خيارات البحث
النتائج 421 - 430 من 1,310
Changes in the chemistry of acidified Adirondack streams from the early 1980s to 2008 النص الكامل
2011
Lawrence, G.B. | Simonin, H.A. | Baldigo, B.P. | Roy, K.M. | Capone, S.B.
Lakes in the Adirondack region of New York have partially recovered in response to declining deposition, but information on stream recovery is limited. Here we report results of Adirondack stream monitoring from the early 1980s to 2008. Despite a 50% reduction in atmospheric deposition of sulfur, overall increases in pH of only 0.28 and ANC of 13 μeq L⁻¹ were observed in 12 streams over 23 years, although greater changes did occur in streams with lower initial ANC, as expected. In the North Tributary of Buck Creek with high dissolved organic carbon (DOC) concentrations, SO₄ ²⁻ concentrations decreased from 1999 to 2008 at a rate of 2.0 μmol L⁻¹ y⁻¹, whereas in the neighboring South Tributary with low DOC concentrations, the decrease was only 0.73 μmol L⁻¹ y⁻¹. Ca²⁺ leaching decreased in the North Tributary due to the SO₄ ²⁻ decrease, but this was partially offset by an increase in Ca²⁺ leaching from increased DOC concentrations.
اظهر المزيد [+] اقل [-]Responses of a soil bacterium, Pseudomonas chlororaphis O6 to commercial metal oxide nanoparticles compared with responses to metal ions النص الكامل
2011
Dimkpa, Christian O. | Calder, Alyssa | Britt, David W. | McLean, Joan E. | Anderson, Anne J.
The toxicity of commercially-available CuO and ZnO nanoparticles (NPs) to pathogenic bacteria was compared for a beneficial rhizosphere isolate, Pseudomonas chlororaphis O6. The NPs aggregated, released ions to different extents under the conditions used for bacterial exposure, and associated with bacterial cell surface. Bacterial surface charge was neutralized by NPs, dependent on pH. The CuO NPs were more toxic than the ZnO NPs. The negative surface charge on colloids of extracellular polymeric substances (EPS) was reduced by Cu ions but not by CuO NPs; the EPS protected cells from CuO NPs-toxicity. CuO NPs-toxicity was eliminated by a Cu ion chelator, suggesting that ion release was involved. Neither NPs released alkaline phosphatase from the cells’ periplasm, indicating minimal outer membrane damage. Accumulation of intracellular reactive oxygen species was correlated with CuO NPs lethality. Environmental deposition of NPs could create niches for ion release, with impacts on susceptible soil microbes.
اظهر المزيد [+] اقل [-]Altitudinal distributions of BDE-209 and other polybromodiphenyl ethers in high mountain lakes النص الكامل
2011
Bartrons, Mireia | Grimalt, Joan O. | Catalan, Jordi
Altitudinal distributions of BDE-209 and other polybromodiphenyl ethers in high mountain lakes النص الكامل
2011
Bartrons, Mireia | Grimalt, Joan O. | Catalan, Jordi
The present study shows the occurrence of 2,2′,3,3′,4,4′,5,5′,6,6′-decabromodiphenyl ether (BDE-209) in microbial biofilms of Pyrenean and Tatra high mountain lakes despite its low vapor pressure and high hydrophobicity. Aerosol air transport is therefore a feasible mechanism for BDE-209 accumulation in sites up to 2688 m above sea level. This compound and other PBDEs exhibit altitudinally-dependent distribution involving higher concentrations with increasing mountain lake elevation. However, the apparently very high enthalpies of the concentration gradients observed, including BDE-209, suggest that bacterial anaerobic debromination also plays a significant role in the resulting altitudinal distributions. This microbial mechanism explains the relative abundances of PBDEs and their within lake differences between rocky and sediment microbial biofilms, thereby showing that the altitudinal pattern observed is not purely due to water temperature control on bacterial activity but also to changes in the availability of anaerobic microenvironments which increase with increasing lake productivity at lower altitudes.
