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421.
In the present study biosorption technique, the passive accumulation of metals by biomass, is used for the removal of nickel from aqueous medium. The brown algae, Sargassum sp., in its natural and acid treated forms are used as a low cost sorbent. The adsorption characteristics of nickel on Sargassum sp. are evaluated as a function of time, pH, adsorbent dosage and initial concentration of nickel. The equilibrium adsorption data are fitted to Freundlich and Langmuir adsorption isotherm models and the model parameters are evaluated. Both the models represent the experimental data satisfactorily. The adsorption follows Lagergren first order kinetic model. The monolayer adsorption capacities of natural and acid treated forms of algae as obtained from Langmuir adsorption model are found to be 181 and 250mg g(-1) respectively. 相似文献
422.
Evidence for the "grasshopper" effect and fractionation during long-range atmospheric transport of organic contaminants 总被引:11,自引:0,他引:11
Gouin T Mackay D Jones KC Harner T Meijer SN 《Environmental pollution (Barking, Essex : 1987)》2004,128(1-2):139-148
Although there is indisputable evidence that long-range atmospheric transport (LRAT) of organic contaminants occurs on a global scale, uncertainties remain about the detailed mechanism and extent of this phenomenon as well as the physical-chemical properties which facilitate LRAT. In this study, we discuss how mass balance models and monitoring data can contribute to a fuller understanding of the mechanism and extent of LRAT. Specifically we address the issues of "grasshopping" or "hopping" (the extent to which molecules are subject to multiple hops as distinct from a single emission-deposition event) and "global fractionation" (the differing behavior of chemicals as they are transported). It is shown that simple mass balance models can be used to assist the interpretation of monitoring data while also providing an instrument that can be used to assess the LRAT potential and the extent of hopping that organic substances may experience. The available evidence supports the notion that many persistent organic pollutants experience varying degrees of "hopping" during their environmental journey and as a consequence become fractionated with distance from source. 相似文献
423.
Polyphenols of natural and synthetic origin are exploited in tanning sector to convert putrescible skin/hide to non-putrescible leather. However, only 30-40% of the inputs have been taken up for processing, the remaining is released as unspent. The existing conventional wastewater treatment systems are inefficient in removing or degrading these unspent polyphenols and thus detrimental to ecosystem. The present study demonstrates the evaluation of impact of both synthetic and natural polyphenols on biochemical and haematological properties of blood and serum in animal models. The results reveal that concentrations of polyphenols play a major role. At higher concentrations, irrespective of their nature, there was a marked change in the lipid profile (81% reduction), followed by insignificant change in glucose levels, RBC and WBC counts and other haematological parameters. At lower concentrations, no significant changes in the above said properties were observed. 相似文献
424.
Rishi P Woodward CL Kim WK Ricke SC 《Journal of environmental science and health. Part. B》2004,39(5-6):861-870
Virulence expression of Salmonella enterica serovar Typhimurium under iron limited condition was measured by beta-galactosidase (beta-gal) assay using a hilA-lacZY fusion strain and calculated as Miller units. hilA-lacZY beta-galactosidase assays were performed in brain heart infusion (BHI) and minimal media (M9), after iron chelation with 2, 2-dipridyl and iron-supplementation respectively. Before performing virulence assays, concentrations of iron in the media were estimated using ferrozine. Iron content was found to be more in BHI (42.6 microg dL(-1)) as compared to M9 (10.03 microg dL(-1)). beta-gal activity of Salmonella Typhimurium in BHI was generally less than that observed in M9. After exposure to various combinations of iron chelator in BHI, hilA-lacZY activity only increased at the highest concentration of chelator (2001 microM) but decreased in M9 media for all iron concentrations when compared to controls with no iron amendment. These results indicate that iron availability may influence S. Typhimurium hilA expression. 相似文献
425.
Anaerobic chemostats were used to investigate the effects of organic and hydraulic shock loads on the production of soluble microbial products (SMP). Production of SMP was found to increase during glucose spikes, reaching up 15% of the influent chemical oxygen demand. These SMP appear to be utilization-associated products produced as a result of the temporarily high organic load, and chemical analysis and ultrafiltration experiments revealed that most of these compounds are difficult to identify and that the majority of them are present in the low molecular weight (MW) range. Production of SMP also increased when the hydraulic retention time was reduced from 15 to 3 days, and an increase in DNA concentration in the bulk solution suggested enhanced cell lysis. Although the cause of lysis was not clear, it is believed that most of the SMP produced under such conditions were biomass-associated products following cell death. While the majority of these compounds lay in the low MW range, as much as 35% were found to have MWs greater than 1 kDa. During the period when the anaerobic chemostat was fed no alkalinity and the pH remained lower than 6.5 for more than a week, a slightly higher production of SMP and a shift in the MW distribution towards the production of higher MW SMP was observed. 相似文献
426.
427.
Pollution indicators and other microorganisms in river sediment 总被引:12,自引:0,他引:12
428.
Persistence of residues in water and sediment of a fresh-water lake after surface application of technical chlordane 总被引:1,自引:0,他引:1
P C Oloffs L J Albright S Y Szeto 《Journal of environmental science and health. Part. B》1978,13(1):47-58
A fresh-water lake, free from detectable pesticide residues before this study, was treated with a commercial formulation of technical chlordane. Water and sediment samples were analysed for chlordane residues 7, 24, 52, 279. and 421 days after treatment. Residues moved rapidly from the water to the lake bottom, supporting earlier results of a laboratory study with other organochlorines. In water, alpha- and gamma-chlordane concentrations remained proportional to total chlordane concentrations, as determined by total-peak area measurements of gas-liquid chromatogrammes. But in bottom sediments, alpha- and gamma-chlordane were more persistent than other constituents of technical chlordane, supporting recent evidence that quantification of technical chlordane residues on the basis of gamma-chlordane quantification only (or that of alpha- and gamma-chlordane only), can lead to incorrect results and that this method, although simple and fast, should no longer be recommended. 相似文献
429.
430.