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Resultados 3541-3550 de 4,033
Grey Tienshan Urumqi Glacier No.1 and light-absorbing impurities
2016
Ming, Jing | Xiao, Cunde | Wang, Feiteng | Li, Zhongqin | Li, Yamin
The Tienshan Urumqi Glacier No.1 (TUG1) usually shows “grey” surfaces in summers. Besides known regional warming, what should be responsible for largely reducing its surface albedo and making it look “grey”? A field campaign was conducted on the TUG1 on a selected cloud-free day of 2013 after a snow fall at night. Fresh and aged snow samples were collected in the field, and snow densities, grain sizes, and spectral reflectances were measured. Light-absorbing impurities (LAIs) including black carbon (BC) and dust, and number concentrations and sizes of the insoluble particles (IPs) in the samples were measured in the laboratory. High temperatures in summer probably enhanced the snow ageing. During the snow ageing process, the snow density varied from 243 to 458 kg m⁻³, associated with the snow grain size varying from 290 to 2500 μm. The concentrations of LAIs in aged snow were significantly higher than those in fresh snow. Dust and BC varied from 16 ppm and 25 ppb in fresh snow to 1507 ppm and 1738 ppb in aged snow, respectively. Large albedo difference between the fresh and aged snow suggests a consequent forcing of 180 W m⁻². Simulations under scenarios show that snow ageing, BC, and dust were responsible for 44, 25, and 7 % of the albedo reduction in the accumulation zone, respectively.
Mostrar más [+] Menos [-]The applied indicators of water quality may underestimate the risk of chemical exposure to human population in reservoirs utilized for human supply—Southern Brazil
2016
dos Santos, Debora Regina | Yamamoto, Flávia Yoshie | Filipak Neto, Francisco | Randi, Marco Antônio Ferreira | Garcia, Juan Esquivel | Costa, Daniele Dietrich Moura | Liebel, Samuel | Campos, Sandro Xavier | Voigt, Carmen Lúcia | de Oliveira Ribeiro, Ciro Alberto
The knowledge concerning associations between chronic chemical exposure and many disorders with complex etiology involving gene–environment interactions is increasing, and new methods must be developed to improve water quality monitoring. The complexity of chemical mixtures in polluted aquatic environments makes the evaluation of toxic potential in those sites difficult, but the use of biomarkers and bioindicators has been recognized as a reliable tool to assess risk of exposure to biota and also the human population. In order to evaluate the use of fish and biomarkers to assess toxic potential and bioavailability of chemicals in human-related hydric resources, an in situ experiment was accomplished in two water reservoirs designated for human supply, which were previously evaluated by the local environmental regulatory agency through a set of physical, chemical, and classical biological parameters. Molecular, biochemical, and morphological biomarkers were performed in caged Oreochromis niloticus kept for 6 months in the studied reservoirs to assess potentially useful biomarkers to evaluate the quality of water for human supply. Chemical analysis of toxic metals in liver and muscle and polycyclic aromatic hydrocarbons (PAHs) in bile was considered to assess the bioavailability of pollutants and highlight human activity impact. The reservoir previously classified by a governmental agency as less impacted presented more risk of exposure to biota. These results were supported by chemical analysis, vitellogenin expression, histopathological findings (gonads, liver, and gills), as well as indicators of neurotoxic effects and oxidative stress in liver. The inclusion of some biomarkers as parameters in regulatory monitoring programs in reservoirs designated for human supply is strongly suggested to evaluate the risks of exposure to the human population. Thus, a revision of the traditional biological and physicochemical analysis utilized to establish the conditions of water quality is necessary.
Mostrar más [+] Menos [-]Levels, distributions and correlations of polybrominated diphenyl ethers in air and dust of household and workplace in Shanghai, China: implication for daily human exposure
2016
Xu, Feng | Tang, Weibiao | Zhang, Wei | Liu, Lili | Lin, Kuangfei
Polybrominated diphenyl ethers (PBDEs) were measured in air (TSP and PM₂.₅) and dust samples collected from 16 households and the corresponding workplaces of eight volunteer citizens in Shanghai, China. The PBDEs concentrations in the workplace air (mean: 281 ± 126 pg m⁻³) were over two times higher than those in the household (121 ± 44.0 pg m⁻³), while the mean levels of PBDEs in dust were 995 ± 547 and 544 ± 188 ng g⁻¹ for workplace and household, respectively. BDE209 was the most abundant congener in all samples. PBDEs appeared to be composed of mostly small particles. The C ₚₐᵣₜᵢcₗₑ/C dᵤₛₜ ratios of less brominated PBDEs in PM₂.₅ were higher than those in TSP, while the values were approximately constant for the more brominated PBDEs. A correlation analysis by network indicated different sources and behavior of the PBDE congeners. The results of a cluster analysis were displayed on a heat map that specified the source and abundance of each PBDE congener. The daily PBDE exposure via dust ingestion was the predominant part of the total intake and was more than 10 times higher than the intake via inhalation.
