خيارات البحث
النتائج 201 - 210 من 711
Responses of wild small mammals to a pollution gradient: Host factors influence metal and metallothionein levels
2010
Fritsch, Clémentine | Cosson, Richard P. | Cœurdassier, Michaël | Raoul, Francis | Giraudoux, Patrick | Crini, Nadia | Vaufleury, Annette de | Scheifler, Renaud
We investigated how host factors (species, age, gender) modulated Cd, Pb, Zn, and Cu concentrations, metallothionein levels (MTs) and their relationships in 7 sympatric small mammal species along a pollution gradient. Cd concentrations in liver and kidneys increased with age in all species. Age effect on other metals and MTs differs among species. Gender did not influence metal and MT levels except in the bank vole. Three patterns linking internal metal concentrations and MTs were observed along the gradient: a low metal accumulation with a (i) high (wood mouse) or (ii) low (bank vole) level of MTs accompanied by a slight or no increase of MTs with Cd accumulation; (iii) an elevated metal accumulation with a sharp increase of MTs (common and pygmy shrews). In risk assessment and biomonitoring perspectives, we conclude that measurements of MTs and metals might be associated because they cannot be interpreted properly when considered separately. Age more than gender and species more than trophic group influence metallic trace element and metallothionein levels and their relationships in wild small mammals exposed to metals.
اظهر المزيد [+] اقل [-]Assessing urban habitat quality based on specific leaf area and stomatal characteristics of Plantago lanceolata L
2010
Kardel, F. | Wuyts, K. | Babnezhad, M. | Vitharana, U.W.A. | Wuytack, T. | Potters, G. | Samson, R.
This study has evaluated urban habitat quality by studying specific leaf area (SLA) and stomatal characteristics of the common herb Plantago lanceolata L. SLA and stomatal density, pore surface and resistance were measured at 169 locations in the city of Gent (Belgium), distributed over four land use classes, i.e., sub-urban green, urban green, urban and industry. SLA and stomatal density significantly increased from sub-urban green towards more urbanised land use classes, while the reverse was observed for stomatal pore surface. Stomatal resistance increased in the urban and industrial land use class in comparison with the (sub-) urban green, but differences between land use classes were less pronounced. Spatial distribution maps for these leaf characteristics showed a high spatial variation, related to differences in habitat quality within the city. Hence, stomatal density and stomatal pore surface are assumed to be potentially good bio-indicators for urban habitat quality. Stomatal characteristics of Plantago lanceolata can be used for biomonitoring of urban habitat quality.
اظهر المزيد [+] اقل [-]Combined effects of elevated CO2 and natural climatic variation on leaf spot diseases of redbud and sweetgum trees
2010
McElrone, Andrew J. | Hamilton, Jason G. | Krafnick, Anthony J. | Aldea, Mihai | Knepp, Rachel G. | DeLucia, Evan H.
Atmospheric CO2 concentrations are predicted to double within the next century and alter climate regimes, yet the extent that these changes will affect plant diseases remains unclear. In this study conducted over five years, we assessed how elevated CO2 and interannual climatic variability affect Cercospora leaf spot diseases of two deciduous trees. Climatic data varied considerably between the five years and altered disease expression. Disease incidence and severity for both species were greater in years with above average rainfall. In years with above average temperatures, disease incidence for Liquidambar styraciflua was decreased significantly. When significant changes did occur, disease incidence and severity always increased under elevated CO2. Chlorophyll fluorescence imaging of leaves revealed that any visible increase in disease severity induced by elevated CO2 was mitigated by higher photosynthetic efficiency in the remaining undamaged leaf tissue and in a halo surrounding lesions. Climatic variation had a greater impact than elevated CO2 on Cercospora diseases, especially since leaf photosynthetic efficiency increased under elevated CO2.
اظهر المزيد [+] اقل [-]Perfluorinated compounds in water, sediment, soil and biota from estuarine and coastal areas of Korea
2010
Naile, Jonathan E. | Khim, Jong Seong | Wang, Tieyu | Chen, Chunli | Luo, Wei | Kwon, Bong-Oh | Park, Jinsoon | Ko, Chʻŏr-hwan | Jones, Paul D. | Lü, Yonglong | Giesy, John P.
