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1.
J Ethnopharmacol ; 264: 113206, 2021 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-32750460

RESUMO

ETHNOPHARMACOLOGICAL RELEVANCE: Berberine is generally extracted from Rhizoma Coptidis (Coptis chinensis Franch), a traditional Chinese medicine, which can be used in the treatment of intestinal diseases, respiratory infections and cardiovascular diseases. Berberine is especially effective for the treatment of gastrointestinal disorders such as diarrhea because of the effect of heat-clearing and detoxifying in traditional Chinese medicine theory. AIM OF THE STUDY: This study aimed to examine the protective effect of berberine (BBR) on the damaged colonic epithelial barrier caused by peritoneal dialysis fluid (PDF). METHODS: The damage to intestinal epithelial barrier was examined by intraperitoneally injecting 4.25% dextrose-containing PDF in mice and establishing a long-term PD model in rats with renal failure. Then, the therapeutic potential of berberine on PD-related colonic injuries was examined. T84 colonic epithelial cells were used to test the effect of PDF and berberine in vitro. The damaging effect of PDF and the protective effect of berberine were evaluated by histology staining, histofluorescence and transmission electron microscopy. The migration of colonic epithelial cell and actin-related protein 2 (Arp2) were tested by wound healing assay and Western blot to determine the possible mechanism in vitro. RESULTS: PD administration induced intestinal epithelial barrier dysfunction in the colon, and berberine alleviated the injury by increasing the tight junction and adhesion junction protein, both in vivo and in vitro. Berberine could also improve the morphology of microvillus. In the wound healing assay, berberine exhibited the ability to promote cell migration, indicating that berberine could probably recover the function of intestinal epithelial cells when the intestinal epithelial barrier was damaged by the PDF. CONCLUSIONS: The present study demonstrates that berberine can ameliorate intestinal epithelial barrier dysfunction in the colon caused by long-term PDF through improving cell migration.

2.
Sci Adv ; 6(46)2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33188015

RESUMO

High-performance lightweight materials are urgently needed, given the pressing quest for weight reduction and the associated energy savings and emission reduction. Here, by incorporating the multi-principal element feature of compositionally complex alloys, we develop the concept of lightweight steels further and propose a new class of compositionally complex steels (CCSs). This approach allows us to use the high solid solution strengthening and shift the alloys' compositions into previously unattainable phase regions where both nanosized shearable κ-carbides and non-shearable B2 particles are simultaneously formed. The achievement of dual-nanoprecipitation in our CCSs leads to materials with ultrahigh specific tensile strength (up to 260 MPa·cm3 g-1) and excellent tensile elongation (13 to 38%), a combination outperforming all other high-strength high-entropy alloys and advanced lightweight steels. Our concept of CCSs is thus useful for guiding the design of ultrastrong lightweight metallic materials.

3.
Chem Biodivers ; 17(11): e1900494, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33022147

RESUMO

Two novel epimerized andrographolides, 8,17-dihydro-7,8-dehydroandrographolide and 10ß-8,17-dihydro-7,8-dehydroandrographolide, were isolated from andrographolide sulfonates. Their structures were elucidated by detailed NMR analysis, single-crystal X-ray diffraction and quantum chemical ECD calculations. In addition, these compounds exhibited suppression of NO production in LPS-stimulated RAW264.7 cells over the range of 1.564 to 25.000 µg/mL.

