خيارات البحث
النتائج 61 - 70 من 456
Response of plankton communities in freshwater pond and stream mesocosms to the herbicide metazachlor النص الكامل
2008
Mohr, S. | Feibicke, M. | Berghahn, R. | Schmiediche, R. | Schmidt, R.
Metazachlor is a frequently used herbicide with concentrations in surface waters up to 100 μg L-1. A long-term mesocosm study was performed in order to investigate effects on stream and pond communities also regarding recovery. Single metazachlor doses of 5, 20, 80, 200, and 500 μg L-1 were given and the aquatic communities monitored for 140 days. In this paper, special attention is paid to the plankton response and the results of the entire study are summarised. Metazachlor strongly affected the stream and pond mesocosm communities at concentrations higher than 5 μg L-1. Direct negative effects were most prominent for chlorophytes whereas diatoms and cryptophytes seemed insensitive. The effects on zooplankton were caused by changes in habitat structure due to the strong decline of macrophytes. The slow degradation of metazachlor combined with the absence of recovery in both chlorophytes and macrophytes is likely to cause long-lasting effects on aquatic ecosystems. Metazachlor at levels >5 μg L-1 is likely to cause long-lasting effects in macrophyte dominated aquatic communities.
اظهر المزيد [+] اقل [-]An assessment of metal contamination along the Irish coast using the seaweed Ascophyllum nodosum (Fucales, Phaeophyceae) النص الكامل
2008
Morrison, L. | Baumann, H.A. | Stengel, D.B.
The relative abundance and variation of Cr, Co, Cd and Pb in Ascophyllum nodosum and intertidal surface sediments from six locations around the coast were assessed over six seasons. Higher Cd and Pb levels in Galway Docks and Cork Harbour were attributed to localised inputs of these metals from municipal and domestic waste, while at a reference site (Ballyconneely), high algal Cr concentrations were considered a function of geological setting rather than anthropogenic loading. Little seasonal variation was observed, with the exception of higher Co levels in plants in winter, associated with growth dynamics and increased fluvial inputs. In comparison with previously published data for metals in A. nodosum from the North Atlantic, with the exception of localised hot spots, the Irish coastline is still a relatively pristine environment. A. nodosum may be successfully and easily used as a biomonitor of metal contamination in coastal waters. This paper provides details of an easily applicable, cost-effective and ecologically relevant approach to assessing the degree of metal contamination in coastal environments.
اظهر المزيد [+] اقل [-]Long-term effects of aided phytostabilisation of trace elements on microbial biomass and activity, enzyme activities, and composition of microbial community in the Jales contaminated mine spoils النص الكامل
2008
Renella, G. | Landi, L. | Ascher, J. | Ceccherini, M.T. | Pietramellara, G. | Mench, M. | Nannipieri, P.
Long-term effects of aided phytostabilisation of trace elements on microbial biomass and activity, enzyme activities, and composition of microbial community in the Jales contaminated mine spoils النص الكامل
2008
Renella, G. | Landi, L. | Ascher, J. | Ceccherini, M.T. | Pietramellara, G. | Mench, M. | Nannipieri, P.
We studied the effectiveness of remediation on microbial endpoints, namely microbial biomass and activity, microbial and plant species richness, of an As-contaminated mine spoil, amended with compost (C) alone and in combination with beringite (B) or zerovalent iron grit (Z), to increase organic matter content and reduce trace elements mobility, and to allow Holcus lanatus and Pinus pinaster growth. Untreated spoil showed the lowest microbial biomass and activity and hydrolase activities, and H. lanatus as sole plant species, whereas the presented aided phytostabilisation option, especially CBZ treatment, significantly increased microbial biomass and activity and allowed colonisation by several plant species, comparable to those of an uncontaminated sandy soil. Microbial species richness was only increased in spoils amended with C alone. No clear correlation occurred between trace element mobility and microbial parameters and plant species richness. Our results indicate that the choice of indicators of soil remediation practices is a bottleneck. Organo-mineral amendment and revegetation of a gold mine spoil increased microbial activity but did not increase microbial species richness.
