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1.
Sci Total Environ ; 713: 136573, 2020 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-31955087

RESUMO

Lignin is a highly complex, plant-derived natural biomass component, the analysis of which requires significant demands on the analytical platform. Fourier transform ion cyclotron mass spectrometry (FT-ICR MS) has been shown to be able to readily assess the complexity of lignin and lignin degradation products by assigning tens of thousands of compounds with elemental formulae. Nevertheless, many experimental and instrumental parameters introduce discrimination towards certain components, which limits the comprehensive MS analysis. As a result, a complete characterization of the lignome remains a challenge. The present study investigated a degraded lignin sample using FT-ICR MS and compared several atmospheric pressure ionization methods, e.g., electrospray ionization, atmospheric-pressure chemical ionization, and atmospheric-pressure photoionization. The results clearly show that the number of heteroatoms (e.g., N, S, P) in the sample greatly increases the chemical diversity of lignin, while at the same time also providing potentially useful biomarkers. We demonstrate here that FT-ICR MS was able to directly isolate isotopically pure single components from the ultra-complex mixture for subsequent structural analysis, without the time-consuming chromatographic separation. CAPSULE: Various ionization techniques coupled to FT-ICR MS provide a powerful tool to assess the lignome coverage.

2.
Sci Total Environ ; 703: 134475, 2020 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-31759721

RESUMO

Organic molecular composition of fine aerosols in the free troposphere is poorly understood. Here, PM2.5 (particles with aerodynamic diameters ≤ 2.5 µm) samples were collected at the summit of Mt. Emei (3080 m a.s.l.) in the Southwestern China on a daytime and nighttime basis during summer 2016 (June-July). The samples were analyzed by solvent-extraction followed by derivatization and gas chromatography/mass spectrometry (GC/MS). Four classes of organic compounds, i.e. n-alkanes, fatty acids, saccharides and lignin/resin acids were measured quantitatively. Fatty acids were found to be the most abundant species with an average concentration of 401 ±â€¯419 ng m-3 (range 25.7-1490 ng m-3) in the daytime, similar to the average concentration at night (399 ±â€¯447 ng m-3, 19.6-1970 ng m-3). However, the concentrations of biomass burning tracers (e.g., levoglucosan), primary biological aerosol tracers (e.g., mannitol and arabitol) and low molecular weight n-alkanes derived from fossil fuel combustion in daytime samples were obviously higher than those in nighttime samples. The results suggest that valley breezes transported a large number of aerosols and their precursors from the ground surface to the summit of Mt. Emei in the daytime. Estimated with tracer-based methods, the contributions of biogenic primary sources (plant debris, fungal spore, and biomass burning) to organic carbon was in the range of 3.28-83.5% (22.0 ±â€¯17.5%) in the daytime and 3.45-37.4% (10.9 ±â€¯8.97%) at night. As the largest contributor, biomass burning was an important anthropogenic/natural source of aerosol particles in the free troposphere over Mt. Emei. CAPSULE: Valley/mountain breeze is an important constraint to the temporal variations in organic aerosols over Mt. Emei.

3.
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.

4.
Chemosphere ; 241: 125133, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31683427

RESUMO

Black carbon (BC) plays a vital role in atmospheric environment and climate change. Temporal variations and transport pathways of BC in Xiamen, China with the impacts of synoptic circulation were investigated in 2014 with Aethalometer. Annual mean BC concentration was 4270 ng m-3. BC exhibited clear diurnal (seasonal) variations, with the maximum of 6182 (4755) ng m-3 at 6:00 (in spring) and minimum of 2847 (3774) ng m-3 at 13:00 (in summer). Conditional probability function analysis indicated that high BC concentrations were associated with northwesterly winds with low wind speed. Air masses originating from the East China Sea and passing along with East China Coast had the highest BC concentrations. Potential source contribution function and concentration weighted trajectory analysis suggested that major sources for BC included the surrounding region, southwestern Fujian and eastern Guangdong to the southwest, Hubei, Hunan and Jiangxi to the northwest, the East China Sea and the South China Sea. Of the nine synoptic circulation patterns, three cyclone-related patterns were associated with low BC concentrations and small biomass burning (BCbb) contributions. Of the six anticyclone-related patterns, the three cold-high circulations around winter were associated with moderate BC concentrations and large BCbb contributions. The two cold-high patterns in spring and autumn were associated with high BC concentrations and small BCbb contributions, while the warm-high pattern was associated with moderate BC concentration and small BCbb contribution. The findings provide insights into the transport mechanisms of BC with the impacts of synoptic pattern in China.