4.
J Int Med Res ; 48(8): 300060520934633, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32776862

RESUMO

OBJECTIVE: This study aimed to investigate application of the urine albumin-to-creatinine ratio (ACR), serum beta 2-microglobulin (ß2-MG), and cystatin C as risk markers in a cohort of women with polycystic ovary syndrome (PCOS) for the incidence of gestational diabetes mellitus (GDM). METHODS: In this cross-sectional study, we analyzed 312 pregnant women with PCOS and classified them as those with and without GDM. For all participants, elbow venous blood and clean middle urine were collected in the morning after 8 hours of an empty stomach. RESULTS: Logistic regression analysis showed that the ACR, urine ß2-MG levels, and serum cystatin C levels were important markers for women with PCOS concomitant with GDM. Receiver operating characteristic curve analysis showed that the area under the curve of CysC was 0.81 with the threshold based on >0.93 and that of ß2-MG was 0.72 with the threshold based on >1.25. CONCLUSIONS: Increased levels of ß2-MG and cystatin C and a high ACR might be risk factors for Chinese women with PCOS and GDM during mid-pregnancy.

5.
Environ Pollut ; 265(Pt B): 114890, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32544787

RESUMO

Maize (Zea mays L.) leaves play an important role in stomatal uptake and surface adsorption of atmospheric mercury (Hg). However, the influence of atmospheric gaseous elemental mercury (GEM) on methylmercury (MeHg) accumulation in maize plants is poorly understood. In this study, we conducted a field open-top chambers (OTCs) experiment and a soil Hg-enriched experiment to investigate the response of MeHg accumulation in maize tissues to different GEM levels in the air. Maize upper leaves had a higher average MeHg concentration (0.21 ± 0.08 ng g-1) than bottom leaves (0.15 ± 0.05 ng g-1) in the OTCs experiment, which was inconsistent with that in the soil Hg-enriched experiment (maize upper leaves: 0.41 ± 0.07 ng g-1, maize bottom leaves: 0.60 ± 0.05 ng g-1). Additionally, significantly positive correlations were found between MeHg concentrations in maize leaves and air Hg levels, suggesting that elevated air Hg levels enhanced MeHg accumulation in maize leaves, which was possibly attributed to methylation of Hg on leaf surfaces. Mature maize grains from the OTCs experiment had low MeHg concentrations (0.12-0.23 ng g-1), suggesting a low accumulation capability of MeHg by maize grains. Approximately 93-96% of MeHg and 51-73% of total Hg in maize grains were lost from the grain-filling stage to the grain-ripening stage at all GEM level treatments, implying that self-detoxification in maize grains occurred. MeHg concentrations in maize roots showed a significant linear relationship (R2 = 0.98, p < 0.01) with soil Hg levels, confirming that MeHg in maize roots is primarily from soil. This study provides a new finding that elevated air GEM levels could enhance MeHg accumulation in maize leaves, and self-detoxification may occur in maize grains. Further studies are needed to clarify these mechanisms of Hg methylation on maize leaf surfaces and self-detoxification of Hg by maize grains.


Assuntos
Mercúrio/análise , Compostos de Metilmercúrio , Poluentes do Solo/análise , Monitoramento Ambiental , Solo , Zea mays
6.
Zhongguo Zhong Yao Za Zhi ; 45(3): 579-583, 2020 Feb.
Artigo em Chinês | MEDLINE | ID: mdl-32237516

RESUMO

This study is to investigate the chemical constituents from the whole plant Corydalis edulis. The chemical constituents were separated and purified by macroporous resin D101, silica gel, Sephadex LH-20, ODS, and semi-preparative HPLC. Their structures were determined by physicochemical properties and spectroscopic data. Four compounds were isolated from the dichloromethane and water extracts of the whole plant C. edulis, and identified as 6'-ß-D-xylosylicariside B2(1),(3S,5R,6S,7E)-5,6-epoxy-3-hydroxy-7-megastigmen-9-one(2), loliolide(3), and 5,5'-dimethoxybiphenyl-2,2'-diol(4), respectively. Compound 1 is a new compound, of which the absolute configuration was established by electronic circular dichroism(ECD) calculations. Compound 4 is obtained from the plants of Papaveraceae family for the first time. Compounds 2 and 3 are firstly isolated from the Corydalis genus.


