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Resultados 141-150 de 233
Pollution of soils and watercourses by wastes from livestock production systems
1994
Webb, J. | Archer, J.R. (ADAS, Nobel House, 17 Smith Square, London SW1P 3JR (United Kingdom))
The use of animal waste as a crop fertilizer
1994
Ap Dewi, I. (School of Agricultural and Forest Sciences, University College of Wales, Bangor, Gwynedd LL57 2UW (United Kingdom))
The pollution potential and flows of nitrogen to waters and the atmosphere from grassland under grazing
1994
Jarvis, S.C. (AFRC Institute of Grassland and Environmental Research, North Wyke, Okehampton, Devon EX20 2SB (United Kingdom))
Bioconcentration of superlipophilic persistent chemicals -Octachlorodibenzo-p-dioxin (OCDD) in fish
1994
Geyer, H.J. (Gesellschaft fuer Strahlen- und Umweltforschung mbH Muenchen, Neuherberg (Germany)) | Muir, D.C.G. | Scheunert, I. | Steinberg, C.E.W. | Kettrup, A.A.W.
According to present understanding, persistent superlipophilic chemicals - such as octachlorodibenzo-p-dioxin, octachlorodibenzofuran, Mirex etc - with log K(OW) over 6 and cross sections over 9.5 A, bioconcentrate in aquatic organisms only little from ambient water. The most convincing argument against it is that in bioconcentration experiments with superlipophilic chemicals amounts applied exceeded water solubility by several orders of magnitude. This paper describes various methods for determining bioconcentration factors (BCF) of superlipophilic compounds. As exemplified with octachlorodibenzo-p-dioxin, BCF values evaluated by these methods match well with those calculated by QSARs for fish and mussels based on log K(OW) and water solubility. As expected, these BCF values exceed previous values by several orders of magnitude. For BCF evaluation of superlipophilic chemicals in aquatic organisms it is recommended: (i) flow-through systems, kinetic method (OECD guideline No. 305 E), (ii) ambient concentrations below water solubility, (iii) during the uptake and especially during the elimination phase no toxic effects of the test organisms should occur.
Mostrar más [+] Menos [-]Polychlorinated dibenzo-p-dioxins (PCDDs) and furans (PCDFs) in urban air and deposition in the United Kingdom
1994
Duarte-Davidson, R. (Lancaster Univ. (United Kingdom). Inst. of Environmental and Biological Sciences) | Clayton, P. | Coleman, P. | Davis, B.J. | Halsall, C.J. | Harding-Jones, P. | Pettit, K. | Woodfield, M.J. | Jones, K.C.
Polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) have been monitored in air and deposition at four UK urban sites (London, Cardiff, Manchester and Stevenage) since the beginning of 1991; data from the first 2 years are presented here. Median Sigma 2,3,7,8-substituted PCDD/F concentrations in air were 3.2, 4.0, 3.5 and 2.6 pg/cubic metre respectively for London, Cardiff, Manchester and Stevenage. Median Sigma 2,3,7,8-substituted PCDD/F deposition fluxes were 1.5 ng/m** (2)/day in London, 1.4 ng/m** (2)/day in Cardiff and Manchester and 0.79 ng/m** (2)/day in Stevenage. Seasonal variations in the PCDD/F concentrations were observed at all sites for both air and deposition, with concentrations/fluxes generally elevated during the winter.
Mostrar más [+] Menos [-]Commentary Article: Regulatory advances - Guide values for contaminated sites in Baden-Wuerttemberg
1994
Trenck, K.T. von der (Landesanstalt fuer Umweltschutz Baden-Wuerttemberg, Karlsruhe (Germany)) | Ruf, J. | Flittner, M.
The treatment of hazardous sites in Baden-Wuerttemberg is based on three legal documents: the state waste disposal act (LAbfG, 1990), the assessment committee directive (Kommissions VO, 1990), and the guide values directive (UM and SM B-W, 1993). The guide values directive was commonly issued by the Ministry of Labor, Health and Social Affairs and the Ministry of the Environment of the state of Baden-Wuerttemberg (UM and SM B-W, 1993) and contains a three-level hierarchy of numerical criteria and rules which serve as both screening levels during the investigation and as remediation objectives. The decision for the appropriate level of remediation is based on feasibility and environmental balance considerations. The levels are ordered as follows: - 1. (Background-Values) On principle, all remediations have to be based first on background levels. In the case of lack of feasibility or negative environmental balance for level-1 objectives use-specific requirements are considered next. - 2. (Assessment-Values for Worst Case Exposure Conditions) The generic requirements underlying level 2 afford appropriate protection for humans regarding the most sensitive uses of the environment. At least four resources are considered on this level: Groundwater as such and its use, the health of humans on contaminated sites, and soil with respect to growth and quality of plants. Barriers against migration of the contaminants, the effect of dilution, and abandonment of certain uses, etc., are not taken into consideration on level 2. - 3. (Site-Specific Requirements) Lack of feasibility or a negative environmental balance of level-2 objectives lead to consideration of site-specific circumstances which may alleviate the requirements.
