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61.
As part of a program aimed at developing a field process for cleanup of PCB contaminated soils using photochemistry in basic 2-propanol, additional details of the dechlorination pathway are presented. The mechanism involves a chain reaction with both homolytic photochemical C-Cl bond fission and electron transfer steps producing PCB anion radicals. Kinetics of dechlorination of various congeners show patterns of relative rates associated with the basic 2-propanol medium that are not found in other media because both electron transfer and photochemical homolysis steps determine overall rates of dechlorination and govern the pathways and relative concentrations of intermediates. The electron transfer steps display opposite structure-reactivity correlations to the photo-homolysis, C-Cl bond fission steps. Oxygen quenching is shown to differentially affect both types of steps. In contrast to the suggestion that inter system crossing can be highly efficient with reaction originating from a PCB triplet, oxygen quenching data suggest that a significant minimum of the quantum yield is non-quenchable, presumably because of a reaction path from the PCB singlet. This may help to explain why exclusion of air is not entirely necessary in practice. 相似文献
62.
Avijit?DasEmail author KVSS?Krishna Rajeev?Kumar Anindya?Das Siladitya?Sengupta Joy?Gopal?Ghosh 《Environmental science and pollution research international》2016,23(22):22454-22466
Lead isotopic ratios (LIR) of eight common food items, street dust, coal, diesel, sediments, lead ore and rainwater from India have been reported for the first time in this paper. This study characterized the source and extent of lead pollution in the different foodstuff consumed in Kolkata, a major metropolis of eastern India. The atmospheric lead input to the food items, sold openly in busy roadside markets of the city, has been quantified. The mean 207/206 and 208/206 LIRs of the eight food items ranged from 0.8847 to 0.8924 and 2.145 to 2.167, respectively. Diesel had the highest mean 207/206 and 208/206 values of 0.9015 and 2.1869, respectively, apart from the lead ore. The food items had a mean lead concentration between 3.78 and 43.35 mg kg?1. The two ratio scatter plots of all the different environmental matrices were spread linearly between the uncontaminated Ichapur sediment and diesel. The 207/206 LIRs of the coal with a mean of 0.8777 did not fall in the linear trend, while the street dust and food samples overlapped strongly. The rainwater sample had a 207/206 LIR of 0.9007. Contaminated sediments in Dhapa, the repository of the city’s municipal garbage, had a mean 207/206 LIR of 0.8658. The corresponding value obtained from the sewage-fed vegetable grown there was 0.8058. The present study indicated that diesel was one of the main contributor to Pb pollution. The atmospheric lead contribution to the food items was in the range of 68.48–86.66 %. 相似文献
63.
64.
Pooja Doshi Gopal Srivastava Gauri Pathak Madhurima Dikshit 《Waste management (New York, N.Y.)》2014,34(10):1836-1846
The present study aims to investigate the potential of nonedible oilseed Jatropha (Jatropha curcas) and Karanja (Pongamia pinnata) defatted residual biomasses (whole seed, kernel, and hull), as solid biofuel. These biomasses showed good carbon contents (39.8–44.5%), whereas, fewer amounts were observed for sulfur (0.15–0.90%), chlorine (0.64–1.76%), nitrogen (0.9–7.2%) and ash contents (4.0–8.7%). Their volatile matter (60.23–81.6%) and calorific values (17.68–19.98 MJ/kg) were found to be comparable to coal. FT-IR and chemical analyses supported the presence of good amount of cellulose, hemicellulose and lower lignin. The pellets prepared without any additional binder, showed better compaction ratio, bulk density and compressive strength. XRF analysis carried out for determination of slagging–fouling indices, suggested their ash deposition tendencies in boilers, which can be overcome significantly with the optimization of the blower operations and control of ash depositions. Thus, overall various chemical, physical properties, thermal decomposition, surface morphological studies and their high biofuel reactivity indicated that residual biomasses of Jatropha and Karanja seeds have high potential to be utilized as a solid biofuel. 相似文献
65.
M. Shah Nawaz Chowdhury M. Shahadat Hossain Nani Gopal Das Prabal Barua 《Journal of Coastal Conservation》2011,15(1):163-180
The Naaf River estuary is one of the large estuaries in the Bangladesh coastal region not to have been affected by extensive
human disturbance. This research provides information about the fisheries diversity status by Estuarine Set Bag Net (ESBN)
sampling relation to physicochemical variables in both spatio-temporal scales. About 25 km of the lower estuary was divided
into six zones for sample collection by considering the accessibility and availability of the ESBN operation, fish landing
centers and location of the fishing villages. In total 48 samples have been analyzed which were taken throughout March to
October 2006. To quantify the species diversity, all fisheries data were analyzed by using EstimateS and EcoSim software which
accounts the different diversity indices viz., species richness, Shannon–Wiener diversity Index, Dominance and Evenness index.
The research results demonstrate that the Naaf River estuary is a habitat of 161 (species richness, Sobs = 161, Choa 1 = 162 ± 2.34,
ACE = 161.73) different species which belong to 98 fin fishes, 23 shrimps and prawns, 13 crabs, 11 molluscs, 3 echinoderms,
4 other crustaceans; while 9 remain unidentified. Results on the aquatic environment, mainly salinity and turbidity were found
to have a major influence on their occurrence and distribution. All the findings indicated that the Naaf River estuary is
a highly productive system and provides a favourable environment for large variety of estuarine species assemblages. 相似文献
66.