Assuntos
Corydalis/química , Glicosídeos/isolamento & purificação , Sesquiterpenos/isolamento & purificação , Cromatografia Líquida de Alta Pressão , Estrutura Molecular , Compostos Fitoquímicos/isolamento & purificação
7.
Environ Res ; 182: 109092, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32069770

RESUMO

Four cruises were performed in the Bohai Sea (BS) and Yellow Sea (YS) to ascertain the levels and distributions of gaseous elemental mercury (GEM), dissolved gaseous mercury (DGM), methylmercury (MeHg), and total mercury (THg) during 2012 and 2014. Their concentrations and Hg0 flux exhibited clear spatial-temporal distributions. The GEM level over the BS in spring (2.71 ± 0.49 ng m-3) was significantly higher than that in fall (1.98 ± 0.91 ng m-3). Air masses with elevated GEM mainly originated from northern China. During the two cruises in 2012 over the BS, the mean DGM concentration in spring (35.7 ± 4.6 pg l-1) was comparable to that in fall (32.4 ± 4.6 pg l-1). During the spring cruise of 2014, the mean DGM concentration in the BS (52.8 ± 12.5 pg l-1) was comparable to that in the YS (52.4 ± 14.1 pg l-1), while during the fall cruise of 2014, it was significantly lower in the BS (26.7 ± 14.4 pg l-1) than in the YS (57.2 ± 17.9 pg l-1). DGM represents a small portion of unfiltered THg in the BS (3.95%) and YS (5.12%). The MeHg and MeHg% values were higher in nearshore areas than in open sea, indicating higher productivity in coastal regions. The Hg0 flux in the YS (4.56 ng m-2 h-1) was about twice that in the BS. The annual emission Hg0 fluxes from the BS and YS were 2.71 and 23.68 tons yr-1, respectively.


Assuntos
Mercúrio , Poluentes Químicos da Água , China , Monitoramento Ambiental , Gases , Mercúrio/química , Oceanos e Mares , Água do Mar , Poluentes Químicos da Água/química
8.
Environ Pollut ; 259: 113833, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31887599

RESUMO

The emission of mercury (Hg) from cropland soil greatly affects the global Hg cycle. Combinations of different crop cultivars and planting densities will result in different light transmittance under canopies, which directly affects the solar and heat radiation flux received by the soil surface below crops. In turn, this might lead to differences in the soil-air total gaseous mercury (TGM) exchange under different cropping patterns. However, soil-air TGM exchange fluxes in croplands under differing canopies have been poorly investigated. Here, a one-year observation of TGM exchange flux was conducted for cropland soils covering five different crop cultivars and three planting densities in North China Plain using the dynamic flux chamber method. The results showed that light transmittance under the canopies was the key control on soil-air TGM exchange fluxes. High light transmittance can enhance soil TGM emission rates and increase the magnitude of diurnal variations in soil-air TGM exchange fluxes. Furthermore, we found that there were piecewise-function relationships (Peak function-constant equation) between light transmittance under the different canopies and the numbers of days after crop sowing. The soil-air TGM exchange fluxes showed a parabolic response to changes in light transmittance under the different canopies. A second-order model was established for the response relationship between soil-air TGM exchange flux and soil Hg concentration, total solar radiation above the canopy, and numbers of days after sowing. The estimated annual average soil-air TGM exchange flux was 5.46 ± 21.69 ng m-2 h-1 at corn-wheat rotation cropland with 30 cm row spacing using this second-order model. Our results might a data reference and a promising foundation for future model development of soil-air TGM exchange in croplands under different crop cultivars and planting densities.