اظهر المزيد [+] اقل [-]Altitudinal distributions of BDE-209 and other polybromodiphenyl ethers in high mountain lakes النص الكامل
2011
Bartrons, Mireia | Grimalt, Joan O. | Catalán, Jordi
24 páginas, 3 tablas, 4 figuras. | The present study shows the occurrence of 2,2′,3,3′,4,4′,5,5′,6,6′-decabromodiphenyl ether (BDE-209) in microbial biofilms of Pyrenean and Tatra high mountain lakes despite its low vapor pressure and high hydrophobicity. Aerosol air transport is therefore a feasible mechanism for BDE-209 accumulation in sites up to 2688 m above sea level. This compound and other PBDEs exhibit altitudinally-dependent distribution involving higher concentrations with increasing mountain lake elevation. However, the apparently very high enthalpies of the concentration gradients observed, including BDE-209, suggest that bacterial anaerobic debromination also plays a significant role in the resulting altitudinal distributions. This microbial mechanism explains the relative abundances of PBDEs and their within lake differences between rocky and sediment microbial biofilms, thereby showing that the altitudinal pattern observed is not purely due to water temperature control on bacterial activity but also to changes in the availability of anaerobic microenvironments which increase with increasing lake productivity at lower altitudes. Capsule: Decabromodiphenyl ether and the other polybromodiphenyl congeners show vertical distributions in high mountains due to temperature effects and microbial degradation. | This work has been supported by the EU Projects Euro-Limpacs (GOCE-CT-2003- 505540) and ArcRisk (FP7-ENV-2008-1-226534), Spanish MEC project Trazas (CGL2004-02989) and Consolider Ingenio “GRACCIE” program (CSD2007-00067). Technical assistance in instrumental analysis by R. Chaler, D. Fanjul, and R. Mas, analytical advice by J. López and P. Fernández, field help by L. Camarero, M. Bacardit, G. Mendoza, E. Gallego, and S. Jarque is acknowledged. One of the authors, M.B., thanks a FPU grant of the Spanish Ministry of Education and Science. | Peer reviewed
اظهر المزيد [+] اقل [-]DNA damage in caged Gammarus fossarum amphipods: A tool for freshwater genotoxicity assessment النص الكامل
2011
Lacaze, Emilie | Devaux, Alain | Mons, Raphaël | Bony, Sylvie | Garric, Jeanne | Geffard, Alain | Geffard, Olivier
DNA damage in caged Gammarus fossarum amphipods: A tool for freshwater genotoxicity assessment النص الكامل
2011
Lacaze, Emilie | Devaux, Alain | Mons, Raphaël | Bony, Sylvie | Garric, Jeanne | Geffard, Alain | Geffard, Olivier
The aim of this study was to propose a tool for freshwater environmental genotoxicity assessment using Gammarus fossarum, a high ecologically relevant species. In a first part, gammarids were caged upstream and downstream wastewater treatment plant effluent output. The sensitivity of genotoxic responses of haemocytes, oocytes and spermatozoa was compared using the Comet assay. Spermatozoa appeared to be the most sensitive, suitable and relevant cell type for genotoxicity risk assessment. In a second part, a watershed-scale study was conducted over 2 years to evaluate the applicability of our caging procedure. The genotoxic impact of a contamination was followed, taking into account seasonal variability. DNA damage in spermatozoa exhibited low basal level and low variability in control upstream sites, providing a reliable discrimination of polluted sites. Finally, DNA damage in caged G. fossarum has been proved to be a sensitive and reproducible tool for freshwater genotoxicity assessment.