Mostrar más [+] Menos [-]Deposition of semivolatile organic compounds to spruce needles. 1. Calculation of dry and wet fluxes
1994
Umlauf, G. (Bayreuth Univ. (Germany). Lehrstuhl fuer Oekologische Chemie und Geochemie) | McLachlan, M.
The deposition of atmospheric tetrachlorobenzene, pentachlorobenzene, hexachlorobenzene, alpha-HCH, gamma-HCH, DDT, DDE and the PCB congeners 52, 101, 138, 153 and 180 to spruce needles (Picea abies) was estimated for a period of 9 months. Accumulation in spruce as a result of dry gaseous deposition, particle bound deposition and wet deposition was calculated on the basis of the corresponding deposition rates and the compounds' concentrations in the different atmospheric compartments. The comparison of the calculated values with the concentrations of the compounds measured in 9-month-old spruce needles showed that for many compounds each deposition pathway could explain a large part of the concentrations found in the needles.
Mostrar más [+] Menos [-]Evaluation of fate and exposure models - Simulation of pesticide runoff at Rosemaund Farm (UK) using the SoilFug model
1994
Di Guardo, A. (Toronto Univ., Ontario (Canada). Inst. for Environmental Studies) | Williams, R.J. | Matthiessen, P. | Brooke, D.N. | Calamari, D.
A validation exercise of the SoilFug model using field runoff data from Rosemaund Farm (UK) is described. A comparison has been made of modelled and measured concentrations of several pesticides in surface water and soil during and after specific rain events following application. The field experiments were designed to obtain data on rainfall, outflows of water, pesticide application rates and concentrations in soil and water. The results were satisfactory for the undissociated pesticides (atrazine, carbofuran, dimethoate, isoproturon, lindane, simazine and trifluralin), whose concentrations in water were mostly predicted within an order of magnitude of measured data. The results for the dissociated pesticides (dichlorprop, MCPA, mecoprop) were less satisfactory, giving generally much higher predicted concentrations in water. The use of the SoilFug model is suggested for the calculation of predicted environmental concentrations (PECs) in water, since it generally produces acceptable results from a relatively small set of input data, most of which is generally available.
Mostrar más [+] Menos [-]Surfactant solubilization of hydrophobic compounds in soil and water. 1. Dodecylsulphate monomer and micellar partition coefficients for 28 polychlorinated biphenyls (PCBs) (41)
1994
Rahman, M.S. (Bangladesh Atomic Energy Commission, Dhaka (Bangladesh). Inst. of Food and Radiation Biology) | Paya-Perez, A.B. | Skejo-Andresen, H. | Larsen, B.R.
Reductions in the apparent soil-water partition coefficients (K(d)* ) for 28 polychlorinated biphenyls (PCBs) caused by the surfactant sodium dodecylsulphate (SDS) in the aqueous phase were studied. Above the critical micelle concentration (CMC) of the surfactant, K(d)* was reduced by 2-3 orders of magnitude, but even far below CMC at environmentally relevant surfacant concentrations significant reductions in Kd3 were observed. The plot of the soil-water partition coefficient (K(d)) divided by K(d)* versus the concentration of SDS allowed for the calculation of monomer (K(mn)(oc)) and micellar (K(mc)(oc)) surfactant-water parrition coefficients normalized to organic carbon for each PCB congener. K(mn)(oc) values were comparable with published values for the partition of PCBs between natural dissolved organic matter and lake water. K(mc)(oc) values were up to 30 times higher than K(mn)(oc) values and comparable with published octanol-water distribution coefficients. The findings of the present study underline the potential of surfactants at concentrations below their CMC to mobilize otherwise strongly bound hydrophobic compounds in soil-water systems.
Mostrar más [+] Menos [-]Determination of microbial activity in activated sewage sludge by dimethyl sulphoxide reduction - Evaluation of method and application
1994
Sklorz, M. (Bayreuth Univ. (Germany). Lehrstuhl fuer Oekologische Chemie und Geochemie) | Binert, J.
A method was developed to determine the dimethyl sulphoxide (DMSO) reduction rate in activated sewage sludge at nearly natural conditions. Linearity of microbially produced dimethyl sulphide with incubation time and sample size was shown. Apart from a fast, sensitive and highly reproducible automatic analysis of dimethyl sulphide, simultaneous determination of mineralisation, respiration and phenol degradation rates was possible. The DMSO reduction rate of samples taken from a municipal sewage plant ranged between 2 and 3 micromol/(g dry matter per h), respiration and mineralisation rates between 30 and 80 micromol/(g per h). Added (13)C(6)-phenol was completely degradated after 96 h of incubation. A half-life of 14 h was calculated assuming first order decay. Dose response curves were obtained by incubating samples for 2, 6, 25, and 96 hours after addition of pentachlorophenol. At an incubation time of 6 h, the EC(50) values ranged from 20 mg/L (DMSO reduction) to 30 mg/L (phenol degradation) up to 180 mg/L (respiration and mineralisation). Increasing the incubation time to 96 h resulted in a lower EC(50) of 9 mg/L for DMSO reduction, whereas it increased to 500 mg/L for respiration and mineralisation.
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