Assuntos
Monitoramento Ambiental , Mercúrio , Poluentes do Solo , China , Plantas , Solo
9.
Environ Sci Technol ; 53(16): 9453-9461, 2019 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-31402663

RESUMO

Dimethyl mercury (CH3HgCH3, DMeHg) has been observed in upwelling marine environments and the deep ocean. However, little is known about the occurrence and mechanisms of DMeHg formation in freshwater environments. In this study, concentrations of dissolved gaseous DMeHg were investigated in floodwaters of rice paddies in China that have been contaminated by mercury from mining. Values of DMeHg in rice paddies were compared with measurements from nearshore surface seawater in the Bohai Gulf. High concentrations of dissolved gaseous DMeHg occurred in rice paddies. Average DMeHg concentration was 12 ± 22 pg L-1 with range of 0.39 to 91 pg L-1 in rice paddies at Shuijing, China, a site impacted by an abandoned mercury mine. These concentrations are comparable to those previously observed in the deep seawater and coastal upwelling environments (2.3-115pg L-1). An alkaline environment was found to be necessary for DMeHg formation in rice paddies. Associated incubation experiments showed that production of DMeHg in paddy soil was limited by Hg availability. Although iron amendments accelerated the production of gaseous methylmercury (MeHg) species to floodwaters, available Hg2+ is crucial for this production in flooded rice paddies. These observations are the first to demonstrate the occurrence of DMeHg and reveal factors affecting DMeHg production in rice paddies. Given the high volatility of DMeHg, these measurements also suggest a source for observations of MeHg in atmospheric deposition and advance understanding of a potentially important aspect of the biogeochemical cycling of Hg.


Assuntos
Mercúrio , Compostos de Metilmercúrio , Oryza , Poluentes do Solo , China , Monitoramento Ambiental , Solo
10.
Sci Total Environ ; 681: 183-190, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31103656

RESUMO

The characteristics and sources of methylmercury (MeHg) in atmospheric fine particles remain poorly elucidated. We obtained the concentrations of MeHg bound to atmospheric fine particles in four seasons, from September 2015 to July 2016, at an urban site in Beijing, China. Concentrations ranged from <0.01 to 1.33 pg m-3, averaging at 0.21 ±â€¯0.17 pg m-3. The highest concentration of MeHg in atmospheric fine particles occurred in summer. Relatively high mass composition of MeHg in atmospheric fine particles occurred when the concentrations of PM2.5 were low. Intense sunlight and atmospheric oxidants promoted the formation of MeHg that was then enriched on atmospheric fine particles. Moreover, precipitation scavenged 29.4-77.0% of the MeHg bound to atmospheric fine particles. The possible sources of MeHg in atmospheric fine particles were identified using Positive Matrix Factorization (PMF) model. Dimethylmercury (DMeHg) decomposition and MeHg surface volatilization, combustion and marine sources, dust, and heterogeneous reactions contributed 47.8%, 18.7%, 16.4%, and 13.2% of the MeHg in atmospheric fine particle, respectively. This study supplements knowledge on the concentrations, atmospheric processes, and sources of MeHg in atmospheric fine particles.

11.
Environ Pollut ; 249: 13-23, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30877965

RESUMO

Measurements of speciated atmospheric mercury play a key role in identifying mercury behavior in the atmosphere. In this study, we measured speciated atmospheric mercury, including gaseous elemental mercury (GEM), reactive gaseous mercury (RGM), and particulate bound mercury (PBM) (<2.5 µm), in 2015 and 2016 at an urban site in Beijing, China. The mean concentrations of GEM, RGM, and PBM were 4.70 ±â€¯3.53 ng m-3, 18.47 ±â€¯22.27 pg m-3, and 85.18 ±â€¯95.34 pg m-3, respectively. The concentration of PM2.5 significantly affected the distribution of reactive mercury between the gaseous and particulate phases. With the raising of PM2.5 levels, PBM concentrations increased, on the contrary, the concentrations of RGM decreased gradually. The mean concentration of PBM during air-pollution events was more than three times that during clear days. During days with air pollution, the relative humidity significantly affected the gas-particle partitioning of reactive mercury. The linear relationships between gas-particle partitioning coefficient and meteorological factors (air temperature and relative humidity) were obtained over the four seasons. The data also showed that the gas-particle partitioning coefficient of reactive mercury was related to particle composition (e.g., Cl-, BC). The data present in this paper suggested the influence of anthropogenic emissions on reactive mercury in Beijing urban. And the findings will contribute to understand the gas-particle partitioning of reactive mercury and its influencing factors with complex urban pollution.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental , Mercúrio/análise , Poluição do Ar , Atmosfera/química , Pequim , China , Poeira , Gases/análise , Conceitos Meteorológicos , Estações do Ano
12.
Glob Chang Biol ; 25(5): 1765-1778, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30776171

