خيارات البحث
النتائج 111 - 120 من 798
Leaching of hydrophobic Cu and Zn from discarded marine antifouling paint residues: Evidence for transchelation of metal pyrithiones النص الكامل
2009
Holmes, Luke | Turner, Andrew
Leaching of Cu and Zn from a composite of discarded antifouling paint residues ([Cu] = 288 mg g−1; [Zn] = 96 mg g−1) into natural sea water has been studied over a period of 75 h. Total Cu and Zn were released according to a pseudo first-order reaction, with rate constants on the order of 0.3 and 2.5 (mg L−1)−1 h−1, respectively, and final concentrations equivalent to the dissolution of about 8 and 2% of respective concentrations in the composite. Time-distributions of hydrophobic metals, determined by solid phase extraction-methanol elution, were more complex. Net release of hydrophobic Cu was greater in the absence of light than under a sequence of light–dark cycles; however, hydrophobic Zn release was not detected under the former conditions but contributed up to 50% of total aqueous Zn when light was present. These observations are interpreted in terms of the relative thermodynamic and photolytic stabilities of biocidal pyrithione complexes. Hydrophobic Cu and Zn leached from antifouling paint particles into sea water appear to be pyrithione complexes.
اظهر المزيد [+] اقل [-]A simple chemical free arsenic removal method for community water supply – A case study from West Bengal, India النص الكامل
2009
Sen Gupta, B. | Chatterjee, S. | Rott, U. | Kauffman, H. | Bandyopadhyay, A. | DeGroot, W. | Nag, N.K. | Carbonell-Barrachina, A.A. | Mukherjee, S.
This report describes a simple chemical free method that was successfully used by a team of European and Indian scientists (www.qub.ac.uk/tipot) to remove arsenic (As) from groundwater in a village in West Bengal, India. Six such plants are now in operation and are being used to supply water to the local population (www.insituarsenic.org). The study was conducted in Kasimpore, a village in North 24 Parganas District, approximately 25 km from Kolkata. In all cases, total As in treated water was less than the WHO guideline value of 10 μg L−1. The plant produces no sludge and the operation cost is 1.0 US$ per day for producing 2000 L of potable water. This work presents the chemical free arsenic removal method from groundwater and its successful implementation in West Bengal for community water supply.
اظهر المزيد [+] اقل [-]Assessing the genotoxicity of urban air pollutants using two in situ plant bioassays النص الكامل
2009
Villarini, M. | Fatigoni, C. | Dominici, L. | Maestri, S. | Ederli, L. | Pasqualini, S. | Monarca, S. | Moretti, M.
Genotoxicity of urban air has been analysed almost exclusively in airborne particulates. We monitored the genotoxic effects of airborne pollutants in the urban air of Perugia (Central Italy). Two plant bioindicators with different genetic endpoints were used: micronuclei in meiotic pollen mother cells using Tradescantia-micronucleus bioassay (Trad-MCN) and DNA damage in nuclei of Nicotiana tabacum leaves using comet assay (Nicotiana-comet). Buds of Tradescantia clone # 4430 and young N. tabacum cv. Xanthi plants were exposed for 24 h at three sites with different pollution levels. One control site (indoor control) was also used. The two bioassays showed different sensitivities toward urban pollutants: Trad-MCN assay was the most sensitive, but DNA damage in N. tabacum showed a better correlation with the pollutant concentrations. In situ biomonitoring of airborne genotoxins using higher plants combined with chemical analysis is thus recommended for characterizing genotoxicity of urban air. Plant bioassays used to explore in situ the correlation between air pollution and genotoxicity.
اظهر المزيد [+] اقل [-]How do long-term development and periodical changes of river–floodplain systems affect the fate of contaminants? Results from European rivers النص الكامل
2009
Lair, G.J. | Zehetner, F. | Fiebig, M. | Gerzabek, M.H. | Gestel, C.A.M van | Hein, T. | Hohensinner, S. | Hsu, P. | Jones, K.C. | Jordan, G. | Koelmans, A.A. | Poot, A. | Slijkerman, D.M.E. | Totsche, K.U. | Bondar-Kunze, E. | Barth, J.A.C.
