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971.
Kumari B Madan VK Singh J Singh S Kathpal TS 《Environmental monitoring and assessment》2004,90(1-3):65-71
Analysis of 84 farm gate samples of seasonal vegetables carried out on GC-ECD and GC-NPD systems equipped with capillary columns by using a multi residue analytical technique revealed that 26% samples contained residues above MRL values. The contamination was mainly with organophosphates followed by synthetic pyrethroids and organochlorines. Among organophosphates, residues of monocrotophos, quinalphos and chlorpyriphos exceeded the MRL value in 23% samples. Residues of monocrotophos were higher than MRL value in 3 samples of brinjal and one sample each of okra, cauliflower and smooth gourd, of chlorpyriphos in 3 samples of cauliflower and 8 of cabbage and of quinalphos in one sample each of okra and cauliflower. Among synthetic pyrethroids, cypermethrin was the major contaminant and its residue exceeded the MRL value in one sample each of brinjal, okra and cucumber. Only aldicarb among the carbamates was detected in potato. The residues of some organochlorines, i.e. HCH, DDT and endosulfan were found in all the samples but did not exceed the tolerence limit. 相似文献
972.
OBJECTIVE: To assess the effects of Washington, D.C. law prohibiting drivers' use of hand-held cell phones on such use. METHODS: Daytime observations of drivers were conducted at signalized intersections in D.C. in March 2004, several months before the law took effect on July 1, 2004, and again in October 2004. As a comparison, observations also were conducted in areas of Virginia and Maryland located close to the D.C. border. Maryland and Virginia placed no limitations on drivers' phone use. Use was observed for 36,091 vehicles in D.C., 25,151 vehicles in Maryland, and 28,483 vehicles in Virginia. RESULTS: The rate of talking on hand-held cell phones among drivers in D.C. declined significantly from 6.1% before the law to 3.5% after. Phone use declined slightly in Maryland and increased significantly in Virginia so that, relative to the patterns of hand-held phone use in the two states, phone use in D.C. declined 50%. Hand-held phone use in D.C. declined comparably among drivers of vehicles registered in all three jurisdictions. D.C. police issued 2,556 citations and 1,232 warnings for cell phone violations during July-November 2004. There were spates of media coverage when the law was passed and when it took effect. CONCLUSIONS: D.C.'s law prohibiting drivers' hand-held phone use had a strong effect on such use among drivers in D.C. Without ongoing publicized enforcement of the law, long-term compliance may be difficult to achieve. 相似文献
973.
J. Grune K. Sempert H. Haberstroh M. Kuznetsov T. Jordan 《Journal of Loss Prevention in the Process Industries》2013,26(2):317-323
This paper presents results of an experimental investigation on the deflagration and deflagration-to-detonation transition (DDT) in an obstructed (blockage ratio BR = 50%), semi-confined flat layer filled with uniform hydrogen–air mixtures. The effect of mixture reactivity depending on flat layer thickness and its width is studied to evaluate the critical conditions for sonic flame propagation and the possibility for detonation onset. The experiments were performed in a transparent, rectangular channel with a length of 2.5 m. The flat layer thickness was varied from 0.06 to 0.24 m and the experiments were performed for different channel widths of 0.3, 0.6 and 0.9 m. The experimental results show flame velocity vs. hydrogen concentration for different thicknesses and widths of the semi-confined flat layer. Three different flame propagation regimes were observed: slow subsonic flame (M << 1), sonic deflagration (M ~ 1) and detonation (M >> 1). It is shown that flame acceleration (FA) to sonic speed is independent of the width of the flat layer. The critical expansion ratio for effective flame acceleration to sonic speed was found to be linearly dependent on the reciprocal layer thickness. 相似文献
974.
Relationship between water solubility of chlorobenzenes and their effects on a freshwater green alga
The effective concentrations of benzene and 12 chlorobenzenes that reduced 50% of the primary productivity (EC50) of a freshwater green alga, , were determined. Benzene was the least toxic chemical and the toxicity increased as the degree of chlorine substitution in the aromatic ring increased. No EC50 value could be obtained for HCB. A quantitative relationship was found to exist between water solubility, lipophilicity and the EC50. A good correlation was also observed between the EC50 for this alga and other toxicity data for various aquatic biota. 相似文献
975.