5.
J Hazard Mater ; 383: 121131, 2020 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-31513950

RESUMO

We investigated the effect of the temporary ban of local industrial activities during the Asia-Pacific Economic Cooperation (APEC) summit (4th-14th Nov 2014) in Beijing, China on total suspended particulate mercury (HgTSP) concentrations and isotope compositions. We measured Hg concentrations and isotope ratios in 33 TSP samples from central Beijing, including 21 samples collected from Jun 2012 to Apr 2014, and 12 samples collected from 14th Oct-19th Nov 2014. Volumetric concentrations of both TSP and HgTSP during the APEC summit were a factor of 2 lower than during the pre-APEC period, indicating substantial reductions in total particulate matter and HgTSP as a result of emissions controls. However, mass-normalized concentrations and mercury isotope ratios of HgTSP did not vary significantly between samples collected before, during, or after the APEC summit. These results show that local emissions are important sources of particle bound mercury (PBM) in Beijing and that their control can be used to immediately lower the volumetric concentration of HgTSP. They also indicate that a similarly complex mixture of sources contributed to PBM in Beijing before and during emissions controls were put in place and that PBM concentrations in Beijing are primarily controlled by emissions and secondarily by photoreduction.

6.
Sci Total Environ ; 709: 134496, 2020 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-31874340

RESUMO

Penguin colonies in Antarctica offer an ideal "natural laboratory" to investigate ecosystem function and the nitrogen (N) cycle. This study assessed the spatial distribution of penguin-derived N from guano and quantitatively assessed its impact on plant N utilization strategies in Victoria Land, Ross Sea region, Antarctica. Soil, moss, and aquatic microbial mats were collected inside and outside an active Adélie penguin (Pygoscelis adeliae) colony and analyzed for δ15N of total and inorganic nitrogen (NH4+-N and NO3--N). The soil total nitrogen (TN), NH4+-N, and NO3--N concentrations, as well as their δ15N values were significantly higher in guano-impacted areas than those in guano-free areas, verifying that guano is an important N source at and near penguin colonies. However, even far from the penguin colonies, soil δ15N values resembled those in penguin colonies, suggesting strong spatial impacts of penguin-derived N. The moss impacted by guano was more enriched in δ15N than in guano-free areas. The δ15N values of NH4+-N and NO3--N in soils covered with moss revealed that the moss might prefer inorganic N in the absence of guano, while the dissolved organic N would become an important source for moss growing on ornithogenic soils. Aquatic microbial mat samples near penguin colonies were 15N-enriched, but 15N-depleted at upland sites.