In many densely populated areas, riverine floodplains have been strongly impacted and degraded by river channelization and flood protection dikes. Floodplains act as buffers for flood water and as filters for nutrients and pollutants carried with river water and sediment from upstream source areas. Based on results of the EU-funded “AquaTerra” project (2004–2009), we analyze changes in the dynamics of European river–floodplain systems over different temporal scales and assess their effects on contaminant behaviour and ecosystem functioning. We find that human-induced changes in the hydrologic regime of rivers have direct and severe consequences on nutrient cycling and contaminant retention in adjacent floodplains. We point out the complex interactions of contaminants with nutrient availability and other physico-chemical characteristics (pH, organic matter) in determining ecotoxicity and habitat quality, and draw conclusions for improved floodplain management. Human activities have changed the hydraulics and contaminant fate in river–floodplain ecosystems.
اظهر المزيد [+] اقل [-]Sorption behavior of bensulfuron-methyl on andisols and ultisols volcanic ash-derived soils: Contribution of humic fractions and mineral–organic complexes النص الكامل
2009
Espinoza, Jeannette | Fuentes, Edwar | Báez, Maria E.
Bensulfuron-methyl sorption was studied in Andisol and Ultisol soils in view of their characteristic physical and chemical properties, presenting acidic pH and variable charge. Humic and fulvic acids (HA and FA) and humin (HUM) contributions were established. Sorption was studied by using two synthetic sorbents, an aluminum-silicate with iron oxide coverage and the same sorbent coated with humic acid. Freundlich model described Bensulfuron-methyl behavior in all sorbents (R2 0.969–0.998). Kf for soils (8.3–20.7 μg1−1/n mL1/n g−1) were higher than those reported in the literature. Organic matter, halloysite or kaolinite, and specific surface area contributed to the global process. The highest Kf for HA, FA and HUM were 539.5, 82.9, and 98.7 μg1−1/n mL1/n g−1. Model sorbents described the participation of variable charge materials with high adsorption capacity. The constant capacitance model was used to assess effects of Bensulfuron-methyl adsorption on the distribution of SOH, SOH2+ and SO− sites of sorbents. Organic matter, phyllosilicates, variable charge minerals and organo-mineral complexes contribute to bensulfuron-methyl sorption on volcanic ash-derived soils.
اظهر المزيد [+] اقل [-]Identification of Chinese cabbage genotypes with low cadmium accumulation for food safety النص الكامل
2009
Liu, Weitao | Zhou, Qixing | Sun, Yuebing | Liu, Rui
The pot-culture experiment and field studies were conducted to screen out and identify cadmium (Cd) excluders from 40 Chinese cabbage genotypes for food safety. The results of the pot-culture experiment indicated that the shoot Cd concentrations under three treatments (1.0, 2.5 and 5.0 mg Cd kg⁻¹ Soil) varied significantly (p < 0.05), with average values of 0.70, 3.07 and 5.83 mg kg⁻¹, respectively. The Cd concentrations in 12 cabbage genotypes were lower than 0.50 mg kg⁻¹. The enrichment factors (EFs) and translocation factors (TFs) in 8 cabbage genotypes were lower than 1.0. The field studies further identified Lvxing 70 as a Cd-excluder genotype (CEG), which is suitable to be planted in low Cd-contaminated soils (Cd concentration should be lower than 1.25 mg kg⁻¹) for food safety. Lvxing 70 was identified as a Cd-excluder genotype (CEG) and suitable to be cultivated in low Cd-contaminated soils for food safety.
اظهر المزيد [+] اقل [-]POP bioaccumulation in macroinvertebrates of alpine freshwater systems النص الكامل
2009
Bizzotto, E.C. | Villa, S. | Vighi, M.
This study serves to investigate the uptake of POPs in the different trophic levels (scrapers, collectors, predators, shredders) of macroinvertebrate communities sampled from a glacial and a non-glacial stream in the Italian Alps. The presented results show that the contaminant concentrations in glacial communities are generally higher compared to those from non-glacial catchments, highlighting the importance of glaciers as temporary sinks of atmospherically transported pollutants. Moreover, the data also suggests that in mountain systems snow plays an important role in influencing macroinvertebrate contamination. The main chemical uptake process to the macroinvertebrates is considered to be bioconcentration from water, as similar contaminant profiles were observed between the different trophic levels. The role of biomagnification/bioaccumulation is thought to be absent or negligible. The enrichment of chemicals observed in the predators is likely to be related to their greater lipid content compared to that of other feeding groups. Influence of POP release in glacial-fed streams, enhanced by global warming, on pristine aquatic ecosystems.
