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1.
Environ Pollut ; 268(Pt A): 115906, 2020 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-33120333

RESUMO

Fluorescence spectroscopy is a commonly used technique to analyze dissolved organic matter in aquatic environments. Given the high sensitivity and non-destructive analysis, fluorescence has recently been used to study water-soluble organic carbon (WSOC) in atmospheric aerosols, which have substantial abundance, various sources and play an important role in climate change. Yet, current research on WSOC characterization is rather sparse and limited to a few isolated sites, making it challenging to draw fundamental and mechanistic conclusions. Here we presented a review of the fluorescence properties of atmospheric WSOC reported in various field and laboratory studies, to discuss the current advances and limitations of fluorescence applications. We highlighted that photochemical reactions and relevant aging processes have profound impacts on fluorescence properties of atmospheric WSOC, which were previously unnoticed for organic matter in aquatic environments. Furthermore, we discussed the differences in sources and chemical compositions of fluorescent components between the atmosphere and hydrosphere. We concluded that the commonly used fluorescence characteristics derived from aquatic environments may not be applicable as references for atmospheric WSOC. We emphasized that there is a need for more systematic studies on the fluorescence properties of atmospheric WSOC and to establish a more robust reference and dataset for fluorescence studies in atmosphere based on extensive source-specific experiments.

2.
Sci Total Environ ; 738: 139836, 2020 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-32526422

RESUMO

Strengthening the research of riverine mercury (Hg) export is of great significance for understanding the regional and global Hg cycle, especially for the data lacking trans-Himalayan rivers. In this study, three systematic sampling campaigns were conducted in the Koshi River Basin (KRB) during the post-monsoon, pre-monsoon and monsoon seasons. Hg speciation and distribution of river water were analyzed among the different seasons for a total of 88 water samples. The total Hg (THg) concentration of surface water in the KRB ranged from 0.64 to 32.96 ng·L-1 with an average of 5.83 ± 6.19 ng·L-1 and decreased in the order of post-monsoon (8.79 ± 7.32 ng·L-1) > monsoon (6.68 ± 6.12 ng·L-1) > pre-monsoon (2.18 ± 1.29 ng·L-1). Particulate Hg (PHg) accounted for 63% of THg on average and had a positive correlation with THg among all the three sampling seasons, indicating that the differences in PHg concentration were likely one of the main factors leading to the seasonal and spatial variations in THg in the KRB surface water. The annual Hg exports and fluxes were estimated to be 339.04 kg and 3.88 µg·m-2·yr-1, respectively. Furthermore, Hg export from the KRB had significant seasonal variation and decreased in the order of monsoon (259.47 kg) > post-monsoon (61.18 kg) > winter (9.31 kg) > pre-monsoon (9.08 kg), and this pattern was mainly related to seasonal changes in river runoff. The annual Hg export is projected to increase in the future, especially in the post-monsoon season. Therefore, more attention should be paid to river runoff observations and riverine Hg research for water resources management in the Himalaya.

3.
ACS Appl Mater Interfaces ; 12(21): 23904-23913, 2020 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-32362118

RESUMO

Recently, benefiting from the merits of small-molecule acceptors (NFAs), polymer solar cells (PSCs) have achieved tremendous advances. From the perspective of the structural characteristics of the π-conjugated acceptor-donor-acceptor (A-D-A) type of organic molecules, the backbone's planarity and the terminal groups and their substituents have strong influences on the performances of the constructed NFAs. Through enlarging the dihedral angle of the conjugated main chain of NFAs, a certain degree of enhancement of photovoltaic parameters has been achieved. To further probe the influences of ending groups on the performances of nonplanar NFAs, we synthesized two new NFAs i-cc23 and i-cc34 with isomerized thiophene-fused ending groups and a twisted π-conjugated main chain. Compared to i-cc23 containing the 2-(6-oxo-5,6-dihydro-4H-cyclopenta[b]thiophen-4-ylidene)malononitrile ending group, the acceptor i-cc34 containing 2-(6-oxo-5,6-dihydro-4H-cyclopenta[c]thiophen-4-ylidene)malononitrile has a relatively higher molar extinction coefficient, bathochromic-shifted absorption spectrum, and deepened energy levels. When mixed with PBDB-T in solar cells, the i-cc23-based device achieved an excellent open-circuit voltage (VOC) of 1.10 V and a moderate power conversion efficiency of 7.34%. Although the VOC of the i-cc34-related device was decreased to 0.96 V, the short-circuit current density and fill factor were improved, giving rise to an enhanced efficiency of 9.51%. Apart from the distinct photovoltaic performances, the two isomer-based devices exhibit a high radiative efficiency of 8 × 10-4, leading to a very small nonradiative loss of 0.19 V. Our results emphasize the importance of the isomerized thiophene-fused ending groups on the performances of nonplanar NFA-based PSCs.