7.
Environ Pollut ; 255(Pt 2): 113345, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31610508

RESUMO

Despite substantial mitigation of particulate matter (PM) pollution during the past decade in Beijing, the response of aerosol chemistry to clean air action and meteorology remains less understood. Here we characterized the changes in aerosol composition as responses to emission reductions by using two-year long-term measurements in 2011/2012 and 2017/2018, and WRF-Chem model. Our results showed substantial decreases for all aerosol species except nitrate from 2011/2012 to 2017/2018. Chloride exhibited the largest decrease by 65-89% followed by organics (37-70%), mainly due to reductions in coal combustion emissions in winter and agriculture burning in June. Primary and secondary organic aerosol (SOA) showed comparable decreases by 61-70% in fall and winter, and 34-63% in spring and summer, suggesting that reductions in primary emissions might also suppress SOA formation. The changes in nitrate were negligible and even showed increases due to less reductions in NOx emissions and increased formation potential from N2O5 heterogeneous reactions. As a result, nitrate exceeded sulfate and became the major secondary inorganic aerosol species in PM with the contribution increasing from 14-21% to 22-32%. Further analysis indicated that the reductions in aerosol species from 2011/2012 to 2017/2018 were mainly caused by the decreases of severely polluted events (PM1 > 100 µg m-3). WRF-Chem simulations suggested that the decreases in OA and sulfate in fall and winter were mainly resulted from emission reductions (27-36% and 25-43%) and favorable meteorology (4-10% and 19-30%), while they were dominantly contributed by emission changes in spring and summer. Comparatively, the changes in nitrate were mainly associated with meteorological variations while the contributions of emissions changes were relatively small. Our results highlight different chemical responses of aerosol species to emission changes and meteorology, suggesting that future mitigation of air pollution in China needs species-targeted control policy.


Assuntos
Aerossóis/análise , Poluentes Atmosféricos/análise , Poluição do Ar/estatística & dados numéricos , Monitoramento Ambiental , Material Particulado/análise , Poluição do Ar/análise , Pequim , China , Óxidos de Nitrogênio/análise , Estações do Ano , Sulfatos/análise
8.
Environ Sci Technol ; 53(21): 12506-12518, 2019 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-31536707

RESUMO

Highly oxygenated molecules (HOMs) play an important role in the formation and evolution of secondary organic aerosols (SOA). However, the abundance of HOMs in different environments and their relation to the oxidative potential of fine particulate matter (PM) are largely unknown. Here, we investigated the relative HOM abundance and radical yield of laboratory-generated SOA and fine PM in ambient air ranging from remote forest areas to highly polluted megacities. By electron paramagnetic resonance and mass spectrometric investigations, we found that the relative abundance of HOMs, especially the dimeric and low-volatility types, in ambient fine PM was positively correlated with the formation of radicals in aqueous PM extracts. SOA from photooxidation of isoprene, ozonolysis of α- and ß-pinene, and fine PM from tropical (central Amazon) and boreal (Hyytiälä, Finland) forests exhibited a higher HOM abundance and radical yield than SOA from photooxidation of naphthalene and fine PM from urban sites (Beijing, Guangzhou, Mainz, Shanghai, and Xi'an), confirming that HOMs are important constituents of biogenic SOA to generate radicals. Our study provides new insights into the chemical relationship of HOM abundance, composition, and sources with the yield of radicals by laboratory and ambient aerosols, enabling better quantification of the component-specific contribution of source- or site-specific fine PM to its climate and health effects.


Assuntos
Poluentes Atmosféricos , Material Particulado , Aerossóis , Pequim , China , Finlândia
9.
Environ Sci Technol ; 53(14): 7984-7995, 2019 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-31257870

RESUMO

Atmospheric aerosols over polar regions have attracted considerable attention for their pivotal effects on climate change. In this study, temporospatial variations in single-particle-based depolarization ratios (δ: s-polarized component divided by the total backward scattering intensity) were studied over the Northwest Pacific and the Arctic Ocean using an optical particle counter with a depolarization module. The δ value of aerosols was 0.06 ± 0.01 for the entire observation period, 61 ± 10% lower than the observations for coastal Japan (0.12 ± 0.02) ( Pan et al. Atmos. Chem. Phys. 2016 , 16 , 9863 - 9873 ) and inland China (0.19 ± 0.02) ( Tian et al. Atmos. Chem. Phys. 2018 , 18 , 18203 - 18217 ) in summer. The volume concentration showed two dominant size modes at 0.9 and 2 µm. The supermicrometer particles were mostly related to sea-salt aerosols with a δ value of 0.09 over marine polar areas, ∼22% larger than in the low-latitude region because of differences in chemical composition and dry air conditions. The δ values for fine particles (<1 µm) were 0.05 ± 0.1, 50% lower than inland anthropogenic pollutants, mainly because of the complex mixtures of submicrometer sea salts. High particle concentrations in the Arctic Ocean could mostly be attributed to the strong marine emission of sea salt associated with deep oceanic cyclones, whereas long-range transport pollutants from the continent were among the primary causes of high particle concentrations in the Northwest Pacific region.


