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491.
The emissions of greenhouse gas (GHG) from soils are of significant importance for global warming. The biological and physico-chemical characteristics of soil affect the GHG emissions from soils of different land use types. Methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) production rates from six forest and agricultural soil types in the Koteshwar hydropower reservoir catchments located in the Uttarakhand, India, were estimated and their relations with physico-chemical characteristics of soils were examined. The samples of different land use types were flooded and incubated under anaerobic condition at 30 °C for 60 days. The cumulative GHG production rates in reservoir catchment are found as 1.52 ± 0.26, 0.13 ± 0.02, and 0.0004 ± 0.0001 μg g soil?1 day?1 for CO2, CH4, and N2O, respectively, which is lower than global reservoirs located in the same eco-region. The significant positive correlation between CO2 productions and labile organic carbon (LOC), CH4 and C/N ratio, while N2O and N/P ratio, while pH of soils is negatively correlated, conforms their key role in GHG emissions. Carbon available as LOC in the reservoir catchment is found as 3–14% of the total ?C” available in soils and 0–23% is retained in the soil after the completion of incubation. The key objective of this study to signify the C, N, and P ratios, LOC, and pH with GHG production rate by creating an incubation experiment (as in the case of benthic soil/sediment) in the lab for 60 days. In summary, the results suggest that carbon, as LOC were more sensitive indicators for CO2 emissions and significant C, N, and P ratios, affects the GHG emissions. This study is useful for the hydropower industry to know the GHG production rates after the construction of reservoir so that its effect could be minimized by taking care of catchment area treatment plan. 相似文献
492.
493.
This paper presents an analysis using temporal moments to study multi-species radionuclide transport along a single fracture with variable fracture aperture in a fracture-skin-matrix system. In the present study, a decay chain having three elements is considered and transport of each member in the decay chain is modeled by solving a coupled system of partial differential equations for fracture, fracture-skin, and rock matrix using explicit finite difference method. Having obtained the concentration distribution, lower order temporal moments of radionuclide distribution are computed to analyze the effective velocity and macro-dispersion coefficient of radionuclides in the fracture. In the present study, effect of varying fracture aperture on transport characteristics of radionuclides is also analyzed. It is found that the fracture aperture variation profile has significant impact on radionuclide distribution along the fracture. Sensitivity analysis is carried out in a fracture-skin-matrix system with sinusoidal fracture aperture to study the effect of various parameters like fracture aperture thickness, fracture-skin porosity, fracture-skin diffusion coefficient, flow rate, radioactive decay constant, and Freundlich sorption isotherm exponent on transport characteristics of radionuclide. The results suggest that the above mentioned parameters significantly influence concentration, distribution, mobility, and effective macro-dispersion coefficient of radionuclides along the fracture. 相似文献
494.
495.
Thombare NS Aggarwal N Kumar R Gopal M 《Journal of environmental science and health. Part. B》2012,47(4):326-335
Crop losses due to bacterial pathogens are a major global concern. Most of the available pesticides for these pathogens suffer from various drawbacks such as complicated synthesis, high cost, high toxicity, pesticide resistance and environmental hazards. To overcome these drawbacks, the present study was undertaken to find a potent bactericide. Therefore, a series of compounds comprising bioactive furyl and oxazolone rings was synthesized under microwave irradiation and screened for in vitro antibacterial activity. The reactions were completed in fewer than 2 minutes with minimal use of solvents and resulted in high yields. These compounds were screened for antibacterial activity against plant pathogens, Xanthomonas oryzae, Ralstonia solanacearum and nitrifying bacteria, Nitrosomonas species under laboratory conditions. Five compounds were active as antibacterial agents against Xanthomonas oryzae and Ralstonia solanacearum. However, all compounds were effective against the Nitrosomonas species and the best one was 2-furyl-4-(3-methoxy-4-hydroxybenzylidene)-5(4H)-oxazolone. The study revealed the fast and environmentally friendly synthesis of bioactive title compounds, which also hold promise to be used as prototypes for the discovery of potent analogues. 相似文献
496.
Gupta B Rani M Kumar R Dureja P 《Journal of environmental science and health. Part. B》2012,47(8):823-831
In order to evaluate the deleterious effects of exposure to pesticides on a target population, a comprehensive study on their degradation in the various segments of ecosystem under varying environmental conditions is needed. In view of this, a study has been carried out on the metabolic pathways of thiram, a dithiocarbamate fungicide, in a variety of matrices namely water and soil under controlled conditions and plants in field conditions. The identification of degradation products was carried out in samples collected at various time points using LC-MS. The degradation products identified can be rationalized as originating by a variety of processes like hydrolysis, oxidation, N-dealkylation and cyclization. As a result of these processes the presence of some metabolites like dimethyl dithiocarbamate, bis(dimethyl carbamoyl) disulphide, bis(dimethyl dithiocarbamoyl) trisulphide and N-methyl-amino-dithiocarbamoyl sulphide was observed in all the cases. However, some different metabolites were observed with the change in the matrix or its characteristics such as cyclised products 2(N, N-dimethyl amino)thiazoline carboxylic acid and 2-thioxo-4-thiazolidine were observed only in plants. The investigations reflect that degradation initiates with hydrolysis, subsequently oxidation/dealkylation, followed by different types of reactions. The pathways seem to be complex and dependent on the matrices. Dimethyl dithiocarbamate and oxon metabolites, which are more toxic than parent compound, seem to persist for a longer time. Results indicate persistence vis-a-vis toxicity of pesticide and its metabolites and also provide a data bank of metabolites for forensic and epidemiological investigations. 相似文献
497.
