خيارات البحث
النتائج 291 - 300 من 767
Microbial transformation of synthetic estrogen 17α-ethinylestradiol
2009
Cajthaml, Tomáš | Křesinová, Zdena | Svobodová, Kateřina | Sigler, Karei | Řezanka, Tomáš
Natural estrogens such as estrone, 17β-estradiol, estriol, and the particularly recalcitrant synthetic estrogen 17α-ethinylestradiol used as oral contraceptive, accumulate in the environment and may give rise to health problems. The processes participating in their removal from soil, wastewater, water-sediments, groundwater-aquifer material, and wastewater or sewage treatment plant effluents may involve the action of bacterial and microbial consortia, and in some cases fungi and algae. This review discusses the different efficiencies of bacterial degradation of 17α-ethinylestradiol under aerobic and anaerobic conditions, the role of sulfate-, nitrate-, and iron-reducing conditions in anaerobic degradation, and the role of sorption. The participation of autotrophic ammonia oxidizing bacteria and heterotrophic bacteria in cometabolic degradation of estrogens, the estrogen-degrading action of ligninolytic fungi and their extracellular enzymes (lignin peroxidase, manganese-dependent peroxidase, versatile peroxidase, laccase), and of algae are discussed in detail. Current knowledge of 17α-ethinylestradiol microbial transformation is summarized.
اظهر المزيد [+] اقل [-]Effects of arsenic on nitrate metabolism in arsenic hyperaccumulating and non-hyperaccumulating ferns
2009
Singh, Nandita | Ma, Lena Q. | Vu, Joseph C. | Raj, Anshita
This study investigated the effects of arsenic on the in vitro activities of the enzymes (nitrate reductase and nitrite reductase) involved in nitrate metabolism in the roots, rhizomes, and fronds of four-month old Pteris vittata (arsenic - hyperaccumulator) and Pteris ensiformis (non-arsenic--hyperaccumulator) plants. The arsenic treatments (0, 150, and 300 μM as sodium arsenate) in hydroponics had adverse effects on the root and frond dry weights, and this effect was more evident in P. ensiformis than in P. vittata. Nitrate reductase and nitrite reductase activities of arsenate-treated plants were reduced more in P. ensiformis than in P. vittata. This effect was accompanied by similar decreases in tissue NO₃⁻ concentrations. Therefore, this decrease is interpreted as being indirect, i.e., the consequence of the reduced NO₃⁻ uptake and translocation in the plants. The study shows the difference in the tolerance level of the two Pteris species with varying sensitivity to arsenic. Arsenic reduced the activity of nitrate and nitrite reductase more in Pteris ensiformis than Pteris vittata.
اظهر المزيد [+] اقل [-]Highly charged swelling mica reduces Cu bioavailability in Cu-contaminated soils
2009
Stuckey, Jason W. | Neaman, Alexander | Ravella, Ramesh | Komarneni, Sridhar | Martínez, Carmen Enid
This is the first test of a highly charged swelling mica's (Na-2-mica) ability to reduce the plant-absorbed Cu in Cu-contaminated soils from Chile. Perennial ryegrass (Lolium perenne L.) was grown in two acid soils (Sector 2: pH 4.2, total Cu = 172 mg Cu kg-1 and Sector 3: pH 4.2, total Cu = 112 mg Cu kg-1) amended with 0.5% and 1% (w/w) mica, and 1% (w/w) montmorillonite. At 10 weeks of growth, both mica treatments decreased the shoot Cu of ryegrass grown in Sector 2 producing shoot Cu concentrations above 21-22 mg Cu kg-1 (the phytotoxicity threshold for that species), yet the mica treatments did not reduce shoot Cu concentrations when grown in Sector 3, which were at a typical level. The mica treatments improved shoot growth in Sector 3 by reducing free and extractable Cu to low enough levels where other nutrients could compete for plant absorption and translocation. In addition, the mica treatments improved root growth in both soils, and the 1% mica treatment reduced root Cu in both soils. This swelling mica warrants further testing of its ability to assist re-vegetation and reduce Cu bioavailability in Cu-contaminated surface soils. In situ remediation of Cu-contaminated soils with a synthetic mica (Na-2-mica) will aid in re-vegetative efforts.