Assuntos
Poluentes Atmosféricos , Aerossóis , Regiões Árticas , China , Monitoramento Ambiental , Japão , Oceanos e Mares , Oceano Pacífico , Tamanho da Partícula
10.
Environ Sci Technol ; 53(13): 7380-7390, 2019 07 02.
Artigo em Inglês | MEDLINE | ID: mdl-31117537

RESUMO

Aerosol proteinaceous matter is comprised of a substantial fraction of bioaerosols. Its origins and interactions in the atmosphere remain poorly understood. We present observations of total proteins, combined, and free amino acids (CAAs and FAAs) in fine particulate matter (PM2.5) samples in urban Beijing before and during the 2014 Asia-Pacific Economic Cooperation (APEC) summit. The decreases in proteins, CAAs and FAAs levels were observed after the implementation of restrictive emission controls. Significant changes were observed for the composition profiles in FAAs with the predominance of valine before the APEC and glycine during the APEC, respectively. These variations could be attributed to the influence of sources, atmospheric processes, and meteorological conditions. FAAs (especially valine and glycine) were suggested to be released by the degradation of high molecular weight proteins/polypeptides by atmospheric oxidants (i.e., ozone and free radicals) and nitrogen dioxide. Besides daytime reactions, nighttime chemistry was found to play an important role in the atmospheric formation of valine during the nights, suggesting the possible influence of NO3 radicals. Our findings provide new insights into the significant impacts of atmospheric oxidation capacity on the occurrence and transformation of aerosol proteinaceous matter which may affect its environmental, climate and health effects.


Assuntos
Poluentes Atmosféricos , Aerossóis , Ásia , Pequim , Monitoramento Ambiental , Material Particulado
11.
Sci Total Environ ; 681: 226-234, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31103660

RESUMO

To understand the temporal characteristics and vertical distributions of ammonia (NH3) and ammonium (NH4) in urban Beijing, we conducted ground-based and tower-based measurements of gaseous NH3 and submicron aerosol composition. The average mixing ratio of NH3 was 16.5 ±â€¯7.4 ppb, ranging from 3.8 to 36.9 ppb. Gas-to-particle partitioning of NHx (=NH3 + NH4) played a significant role on NH3 concentration as the molar ratio of NH3 to NHx decreased as a function of NH4 concentration. The NH3 concentrations increased as a function of PM1 at lower levels (<125 µg m-3), but remained relatively constant at higher PM and NH4 levels, indicating an enhanced gas-to-particle conversion of NH3 during highly polluted conditions. The potential sources of NHx were found to include fossil fuel combustion and biomass burning. Regional transport could also play an important role on NH3 concentration during the formation stage of haze episodes due to particle-to-gas conversion. Four distinctive types of vertical profiles (87% of the time) of both NH3 and fine particle light extinction coefficient (bext) were observed and they were associated with well-mixed atmosphere, fast accumulation of local emissions, regional transport aloft, and the formation of low urban boundary layer, respectively. However, the vertical profiles of NH3 typically (96% of the time) showed a more homogeneous characteristic than those of bext below 260 m, except periods with both strong temperature inversion and large aerosol gradient, the formation of urban boundary layer shall cause a significant transition in the vertical distribution of NH3 below 260 m. During highly polluted situations (PM1 > 125 µg m-3), the strong effect of gas-to-particle partitioning of NHx sometimes (7% of the time) caused opposite trends in vertical profiles of NH3 and bext.