4.
Environ Pollut ; 257: 113616, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31761583

RESUMO

Brown carbon (BrC) has been proposed as an important driving factor in climate change due to its light absorption properties. However, our understanding of BrC's chemical and optical properties are inadequate, particularly at remote regions. This study conducts a comprehensive investigation of BrC aerosols in summer (Aug. 2013) and winter (Jan. 2014) at Southeast Tibetan Plateau, which is ecologically fragile and sensitive to global warming. The concentrations of methanol-soluble BrC (MeS-BrC) are approximately twice of water-soluble BrC (WS-BrC), demonstrating the environmental importance of water-insoluble BrC are previously underestimated with only WS-BrC considered. The mass absorption efficiency of WS-BrC (0.27-0.86 m2 g-1) is lower than those in heavily polluted South Asia, indicating a distinct contrast between the two sides of Himalayas. Fluorescence reveals that the absorption of BrC is mainly attributed to humic-like and protein-like substances, which broaden the current knowledge of BrC's chromophores. Combining organic tracer, satellite MODIS data and air-mass backward trajectory analysis, this study finds BrC is mainly derived from bioaerosols and secondary formation in summer, while long-range transport of biomass burning emissions in winter. Our study provides new insights into the optical and chemical properties of BrC, which may have implications for environmental effect and sources of organic aerosols.


Assuntos
Aerossóis/química , Poluentes Atmosféricos/análise , Carbono , Monitoramento Ambiental , Aerossóis/análise , Poluentes Atmosféricos/química , Ásia , Fluorescência , Tibet
5.
ACS Appl Mater Interfaces ; 12(1): 789-797, 2020 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-31801347

RESUMO

Recently, main-chain twisted small molecules are attractive as electron-acceptors in polymer solar cells (PSCs) for their upshifted molecular energy levels, enhanced extinction coefficients, and better charge extraction properties along with longer carrier lifetimes and lower recombination rates relative to their planar analogues, which are conducive to the power conversion efficiency (PCE) promotion of PSCs. To further probe the "structure-performance" correlation of main-chain twisted acceptors, in particular the monofluorine-substituted sites on the performances of the resultant acceptors, two new main-chain twisted small molecules were synthesized, in which a fluorine atom was introduced at different sites on the end-capping group 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (INCN). Although fine structural modification was adopted, quite different performances were obtained for the two acceptors. Compared to the 3-fluorinated analogue (i-IEICO-F3), a mixture of 4-fluorinated and 5-fluorinated isomers (i-IEICO-2F) exhibited a higher dipole moment, enlarged molar extinction coefficient with a bathochromic-shifted absorption region, suppressed charge recombinations with balanced charge mobilities, and slightly enhanced crystallinity. In combination with a fluorobenzotriazole-based medium-band gap polymer (J52), a high efficiency of 12.86% was resultantly achieved in an i-IEICO-2F-based device, which is superior to the result (7.65%) of the i-IEICO-F3 device, revealing the importance of monofluorinated positions on the performances of main-chain twisted non-fullerene acceptors.

6.
Environ Sci Technol ; 53(21): 12247-12256, 2019 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-31558018

RESUMO

Nitrogenous aerosols are ubiquitous in the environment and thus play a vital role in the nutrient balance as well as the Earth's climate system. However, their abundance, sources, and deposition are poorly understood, particularly in the fragile and ecosensitive Himalayan and Tibetan Plateau (HTP) region. Here, we report concentrations of nitrogen species and isotopic composition (δ15N) in aerosol samples collected from a forest site in the HTP (i.e., Southeast Tibet). Our results revealed that both organic and inorganic nitrogen contribute almost equally with high abundance of ammonium nitrogen (NH4+-N) and water-insoluble organic nitrogen (WION), contributing ∼40% each to aerosol total nitrogen (TN). The concentrations and δ15N exhibit a significant seasonality with ∼2 times higher in winter than in summer with no significant diurnal variations for any species. Moreover, winter aerosols mainly originated from biomass burning emissions from North India and East Pakistan and reached the HTP through a long-range atmospheric transport. The TN dry deposition and total deposition fluxes were 2.04 kg ha-1 yr-1 and 6.12 kg ha-1 yr-1 respectively. Our results demonstrate that the air contamination from South Asia reach the HTP and is most likely impacting the high altitude ecosystems in an accepted scenario of increasing emissions over South Asia.