Adak T Kumar J Dey D Shakil NA Walia S 《Journal of environmental science and health. Part. B》2012,47(3):226-231
Controlled release (CR) formulations of imidacloprid (1-(6 chloro-3-pyridinyl methyl)-N- nitro imidazolidin-2- ylideneamine) were prepared using novel amphiphilic polymers synthesized from polyethylene glycol and aliphatic diacids employing encapsulation technique. The bioefficacy of the prepared CR formulations was evaluated against major pests of soybean, namely stem fly, Melanagromyza sojae Zehntmer and white fly, Bemisia tabaci Gennadius along with a commercial formulation at the experimental farm of Indian Agricultural Research Institute (IARI), New Delhi during kharif 2009 and 2010. Most of the CR formulations of imidacloprid gave significantly better control of the pests compare to its commercial formulations, however the CR formulations, Poly [poly (oxyethylene-1000)-oxy suberoyl] amphiphilic polymer based formulation performed better over others for controlling of both stem fly incidence and Yellow Mosaic Virus (YMV) infestation transmitted by white fly. Some of the developed CR formulations recorded higher yield over commercial formulation and control. Nodulation pattern of soybean was not affected due to treatment of CR and commercial formulations of imidacloprid. Also the residues of imidacloprid in seed and soil at harvest were not detectable for both CR and commercial formulations. 相似文献
498.
KH Kim DX Ho CG Park CJ Ma SK Pandey SC Lee HJ Jeong SH Lee 《Environmental engineering science》2012,29(9):875-889
To investigate the environmental behavior of volatile organic compounds (VOCs) in urban areas, their concentrations were measured at four urban monitoring sites (namely, N, S, E, and W) in Seoul, Korea (February to December 2009). A total of 27 compounds were quantified that consist of four chemical groups: aromatic (AR), halogenated aromatic, halogenated paraffin, and halogenated olefin. Results were evaluated by focusing on these four functional groups just mentioned and their summation term as total VOC (TVOC) along with several individual species (mainly AR species, that is, benzene, toluene, ethylbenzene, and xylene). The highest concentration of chemical groups was found from AR (71.1±42.1?ppbC), while that for individual species confirmed the dominance of toluene (7.48±3.88?ppb). The analysis of spatial distribution indicated that high TVOC levels were recorded at sites N and W, while it was not so significant such as S and E in terms of TVOC budget. Seasonal variation of these VOCs was characterized by the peak values in December to reflect the combined effects of pronounced source activities and meteorological conditions. Analysis of spatial variations in VOC levels between the four urban sites indicated that their distributions are tightly affected by local source processes in each area. 相似文献
499.
Najam Akhtar Shakil Jitendra Kumar Pankaj Alka Pandey Vivek Ahluwalia Manish K. Singh 《Journal of environmental science and health. Part. B》2013,48(4):344-349
A series of novel N-alkyl-N-[1-(2-hydroxyphenyl) ethyl]amines were synthesized as potential new agents to control pests. Their structures were confirmed on the basis of IR, NMR and elemental analyses. Six new N-alkyl-N-[1-(2-hydroxyphenyl) ethyl]amines were prepared by reduction of corresponding Schiff bases using sodium borohydride in 80–87 % yields. These compounds were tested for their antifungal activity against two pathogenic fungi viz., Rhizoctonia bataticola ITCC 0482 and Sclerotium rolfsii ITCC 5226 and for insecticidal activity against insects of stored grain pest Callosobruchus analis. Fungicidal bioassay revealed that compound N-Decyl-N-[1-(2-hydroxyphenyl)ethyl]amine, was highly effective against R. bataticola (ED50 6.86 mg L?1) which was comparable with that of commercial fungicide hexaconazole (ED50 6.35 mg L?1). Also compounds N-Heptyl-N-[1-(2-hydroxyphenyl)ethyl]amine, N-Octyl-N-[1-(2-hydroxyphenyl)ethyl]amine and N-Nonyl-N-[1-(2-hydroxyphenyl)ethyl]amine displayed promising fungitoxicity against same pathogen. However, compound N-Heptyl-N-[1-(2-hydroxyphenyl)ethyl]amine was also found to be effective against S. rolfsii (ED50 4.92 mg L?1 as against 1.27 mg L?1 for hexaconazole). Compound N-Hexyl-N-[1-(2-hydroxyphenyl)ethyl]amine was most effective as insecticide followed by compound N-Octyl-N-[1-(2-hydroxyphenyl)ethyl]amine. LC50 values for these compounds were 155.0 and 275.0 mg L?1 respectively as against 36.70 mg L?1 for commercial insecticide dichlorovos. The results obtained from bioassays indicate that this class of compounds can be utilized for the design of new substances endowed with pesticidal activities. 相似文献
500.
A novel mixed bacterial culture was enriched from an endosulfan (6, 7, 8, 9, 10, 10 – hexachloro-1, 5, 5a, 6, 9, 9a-hexahydro-6, 9-methano-2, 3, 4-benzo (e) dioxathiepin-3-oxide) processing industrial surface soil. The cultures were successful in the degradation of aqueous phase endosulfan in both aerobic and anaerobic conditions. Using the cultures, endosulfan degradation in silty gravel with sand (GM) was examined via pilot scale reactor at an endosulfan concentration of 0.78 ± 0.01 mg g? 1 of soil, and optimized moisture content of 40 ± 1%. During operation, vertical spatial variability in endosulfan degradation was observed within the reactor. At the end of 56 days, maximum endosulfan degradation efficiency of 78 ± 0.2% and 86.91 ± 0.2% was observed in the top and bottom portion of the reactor, respectively. Both aerobic and anaerobic conditions were observed within the reactor. However, endosulfan degradation was predominant in anaerobic condition and the total protein concentration in the reactor was declined progressively down the soil depth. Throughout the study, no known intermediate metabolites of endosulfan reported by previous researchers were observed. 相似文献