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 Sci Technol ; 53(5): 2881-2891, 2019 03 05.
Artigo em Inglês | MEDLINE | ID: mdl-30730710

RESUMO

Growing literature has documented varying toxic potencies of source- or site-specific fine particulate matter (PM2.5), as opposed to the practice that treats particle toxicities as independent of composition given the incomplete understanding of the toxicity of the constituents. Quantifying component-specific contribution is the key to unlocking the geographical disparities of particle toxicity from a mixture perspective. In this study, we performed integrated mixture-toxicity experiments and modeling to quantify the contribution of metals and polycyclic aromatic hydrocarbons (PAHs), two default culprit component groups of PM2.5 toxicity, to in vitro oxidative stress caused by wintertime PM2.5 from Beijing and Guangzhou, two megacities in China. PM2.5 from Beijing exhibited greater toxic potencies at equal mass concentrations. The targeted chemical analysis revealed higher burden of metals and PAHs per unit mass of PM2.5 in Beijing. These chemicals together explained 38 and 24% on average of PM2.5-induced reactive oxygen species in Beijing and Guangzhou, respectively, while >60% of the effects remained to be resolved in terms of contributing chemicals. PAHs contributed approximately twice the share of the PM2.5 mixture effects as metals. Fe, Cu, and Mn were the dominant metals, constituting >80% of the metal-shared proportion of the PM2.5 effects. Dibenzo[ a, l]pyrene alone explained >65% of the PAH-shared proportion of the PM2.5 toxicity effects. The significant contribution from coal combustion and vehicular emissions in Beijing suggested the major source disparities of toxicologically active PAHs between the two cities. Our study provided novel quantitative insights into the role of varying toxic component profiles in shaping the differential toxic potencies of city-specific PM2.5 pollution.


Assuntos
Poluentes Atmosféricos , Hidrocarbonetos Policíclicos Aromáticos , Pequim , China , Cidades , Monitoramento Ambiental , Estresse Oxidativo , Material Particulado , Estações do Ano
14.
Environ Pollut ; 247: 541-549, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30708316

RESUMO

Excess ammonia (NH3) emissions and deposition can have negative effects on air quality and terrestrial ecosystems. Identifying NH3 sources is a critical step for effectively reducing NH3 emissions, which are generally unregulated around the world. Stable nitrogen isotopes (δ15N) of ammonium (NH4+) in precipitation have been directly used to partition NH3 sources. However, nitrogen isotope fractionation during atmospheric processes from NH3 sources to sinks has been previously overlooked. Here we measured δ15NNH4+ in precipitation on a daily basis at a rural forested site in Northeast China over three years to examine its seasonal pattern and attempt to constrain the NH3 sources. We found that the NH4+ concentrations in precipitation ranged from 5 to 1265 µM, and NH4+ accounted for 65% of the inorganic nitrogen deposition (20.0 kg N ha-1 yr-1) over the study period. The δ15N values of NH4+ fluctuated from -24.6 to +16.2‰ (average -6.5‰) and showed a repeatable seasonal pattern with higher values in summer (average -2.3‰) than in winter (average -16.4‰), which could not be explained by only the seasonal changes in the NH3 sources. Our results suggest that in addition to the NH3 sources, isotope equilibrium fractionation contributed to the seasonal pattern of δ15NNH4+ in precipitation, and thus, nitrogen isotope fractionation should be considered when partitioning NH3 sources based on δ15NNH4+ in precipitation.


Assuntos
Poluentes Atmosféricos/análise , Poluição do Ar/estatística & dados numéricos , Compostos de Amônio/análise , Monitoramento Ambiental , Florestas , Isótopos de Nitrogênio/análise , Amônia/análise , China , Ecossistema , Nitrogênio/análise , Chuva/química , Estações do Ano
15.
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
16.
Environ Sci Technol ; 53(2): 963-972, 2019 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-30525504