RESUMO

Increasing nitrogen (N) deposition in subtropical forests in south China causes N saturation, associated with significant nitrate (NO3 - ) leaching. Strong N attenuation may occur in groundwater discharge zones hydrologically connected to well-drained hillslopes, as has been shown for the subtropical headwater catchment "TieShanPing", where dual NO3 - isotopes indicated that groundwater discharge zones act as an important N sink and hotspot for denitrification. Here, we present a regional study reporting inorganic N fluxes over two years together with dual NO3 - isotope signatures obtained in two summer campaigns from seven forested catchments in China, representing a gradient in climate and atmospheric N input. In all catchments, fluxes of dissolved inorganic N indicated efficient conversion of NH4 + to NO3 - on well-drained hillslopes, and subsequent interflow of NO3 - over the argic B-horizons to groundwater discharge zones. Depletion of 15 N- and 18 O-NO3 - on hillslopes suggested nitrification as the main source of NO3 - . In all catchments, except one of the northern sites, which had low N deposition rates, NO3 - attenuation by denitrification occurred in groundwater discharge zones, as indicated by simultaneous 15 N and 18 O enrichment in residual NO3 - . By contrast to the southern sites, the northern catchments lack continuous and well-developed groundwater discharge zones, explaining less efficient N removal. Using a model based on 15 NO3 - signatures, we estimated denitrification fluxes from 2.4 to 21.7 kg N ha-1 year-1 for the southern sites, accounting for more than half of the observed N removal. Across the southern catchments, estimated denitrification scaled proportionally with N deposition. Together, this indicates that N removal by denitrification is an important component of the N budget of southern Chinese forests and that natural NO3 - attenuation may increase with increasing N input, thus partly counteracting further aggravation of N contamination of surface waters in the region.


Assuntos
Clima , Florestas , Nitratos/análise , Ciclo do Nitrogênio , Nitrogênio/isolamento & purificação , China , Desnitrificação , Monitoramento Ambiental , Água Subterrânea/química , Hidrologia , Nitrogênio/análise
13.
Sci Total Environ ; 647: 932-941, 2019 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-30096681

RESUMO

There is growing interest in how heavy metals in remote ecosystems are elevated and affect environmental health. However, no studies have investigated atmospheric lead (Pb) deposition influences on the Pb bioaccumulation in insects in forests. Here we measure Pb concentrations and pools in forest vegetation, litterfall, organic soil, mineral soil, as well as litterfall deposition fluxes in a region severely affected by atmospheric deposition. We also analyzed Pb in insects which feed in the polluted forest vegetation and litter. Assessment of high Pb loads causing potential ecological risk to insects was also studied. Total Pb pool in the vegetation was 0.12 g m-2 and annual litterfall deposition flux of Pb was 13.42 mg m-2, which was much higher than those in the background areas. Pools of Pb from litter to mineral topsoil averaged 4.3 g m-2, which accounted for 97.3% of total pools (biomass + soil) in the forest ecosystem. Pools of Pb in surface soils were correlated significantly with the pools of total organic matter and elevation. Atmospheric deposition was inferred the major source of Pb in the forest ecosystem, which can be supported by the highest Pb concentrations in the moss and overstory foliage. The maximum Pb concentration was showed in the dung beetle (12.1 mg kg-1) residing in the soils compared that in the longicorn and of cicada, which would potentially pose negatively influence to predators along food chains.