اظهر المزيد [+] اقل [-]Effective pollutant emission heights for atmospheric transport modelling based on real-world information
2009
Pregger, Thomas | Friedrich, Rainer
Emission data needed as input for the operation of atmospheric models should not only be spatially and temporally resolved. Another important feature is the effective emission height which significantly influences modelled concentration values. Unfortunately this information, which is especially relevant for large point sources, is usually not available and simple assumptions are often used in atmospheric models. As a contribution to improve knowledge on emission heights this paper provides typical default values for the driving parameters stack height and flue gas temperature, velocity and flow rate for different industrial sources. The results were derived from an analysis of the probably most comprehensive database of real-world stack information existing in Europe based on German industrial data. A bottom-up calculation of effective emission heights applying equations used for Gaussian dispersion models shows significant differences depending on source and air pollutant and compared to approaches currently used for atmospheric transport modelling.
اظهر المزيد [+] اقل [-]Equilibrium partitioning theory to predict the sediment toxicity of the anionic surfactant C12-2-LAS to Corophium volutator
2009
Rico-Rico, Angeles | Temara, Ali | Hermens, Joop L.M.
The study of the effect of the sorption of linear alkylbenzene sulfonates (LAS) on the bioavailability to marine benthic organisms is essential to refine the environmental risk assessment of these compounds. According to the equilibrium partitioning theory (EqP), the effect concentration in water-only exposure will be similar to the effect concentration in the sediment pore water. In this work, sorption and desorption experiments with two marine sediments were carried out using the compound C12-2-LAS. The effect of the sediment sorption on the toxicity of benthic organisms was studied in water-only and in sediment bioassays with the marine mud shrimp Corophium volutator. In addition, three common spiking methods were tested for its application in the toxicity tests, as well as the stability of the surfactant during the water-only and sediment-water test duration. LC50 values obtained from water-only exposure showed a good correspondence with the pore water concentrations calculated from the sorption and desorption isotherms in the spiked sediments.
اظهر المزيد [+] اقل [-]Leaching of copper and zinc from spent antifouling paint particles
2009
Singh, Nimisha | Turner, Andrew
Leaching of Cu and Zn from a composite of spent antifouling paint particles, containing about 300 mg g−1 and 110 mg g−1 of the respective metals, was studied in batch experiments. For a given set of simulated environmental conditions, release of Cu was independent of paint particle concentration due to attainment of pseudo-saturation, but Zn was less constrained by solubility effects and release increased with increasing particle concentration. Leaching of Cu increased but Zn decreased with increasing salinity, consistent with mechanisms governing the dissolution of Cu2O in the presence of chloride and Zn acrylates in the presence of seawater cations. Because of complex reaction kinetics and the presence of calcium carbonate in the paint matrix, metal leaching appeared to be greater at 4 °C than 19 °C under many conditions. These findings have important environmental and biological implications regarding the deliberate or inadvertent disposal of antifouling paint residues.
اظهر المزيد [+] اقل [-]Mitigation of two pyrethroid insecticides in a Mississippi Delta constructed wetland
2009
Moore, M.T. | Cooper, C.M. | Smith, S. Jr | Cullum, R.F. | Knight, S.S. | Locke, M.A. | Bennett, E.R.