RESUMO

Airborne transmission is one of the environmental dissemination pathways of antibiotic resistance genes (ARGs), and has critical implications for human exposure through inhalation. In this study, we focused on three regions of China to reveal some unique spatiotemporal features of airborne bacteria and ARGs in fine aerosols (PM2.5): (1) greater seasonal variations in the abundance of bacteria and ARGs in temperate urban Beijing than in the subtropical urban areas of the Yangtze River Delta (YRD) and Pearl River Delta (PRD) regions, with regional disparities in bacterial communities; (2) geographical fingerprints of ARG profiles independent of seasonal cycles and land-use gradients within each region; (3) region-independent associations between the targeted ARGs and limited bacterial genera; (4) common correlations between ARGs and mobile genetic elements (MGEs) across regions; and (5) PM2.5 at the higher end of ARG enrichment across various environmental and human media. The spatiotemporally differentiated bacterial communities and ARG abundances, and the compositions, mobility, and potential hosts of ARGs in the atmosphere have strong implications for human inhalational exposure over spatiotemporal scales. By comparing other contributing pathways for the intake of ARGs (e.g., drinking water and food ingestion) in China and the U.S.A., we identified the region-specific importance of inhalation in China as well as country-specific exposure scenarios. Our study thus highlights the significance of inhalation as an integral part of the aggregate exposure pathways of environmentally disseminated ARGs, which, in turn, may help in the formulation of adaptive strategies to mitigate the exposure risks in China and beyond.


Assuntos
Antibacterianos , Genes Bacterianos , Bactérias , Pequim , China , Resistência Microbiana a Medicamentos , Humanos , Material Particulado
17.
Sci Total Environ ; 651(Pt 2): 2679-2688, 2019 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-30463123

RESUMO

Awareness of the importance of marine atmosphere for accurately estimating global aerosol budget and climate impacts has arisen recently. However, studies are limited due to the difficulty and inconvenience in sampling as well as the diversity of sources. In this study, the Community Multiscale Air Quality (CMAQ) model was applied to investigate the fine particulate matter (PM2.5) and its chemical components over the East China Sea (ECS) and offshore regions. In spite of slight under-predictions, model predictions agree well with observations over the ECS and along the coast. PM2.5 and its major components in the mainland are higher than in marine area, suggesting Asian continent is a major emitter of marine aerosols. PM2.5 and its components in marine regions show higher abundance during daytime than nighttime, while it is opposite in continental regions. Aerosol phase SO42- is the most abundant component of PM2.5 over the ECS with an average concentration of 5.12 µg m-3, followed by NH4+ (1.02 µg m-3) and primary organic aerosol (POA) (0.92 µg m-3). Industry and ship emissions are the top two contributors to primary (PPM) and total PM2.5 over the ECS, while industry and agriculture sectors are major sources for secondary inorganic aerosols (SIA), followed by ship emissions. For terrestrial regions, industry and agriculture are predominant sources of PM2.5 and SIA, while industry and residential activities are the top two contributors to PPM. This study improves the understanding of transport and accumulation of air pollutants over the ECS and adjacent regions, and provides useful information for designing efficient control strategies.

18.
Ecol Evol ; 8(17): 8853-8864, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30271550

RESUMO

Compound-specific 15N analysis of amino acids (AAs) is a powerful tool to determine the trophic position (TP) of organisms. However, it has only been used in a few studies of avian ecology because the AA patterns in the consumer-diet nitrogen trophic discrimination factor (TDFG lu-Phe = ∆15 NG lu-∆15 NP he) were unknown in birds until recently, and tropical seabirds have never been investigated with this methodology. Here, we explore the application of this method to tropical seabirds. In this study, we recovered the fossilized bones of tropical seabirds from ornithogenic sediments on two coral islands in the Xisha Islands, South China Sea, as well as the bones and muscle of their predominant food source, flying fish (Exocoetus volitans). Compound-specific 15N and 13C analyses of AAs in both seabird and fish bone collagen were conducted. The TP of flying fish was calculated based on a widely used single TDFG lu-Phe approach. We then calculated the TP of tropical seabirds in three different ways: (a) according to the composition of their diet; (b) based on the single TDFG lu-Phe approach; and (c) using a multi-TDFG lu-Phe approach. The results of the multi-TDFG lu-Phe approach were much closer to the results based on the composition of the seabird diet than the results of the single TDFG lu-Phe approach, confirming its applicability for tropical seabirds. For seabird bone samples of different ages, TP determined from the multi-TDFG lu-Phe approach was most similar to that of bulk δ15N of bird collagen, with seabirds occupying higher TPs during the Little Ice Age, as previously shown. In addition, the 13C Suess effect was reflected in the AAs δ13C in our samples. This study applied a compound-specific 15N analysis of AAs to determine the TP of tropical seabirds that has potential to extend to all tropical seabirds many of which are widely distributed and play a key role in the evolution of coral island ecosystems.