Assuntos
Monitoramento Ambiental , Florestas , Chumbo/análise , Poluentes do Solo/análise , Animais , Ecossistema , Insetos , Solo , Árvores
14.
Molecules ; 23(10)2018 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-30248930

RESUMO

We sequenced and analyzed the complete chloroplast genome of Aster tataricus (family Asteraceae), a Chinese herb used medicinally to relieve coughs and reduce sputum. The A. tataricus chloroplast genome was 152,992 bp in size, and harbored a pair of inverted repeat regions (IRa and IRb, each 24,850 bp) divided into a large single-copy (LSC, 84,698 bp) and a small single-copy (SSC, 18,250 bp) region. Our annotation revealed that the A. tataricus chloroplast genome contained 115 genes, including 81 protein-coding genes, 4 ribosomal RNA genes, and 30 transfer RNA genes. In addition, 70 simple sequence repeats (SSRs) were detected in the A. tataricus chloroplast genome, including mononucleotides (36), dinucleotides (1), trinucleotides (23), tetranucleotides (1), pentanucleotides (8), and hexanucleotides (1). Comparative chloroplast genome analysis of three Aster species indicated that a higher similarity was preserved in the IR regions than in the LSC and SSC regions, and that the differences in the degree of preservation were slighter between A. tataricus and A. altaicus than between A. tataricus and A. spathulifolius. Phylogenetic analysis revealed that A. tataricus was more closely related to A. altaicus than to A. spathulifolius. Our findings offer valuable information for future research on Aster species identification and selective breeding.


Assuntos
Aster/genética , Genoma de Cloroplastos , Análise de Sequência de DNA/métodos , Cloroplastos/genética , Evolução Molecular , Tamanho do Genoma , Anotação de Sequência Molecular , Filogenia
15.
Cell Death Dis ; 9(9): 882, 2018 08 29.
Artigo em Inglês | MEDLINE | ID: mdl-30158539

RESUMO

Spinal cord injury (SCI) is associated with a dismal prognosis including severe voluntary motor and sensory deficits in the presence of the current therapies, thus new and efficient treatment strategies are desperately required. Along with several advantages, such as easy accessibility, high-yield, potential of enormous proliferation, menstrual blood-derived mesenchymal stem cells (MenSCs) have been proposed as a promising strategy in regeneration medicine. In this study, the MenSCs were transplanted into incomplete thoracic (T10) spinal cord injury (SCI) rats, all rats were sacrificed at 7, 14, and 28 days after surgery. Based on the results, we found that MenSCs transplantation improved the hind limb motor function. Besides, H&E staining showed that MenSCs treatment markedly reduced cavity formation in the lesion site. Furthermore, treatment by MenSCs showed more MAP2-positive mature neurons, as well as axonal regeneration manifested by NF-200 and less expression of chondroitin sulfate proteoglycans (CSPGs) than the non-treatment in the lesion site. Additionally, immunofluorescence, Western blot, and qRT-PCR methods showed that levels of brain-derived neurotrophic factor (BDNF) were significantly higher in the injured spinal cord after implantation of MenSCs. Results of qRT-PCR indicated that inflammatory factors, including TNF-α and IL-1ß were inhibited after MenSCs transplantation. The improved motor function of hind limb and the increased cell body area of motor neurons were suppressed by blocking of the BDNF-TrkB signaling. It was eventually revealed that MenSCs implantation had beneficial therapeutic effects on the rehabilitation of the rat spinal cord hemisection model, mainly by enhancing the expression of BDNF. MenSCs transplantation may provide a novel therapeutic strategy for patients with SCI in the future.