Assuntos
Poluentes Atmosféricos , Nitrogênio , Aerossóis , Ecossistema , Monitoramento Ambiental , Florestas , Índia , Paquistão , Estações do Ano , Tibet
7.
Environ Sci Technol ; 53(16): 9472-9480, 2019 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-31310123

RESUMO

Little is currently known about the trophic transfer behavior of short-chain chlorinated paraffins (SCCPs) in terrestrial ecosystems. The trophodynamics of SCCPs were investigated in a typical terrestrial food chain (plant-plateau pika-eagle) from the interior of the Tibetan Plateau with an altitude of 4730 m. Pervasive contamination by SCCPs was found in the Tibetan Plateau samples, and the average concentrations of SCCPs in soil, plant, plateau pika, eagle, and gut content of eagle samples were 81.6 ± 31.1, 173 ± 70.3, 258 ± 126, 108 ± 59.6, and 268 ± 93.9 ng/g (average ± standard deviation, dry weight, dw), respectively. The trophic magnification factor (TMF) of SCCPs was 0.37, implying the trophic dilution of SCCPs in this terrestrial food chain. The TMF values of individual congener groups were positively correlated with the values of log Kow, log Koa and biotransformation half-life. As a result of long-range transport, SCCPs congeners with low molecular weight dominated in Tibetan Plateau species (C10+11 congeners = 76.9%, Cl5+6+7 congeners = 71.5%), which could partly explain the low biomagnification factors (BMFs) of SCCPs in the Tibetan Plateau.


Assuntos
Águias , Hidrocarbonetos Clorados , Lagomorpha , Animais , China , Ecossistema , Monitoramento Ambiental , Cadeia Alimentar , Parafina , Tibet
8.
Environ Pollut ; 253: 49-60, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31302402

RESUMO

Carbonaceous aerosols (CAs) scatter and absorb incident solar radiation in the atmosphere, thereby influencing the regional climate and hydrological cycle, particularly in the Third Pole (TP). Here, we present the characteristics of CAs at 19 observation stations from the Atmospheric Pollution and Cryospheric Change network to obtain a deep understanding of pollutant status in the TP. The organic carbon (OC) and elemental carbon (EC) concentrations decreased noticeably inwards from outside to inland of the TP, consistent with their emission load and also affected by transport process and meteorological condition. Urban areas, such as Kathmandu, Karachi, and Mardan, exhibited extremely high OC and EC concentrations, with low and high values occurring in the monsoon and non-monsoon seasons, respectively. However, remote regions inland the TP (e.g., Nam Co and Ngari) demonstrated much lower OC and EC concentrations. Different seasonal variations were observed between the southern and northern parts of the TP, suggesting differences in the patterns of pollutant sources and in distance from the sources between the two regions. In addition to the influence of long-range transported pollutants from the Indo-Gangetic Plain (IGP), the TP was affected by local emissions (e.g., biomass burning). The OC/EC ratio also suggested that biomass burning was prevalent in the center TP, whereas the marginal sites (e.g., Jomsom, Dhunche, and Laohugou) were affected by fossil fuel combustion from the up-wind regions. The mass absorption cross-section of EC (MACEC) at 632 nm ranged from 6.56 to 14.7 m2 g-1, with an increasing trend from outside to inland of the TP. Urban areas had low MACEC values because such regions were mainly affected by local fresh emissions. In addition, large amount of brown carbon can decrease the MACEC values in cities of South Asia. Remote sites had high MACEC values because of the coating enhancement of aerosols. Influenced by emission, transport process, and weather condition, the CA concentrations and MACEC presented decreasing and increasing trends, respectively, from outside to inland of the TP.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental , Material Particulado/análise , Aerossóis/análise , Ásia , Atmosfera/química , Biomassa , Carbono/análise , Cidades , Clima , Poluição Ambiental , Combustíveis Fósseis , Estações do Ano , Tempo (Meteorologia) , Vento
9.
Environ Sci Technol ; 53(12): 6632-6639, 2019 06 18.
Artigo em Inglês | MEDLINE | ID: mdl-31117527