Soil, sediment, water, and biota collected from the western coast of Korea were analyzed to determine occurrence and sources of perfluorinated compounds (PFCs). PFCs were significantly concentrations of PFCs were measured in some water and biological samples, while concentrations of PFCs in soils and sediments were relatively low. The most widely detected compound was found to be perfluorooctanesulfonate (PFOS), with a maximum concentration in water of 450 ng/L and in fish of 612 ng/g, dw. PFOS concentrations in water and biota were both less than those thought to cause toxicity. However, in both cases concentrations were within a factor of 10 of the toxicity threshold concentration. Concentrations of PFCs were significantly greater downstream than those upstream on the same river, suggesting point sources. Overall, the detection of PFCs at relatively great concentrations in various environmental matrixes from this region of Korea suggests that further studies characterizing PFCs and their potential risk to both humans and wildlife are needed.
اظهر المزيد [+] اقل [-]Identification of a phytotoxic photo-transformation product of diclofenac using effect-directed analysis
2010
Schulze, Tobias | Weiss, Sara | Schymanski, Emma | Ohe, Peter Carsten von der | Schmitt-Jansen, Mechthild | Altenburger, R. | Streck, Georg | Brack, Werner
The pharmaceutical diclofenac (DCF) is released in considerably high amounts to the aquatic environment. Photo-transformation of DCF was reported as the main degradation pathway in surface waters and was found to produce metabolites with enhanced toxicity to the green algae Scenedesmus vacuolatus. We identified and subsequently confirmed 2-[2-(chlorophenyl)amino]benzaldehyde (CPAB) as a transformation product with enhanced toxicity using effect-directed analysis. The EC50 of CPAB (4.8 mg/L) was a factor of 10 lower than that for DCF (48.1 mg/L), due to the higher hydrophobicity of CPAB (log Kow = 3.62) compared with DCF (log Dow = 2.04) at pH 7.0.
اظهر المزيد [+] اقل [-]Anchoring novel molecular biomarker responses to traditional responses in fish exposed to environmental contamination
2010
Nogueira, Patrícia | Pacheco, Mario | Pereira, M Lourdes | Mendo, Sónia | Rotchell, Jeanette M.
The responses of Dicentrarchus labrax and Liza aurata to aquatic pollution were assessed in a contaminated coastal lagoon, using both traditional and novel biomarkers combined. DNA damage, assessed by comet assay, was higher in both fish species from the contaminated sites, whereas levels of cytochrome P450 1A1 gene expression were not significantly altered. The liver histopathological analysis also revealed significant lesions in fish from contaminated sites. Alterations in ras and xpf genes were analysed and additional pollutant-responsive genes were identified. While no alterations were found in ras gene, a downregulation of xpf gene was observed in D. labrax from a contaminated site. Suppression subtractive hybridization applied to D. labrax collected at a contaminated site, revealed altered expression in genes involved in energy metabolism, immune system activity and antioxidant response. The approach and results reported herein demonstrate the utility of anchoring traditional biomarker responses alongside novel biomarker responses.
اظهر المزيد [+] اقل [-]Organochlorine pesticides and PCBs in fish from lakes of the Tibetan Plateau and the implications
2010
Yang, Ruiqiang | Wang, Yawei | Li, An | Zhang, Qinghua | Jing, Chuanyong | Wang, Thanh | Wang, Pu | Li, Yingming | Jiang, Guibin
High mountains may play significant roles in the global transport of persistent organic pollutants (POPs). This work aims to investigate the levels, patterns and distribution of semi-volatile organoclorine pollutants and to improve the understanding of the long-range atmospheric transport and fate of contaminants on the Tibetan Plateau. A total of 60 fish samples were collected from eight lakes located between 2813 and 4718 m above sea level across the Plateau. Concentrations of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) including dichlorodiphenyltrichloroethane and its metabolites (DDTs), hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) were measured in fish muscle. The results showed that concentrations of DDT, HCH and HCB were comparable to or lower than those found in remote mountains of Europe, Canada and US, while PCB concentrations in fish were, on average, about 4-150 times lower on Tibet than at other mountain areas. The transport and fate of contaminants in the Plateau are significantly influenced by the unique climatological and meteorological conditions, particularly by the summer Indian monsoon and winter westerly jet stream.