اظهر المزيد [+] اقل [-]Long-term effects of aided phytostabilisation of trace elements on microbial biomass and activity, enzyme activities, and composition of microbial community in the Jales contaminated mine spoils النص الكامل
2008
Renella, Giancarlo | Landi, Loretta | Ascher, Judith | Ceccherini, Maria Teresa | Pietramellara, Giacomo | Mench, Michel | Nannipieri, Paolo | Università degli Studi di Firenze = University of Florence = Université de Florence (UniFI) | Biodiversité, Gènes & Communautés (BioGeCo) ; Institut National de la Recherche Agronomique (INRA)-Université de Bordeaux (UB)
International audience | We studied the effectiveness of remediation on microbial endpoints, namely microbial biomass and activity, microbial and plant species richness, of an As-contaminated mine spoil, amended with compost (C) alone and in combination with beringite (B) or zerovalent iron grit (Z), to increase organic matter content and reduce trace elements mobility, and to allow Holcus lanatus and Pinus pinaster growth. Untreated spoil showed the lowest microbial biomass and activity and hydrolase activities, and H. lanatus as sole plant species, whereas the presented aided phytostabilisation option, especially CBZ treatment, significantly increased microbial biomass and activity and allowed colonisation by several plant species, comparable to those of an uncontaminated sandy soil. Microbial species richness was only increased in spoils amended with C alone. No clear correlation occurred between trace element mobility and microbial parameters and plant species richness. Our results indicate that the choice of indicators of soil remediation practices is a bottleneck. Organo-mineral amendment and revegetation of a gold mine spoil increased microbial activity but did not increase microbial species richness.
اظهر المزيد [+] اقل [-]Mercury biomethylation assessment in the estuary of Bilbao (North of Spain) النص الكامل
2008
Raposo, J.C. | Ozamiz, G. | Etxebarria, N. | Tueros, I. | Munoz, C. | Muela, A. | Arana, I. | Barcina, I.
The relationship between the microbial methylation of mercury and the microbial activities in sediments and water collected from the estuary of Bilbao (North of Spain) was studied in three different sampling points and in two different seasons. Three different cultures were prepared with a sediment slurry to distinguish between biotic and abiotic methylation pathways and the variations of the methylmercury concentration and the variations of the population of total number of bacteria (TDC), anaerobic heterotrophic bacteria (AHB), sulphate-reducing bacteria (SRB) and Desulfovibrio were measured. From this work, it can be concluded that the variation of MeHg concentrations is a result of the methylation/demethylation processes in the sediments, and that the abiotic processes have a negligible contribution to those processes. According to the statistical analysis of the results (partial least squares analysis) a significant statistical correlation was established between methylmercury and the SRB counts.The methylation of mercury follows a stationary pattern linked to the variation of sulphate-reducing bacteria.
اظهر المزيد [+] اقل [-]Forest health conditions in North America النص الكامل
2008
Tkacz, Borys | Moody, Ben | Villa Castillo, Jamie | Fenn, Mark E.
Some of the greatest forest health impacts in North America are caused by invasive forest insects and pathogens (e.g., emerald ash borer and sudden oak death in the US), by severe outbreaks of native pests (e.g., mountain pine beetle in Canada), and fires exacerbated by changing climate. Ozone and N and S pollutants continue to impact the health of forests in several regions of North America. Long-term monitoring of forest health indicators has facilitated the assessment of forest health and sustainability in North America. By linking a nationwide network of forest health plots with the more extensive forest inventory, forest health experts in the US have evaluated current trends for major forest health indicators and developed assessments of future risks. Canada and Mexico currently lack nationwide networks of forest health plots. Development and expansion of these networks is critical to effective assessment of future forest health impacts.
اظهر المزيد [+] اقل [-]Cadmium accumulation and its effect on the in vitro growth of woody fleabane and mycorrhized white birch النص الكامل
2008
Fernández, R. | Bertrand, A. | Casares, A. | García, R. | González, A. | Tamés, R.S.