Constructed wetlands are a suggested best management practice to help mitigate agricultural runoff before entering receiving aquatic ecosystems. A constructed wetland system (180 m x 30 m), comprising a sediment retention basin and two treatment cells, was used to determine the fate and transport of simulated runoff containing the pyrethroid insecticides lambda-cyhalothrin and cyfluthrin, as well as suspended sediment. Wetland water, sediment, and plant samples were collected spatially and temporally over 55 d. Results showed 49 and 76% of the study's measured lambda-cyhalothrin and cyfluthrin masses were associated with vegetation, respectively. Based on conservative effects concentrations for invertebrates and regression analyses of maximum observed wetland aqueous concentrations, a wetland length of 215 m x 30 m width would be required to adequately mitigate 1% pesticide runoff from a 14 ha contributing area. Results of this experiment can be used to model future design specifications for constructed wetland mitigation of pyrethroid insecticides. A wetland length of 215 m x 30 m mitigated pyrethroid runoff from a 14 ha field.
اظهر المزيد [+] اقل [-]Arsenic mobility in brownfield soils amended with green waste compost or biochar and planted with Miscanthus
2009
Hartley, William | Dickinson, Nicholas M. | Riby, Philip | Lepp, N. W. (Nicholas W)
Degraded land that is historically contaminated from different sources of industrial waste provides an opportunity for conversion to bioenergy fuel production and also to increase sequestration of carbon in soil through organic amendments. In pot experiments, As mobility was investigated in three different brownfield soils amended with green waste compost (GWC, 30% v/v) or biochar (BC, 20% v/v), planted with Miscanthus. Using GWC improved crop yield but had little effect on foliar As uptake, although the proportion of As transferred from roots to foliage differed considerably between the three soils. It also increased dissolved carbon concentrations in soil pore water that influenced Fe and As mobility. Effects of BC were less pronounced, but the impacts of both amendments on SOC, Fe, P and pH are likely to be critical in the context of As leaching to ground water. Growing Miscanthus had no measurable effect on As mobility. Green waste compost enhances water-soluble iron, phosphorus and carbon, increasing arsenic mobility in soil pore water.
اظهر المزيد [+] اقل [-]Evaluation of soil characteristics potentially affecting arsenic concentration in paddy rice (Oryza sativa L.)
2009
Bogdan, Katja | Schenk, Manfred K.
Paddy rice may contribute considerably to the human intake of As. The knowledge of soil characteristics affecting the As content of the rice plant enables the development of agricultural measures for controlling As uptake. During field surveys in 2004 and 2006, plant samples from 68 fields (Italy, Po-area) revealed markedly differing As concentration in polished rice. The soil factors total As(aqua regia), pH, grain size fractions, total C, plant available P(CAL), poorly crystalline Fe(oxal.) and plant available Si(Na-acetate) content that potentially affect As content of rice were determined. A multiple linear regression analysis showed a significant positive influence of the total As(aqua regia) and plant available P(CAL) content and a negative influence of the poorly crystalline Fe(oxal.) content of the soil on the As content in polished rice and rice straw. Si concentration in rice straw varied widely and was negatively related to As content in straw and polished rice. Field selection for total As, poorly crystalline Fe and plant available P in soil might contribute to control As content of paddy rice.
اظهر المزيد [+] اقل [-]Source-pathway-receptor investigation of the fate of trace elements derived from shotgun pellets discharged in terrestrial ecosystems managed for game shooting
2009
Sneddon, Jennifer | Clemente, Rafael | Riby, Philip | Lepp, N. W. (Nicholas W)
Spent shotgun pellets may contaminate terrestrial ecosystems. We examined the fate of elements originating from shotgun pellets in pasture and woodland ecosystems. Two source-receptor pathways: i) soil-soil pore water-plant and ii) whole earthworm/worm gut contents - washed and unwashed small mammal hair were investigated. Concentrations of Pb and associated contaminants were higher in soils from shot areas than controls. Arsenic and lead concentrations were positively correlated in soils, soil pore water and associated biota. Element concentrations in biota were below statutory levels in all locations. Bioavailability of lead to small mammals, based on concentrations in washed body hair was low. Lead movement from soil water to higher trophic levels was minor compared to lead adsorbed onto body surfaces. Lead was concentrated in earthworm gut and some plants. Results indicate that managed game shooting presents minimal risk in terms of element transfer to soils and their associated biota.
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