اظهر المزيد [+] اقل [-]Dynamics of PCB removal and detoxification in historically contaminated soils amended with activated carbon
2010
Vasilyeva, Galina K. | Strijakova, Elena R. | Nikolaeva, Svetlana N. | Lebedev, Albert T. | Shea, Patrick J.
Activated carbon (AC) can help overcome toxicity of pollutants to microbes and facilitate soil bioremediation. We used this approach to treat a Histosol and an Alluvial soil historically contaminated with PCB (4190 and 1585 mg kg−1, respectively; primarily tri-, tetra- and pentachlorinated congeners). Results confirmed PCB persistence; reductions in PCB extractable from control and AC-amended soils were mostly due to a decrease in tri- and to some extent tetrachlorinated congeners as well as formation of a bound fraction. Mechanisms of PCB binding by soil and AC were different. In addition to microbial degradation of less chlorinated congeners, we postulate AC catalyzed dechlorination of higher chlorinated congeners. A large decrease in bioavailable PCB in AC-amended soils was demonstrated by greater clover germination and biomass. Phytotoxicity was low in treated soils but remained high in untreated soils for the duration of a 39-month experiment. These observations indicate the utility of AC for remediation of soils historically contaminated with PCB. Activated carbon promotes remediation of soils historically contaminated with PCB.
اظهر المزيد [+] اقل [-]Urbanization-related changes in European aspen (Populus tremula L.): Leaf traits and litter decomposition
2010
Nikula, Suvi | Vapaavuori, Elina | Manninen, Sirkku
We investigated foliar and litter responses of European aspen (Populus tremula L.) to urbanization, including factors such as increased temperature, moisture stress and nitrogen (N) deposition. Leaf samples were collected in 2006-2008 from three urban and three rural forest stands in the Helsinki Metropolitan Area, southern Finland, and reciprocal litter transplantations were established between urban and rural sites. Urban leaves exhibited a higher amount of epicuticular waxes and N concentration, and a lower C:N ratio than rural ones, but there was no difference in specific leaf area. Urban litter had a slightly higher N concentration, lower concentrations of lignin and total phenolics, and was more palatable to a macrofaunal decomposer. Moreover, litter decay was faster at the urban site and for urban litter. Urbanization thus resulted in foliar acclimatization in terms of increased amount of epicuticular waxes, as well as in accelerated decomposition of the N-richer leaf litter.
اظهر المزيد [+] اقل [-]Detection of antibiotic resistance and tetracycline resistance genes in Enterobacteriaceae isolated from the Pearl rivers in South China
2010
Tao, Ran | Ying, Guang-Guo | Su, Hao-Chang | Zhou, Hong-Wei | Sidhu, Jatinder P.S.
This study investigated antibiotic resistance profiles and tetracycline resistance genes in Enterobacteriaceae family isolates from the Pearl rivers. The Enterobacteriaceae isolates were tested for susceptibility to seven antibiotics ampicillin, chloramphenicol, ciprofloxacin, levofloxacin, sulphamethoxazole/trimethoprim, tetracycline and trimethoprim. In Liuxi reservoir, with an exception to ampicillin resistant strains (11%) no other antibiotic resistance bacterial strains were detected. However, multiple drug resistance in bacterial isolates from the other sites of Pearl rivers was observed which is possibly due to sewage discharge and input from other anthropogenic sources along the rivers. Four tetracycline resistance genes tet A, tet B, tet C and tet D were detected in the isolates from the rivers. The genes tet A and tet B were widely detected with the detection frequencies of 43% and 40% respectively. Ciprofloxacin and levofloxacin resistant enteric bacteria were also isolated from the pig and duck manures which suggest a wider distribution of human specific drugs in the environment. This investigation provided a baseline data on antibiotic resistance profiles and tetracycline resistance genes in the Pearl rivers delta.
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