اظهر المزيد [+] اقل [-]DNA damage in caged Gammarus fossarum amphipods: A tool for freshwater genotoxicity assessment النص الكامل
2011
Lacaze, Emilie | Devaux, Alain | Mons, Raphaël | Bony, Sylvie | Garric, Jeanne | Geffard, Alain | Geffard, Olivier | Milieux aquatiques, écologie et pollutions (UR MALY) ; Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA) | Laboratoire d'Ecologie des Hydrosystèmes Naturels et Anthropisés (LEHNA) ; Université Claude Bernard Lyon 1 (UCBL) ; Université de Lyon-Université de Lyon-École Nationale des Travaux Publics de l'État (ENTPE)-Centre National de la Recherche Scientifique (CNRS) | Équipe 5 - Impacts des Polluants sur les Écosystèmes (LEHNA IPE) ; Laboratoire d'Ecologie des Hydrosystèmes Naturels et Anthropisés (LEHNA) ; Université Claude Bernard Lyon 1 (UCBL) ; Université de Lyon-Université de Lyon-École Nationale des Travaux Publics de l'État (ENTPE)-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL) ; Université de Lyon-Université de Lyon-École Nationale des Travaux Publics de l'État (ENTPE)-Centre National de la Recherche Scientifique (CNRS) | Laboratoire d'Eco-Toxicologie ; Université de Reims Champagne-Ardenne (URCA)
International audience | The aim of this study was to propose a tool for freshwater environmental genotoxicity assessment using Gammarus fossarum, a high ecologically relevant species. In a first part, gammarids were caged upstream and downstream wastewater treatment plant effluent output. The sensitivity of genotoxic responses of haemocytes, oocytes and spermatozoa was compared using the Comet assay. Spermatozoa appeared to be the most sensitive, suitable and relevant cell type for genotoxicity risk assessment. In a second part, a watershed-scale study was conducted over 2 years to evaluate the applicability of our caging procedure. The genotoxic impact of a contamination was followed, taking into account seasonal variability. DNA damage in spermatozoa exhibited low basal level and low variability in control upstream sites, providing a reliable discrimination of polluted sites. Finally, DNA damage in caged G. fossarum has been proved to be a sensitive and reproducible tool for freshwater genotoxicity assessment. (C) 2011 Elsevier Ltd. All rights reserved.
اظهر المزيد [+] اقل [-]Occurrence of arsenic in brown rice and its relationship to soil properties from Hainan Island, China النص الكامل
2011
Fu, Yangrong | Chen, Mulong | Bi, Xiangyang | He, Yusheng | Ren, Limin | Xiang, Wu | Qiao, Shengying | Yan, Sen | Li, Zhonggen | Ma, Zhendong
The acquaintance of arsenic concentrations in rice grain is vital in risk assessment. In this study, we determined the concentration of arsenic in 282 brown rice grains sampled from Hainan Island, China, and discussed its possible relationships to the considered soil properties. Arsenic concentrations in the rice grain from Hainan Island varied from 5 to 309 μg/kg, with a mean (92 μg/kg) lower than most published data from other countries/regions and the maximum contaminant level (MCL) for Asᵢ in rice. The result of correlation analysis between grain and soil properties showed that grain As concentrations correlated significantly to soil arsenic speciation, organic matter and soil P contents and could be best predicted by humic acid bound and Fe–Mn oxides bound As fractions. Grain arsenic rises steeply at soil As concentrations lower than 3.6 mg/kg and gently at higher concentrations.
اظهر المزيد [+] اقل [-]Occurrence of polycyclic aromatic hydrocarbons in surface sediments of a highly urbanized river system with special reference to energy consumption patterns النص الكامل
2011
Zhang, Kai | Wang, Ji-Zhong | Liang, Bo | Zeng, E. Y. (Eddy Y.)
Sediment samples collected from downstream of the Dongjiang River, a highly urbanized river network within the Pearl River Delta of South China, were analyzed for 28 polycyclic aromatic hydrocarbons (PAHs). Total concentrations of 28 PAHs, 16 priority PAHs designated by the United States Environmental Protection Agency (USEPA) and the seven carcinogenic PAHs classified by the USEPA ranged from 480 to 4600, 100 to 3400 and 10 to 1700 ng/g dry weight, respectively. Principal component analysis-based stepwise multivariate linear regression showed that sediment PAHs were predominantly derived from coal combustion, refined fossil fuel combustion and oil spills, accounting for 37%, 32% and 23%, respectively, of the total loading. The levels of sediment PAHs remained steady from 2002 to 2008, during which fossil fuel consumption had doubled, probably reflecting efforts to control PAH emissions from fossil fuel combustion. Finally, use of natural gas and liquefied petroleum gas in automobiles should be encouraged to improve environmental quality.
اظهر المزيد [+] اقل [-]Temporal and spatial distribution of atmospheric antimony emission inventories from coal combustion in China النص الكامل
2011
Tian, H.Z. | Zhao, D. | He, M.C. | Wang, Y. | Cheng, K.