19.
Environ Pollut ; 243(Pt B): 1579-1587, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30293040

RESUMO

Sugars and n-alkanes are important organic constituents of atmospheric fine particulate matter (PM2.5). For better understanding their sources and seasonal variations in urban atmosphere, sugar compounds (anhydrosugars, sugars and sugar alcohols) and homologue n-alkanes (C18-C37) were studied in PM2.5 samples collected from September 2013 to July 2014 in Beijing, China. In general, all measured compounds showed the lowest levels in summer. Higher concentrations of sugar compounds and n-alkanes were observed in winter, probably due to elevated combustion emissions (e.g., coal, biofuel and agricultural residue burning) and stable meteorological conditions during heating season. Levoglucosan was the major sugar species in all seasons particularly in autumn and winter, highlighting the significant contribution of biomass burning to fine organic aerosols throughout the whole year especially in cold seasons. Plant waxes contributed to n-alkanes the most in late spring (54.5%) and the least in winter (11.6%); while fossil fuel combustion had the largest contribution in winter (385 ng m-3). The weak odd-carbon predominance of n-alkanes in wintertime aerosols also suggests fossil fuel combustion as the important source of organic aerosols in the heating season. Soil resuspension, fossil fuel combustion and biomass burning, and secondary sources are the main sources of OC in PM2.5 at Beijing. The seasonal variation in source contributions indicates that meteorological condition is a key factor in controlling PM2.5 levels. Furthermore, dust storms in spring can strongly enhance the atmospheric level of fine organic matter in Beijing.


Assuntos
Poluentes Atmosféricos/análise , Alcanos/análise , Monitoramento Ambiental/métodos , Combustíveis Fósseis/análise , Material Particulado/análise , Material Particulado/química , Açúcares/análise , Aerossóis/análise , Atmosfera/química , Pequim , Biomassa , Carbono/análise , China , Estações do Ano , Solo/química
20.
Environ Pollut ; 243(Pt B): 919-928, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30245454

RESUMO

Organic tracers are useful for investigating the sources of carbonaceous aerosols but there are still no adequate studies in China. To obtain insights into the diurnal variations, properties, and the influence of regional emission controls on carbonaceous aerosols in Beijing, day-/nighttime PM2.5 samples were collected before (Oct. 15th - Nov. 2nd) and during (Nov. 3rd - Nov. 12th) the 2014 Asia-Pacific Economic Cooperation (APEC) summit. Eleven organic compound classes were analysed using gas chromatography/mass spectrometry (GC/MS). In addition, the stable carbon isotope ratios (δ13CTC) of total carbon (TC) were detected using an elemental analyser/isotope ratio mass spectrometry (EA/irMS). Most of the organic compounds were more abundant during the night than in the daytime, and their concentrations generally decreased during the APEC. These features were associated with the strict regional emission controls and meteorological conditions. The day/night variations of δ13CTC were smaller during the APEC than those before the APEC the summit, suggesting that regionally transported aerosols are potentially played an important role in the loading of organic aerosols in Beijing before the APEC summit. The source apportionment based on the organic tracers suggested that biomass burning, plastic and microbial emissions, and fossil fuel combustion were important sources of organic aerosols in Beijing. Furthermore, a similar contribution of biomass burning to OC before and during the APEC suggests biomass burning was a persistent contributor to PM2.5 in Beijing and its surroundings.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental , Material Particulado/análise , Aerossóis/análise , Poluição do Ar/estatística & dados numéricos , Ásia , Pequim , Biomassa , Carbono/análise , Isótopos de Carbono/análise , China , Cromatografia Gasosa-Espectrometria de Massas , Compostos Orgânicos/análise , Estações do Ano
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