Detection of Lead in Vegetables with New Chromogenic Reagent by Spectrophotometry

A new simple, rapid selective and highly sensitive chromogenic reagent dibromo-p-methyl-carboxyazo (DBMCA) was synthesized and studied in detail for the spectrophotometric detection of lead. In 0.25 M phosphoric acid medium, which greatly increases the selectivity, Lead reacts with DBMCA to form a 1:2 blue complex having a sensitivity absorption peak at 646 nm. Under optimal conditions, Beer's Law is obeyed over the range from 0.09 to 0.8 microg mL(-1) Pb (II) and the apparent molar absorptivity is 1.03 x 10(5) mL(-1) cm(-1). The detection limit and the variation coefficient were found to be 2.12 microg mL(-1) and 1.0% respectively. It is found that, except for Ca (II) and Ba (II) all foreign ions studied do not interfere with detection. The interference caused by Ca (II) and Ba (II) can be easily eliminated by prior extraction with potassiumiodide-methylisobutylketone. The proposed method has been applied successfully for to the detection of Lead in vegetable leaves with good results.     

Bacterial communities and enzyme activities of PAHs polluted soils

Three soils (i.e. a Belgian soil, B-BT, a German soil, G, and an Italian agricultural soil, I-BT) with different properties and hydrocarbon-pollution history with regard to their potential to degrade phenanthrene were investigated. A chemical and microbiological evaluation of soils was done using measurements of routine chemical properties, bacterial counts and several enzyme activities. The three soils showed different levels of polycyclic aromatic hydrocarbons (PAHs), being their contamination strictly associated to their pollution history. High values of enzyme activities and culturable heterotrophic bacteria were detected in the soil with no or negligible presence of organic pollutants. Genetic diversity of soil samples and enrichment cultures was measured as bands on denaturing gradient gel electrophoresis (DGGE) of amplified 16S rDNA sequences from the soil and enrichment community DNAs. When analysed by Shannon index (H'), the highest genetic biodiversity (H'=2.87) was found in the Belgian soil B-BT with a medium-term exposition to PAHs and the poorest biodiversity (H'=0.85) in the German soil with a long-term exposition to alkanes and PAHs and where absence, or lower levels of enzyme activities were measured. For the Italian agricultural soil I-BT, containing negligible amounts of organic pollutants but the highest Cu content, a Shannon index=2.13 was found. The enrichment of four mixed cultures capable of degrading solid phenanthrene in batch liquid systems was also studied. Phenanthrene degradation rates in batch systems were culture-dependent, and simple (one-slope) and complex (two-slope) kinetic behaviours were observed. The presence of common bands of microbial species in the cultures and in the native soil DNA indicated that those strains could be potential in situ phenanthrene degraders. Consistent with this assumption are the decrease of PAH and phenanthrene contents of Belgian soil B-BT and the isolation of phenanthrene-degrading bacteria. From the fastest phenanthrene-degrading culture C(B-BT), representative strains were identified as Achromobacter xylosoxidans (100%), Methylobacterium sp. (99%), Rhizobium galegae (99%), Rhodococcus aetherovorans (100%), Stenotrophomonas acidaminiphila (100%), Alcaligenes sp. (99%) and Aquamicrobium defluvium (100%). DGGE-profiles of culture C(B-BT) showed bands attributable to Rhodococcus, Achromobacter, Methylobacterium rhizobium, Alcaligenes and Aquamicrobium. The isolation of Rhodococcus aetherovorans and Methylobacterium sp. can be consistent with the hypothesis that different phenanthrene-degrading strategies, cell surface properties, or the presence of xenobiotic-specific membrane carriers could play a role in the uptake/degradation of solid phenanthrene.     

Oxygenated fuel induced cosolvent effects on the dissolution of polynuclear aromatic hydrocarbons from contaminated soil

The cosolvent-induced dissolution of polynuclear aromatic hydrocarbons (PAHs) from contaminated soil caused by oxygenated fuel spills was studied. Oxygenated fuel induces a solvent flushing effect on the contaminated soil due to the high content of oxygenated compounds (i.e., methanol, ethanol, and methyl tert butyl ether (MTBE)). The miscible displacement techniques were applied to evaluate the increased potential for secondary contamination in an impacted site. Significant solubility enhancement of the 18 PAHs monitored during fuel spill simulation and cosolvent flushing is clearly evident when compared to normal water dissolution. The breakthrough concentration profile for each PAH constituent was integrated over the cumulative effluent volume (i.e., the zeroth moment) to determine the total PAH mass removed during the experiment. The removal efficiency of PAHs ranges from 46.6% to 99.9% in three oxygenated fuels (i.e., M85, E85, and oxygenated gasoline) during the fuel spill. Several factors including hydrophobicity of compounds, nonequilibrium dissolution due to nonuniform coal tar distribution, and heterogeneous media properties affect the oxygenated compound-induced dissolution process. This study provides a basis to predict the facilitated transport of hydrophobic organic compounds from subsurface environment due to the cosolvent effects of oxygenated fuels.     