Mostrar más [+] Menos [-]Research and application of method of oxygen isotope of inorganic phosphate in Beijing agricultural soils
2016
Tian, Liyan | Guo, Qingjun | Zhu, Yongguan | He, Huijun | Lang, Yunchao | Hu, Jian | Zhang, Han | Wei, Rongfei | Han, Xiaokun | Peters, Marc | Yang, Junxing
Phosphorus (P) in agricultural ecosystems is an essential and limited element for plants and microorganisms. However, environmental problems caused by P accumulation as well as by P loss have become more and more serious. Oxygen isotopes of phosphate can trace the sources, migration, and transformation of P in agricultural soils. In order to use the isotopes of phosphate oxygen, appropriate extraction and purification methods for inorganic phosphate from soils are necessary. Here, we combined two different methods to analyze the oxygen isotopic composition of inorganic phosphate (δ¹⁸OP) from chemical fertilizers and different fractions (Milli-Q water, 0.5 mol L⁻¹ NaHCO₃ (pH = 8.5), 0.1 mol L⁻¹ NaOH and 1 mol L⁻¹ HCl) of agricultural soils from the Beijing area. The δ¹⁸OP results of the water extracts and NaHCO₃ extracts in most samples were close to the calculated equilibrium value. These phenomena can be explained by rapid P cycling in soils and the influence of chemical fertilizers. The δ¹⁸OP value of the water extracts and NaHCO₃ extracts in some soil samples below the equilibrium value may be caused by the hydrolysis of organic P fractions mediated by extracellular enzymes. The δ¹⁸OP values of the NaOH extracts were above the calculated equilibrium value reflecting the balance state between microbial uptake of phosphate and the release of intracellular phosphate back to the soil. The HCl extracts with the lowest δ¹⁸OP values and highest phosphate concentrations indicated that the HCl fraction was affected by microbial activity. Hence, these δ¹⁸Oₚ values likely reflected the oxygen isotopic values of the parent materials. The results suggested that phosphate oxygen isotope analyses could be an effective tool in order to trace phosphate sources, transformation processes, and its utilization by microorganisms in agricultural soils.
Mostrar más [+] Menos [-]Trace metals in target tissues and stomach contents of the top predator sailfish Istiophorus platypterus from the Eastern Pacific: concentrations and contrasting behavior of biomagnification
2016
Moreno-Sierra, Dalia | Bergés-Tiznado, Magdalena E. | Márquez-Farías, Fernando | Torres-Rojas, Yassir E. | Ruelas-Inzunza, Jorge R. | Páez Osuna, Federico
Cadmium, lead, copper, and zinc were analyzed in the dorsal muscle, liver, gonad, and stomach contents of 67 sailfish, Istiophorus platypterus, from the Eastern Pacific. Muscle exhibited the following pattern (μg/g wet weight): Zn (15.05 ± 1.24) > Cu (0.461 ± 0.026) > Cd (0.434 ± 0.099) > Pb (0.025 ± 0.001); liver Zn (119.1 ± 7.6) > Cd (95.1 ± 11.0) > Cu (39.7 ± 2.6) > Pb (0.047 ± 0.004); and gonad Zn (96.8 ± 7.8) > Cd (2.16 ± 0.38) > Cu (2.08 ± 0.14) > Pb (0.033 ± 0.003). Significant (p < 0.05) correlations were observed between elements, length, and weight. I. platypterus feed mainly on fishes and cephalopods with variable concentrations (μg/g wet weight) of Cd (0.081–11.41), Pb (0.002–0.057), Cu (0.204–4.35), and Zn (3.23–86.6). Of the four analyzed elements, only Pb was biomagnified (BMF = 1.85). According to the regulatory limits, muscle exhibited Cd concentrations higher than the Official Mexican Standard, WHO, FDA (28 % of samples), and the European Union (40 %) regulations.
Mostrar más [+] Menos [-]Concentration, sources, and flux of dissolved organic carbon of precipitation at Lhasa city, the Tibetan Plateau
2016
Li, Yizhong | Yan, Fangping | Kang, Shichang | Chen, Pengfei | Qu, Bin | Hu, Zhaofu | Sillanpää, Mika
Dissolved organic carbon (DOC) plays an important role in the climate system, but few data are available on the Tibetan Plateau (TP). In this study, 89 precipitation samples were collected at Lhasa, the largest city of southern Tibet, from March to December 2013. The average concentration and wet deposition flux of DOC was 1.10 mg C L⁻¹ and 0.63 g C m⁻² year⁻¹, respectively. Seasonally, low DOC concentration and high flux appeared during the monsoon period, which were in line with heavy precipitation amount, reflecting dilution effect of precipitation for the DOC. Compared to other regions, the values of Lhasa were lower than those of large cities (e.g., Beijing and Seoul) mainly because of less air pollution of Lhasa. The principal component analysis (PCA) of DOC and ions (Ca²⁺, Mg²⁺, Na⁺, K⁺, NH₄ ⁺, Cl⁻, NO₃ ⁻, and SO₄ ²⁻) showed that DOC of Lhasa was derived mainly from the natural sources, followed by anthropogenic burning activities. Furthermore, △¹⁴C value of DOC indicated that fossil fuel combustion contributed around 28 % of the rainwater DOC of Lhasa, indicating that the atmosphere of Lhasa has been influenced by emission from fossil fuel combustion or high-temperature industrial processes.