The effect of Cd on woody fleabane (Dittrichia viscosa (L.) Greuter) and white birch (Betula celtiberica Rothm. & Vasc.) was examined. Woody fleabane and white birch were grown in vitro in Murashige, T., Skoog, F., [1962. A revised medium for rapid growth and bioassays with tobacco tissue cultures. Physiol. Plant. 15, 473-479] (MS) plus Cd (10 mg Cd kg-1) and except for root length in white birch, plant development was inhibited when Cd was added. Cd accumulation in above-ground tissues showed differences among clones, reaching 1300 and 463 mg Cd kg-1 dry wt. in selected clones of woody fleabane and white birch, respectively. Tolerance of Paxillus filamentosus (Scop) Fr. to Cd was also examined before mycorrhization. Plants of mycorrhized white birch grown in the presence of Cd had a better development and accumulated more Cd in their shoots than the non-mycorrhized ones. The use of selected clones of woody fleabane and the mycorrhization of white birch enhance extraction efficiency from contaminated soils in phytoremediation programs. The high accumulation of Cd observed in selected clones of Dittrichia viscosa and mycorrhized Betula celtiberica grown in vitro implies a potential application for phytoextraction.
اظهر المزيد [+] اقل [-]Accumulation of nine metals and one metalloid in the tropical scallop Comptopallium radula from coral reefs in New Caledonia النص الكامل
2008
Metian, M. | Bustamante, P. | Hédouin, L. | Warnau, M.
Accumulation of nine metals and one metalloid in the tropical scallop Comptopallium radula from coral reefs in New Caledonia النص الكامل
2008
Metian, M. | Bustamante, P. | Hédouin, L. | Warnau, M.
Uptake of waterborne Cd, Co, Mn and Zn was determined in laboratory experiments using radiotracer techniques (109Cd, 57Co, 54Mn and 65Zn). Labelled Zn was mainly accumulated in the digestive gland (65%) and Co in kidneys (81%); Cd and Mn were similarly distributed in digestive gland and gills. In a complementary field study, Ag, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, and Zn were analysed in scallops collected at two stations showing different contamination levels. Digestive gland and kidneys displayed the highest concentrations. Ag, As, Cd, and Fe differed in soft tissues from the two stations, suggesting that Comptopallium radula could be a valuable local biomonitor species for these elements. Low Mn and Zn concentrations found in kidneys suggest that their content in calcium-phosphate concretions differs from the other pectinids. Preliminary risk considerations suggest that As would be the only element potentially leading to exposure of concern for seafood consumers. This study investigates metal accumulation behaviour in the tropical scallop Comptopallium radula and preliminary risk assessment for consumers.
اظهر المزيد [+] اقل [-]Accumulation of nine metals and one metalloid in the tropical scallop Comptopallium radula from coral reefs in New Caledonia النص الكامل
2008
Metian, M. | Bustamante, Paco | Hedouin, L. | Warnau, M.
Uptake of waterborne Cd, Co, Mn and Zn was determined in laboratory experiments using radiotracer techniques (Cd-109, Co-57, Mn-54 and Zn-65). Labelled Zn was mainly accumulated in the digestive gland (65%) and Co in kidneys (81%); Cd and Mn were similarly distributed in digestive gland and gills. In a complementary field study, Ag, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, and Zn were analysed in scallops collected at two stations showing different contamination levels. Digestive gland and kidneys displayed the highest concentrations. Ag, As, Cd, and Fe differed in soft tissues from the two stations, suggesting that Comptopallium radula could be a valuable local biomonitor species for these elements. Low Mn and Zn concentrations found in kidneys suggest that their content in calcium-phosphate concretions differs from the other pectinids. Preliminary risk considerations suggest that As would be the only element potentially leading to exposure of concern for seafood consumers. (c) 2007 Elsevier Ltd. All rights reserved.