اظهر المزيد [+] اقل [-]The application of a mulch biofilm barrier for surfactant enhanced polycyclic aromatic hydrocarbon bioremediation النص الكامل
2009
Seo, Youngwoo | Lee, Woo-Hyung | Sorial, George | Bishop, Paul L.
Lab scale mulch biofilm barriers were constructed and tested to evaluate their performance for preventing the migration of aqueous and surfactant solubilized PAHs. The spatial distribution of viable PAH degrader populations and resultant biofilm formation were also monitored to evaluate the performance of the biobarrier and the prolonged surfactant effect on the PAH degrading microorganism consortia in the biobarrier. Sorption and biodegradation of PAHs resulted in stable operation of the system for dissolved phenanthrene and pyrene during 150 days of experimentation. The nonionic surfactant could increase the solubility of phenanthrene and pyrene significantly. However, the biobarrier itself couldn't totally prevent the migration of micellar solubilized phenanthrene and pyrene. The presence of surfactant and the resultant highly increased phenanthrene or pyrene concentration didn't appear to cause toxic effects on the attached biofilm in the biobarrier. However, the presence of surfactant did change the structural composition of the biofilm. Mulch biofilm barrier showed potential for surfactant enhanced bioremediation, and the presence of surfactant changed the structural composition of the biofilm.
اظهر المزيد [+] اقل [-]Tissue distribution, isozyme abundance and sensitivity to chlorpyrifos-oxon of carboxylesterases in the earthworm Lumbricus terrestris النص الكامل
2009
Sanchez-Hernandez, Juan C. | Wheelock, Craig E.
A laboratory-based study was conducted to determine the basal carboxylesterase (CbE) activity in different tissues of the earthworm Lumbricus terrestris, and its sensitivity to the organophosphate (OP) pesticide chlorpyrifos-oxon (CPx). Carboxylesterase activity was found in the pharynx, crop, gizzard, anterior intestine, wall muscle and reproductive tissues of L. terrestris, and multiple tissue-specific isozymes were observed by native gel electrophoresis. Esterase activity and sensitivity to CPx inhibition varied on a tissue- and substrate-specific basis, suggesting isoforms-specific selectivity to OP-mediated inhibition. Three practical issues are recommended for the use of earthworm CbE activity as a biomarker of pesticide exposure: (i) CbE should be measured using several routine substrates, (ii) it should be determined in selected tissues instead of whole organism homogenate, and (iii) earthworm CbE activity should be used in conjuncture with other common biomarkers (e.g., ChE) within a multibiomarker approach to assess field exposure of OPs, and potentially other agrochemicals. The measurement of carboxylesterase inhibition in earthworm is a sensitive and complementary biomarker of pesticide exposure.
اظهر المزيد [+] اقل [-]Bioconcentration of zinc and cadmium in ectomycorrhizal fungi and associated aspen trees as affected by level of pollution النص الكامل
2009
Krpata, Doris | Fitz, Walter | Peintner, Ursula | Langer, Ingrid | Schweiger, Peter
Concentrations of Zn and Cd were measured in fruitbodies of ectomycorrhizal (ECM) fungi and leaves of co-occurring accumulator aspen. Samples were taken on three metal-polluted sites and one control site. Fungal bioconcentration factors (BCF = fruitbody concentration: soil concentration) were calculated on the basis of total metal concentrations in surface soil horizons (BCFtot) and NH4NO3-extractable metal concentrations in mineral soil (BCFlab). When plotted on log-log scale, values of BCF decreased linearly with increasing soil metal concentrations. BCFlab for both Zn and Cd described the data more closely than BCFtot. Fungal genera differed in ZnBCF but not in CdBCF. The information on differences between fungi with respect to their predominant occurrence in different soil horizons did not improve relations of BCF with soil metal concentrations. Aspen trees accumulated Zn and Cd to similar concentrations as the ECM fungi. Apparently, the fungi did not act as an effective barrier against aspen metal uptake by retaining the metals. Populus tremula and associated ectomycorrhizal fungi accumulate zinc and cadmium to similar concentrations.
اظهر المزيد [+] اقل [-]