Three oxbow lakes in northwestern Mississippi, USA, an area of intensive agriculture, were assessed for biological impairment from historic and current-use pesticide contamination using the amphipod, Hyalella azteca. Surface water and sediment samples from three sites in each lake were collected from Deep Hollow, Beasley, and Thighman Lakes from September 2000 to February 2001. Samples were analyzed for 17 historic and current-use pesticides and selected metabolites. Ten-day H. azteca survival and growth (as length and dry weight) were measured to determine the degree of biological impairment. Maximum number of detectable pesticides in surface water from Deep Hollow, Beasley and Thighman Lakes was 10, 11, and 17, respectively. Maximum number of detectable pesticides in lake sediments was 17, 17, and 15, respectively. Bioassay results indicated no observable survival effects on H. azteca exposed to surface water or sediment from any lake examined and no growth impairment in animals exposed to lake sediments. However, growth was significantly impaired in surface water exposures from Deep Hollow Lake (2 sites) and Beasley Lake (1 site). Statistically significant relationships between growth impairment (length) and cyanazine, methyl parathion, λ-cyhalothrin, chlorfenapyr, and pp′DDE surface water concentrations in Deep Hollow Lake as well as trifluralin, atrazine, and methyl parathion in Beasley Lake were observed. Although pesticide frequency and concentrations were typically greater in sediment than surface water, bioassay results indicated decreased availability of these pesticides in sediment due to the presence of clay and organic carbon. Growth impairment observed in surface water exposures was likely due to complex interaction of pesticide mixtures that were present. 相似文献
976.
Grahovac ZM Mitić SS Pecev ET Pavlović AN 《Journal of environmental science and health. Part. B》2010,45(8):783-789
In the present study, a new sensitive and simple kinetic-spectrophotometric method for the determination of the insecticide diflubenzuron [1-(4-chlorophenyl)-3-(2,6-diflubenzoil)urea] is proposed. The method is based on the inhibited effect of diflubenzuron on the oxidation of sulphanilic acid (SA) by hydrogen peroxide in phosphate buffer in presence Cu(II) ion. Diflubenzuron was determined with linear calibration graph in the interval from 0.31 to 3.1 μg mL?1 and from 3.1 to 31.0 μg mL?1. The optimized conditions yielded a theoretical detection limit of 0.18 μg mL?1 corresponding to 0.036 mg kg(-1)mushroom sample based on the 3S(b) criterion. The RSD is 5.03-1.83 % and 2.81-0.71 % for the concentration interval of diflubenzuron 0.31-3.1 μg mL?1 and 3.1-31.0 μg mL?1, respectively. The reaction was followed spectrophotometrically at 370 nm. The kinetic parameters of the reaction are reported, and the rate equations are suggested. The developed procedure was successfully applied to the rapid determination of diflubenzuron in spiked mushroom samples of different mushroom species. The HPLC method was used like a comparative method to verify results. 相似文献
977.
Ramos-Gómez J Coz A Viguri JR Luque A Martín-Díaz ML DelValls TÁ 《Environmental pollution (Barking, Essex : 1987)》2011,159(7):1914-1922
Biomarkers comprising activities of biotransformation enzymes (ethoxyresorufin-O-deethylase -EROD-, dibenzylfluorescein dealkylase -DBF-, glutathione S-transferase -GST), antioxidant enzymes (glutathione reductase -GR- and glutathione peroxidase -GPX), lipid peroxidation -LPO- and DNA strand breaks were analyzed in the clam Ruditapes philippinarum caged at Cádiz Bay, Santander Bay and Las Palmas de Gran Canaria (LPGC) Port (Spain). Sediments were characterized. Digestive gland was the most sensitive tissue to sediment contamination. In Cádiz Bay, changes in LPO regarding day 0 were related with metals. In LPGC Port, DBF, EROD, and GST activity responses suggested the presence of undetermined contaminants which might have led to DNA damage. In Santander Bay, PAHs were related with EROD activity, organic and metal contamination was found to be associated with GR and GST activities and DNA damage presented significant (p < 0.05) induction. R. philippinarum was sensitive to sediment contamination at biochemical level. Biomarkers allowed chemical exposure and sediment quality assessment. 相似文献
978.
J. G. Munson Jr. R.E. Lewis G.T. Weber W.E. Brayton 《Journal of the Air & Waste Management Association (1995)》2013,63(11):1059-1062
At the Clairton Coke Works of the United States Steel Corporation (the world’s largest coke plant), with coal charges of about 30,000 net tons per day, a system designated as “stage charging” has been developed for charging coal into the coke oven chamber without emissions to the atmosphere. The principles of the system are based on controlled sequential flow of the coal from the charging hoppers, during which the oven chamber is maintained under a very slight negative pressure condition by use of steam aspiration in the offtakes for on-the-main charging. The techniques are basic but require knowledge of the coal characteristics, adequate and properly maintained aspirating systems, including clean offtake piping, control of coal volume in the individual hoppers, and last, and probably most important, adherence by the operating crew to specific charging and leveling practices. 相似文献
979.
980.
HERMAN T. FRANSSEN 《Natural resources forum》1977,1(2):157-165
Evaluation of energy options and adoption of appropriate policies require rigorous demand and supply projections. The wider the options, the more difficult the task. The author reviews the various projections which have been made in the United States to support a policy toward energy independence. He sets the stage for a similar review of the 1977 National Energy Outlook, scheduled for publication early in the year, in a subsequent issue of the Forum. 相似文献