A multiple-year inventory of atmospheric antimony (Sb) emissions from coal combustion in China for the period of 1980–2007 has been calculated for the first time. Specifically, the emission inventories of Sb from 30 provinces and 4 economic sectors (thermal power, industry, residential use, and others) are evaluated and analyzed in detail. It shows that the total Sb emissions released from coal combustion in China have increased from 133.19t in 1980 to 546.67t in 2007, at an annually average growth rate of 5.4%. The antimony emissions are largely emitted by industrial sector and thermal power generation sector, contributing 53.6% and 26.9% of the totals, respectively. At provincial level, the distribution of Sb emissions shows significant variation. Between 2005 and 2007, provinces always rank at the top five largest Sb emissions are: Guizhou, Hunan, Hebei, Shandong, and Anhui.
اظهر المزيد [+] اقل [-]Does small mammal prey guild affect the exposure of predators to anticoagulant rodenticides? النص الكامل
2011
Tosh, D.G. | McDonald, R.A. | Bearhop, S. | Lllewellyn, N.R. | Fee, S. | Sharp, E.A. | Barnett, E.A. | Shore, R.F.
Ireland has a restricted small mammal prey guild but still includes species most likely to consume anticoagulant rodenticide (AR) baits. This may enhance secondary exposure of predators to ARs. We compared liver AR residues in foxes (Vulpes vulpes) in Northern Ireland (NI) with those in foxes from Great Britain which has a more diverse prey guild but similar agricultural use of ARs. Liver ARs were detected in 84% of NI foxes, more than in a comparable sample of foxes from Scotland and similar to that of suspected AR poisoned animals from England and Wales. High exposure in NI foxes is probably due to greater predation of commensal rodents and non-target species most likely to take AR baits, and may also partly reflect greater exposure to highly persistent brodifacoum and flocoumafen. High exposure is likely to enhance risk and Ireland may be a sentinel for potential effects on predator populations.
اظهر المزيد [+] اقل [-]Toxic effects of oral 2-amino-4,6-dinitrotoluene in the Western fence lizard (Sceloporus occidentalis) النص الكامل
2011
McFarland, Craig A. | Quinn, Michael J., Jr | Boyce, John | LaFiandra, Emily M. | Bazar, Matthew A. | Talent, Larry G. | Johnson, Mark S.
The compound 2-amino-4,6-dinitrotoluene (2A-DNT) was evaluated under laboratory conditions in the Western fence lizard (Sceloporus occidentalis) to assess the potential for reptile toxicity. Oral LD₅₀ values were 1406 and 1867 mg/kg for male and female lizards, respectively. Based on responses from a 14-day subacute study, a 60-day subchronic experiment followed where lizards were orally dosed at 0, 5, 15, 20, 25, 30 mg/kg-d. At day 60, number of days and survivors, food consumption, and change in body weight were inversely related to dose. Signs of toxicity were characterized by anorexia and generalized cachexia. Significant adverse histopathology was observed in hepatic tissue at ≥15 mg/kg-d, consistent with hepatocellular transdifferentiation. Based on survival, loss of body weight, diminished food intake, changes in liver, kidney, and testes, and increased blood urea nitrogen, these data suggest a LOAEL of 15 mg/kg-d and a NOAEL of 5 mg/kg-d in S. occidentalis.
اظهر المزيد [+] اقل [-]Plant uptake and dissipation of PBDEs in the soils of electronic waste recycling sites النص الكامل
2011
Huang, Honglin | Zhang, Shuzhen | Christie, Peter
Plant uptake and dissipation of weathered PBDEs in the soils of e-waste recycling sites were investigated in a greenhouse study. Eighteen PBDE congeners (tri- through deca-) were detected in the plant tissues. The proportion of lower brominated PBDEs (mono- through hexa-) in plant roots was higher than that in the soils. A concentration gradient was observed of PBDEs in plants with the highest concentrations in the roots followed by the stems and lowest in the leaves. Reduction rates of the total PBDEs in the soils ranged from 13.3 to 21.7% after plant harvest and lower brominated PBDEs were associated with a higher tendency to dissipate than the higher brominated PBDEs. This study provides the first evidence for plant uptake of weathered PBDEs in the soils of e-waste recycling sites and planting contributes to the removal of PBDEs in e-waste contaminated soils.
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