Assuntos
Células-Tronco Mesenquimais/patologia , Traumatismos da Medula Espinal/metabolismo , Traumatismos da Medula Espinal/patologia , Medula Espinal/metabolismo , Medula Espinal/patologia , Células-Tronco/metabolismo , Animais , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Células Cultivadas , Feminino , Humanos , Inflamação/metabolismo , Inflamação/patologia , Interleucina-1beta/metabolismo , Glicoproteínas de Membrana/metabolismo , Transplante de Células-Tronco Mesenquimais/métodos , Células-Tronco Mesenquimais/metabolismo , Regeneração Nervosa/fisiologia , Neurônios/metabolismo , Neurônios/patologia , Ratos , Ratos Sprague-Dawley , Recuperação de Função Fisiológica/fisiologia , Células-Tronco/patologia , Fator de Necrose Tumoral alfa/metabolismo
16.
Environ Sci Technol ; 52(17): 9749-9757, 2018 09 04.
Artigo em Inglês | MEDLINE | ID: mdl-30129363

RESUMO

Rice consumption is the primary pathway for methylmercury (MeHg) exposure at inland mercury (Hg) mining areas of China. The sources and processes of formation and translocation for MeHg in rice plant are complex and remain largely unknown. In this study, rice ( Oryza sativa L.) was exposed to isotopically labeled dimethylmercury (DMe199Hg) in field experiments using open top chambers to explore the response of MeHg accumulation in rice tissues to different levels of DMe199Hg in air. Rice leaves assimilated DMeHg from air, which was subsequently largely stored in aboveground tissues, including the rice grain, with only a small amount reaching the root. Combining these experimental results with field investigations of DMeHg concentrations in air beneath the rice canopy in a Hg mining area, we estimate that 15.5%, 10.8%, and 8.50% MeHg in the brown rice, the leaf, and the upper stalk, respectively, could be derived from atmospheric sources of DMeHg, while 99.5% of MeHg in rice root originated from the rice soil-water system. These findings help refine the mechanism of MeHg accumulation in rice that, in addition to soil, a fraction of MeHg in rice plants can be derived from DMeHg emissions from flooded rice paddies in Hg mining areas.


Assuntos
Mercúrio , Compostos de Metilmercúrio , Oryza , Poluentes do Solo , China , Monitoramento Ambiental , Mineração
17.
Sci Total Environ ; 615: 319-329, 2018 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-28982081

RESUMO

Denitrification characteristics of forest soils from eight headwater catchments in China were investigated in this study, along a climatic gradient from the tropics in the South to the temperate zones. Within each catchment, different landscape positions along hydrological flow paths were also considered, including well-drained soils on hill slopes and poorly drained soils in groundwater discharge zones. The results showed that instantaneous denitrification rates were much greater in soils from the northern sites than those from the southern sites (with the average of 110.0 and 25.4nmolNg-1drysoilh.-1, respectively). Large potentials for nitrous oxide (N2O) loss (evaluated as maximum N2O accumulation before it was reduced to dinitrogen (N2)) were observed in the six tropical and subtropical catchments, particularly in soils with high carbon (C) and nitrogen (N). Meanwhile high N2O/(N2O+N2) stoichiometries were displayed in soils from these southern sites. Within catchments, soils from the groundwater discharge zones showed greater potential denitrification rates but smaller N2O/(N2O+N2) ratios in comparison with those on the hill slopes, implying large N removal potentials of soils from the groundwater discharge zones. Furthermore, our findings suggest soil pH is the key controller for the potential denitrification rates and the N2O/(N2O+N2) stoichiometries. Soil pH, C and N availability affect the potential for N2O loss synergistically. Our findings not only pinpoint the denitrification phenotypes of soils along the climatic gradient, but also confirm the small-scale variations within catchments which reflect the in situ habitat of the denitrifiers. These indicate the importance of discrimination related to different landscape positions when modeling N2O emissions and N removals from regional N loading.