RESUMO

Cryoconite is a granular aggregate, comprised of both mineral and biological material, and known to accumulate atmospheric contaminants. In this study, cryoconite was sampled from seven high-elevation glaciers in Western China to investigate the spatial and altitudinal patterns of atmospheric mercury (Hg) accumulation in the cryoconite. The results show that total Hg (HgT) concentrations in cryoconite were significant with relatively higher Hg accumulation in the southern glaciers (66.0 ± 29.3 ng g-1), monsoon-influenced regions, than those in the northern glaciers (42.5 ± 20.7 ng g-1), westerlies-influenced regions. The altitudinal profile indicates that HgT concentrations in the northern glaciers decrease significantly with altitude, while those in the southern glaciers generally increase toward higher elevations. Unexpectedly high accumulation of methyl-Hg (MeHg) with an average of 1.0 ± 0.4 ng g-1 was also detected in the cryoconite samples, revealing the surface of cryoconite could act as a potential site for Hg methylation in alpine environments. Our preliminary estimate suggests a storage of ∼34.3 ± 17.4 and 0.65 ± 0.28 kg of HgT and MeHg from a single year of formation process in the glacier cryoconite. Therefore, glacier cryoconite could play an important role in Hg storage and transformation, which may result in downstream effects on glacier-fed ecosystems under climate warming scenario.


Assuntos
Camada de Gelo , Mercúrio , China , Ecossistema
10.
Environ Sci Technol ; 53(10): 5641-5651, 2019 05 21.
Artigo em Inglês | MEDLINE | ID: mdl-30994333

RESUMO

Black carbon (BC) is one of the major drivers of climate change, and its measurement in different environment is crucial for the better understanding of long-term trends in the Himalayan-Tibetan Plateau (HTP) as climate warming has intensified in the region. We present the measurement of BC concentration from six lake sediments in the HTP to reconstruct historical BC deposition since the pre-industrial era. Our results show an increasing trend of BC concurrent with increased anthropogenic emission patterns after the commencement of the industrialization era during the 1950s. Also, sedimentation rates and glacier melt strengthening influenced the total input of BC into the lake. Source identification, based on the char and soot composition of BC, suggests biomass-burning emissions as a major contributor to BC, which is further corroborated by open-fire occurrence events in the region. The increasing BC trend continues to recent years, indicating increasing BC emissions, mainly from South Asia.


Assuntos
Lagos , Fuligem , Ásia , Carbono , Monitoramento Ambiental , Sedimentos Geológicos , Tibet
11.
ACS Appl Mater Interfaces ; 11(18): 16795-16803, 2019 May 08.
Artigo em Inglês | MEDLINE | ID: mdl-30987422

RESUMO

A new main-chain twisted small molecular acceptor with nonhalogenated end groups (i-IEICO) is designed and synthesized. In contrast to its planar analogue IECIO, i-IEICO possesses an obviously twisted backbone, leading to significant hypsochromic shift in film absorption, slight enhancement in solution extinction coefficient, and significantly elevated molecular energy level. Benefited from these features, i-IEICO is matched well with two wide band gap polymer donor materials (J52 and PBDB-T) both in absorption spectra and molecular energy levels. Relative to the planar-molecule IEICO-based devices, the open-circuit voltage ( VOC), short-circuit current density, and fill factor of the i-IEICO-based devices are simultaneously improved, giving rising to a 10.48% (with J52) and 8.79% (with PBDB-T) power conversion efficiency, respectively. Moreover, J52:i-IEICO device exhibits a high VOC of 0.96 V accompanied by a small energy loss of 0.64 eV, which can be further improved to 1.01 V and 0.59 eV for the PBDB-T-based device. The obtained VOC of i-IEICO-based devices are among one of the highest values of either J52 or PBDB-T-based binary devices, suggesting the effectiveness of main-chain twisted strategy coupled with end-group modification to achieve highly efficient nonfullerene acceptors with low energy loss and high VOC.