Gopal Jeya Elumalai Ganesan Tajuddin Aimi Asilah Haji Ito Yoshikazu Vajiravelu Sivamurugan Ravikumar Dhanalakshmi 《Journal of Polymers and the Environment》2022,30(6):2614-2630
Journal of Polymers and the Environment - In this investigation, the use of phosphotungstic acid (PWA) and phosphomolybdic acid (PMA) as well as Zn2+ containing kaolin and bentonite explored for... 相似文献
67.
D. G. M. Senevirathna G. Achari J. P. A. Hettiaratchi 《Environmental Modeling and Assessment》2007,12(1):1-11
Errors associated with the closed flux chamber technique, used to measure surface emissions from landfills, were investigated
by using a combination of numerical modeling and laboratory studies. A transient-state, advective–dispersive–reactive model
was developed and used in conjunction with its steady-state version to quantify the errors associated with closed flux chambers.
In developing the model, all four major gases, CH4, O2, CO2, and N2, and the oxidation of CH4 to CO2 were considered. Laboratory experiments were conducted on a monolayered as well as a two-layered landfill cover system to
calibrate and verify the model. The model was used to develop a plot of the percentage errors associated with closed flux
chambers of different dimensions and surface flux rates. 相似文献
68.
Contributing to the debate on the causes of Himalayan environmental degradation, the status and management of four watersheds
in the Upper Pokhara Valley were studied using information available from land use analysis, household surveys conducted in
1989 and 1992, deliberations held with villagers, and field observations. Accordingly, areas under forests and grazing lands
were found being depleted at relatively high rates between 1957 and 1978 due mainly to the government policy of increasing
national revenue by expansion of agricultural lands, nationalization of forests, steadily growing population, and dwindling
household economy. Despite the steady growth of population, this process had remarkably slackened since 1978, owing primarily
to remaining forests being located in very, steep slopes and implementation of the community forestry program. Forests with
relatively sparase tree density, however, and grazing lands in the vicinity of settlements have been undergoing degradation
due to fuelwood and fodder collection and livestock grazing. In many instances, this is aggravated by weak resource management
institutions. Being particularly aware of the economic implication of land degradation, farmers have adopted assorted land
management practices. Still a substantial proportion ofbari lands in the hill slopes is vulnerable to accelerating degradation, as the arable cropping system is being practiced there
as well. The perpetuation of the local subsistence economy is certain to lead, to a further deterioration of the socioeconomic
and environmental conditions of watersheds. To facilitate environmental conservation and ecorestructuring for sustainable
development, a broad watershed management strategy is outlined with focus on alleviating pressure on natural resources. 相似文献
69.
A model to simulate gas, heat, and moisture transport through a sanitary landfill has been developed. The model not only considers
the different processes that go on in a landfill but also the oxidation of methane in the final cover. The model was calibrated
using published results and field data from a pilot scale landfill in Calgary. The model captures the physics of the different
processes quite well. Simulations from the model show that waste permeability had a significant impact on the temperature,
pressure distribution, and flux from a landfill. The presence of the final and intermediate covers enhanced the gas storage
capacity of the landfill. Biodegradation of the waste was enhanced as the final cover minimized the atmospheric influences.
In addition, the composition of landfill gas emitted to the atmosphere was significantly different from the composition of
gas generated in landfill due to the presence of covers as some of the methane is oxidized to carbon dioxide. There was no
significant benefit of using a final cover of higher depth. The presence and number of intermediate covers had an impact on
gas flux and temperature distribution within a landfill. 相似文献
70.
As in other mountain regions of Asia, agricultural lands in the Chittagong Hill Tracts (CHT) of Bangladesh are undergoing
degradation due primarily to environmentally incompatible land-use systems such as shifting cultivation (jhum) and annual cash crops. The suitable land-use systems such as agroforestry and timber tree plantation provide benefit to
the society at large, but they might not provide attractive economic benefits to farmers, eventually constraining a wide-scale
adoption of such land-use systems. Therefore, it is essential to evaluate agricultural land-use systems from both societal
and private perspectives in the pursuit of promoting particularly environmentally sustainable systems. This article evaluated
five major land-use systems being practiced in CHT, namely jhum, annual cash crops, horticulture, agroforestry, and timber plantation. The results of the financial analysis revealed the
annual cash crops as the most attractive land use and jhum as the least attractive of the five land-use systems considered under the study. Horticulture, timber plantation, and agroforestry,
considered to be suitable land-use systems particularly for mountainous areas, held the middle ground between these two systems.
Annual cash crops provided the highest financial return at the cost of a very high rate of soil erosion. When the societal
cost of soil erosion is considered, annual cash crops appear to be the most costly land-use system, followed by jhum and horticulture. Although financially less attractive compared to annual cash crops and horticulture, agroforestry and timber
plantation are the socially most beneficial land-use systems. Findings of the alternative policy analyses indicate that there
is a good prospect for making environmentally sustainable land-use systems, such as agroforestry and timber plantation, attractive
for the farmers by eliminating existing legal and institutional barriers, combined with the provision of necessary support
services and facilities.
相似文献
Golam RasulEmail: |