Assuntos
Clima , Desnitrificação , Florestas , Solo/química , China , Geografia , Água Subterrânea , Nitrogênio/análise , Ciclo do Nitrogênio , Óxido Nitroso/análise , Fenótipo
18.
J Environ Sci (China) ; 56: 140-144, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28571849

RESUMO

Soil acidification caused by acid deposition has been significant in some forests in southern China. We present an approach for assessing the current stage maximum allowed load (SML) of acid deposition for terrestrial system in the country. The main idea was that soil base cation exchange as a finite buffer to acidity was included in the soil acidity mass balance calculation at current acidification stage. We calculated the SML for five forests in southern China. The usual critical loads for the same forests were also calculated by the steady state mass balance model for comparison. The results showed that the SML is a more tolerant limit than the critical load for the forests with soils not acidified seriously at current stage. However, the SML become a more stringent limit to acid deposition when the forest soils have acidified seriously to very low base cation saturation. In this case the SML assessment is beneficial for the soils recovering from a serious acidified state. Based on a national scale database, the SML mapping for non-agricultural soil system in China was carried out.


Assuntos
Chuva Ácida/estatística & dados numéricos , Monitoramento Ambiental , Modelos Teóricos , Solo/química , China
19.
Micron ; 101: 69-77, 2017 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-28662413

RESUMO

An AlCrCuFeNi2 high entropy alloy (HEA) was prepared by arc melting, followed by annealing at different temperatures. The elemental distributions, phase formation, morphology and microstructural evolution of the HEA in both the as-cast state and annealed state were investigated. The results indicate that the HEA undergoes elements segregation, precipitation and spinodal decomposition. The as-cast alloy consists of Cr-Fe-Ni rich FCC dendritic (DR) phase and BCC interdendritic (ID) phase. Spherical Fe-Cr rich BCC precipitates were found to disperse in Al-Ni rich B2 (ordered BCC) matrix. After heat treatments, the distribution of elements clearly changes, along with changes of the constituent phase and morphology. After annealing at 600°C, the DR region remains Cr-Fe-Ni rich phase, while some spherical precipitates transform into the needle-like structure within the ID region. The L12 (ordered FCC) nanorod-shaped phase ((Ni,Cu)3Al) and plate-like Al-Ni rich phase form within the DR region when annealing up to 900°C. The L12 phase almost dissolves in the FCC matrix due to the order-disorder transition and an obvious coarsening of the Fe-Cr rich phase occurs after annealing at 1100°C. The segregation of Cu atoms at the interface between DR and ID regions is found at the as-cast state, while a uniform distribution of Cu atoms in DR and ID regions was observed after annealing at 1100°C.

20.
Environ Sci Pollut Res Int ; 24(11): 10808-10818, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28290087

RESUMO

The temporal variability of leaf ammonia (NH3) emission potentials (the ratio of leaf tissue ammonium to proton concentration) and nitrogen (N) pools of six dominant plant species were investigated at the Tieshanping (TSP) forested catchment, southwest China. The results showed that the NH3 emission potentials and N pools presented small variations among seasons, which were mainly controlled by plant species and the leaf age. Also, high emission potential in one species did not correspond to high tissue N content. Specifically, the Chinese fir (Cunninghamia lanceolata) had higher NH3 emission potential (mean: 46.2) but lower N content (mean: 1.6% of Dw). The leaf privet (Ligustrum quihoui Carr.) was with the moderate emission potential (15) and the highest N content (2.7% of Dw) on average, which for the Masson pine (Pinus massoniana) were both low. Overall, the emission potentials of the six species were too low (<200) to build up a sufficiently high NH3 partial pressure in the leaves. Therefore, the Masson pine dominant subtropical forest at TSP acts as a sink for the atmospheric NH3, indicating that using the N flux in throughfall only may significantly underestimate the N income of the ecosystem. The results are informative for future modeling of plant-atmosphere NH3 exchange and estimating N budget in local or regional scales.


Assuntos
Amônia , Solo , China , Ecossistema , Florestas , Nitrogênio , Folhas de Planta/química , Árvores
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