12.
Environ Sci Technol ; 53(7): 3471-3479, 2019 04 02.
Artigo em Inglês | MEDLINE | ID: mdl-30848122

RESUMO

Brown carbon (BrC) has recently emerged as an important light-absorbing aerosol. This study provides interannual and seasonal variations in light absorption properties, chemical composition, and sources of water-soluble BrC (WS-BrC) based on PM10 samples collected in Godavari, Nepal, from April 2012 to May 2014. The mass absorption efficiency of WS-BrC at 365 nm (MAE365) shows a clear seasonal variability, with the highest MAE365 of 1.05 ± 0.21 m2 g-1 in premonsoon season and the lowest in monsoon season (0.59 ± 0.16 m2 g-1). The higher MAE365 values in nonmonsoon seasons are associated with fresh biomass burning emissions. This is further substantiated by a strong correlation ( r = 0.79, P < 0.01) between Abs365 (light absorption coefficient at 365 nm) and levoglucosan. We found, using fluorescence techniques, that humic-like and protein-like substances are the main chromophores in WS-BrC and responsible for 80.2 ± 4.1% and 19.8 ± 4.1% of the total fluorescence intensity, respectively. BrC contributes to 8.78 ± 3.74% of total light absorption over the 300-700 nm wavelength range. Considering the dominant contribution of biomass burning to BrC over Godavari, this study suggests that reduction in biomass burning emission may be a practical method for climate change mitigation in South Asia.


Assuntos
Carbono , Água , Aerossóis , Ásia , Monitoramento Ambiental , Nepal
13.
Environ Pollut ; 248: 191-208, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30784838

RESUMO

Due to their low temperatures, the Arctic, Antarctic and Tibetan Plateau are known as the three polar regions of the Earth. As the most remote regions of the globe, the occurrence of persistent organic pollutants (POPs) in these polar regions arouses global concern. In this paper, we review the literatures on POPs involving these three polar regions. Overall, concentrations of POPs in the environment (air, water, soil and biota) have been extensively reported, with higher levels of dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH) detected on the Tibetan Plateau. The spatial distribution of POPs in air, water and soil in the three polar regions broadly reflects their distances away from source regions. Based on long-term data, decreasing trends have been observed for most "legacy POPs". Observations of transport processes of POPs among multiple media have also been carried out, including air-water gas exchange, air-soil gas exchange, emissions from melting glaciers, bioaccumulations along food chains, and exposure risks. The impact of climate change on these processes possibly enhances the re-emission processes of POPs out of water, soil and glaciers, and reduces the bioaccumulation of POPs in food chains. Global POPs transport model have shown the Arctic receives a relatively small fraction of POPs, but that climate change will likely increase the total mass of all compounds in this polar region. Considering the impact of climate change on POPs is still unclear, long-term monitoring data and global/regional models are required, especially in the Antarctic and on the Tibetan Plateau, and the fate of POPs in all three polar regions needs to be comprehensively studied and compared to yield a better understanding of the mechanisms involved in the global cycling of POPs.


Assuntos
Monitoramento Ambiental , Poluentes Ambientais/análise , Poluentes Atmosféricos/análise , Regiões Antárticas , Regiões Árticas , Mudança Climática , Clima Frio , DDT , Cadeia Alimentar , Previsões , Hexaclorocicloexano , Hidrocarbonetos Clorados , Solo , Tibet
14.
Environ Pollut ; 247: 216-228, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30677666

RESUMO

Biomass burning (BB) is one of the largest sources of carbonaceous aerosols with adverse impacts on air quality, visibility, health and climate. BB emits a few specific aromatic acids (p-hydroxybenzoic, vanillic, syringic and dehydroabietic acids) which have been widely used as key indicators for source identification of BB-derived carbonaceous aerosols in various environmental matrices. In addition, measurement of p-hydroxybenzoic and vanillic acids in snow and ice cores have revealed the historical records of the fire emissions. Despite their uniqueness and importance as tracers, our current understanding of analytical methods, concentrations, diagnostic ratios and degradation processes are rather limited and scattered in literature. In this review paper, firstly we have summarized the most established methods and protocols for the measurement of these aromatic acids in aerosols and ice cores. Secondly, we have highlighted the geographical variability in the abundances of these acids, their diagnostic ratios and degradation processes in the environments. The review of the existing data indicates that the concentrations of aromatic acids in aerosols vary greatly with locations worldwide, typically more abundant in urban atmosphere where biomass fuels are commonly used for residential heating and/or cooking purposes. In contrast, their concentrations are lowest in the polar regions which are avoid of localized emissions and largely influenced by long-range transport. The diagnostic ratios among aromatic acids can be used as good indicators for the relative amounts and types of biomass (e.g. hardwood, softwood and herbaceous plants) as well as photochemical oxidation processes. Although studies suggest that the degradation processes of the aromatic acids may be controlled by light, pH and hygroscopicity, a more careful investigation, including closed chamber studies, is highly appreciated.