Chronic effects of mercuric chloride on the activities of some enzymes in certain tissues of the fresh water murrel,

Alterations in the activities of some enzymes in the brain, gills, intestine, kidney, liver and muscles have been examined in the fresh water murrel, , after exposure to a sublethal concentration of mercuric chloride (3 μg/1) for 15, 30 and 60 days. The results revealed that after 15 days of exposure amino acid oxidase activity was elevated in brain and liver and inhibited in intestine. The activity of xanthine oxidase was increased in gills, and inhibited in kidney. Thirty days exposure produced significant inhibition in the activities of malate dehydrogenase in liver, glutamate dehydrogenase in gills and brain, aminoacid oxidase in gills, and xanthine oxidase in liver and intestine. In contrast, glutamate dehydrogenase in intestine, kidney and liver and aminoacid oxidase in brain and liver were elevated. After 60 days of treatment, a decrease in the activity of glucose-6-phosphatase was recorded in gills, intestine, kidney and liver. Hexokinase activity in kidney and liver, and malate dehydrogenase in all the six tissues were inhibited. Glutamate dehydrogenase activity in intestine, kidney and liver remained higher than in control fish. In brain, kidney and liver the activity of aminoacid oxidase was elevated, but in gills the enzyme activity decreased. Xanthine oxidase activity was inhibited in intestine and liver.     

Optimum Dose Of Lime And Fly Ash For Treatment Of Hexavalent Chromium–Contaminated Soil

The presence of hexavalent chromium, Cr(VI), in soil is an environmental concern due to its effect on human health. The concern arises from the leaching and the seepage of Cr(VI) from soil to groundwater. In this paper, a stabilization technology to prevent this problem was simulated on an artificial soil contaminated with hexavalent chromium. The process is a physico-chemical treatment in which the toxic pollutant is physically entrapped within a solid matrix formed by the pozzolanic reactions of lime and fly ash to reduce its leachability and, therefore, its toxicity. This paper presents the optimum ratio of fly ash and lime in order to stabilize artificial soils contaminated with 0.4 wt.% of Cr (VI) in a brief term process. The degree of chromium released from the soil was evaluated using a modified Toxicity Characteristic Leaching Procedure (TCLP) by US Environmental Protection Agency (EPA). Overall, experimental results showed reduced leachability of total and hexavalent chromium from soils treated with both fly ash and quicklime, and that leachability reduction was more effective with increasing amount of fly ash and quicklime. Stabilization percentages between 97.3% and 99.7% of the initial chromium content were achieved, with Cr(VI) concentration in the TCLP leachates below the US EPA limit for chromium of 5 mg/l. Adequate treatment was obtained after 1 day of curing with just 25% fly ash and 10% quicklime.     

APPLICATION OF THE HEC-4 MONTHLY STREAM FLOW SIMULATION MODEL1

ABSTRACT: The HEC-4 monthly stream flow simulation model, developed by the Hydrologic Engineering Center, Davis, California, is used to extend the available historical stream flow records in the Central Ohio area. The principal objective of this paper is to examine the effectiveness of the HEC-4 model in generating synthetic monthly flows. Important statistical parameters are evaluated in order to relate the statistical properties of the historical and generated flows. In doing so, it is observed that the mean, standard deviation, and skewness of the generated flows are consistently larger than the corresponding estimates based on historical flows. However, results show that these statistics, as well as the lag-1 serial correlation, are generally well maintained by the generated sequences. The degree to which any statistical dissimilarities would be critical, from an engineering design point of view, is demonstrated by utilizing their low flow characteristics. Estimates of reservoir safe-yields, based on a nonsequential mass-curve analysis of the historical and generated low flows, indicate a nominal difference in this particular study.     

对中国排污收费制度改革的思考

排污收费制度是中国环境政策中一个核心的管理手段。它是我国为强化环境管理，运用经济手段，促进工业企业污染防治的一个独特的制度。在新的市场经济体制下和环境目标下，这项制度已不能适应社会主义市场经济发展的需要，因而在必要进行改革以适应新形势下环境保护工作的需要。在分析现行排污收费制度基础上，对我国现行的收费制度、政策和标准等的改革提出见解。     

云南潞西上芒岗红色粘土型金矿地质特征

潞西上芒岗红色粘土型金矿赋存于下二叠统岩溶面之上的第三、第四系红色粘土层中 ,矿体形态受地形控制明显 ,呈似层状。品位较高 ,规模中等 ,适合于露天开采。矿体的红土化作用不彻底 ,去硅富铁铝能力低 ,常见高岭石与伊利石共生。矿石中石英、褐铁矿、粘土矿物为主要载金矿物。成矿物质来自燕山中晚期形成的中侏罗勐嘎组中段与二叠系的沙子坡组的断层接触破碎带内的卡林型金矿。在湿热条件下 ,金发生活化、迁移、富集 ,在潜水面附近成矿。