خيارات البحث
النتائج 151 - 160 من 240
A wind tunnel for measuring the gaseous losses of environmental chemicals from the soil/plant system under field-like conditions
1994
Stork, A. (Forschungszentrum Juelich GmbH (Germany). Inst. fuer Radioagronomie) | Witte, R. | Fuehr, F.
Volatilization from treated areas is a major source of pesticide residues in air, fog, and rain. This may lead to long-range transport of pesticide residues to remote areas. Up to now most information on pesticide volatilization has come from laboratory experiments under controlled conditions. A new system has been designed and developed to measure the volatile losses of (l4)C-labelled chemicals after application; the method compares with agricultural practice of treating soils or plants grown in lysimeters. Sensitive analytical methods guarantee a distinction between residues of unchanged pesticide, its metabolites or (14)CO2 as a mineralization product released into the air.
اظهر المزيد [+] اقل [-]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.
اظهر المزيد [+] اقل [-]Determination of atrazine in rainfall and surface water by enzyme immunoassay
1994
Dankwardt, A. (Technische Univ. Muenchen, Freising (Germany). Lehrstuhl fuer Botanik) | Wuest, S. | Elling, W. | Thurman, M. | Hock, B.
Rainwater and surface water from four sites in Germany (Bavaria and Lower Saxony) were analyzed for atrazine by enzyme immunoassay from June 1990 until October 1992. The limit of quantification of the immunoassay was 0.02 microgram per litre with a middle of the test at 0.2 microgram per litre. About 60% of the samples contained measurable amounts of atrazine. Seasonal trends were observed, with the highest concentration in the summer months of up to 4 microgram per litre for rainwater and up to 15 microgram per litre for surface waters. The highest concentrations were found in agricultural areas, while in the investigated national parks up to 0.56 microgram per litre could be detected in rain warer. This points to long-range atmospheric transport from agricultural areas to pristine national parks. Samples from forest stands usually showed higher atrazine concentrations than samples from open fields. Deposition rates of 10 - 50 microgram per m** (2) per year were observed in the national parks and 10 - 180 microgram per m** (2) per year at the agricultural sites. Comparison of results obtained by enzyme immunoassay and GC/MS showed a good correlation of r = 0.95.
اظهر المزيد [+] اقل [-]Sulphur emission from large point sources in Europe
1994
Barrett, M. | Protheroe, R.
The ocean as part of the global carbon cycle
1994
Wolf-Gladrow, D. (Alfred-Wegener-Institut fuer Polar- und Meeresforschung, Bremerhaven (Germany))
The ocean plays a central role in the global carbon cycle being by far the largest active reservoir. Atmospheric CO2 level depends on the CO2 concentration in the ocean surface layer, which is relatively low compared to mean oceanic values due to biological and physical carbon pumps. Although the ocean may take up much of the carbon released by the increased burning of fossil fuels, this capacity is limited because of the chemical buffering and a mismatch in time scales (oceanic mixing is much slower than anthropogenic perturbations).
اظهر المزيد [+] اقل [-]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.
اظهر المزيد [+] اقل [-]Analysis of the Chinese energy system: implications for future CO2 emissions.
1994
Zhang, Z.X.
Water contamination and health
1994
Wang, Rhoda G. M.
This practical reference examines every potential means of exposure to water contaminants, provides in-depth discussion on toxicology, explains the most up-to-date techniques for evaluating human health risk, and develops a methodology for assessing the cumulative absorbed dose of contaminants through all routes of exposure, including ingestion, inhalation, and dermal. | Covering both federal and state efforts to monitor and treat water and discussing water safety regulations, Water Contamination and Health addresses indoor exposure to radon from water sources and exposure to chloroform in swimming pools ... highlights epidemiology, including the need to determine the actual correlation between chemical exposure and human health effects ... emphasizes the internal dose concept using a physiologically based pharmacokinetic model ... furnishes a case study on spontaneous abortion in pregnant women who were exposed to a specific chemical from a contaminated well ... explores the potential existence of carcinogens in water for human consumption ... and much more!
اظهر المزيد [+] اقل [-]Remediation of hazardous waste contaminated soils
1994
Wise, Donald L. (Donald Lee) | Trantolo, Debra J.
This unique, single-source reference offers a thorough treatment of the remediation of soils contaminated by hazardous wastes and the scientific and engineering issues that must be addressed in creating practical solutions for their reclamation. Presenting traditional physical and chemical methods as well as current and emerging biological methods, Remediation of Hazardous Waste Contaminated Soils discusses state-of-the-art techniques of site monitoring and assessment ... demonstrates a wide range of technical approaches that can be used in remediation ... elucidates hydrocarbon remediation ... illustrates actual, in-field remediation processes, highlighting bioremediation ... furnishes innovative process modeling studies ... organizes chapters by issues, case studies, traditional methods, and new technologies to facilitate cross-referencing of topics ... and much more. | Written by more than 50 internationally recognized experts from academia, government, and industry, Remediation of Hazardous Waste Contaminated Soils is an incomparable guide for environmental, pollution control, and chemical engineers; environmental scientists; industrial waste specialists; environmental and patent attorneys; remediation technicians; and upper-level undergraduate and graduate students taking courses in environmental management.
اظهر المزيد [+] اقل [-]Pollution control in fertilizer production
1994
Addresses various aspects of pollution control for the mining, production, transportation, and distribution of chemical fertilizers covering technologies for various segments of the industry, including raw materials production, end products, and by-products.
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