Assuntos
Aerossóis/análise , Monitoramento Ambiental/métodos , Poluentes Atmosféricos/análise , Poluição do Ar/estatística & dados numéricos , Atmosfera/química , Biomassa , Fogo , Material Particulado/análise
15.
Bull Environ Contam Toxicol ; 102(5): 672-678, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30643930

RESUMO

Glacierized mountain environments can preserve and release mercury (Hg) and play an important role in regional Hg cycling. In the Tibetan Plateau (TP), most glaciers have been retreating at unprecedented rate in recent decades, acting as one of the most active factors in regional hydrological cycling. In this mini-review, we summarized recent studies on Hg distribution, transport, and accumulation in Tibetan glacierized environments. We highlight that melting glacier may represent a stimulator that exports Hg to glacier-fed ecosystems. We identified major knowledge gaps and proposed future research needs with several emphases, including quantifying Hg in glacier ablation zone, depicting Hg transport and transformation in glacial rivers during spring melt season, and better constraining glacier-export Hg and its environmental risks to the downstream. Besides, Hg isotopic technical, passive sampling and hydrological transport model should be utilized to improve the understanding of Hg cycling in high mountain regions in the TP.


Assuntos
Ecossistema , Monitoramento Ambiental/métodos , Poluentes Ambientais/análise , Camada de Gelo , Mercúrio/análise , Congelamento , Estações do Ano , Tibet
16.
Environ Sci Technol ; 52(13): 7203-7211, 2018 07 03.
Artigo em Inglês | MEDLINE | ID: mdl-29874057

RESUMO

Humic-like substances (HULIS) are major components of light-absorbing brown carbon that play an important role in Earth's radiative balance. However, their concentration, optical properties, and sources are least understood over Tibetan Plateau (TP). In this study, the analysis of total suspended particulate (TSP) samples from central of TP (i.e., Nam Co) reveal that atmospheric HULIS are more abundant in summer than that in winter without obvious diurnal variations. The light absorption ability of HULIS in winter is 2-3 times higher than that in summer. In winter, HULIS are mainly derived from biomass burning emissions in South Asia by long-range transport. In contrast, the oxidation of anthropogenic and biogenic precursors from northeast part of India and southeast of TP are major sources of HULIS in summer.


Assuntos
Poluentes Atmosféricos , Substâncias Húmicas , Aerossóis , Ásia , Monitoramento Ambiental , Índia , Tibet
17.
Sci Total Environ ; 634: 1475-1485, 2018 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-29710646

RESUMO

Brown carbon (BrC), a carbonaceous aerosol which absorbs solar radiation over a broad range of wavelengths, is beginning to be seen as an important contributor to global warming. BrC absorbs both inorganic and organic pollutants, leading to serious effects on human health. We review the fundamental features of BrC, including its sources, chemical composition, optical properties and radiative forcing effects. We detail the importance of including photochemical processes related to BrC in the GEOS-Chem transport model for the estimation of aerosol radiative forcing. Calculation methods for BrC emission factors are examined, including the problems and limitations of current measurement methods. We provide some insight into existing publications and recommend areas for future research, such as further investigations into the reaction mechanisms of the aging of secondary BrC, calculations of the emission factors for BrC from different sources, the absorption of large and long-lived BrC molecules and the construction of an enhanced model for the simulation of radiative forcing. This review will improve our understanding of the climatic and environmental effects of BrC.