اظهر المزيد [+] اقل [-]Patterns and sources of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in surficial sediments of Lakes Erie and Ontario النص الكامل
2008
Shen, Li | Gewurtz, Sarah B. | Reiner, Eric J. | MacPherson, Karen A. | Kolic, Terry M. | Helm, Paul A. | Brindle, Ian D. | Marvin, Chris H.
This study determines spatial trends and congener patterns of 2378-substituted polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in surficial sediments of Lakes Erie and Ontario. Sediments are enriched in 2378-PCDFs in Lake Ontario, and the PCDD/F concentrations increased from shallow near-shore sediments towards deep-water depositional zone sediments. In Lake Erie, sediments were dominated by octachlorodibenzo-p-dioxin, and the highest PCDD/F concentrations were observed in the western basin and the southern shoreline of the central basin with a decrease towards the eastern basin and the northern shoreline of the central basin. Principal components analysis revealed that chemical manufacture and disposal of chemical waste along the Niagara River has been a major PCDD/F source to Lake Ontario; while PCDD/Fs in Lake Erie are from multiple sources including industrial sources along the Detroit River, major tributaries along the southern shoreline of the lake, and atmospherically-derived material from the upper lakes and connecting channels. Lake-wide 2378-PCDD/F congener patterns are first reported in L. Erie and L. Ontario sediments.
اظهر المزيد [+] اقل [-]Groundwater–soil–crop relationship with respect to arsenic contamination in farming villages of Bangladesh – A preliminary study النص الكامل
2008
Kurosawa, Kiyoshi | Egashira, Kazuhiko | Tani, Masakazu | Jahiruddin, M. | Moslehuddin, Abu Zofar Md | Rahman, Zulfikar Md
To clarify the groundwater–soil–crop relationship with respect to arsenic (As) contamination, As concentration was measured in tubewell (TW) water, surface soil from farmyards and paddy fields, and fresh taro (Colocasia esculenta) leaves from farmyards in the farming villages of Bangladesh. The As concentration in TW water from farmyards was at least four times higher than the Bangladesh drinking water standard, and the concentration in fresh taro leaves was equal to or higher than those reported previously for leafy vegetables in Bangladesh. As concentration of surface soils in both farmyards and paddy fields was positively correlated with that of the TW water. Further, the concentration in surface soil was positively correlated with levels in fresh taro leaves in the farmyard. This study, therefore, clarified the groundwater–soil–crop relationship in farmyards and the relationship between groundwater–soil in paddy fields to assess the extent of As contamination in Bangladeshi villages. By extracting arsenic contaminated groundwater from a well, surface soil surrounding the well and crops planted in the surface soil became contaminated with arsenic.
اظهر المزيد [+] اقل [-]Arsenate tolerance in Silene paradoxa does not rely on phytochelatin-dependent sequestration النص الكامل
2008
Arnetoli, M. | Vooijs, R. | Bookum, W ten | Galardi, F. | Gonnelli, C. | Gabrielli, R. | Schat, H. | Verkleij, J.A.C.
Arsenate tolerance, As accumulation and As-induced phytochelatin accumulation were compared in populations of Silene paradoxa, one from a mine site enriched in As, Cu and Zn, the other from an uncontaminated site. The mine population was significantly more arsenate-tolerant. Arsenate uptake and root-to-shoot transport were slightly but significantly higher in the non-mine plants. The difference in uptake was quantitatively insufficient to explain the difference in tolerance between the populations. As accumulation in the roots was similar in both populations, but the mine plants accumulated much less phytochelatins than the non-mine plants. The mean phytochelatin chain length, however, was higher in the mine population, possibly due to a constitutively lower cellular glutathione level. It is argued that the mine plants must possess an arsenic detoxification mechanism other than arsenate reduction and subsequent phytochelatin-based sequestration. This alternative mechanism might explain at least some part of the superior tolerance in the mine plants. Neither decreased uptake nor phytochelatins seem to play a role in the As tolerance in Silene paradoxa.
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