Mostrar más [+] Menos [-]Adsorption of Cd(II) by two variable-charge soils in the presence of pectin
2016
Wang, Ru-hai | Zhu, Xiao-fang | Qian, Wei | Zhao, Min-hua | Xu, Ren-kou | Yu, Yuanjun
Batch experiments were conducted to investigate cadmium(II) (Cd(II)) adsorption by two variable-charge soils (an Oxisol and an Ultisol) as influenced by the presence of pectin. When pectin dosage was less than 30 g kg⁻¹, the increase in Cd(II) adsorption with the increasing dose of pectin was greater than that when the pectin dosage was >30 g kg⁻¹. Although both Langmuir and Freundlich equations fitted the adsorption isotherms of Cd(II) and electrostatic adsorption data of Cd(II) by the two soils well, the Langmuir equation showed a better fit. The increase in the maximum total adsorption of Cd(II) induced by pectin was almost equal in both the soils, whereas the increase in the maximum electrostatic adsorption of Cd(II) was greater in the Oxisol than in the Ultisol because the former contained greater amounts of free Fe/Al oxides than the latter, which, in turn, led to a greater increase in the negative charge on the Oxisol. Therefore, the presence of pectin induced the increase in Cd(II) adsorption by the variable-charge soils mainly through the electrostatic mechanism. Pectin increased the adsorption of Cd(II) by the variable-charge soils and thus decreased the activity and mobility of Cd(II) in these soils.
Mostrar más [+] Menos [-]Monitoring of heavy metal levels in the major rivers and in residents’ blood in Zhenjiang City, China, and assessment of heavy metal elimination via urine and sweat in humans
2016
Sheng, Jianguo | Qiu, Wenhui | Xu, Bentuo | Xu, Hui | Tang, Chong
The coastal areas of China face great challenges, owing to heavy metal contamination caused by rapid industrialization and urbanization. To our knowledge, this study is the first report of the levels of heavy metals in the major rivers of Zhenjiang, one of the most important cities of the Yangtze River Delta in China. In addition, we measured heavy metal levels in the blood of 76 residents of Zhenjiang. The results suggest that the presence of heavy metals in the blood may threaten human health and the distribution appeared to correspond to most highly populated areas and/or areas with high traffic. We also found that the concentration of heavy metals in human blood showed an accumulation effect with increase in age. Moreover, the levels of most heavy metals were lower in participants who regularly exercised than in those who did not. We studied heavy metal levels in the urine and sweat of another 17 volunteers to monitor the elimination of bioaccumulated heavy metal. Heavy metals were found in the urine and sweat of all the 17 participants and were more concentrated in sweat. Induced micturition and sweating appear to be potential methods for the elimination of heavy metals from the human body.
Mostrar más [+] Menos [-]Mass size distribution and source identification of particulate matter metal components at four urban sites and a background site of Istanbul
2016
Şahin, Ülkü Alver | Polat, Gülfem | Onat, Burcu
In this study, the size distribution characteristics and metal contents of particulate matter (PM) have been determined. In this scope, PM sampling has been done at five stations in Istanbul. PM filter samples were collected for eight different sizes using the Anderson cascade impactor. PM filters were decomposed and analyzed for 20 metals. The highest median concentration for Fe, Ca, K, and Mg, known as soil metals, were observed as follows: Fe and Ca were observed at Goztepe station (1.20 and 8.28 μg/m³), K was observed at Kilyos station (0.33 μg/m³), and Mg was observed at Avcilar station (0.37 μg/m³). The highest median concentrations for Zn, Cu, Pb, Ni, Cr, V, As, Se, Co, and Cd, known as anthropogenic metals, were observed at Avcilar, Goztepe, and Besiktas stations. Although the lowest metal concentrations was determined at Kilyos stations that was selected as the urban background. The enrichment factors (EFs) of most metals in the fine PM is higher than those in the coarse mode. According to the factor analyses, the most important emission source was observed to be industrial facilities at Avcilar; traffic at Besiktas; traffic and domestic heating at Goztepe; and domestic heating, sea salt aerosols, and ship traffic (in the Bosphorus Channel of Istanbul) at Rasathane.
Mostrar más [+] Menos [-]Report on the fifth meeting of INRA’s national network of ecotoxicologists, ECOTOX
2016
Mougin, Christian | Bouchez, Agnès | Denaix, Laurence | Lamy, Isabelle | Laurent, François | Martin-Laurent, Fabrice | Mench, Michel
The fifth meeting of INRA’s national network of ecotoxicologists took place on 25 to 27 November 2014 in Biarritz, France. The main aim of the meeting was to bring together ecotoxicologists from INRA and associated partners, providing them ample opportunity to share and discuss their latest scientific results as well as the national policy of research in ecotoxicology and to precise perspectives for the network.
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