18.
Sci Total Environ ; 631-632: 270-278, 2018 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-29525706

RESUMO

Glacierized mountain environments can preserve and release mercury (Hg) and play an important role in regional Hg biogeochemical cycling. However, the behavior of Hg in glacierized mountain environments and its environmental risks remain poorly constrained. In this research, glacier meltwater, runoff and wetland water were sampled in Zhadang-Qugaqie basin (ZQB), a typical glacierized mountain environment in the inland Tibetan Plateau, to investigate Hg distribution and its relevance to environmental risks. The total mercury (THg) concentrations ranged from 0.82 to 6.98ng·L-1, and non-parametric pairwise multiple comparisons of the THg concentrations among the three different water samples showed that the THg concentrations were comparable. The total methylmercury (TMeHg) concentrations ranged from 0.041 to 0.115ng·L-1, and non-parametric pairwise multiple comparisons of the TMeHg concentrations showed a significant difference. Both the THg and MeHg concentrations of water samples from the ZQB were comparable to those of other remote areas, indicating that Hg concentrations in the ZQB watershed are equivalent to the global background level. Particulate Hg was the predominant form of Hg in all runoff samples, and was significantly correlated with the total suspended particle (TSP) and not correlated with the dissolved organic carbon (DOC) concentration. The distribution of mercury in the wetland water differed from that of the other water samples. THg exhibited a significant correlation with DOC as well as TMeHg, whereas neither THg nor TMeHg was associated with TSP. Based on the above findings and the results from previous work, we propose a conceptual model illustrating the four Hg distribution zones in glacierized environments. We highlight that wetlands may enhance the potential hazards of Hg released from melting glaciers, making them a vital zone for investigating the environmental effects of Hg in glacierized environments and beyond.

19.
Environ Sci Pollut Res Int ; 25(15): 14868-14881, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29546514

RESUMO

For the first time, aerosol optical properties are measured over Lumbini, Nepal, with CIMEL sunphotometer of the Aerosol Robotic Network (AERONET) program. Lumbini is a sacred place as the birthplace of Lord Buddha, and thus a UNESCO world heritage site, located near the northern edge of the central Indo-Gangetic Plains (IGP) and before the Himalayan foothills (and Himalayas) to its north. Average aerosol optical depth (AOD) is found to be 0.64 ± 0.38 (0.06-3.28) over the sampling period (January 2013-December 2014), with the highest seasonal AOD during the post-monsoon season (0.72 ± 0.44). More than 80% of the daily averaged AOD values, during the monitoring period, are above 0.3, indicating polluted conditions in the region. The levels of aerosol load observed over Lumbini are comparable to those observed at several heavily polluted sites in the IGP. Based on the relationship between AOD and Ångstrom exponent (α), anthropogenic, biomass burning, and mixed aerosols are found to be the most prevalent aerosol types. The aerosol volume-size distribution is bi-modal during all four seasons with modes centered at 0.1-0.3 and 3-4 µm. For both fine and coarse modes, the highest volumetric concentration of ~ 0.08 µm-3 µm-2 is observed during the post-monsoon and pre-monsoon seasons. As revealed by the single-scattering albedo (SSA), asymmetry parameter (AP), and refractive index (RI) analyses, aerosol loading over Lumbini is dominated by absorbing, urban-industrial, and biomass burning aerosols.


Assuntos
Aerossóis/análise , Poluentes Atmosféricos/análise , Monitoramento Ambiental , Nepal , Estações do Ano
20.
Environ Geochem Health ; 40(5): 1877-1886, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-28357613

RESUMO

Perfluoroalkyl acids (PFAAs) are ubiquitous in the environment. They are prone to accumulate in organisms and have raised public attention in recent decades. Feather samples have been successfully applied as nondestructive indicators for several contaminants. However, a sophisticated analytical method for determining PFAAs in feathers is still lacking. In the present study, a series of conditions, such as the use of the solid-phase extraction cartridge type and extraction/digestion methods, were optimized for the analysis of 13 PFAAs in feathers. According to the spiked recoveries, a weak-anion exchange cartridge was chosen and the methanol was selected as the extraction solvent. In the present study, an optimized pretreatment procedure combined with high-performance liquid chromatography-electrospray ionization-tandem mass spectrometric (HPLC-ESI-MS/MS) method was established for the determination of PFAAs in feathers. The recoveries and method detection limits of the PFAAs ranged from 71 to 120% and 0.16 to 0.54 ng/g, respectively. Finally, 13 PFAAs in four accipiter feather samples from Nam Co Basin, Tibetan Plateau, were analyzed, indicating that PFOS was the predominant PFAA in accipiter feathers, with an average of 4.67 ng/g, followed by the short-chain PFAAs, PFBS and PFBA, with averages of 1.91 and 1.39 ng/g, respectively. These results partly indicated the current situation of PFAA pollution in the Nam Co Basin, especially the existence of short-chain PFAAs in this region.


Assuntos
Monitoramento Ambiental/métodos , Fluorcarbonetos/análise , Poluentes Químicos da Água/análise , Animais , Cromatografia Líquida de Alta Pressão , Plumas , Extração em Fase Sólida , Espectrometria de Massas em Tandem , Tibet
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