosols.
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| 19. |
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| 20. |
- Holmstrand, Henry, et al.
(författare)
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Chlorine isotope evidence for the anthropogenic origin of tris-(4-chlorophenyl)methane
- 2010
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Ingår i: Applied Geochemistry. - : Elsevier BV. - 0883-2927 .- 1872-9134. ; 25:9, s. 1301-1306
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Tidskriftsartikel (refereegranskat)abstract
- Compound-specific Cl-isotope analysis was performed on the persistent and bioaccumulating compound tris-(4-chlorophenyl)methane (4,4',4 ''-TCPMe, referred to as TCPMe in this study) to elucidate whether its main source is natural or anthropogenic. Blubber from the Baltic grey seal (Halichoerus grypus) was extracted by continuous acetonitrile partitioning, and the TCPMe was isolated from the extract by preparative-capillary gas chromatography. Chlorine isotope analysis was subsequently performed by sealed-tube combustion in conjunction with thermal-ionization mass spectrometry (TIMS). The delta Cl-37 of TCPMe was -3.5 +/- 0.5 parts per thousand, similar to the previously reported delta Cl-37 of technical grade p,p'-DDT (referred to as DDT in this study). The data is not consistent with a putative marine natural source of TCPMe, as enzymatic (biotic) production is reported to give values of delta Cl-37 < - 10 parts per thousand. The delta Cl-37-TCPMe data thus supports the hypothesis that TCPMe is produced as a byproduct during DDT synthesis and is released to the environment through the same pathways as DDT. It is also consistent with tris-(4-chlorophenyl)methanol as the primary biotransformation product of TCPMe.
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| 21. |
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| 22. |
- Holmstrand, Henry, et al.
(författare)
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Compound-specific bromine isotope analysis of brominated diphenyl ethers using gas chromatography multiple collector/inductively coupled plasma mass spectrometry
- 2010
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Ingår i: Rapid Communications in Mass Spectrometry. - : Wiley. - 0951-4198 .- 1097-0231. ; 24:14, s. 2135-2142
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Tidskriftsartikel (refereegranskat)abstract
- The bromine isotope composition is potentially diagnostic in both degradation monitoring and source apportionment of organobromines in the environment. A method for compound-specific bromine isotope analysis (delta Br-81) based on gas chromatography multiple collector inductively coupled plasma mass spectrometry (GC/ICPMS) was developed for common brominated diaromatic compounds. Brominated diphenyl ethers (BDEs) in Bromkal 70-5DE, a technical flame-retardant mixture containing mainly BDEs #47, #99 and #100, were used as test substances, with standard bracketing for the samples achieved through co-injected monobromobenzene (MBB) with a known delta Br-81 of -0.39 parts per thousand vs. Standard Mean Ocean Bromine (SMOBr). Three different heated transfer lines were constructed and tested to achieve efficient conduction of the BDEs from the gas chromatograph to the ICPMS instrument. The MBB was analyzed with a precision of 0.4 parts per thousand (1 s, n = 18). The precision for BDEs was 1.4-1.8 parts per thousand (1 s, n = 10-12 depending on the congener). The lower precision for the BDEs than for MBB may reflect the heat required to prevent condensation of the analytes in ICP torch assembly. The use of an internal standard of similar chemical structure to the analytes alleviates this problem, as illustrated by a difference of 0.3 +/- 0.7 parts per thousand (1 s, n = 6) between the (delta Br-81 values of co-injected methoxy BDE-47 and BDE-47 extracted from whale blubber. Improvements in precision and accuracy may be achieved by the use of a more efficient heating of the torch assembly in conjunction with a set of internal standards that match the target compounds.
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| 23. |
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| 24. |
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| 25. |
- Holmstrand, Henry, 1974-
(författare)
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Compound-specific stable chlorine isotope analysis : A versatile tool for investigating biochemical and geochemical processes of organochlorine substances
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Chlorinated organic compounds (OCls) from anthropogenic sources are generally considered to be a class of chemicals with high potential for ecotoxicity, including infamous substances such as polychlorinated biphenyls (PCB), dichloro-dibenzo-trichloroethane (DDT) and polychlorinated dibenzo-p-dioxins (PCDD). OCls are also produced naturally, sometimes at the same order of magnitude as anthropogenic compounds. The scope of this thesis was to develop and apply a method for isotope analysis of OCls, as a part of compound-specific chlorine isotope analysis (CSIA-δ37Cl) of trace level compounds. Isotope analysis of chlorine was performed with sealed-tube combustion and thermal-ionization mass spectrometry (TIMS), in order to improve the analytical sensitivity by a factor 20 relative to conventional techniques. Chlorine isotope signatures of organochlorines (δ37Cl-OCl) can be used for source apportionment in the natural vs. anthropogenic spectrum. CSIA-δ37Cl was tested as a tool to resolve the origin of putatively natural PCDD found in ball clay from the Mississippi Embayment, USA. Combined with results from 14C analysis, the δ37Cl-PCDD was consistent with a natural abiotic formation of PCDD. Reactions involving the scission of a chemical bond to a molecular chlorine substituent will induce a shift in the δ37Cl-OCl of the remaining reactant. This concept was used to calculate the undegraded fraction of DDT in the Baltic marine environment (~7% DDT remaining) based on δ37Cl-OCl measurements of DDT harvested from seal blubber. Hence, it is suggested that CSIA-δ37Cl may be very useful in studies of fate and origin of OCls in the environment, and that further applications of the technique are warranted.
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