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341.
Subsurface-flow constructed wetlands (CWs) wastewater treatment typically results in satisfactory organics removal. However, the removal of nutrients, particularly nitrogen, is often unreliable, and typically less than desired, and nitrogen transformations in wetlands systems are not well-understood. The principal objective of this study was to establish a basis for quantification of nitrogen transformations through subsurface flow CW systems. Actual performance data from a full-scale facility located near Lincoln, Nebraska, were used to calibrate a proposed nitrogen transformations model, which, in turn, was used to replicate and predict the wetlands performance. To realize this objective, a compartmental analysis technique, which uses a set of differential equations and nonlinear optimization numerical methods, was used for solving nitrogen transformation rates and for predicting wetland performance. The model satisfactorily reproduced the mean effluent concentrations for organic nitrogen, ammonium-nitrogen, and nitrate-nitrogen, but with lesser accuracy with respect to peak high and low effluent concentrations. Nitrogen mass balance in the wetland was used to identify likely nitrogen transformation pathways. Generally, it was found that approximately one-third of the influent nitrogen mass was removed through nitrification and denitrification, one-third was removed through vegetative assimilation, and the remainder was discharged in the wetland effluent. 相似文献
342.
Yallappa Rajashekar Lingamallu J. M. Rao Thimmappa Shivanandappa 《Die Naturwissenschaften》2012,99(10):843-852
Natural sources for novel insecticide molecules hold promise in view of their eco-friendly nature, selectivity, and mammalian safety. Recent progress in understanding the biology of insect olfaction and taste offers new strategies for developing selective pest control agents. We have isolated two natural insecticidal molecules from edible roots of Decalepis hamiltonii named Decalesides I and II, which are novel trisaccharides, highly toxic to household insect pests and stored-product insects. We have experimentally shown that insecticidal activity requires contact with tarsi on the legs but is not toxic orally. The insecticidal activity of molecules is lost by hydrolysis, and various sugars modify toxic response, showing that the insecticidal activity is via gustatory sites on the tarsi. Selective toxicity to insects by virtue of their gustatory site of action and the mammalian safety of the new insecticides is inherent in their chemical structure with 1-4 or 1-1 α linkage that is easily hydrolyzed by digestive enzymes of mammals. Decalesides represent a new chemical class of natural insecticides with a unique mode of action targeting tarsal chemosensory/gustatory system of insects. 相似文献
343.
基于非本地物种的毒性数据推导出的水质基准一直存在争议,质疑者提出应有针对不同生物区系的水质基准。而这个问题在中国尤为突出。本文作者搜集了38种污染物对本地物种和非本地物种的毒性数据,比较了这些生物的HC5和物种敏感度分布,结果显示,基于非本地物种推导的水质基准有74%的确定性可以有效保护中国的水生态系统。如果采用评价因子(AF=5)来校正基准,那么可以获得90%的确定性。
精选自Xiaowei Jin, Zijian Wang, Yeyao Wang, Yibing Lv, Kaifeng Rao, Wei Jin, John P. Giesy and Kenneth M. Y. Leung. Do water quality criteria based on nonnative species provide appropriate protection for native species? Environmental Toxicology and Chemistry: Volume 34, Issue 8, pages 1744–1750, August 2015. DOI: 10.1002/etc.2985
详情请见http://onlinelibrary.wiley.com/doi/10.1002/etc.2985/full 相似文献
344.
Satyavathi Chinni Ritindra N. Khan V. Uma Devi Prabhakara Rao Yallaprgada 《Chemistry and Ecology》2013,29(3):157-170
Lead tolerance in Penaeus indicus post-larvae (PL) was studied in relation to the water variables: salinity, temperature and pH. the LC50 for 96 hrs was 7.22 ppm at ambient conditions of salinity (20%o), temperature (29°C) and pH (7.2). the post-larvae were found to be sensitive to salinity variations with a significant (P < 0.05) low LC50 values at lower (2%o) and higher (29%o) ranges. Though a decrease in LC50 value was observed both at higher (45°C) and lower (10°C) temperatures, it was significantly (P < 0.05) low only at higher temperature indicating more toxicity. the LC50 values also showed a significant (P < 0.05) decrease in acidic (pH 2.8) and alkaline (pH 11.0) conditions. the data indicate that lead toxicity increases in the PL of P. indicus with variations in the water variables. 相似文献
345.
K. N. Chetty D.S.V. Subba Rao L. Drummond D. Desaiah 《Journal of environmental science and health. Part. B》2013,48(5):525-544
Abstract The immuno‐biochemical effects of cobaltous chloride in rats receiving iron‐sufficient and deficient diets were investigated. Rats receiving 100 ppm or more cobalt showed a significant reduction in thymus and body weights along with a marked decrease in hemoglobin, hematocrit, sheep agglutinins and plaque forming cells. These effects were more pronounced in rats receiving cobalt mixed with iron‐deficient diet than those fed on iron‐sufficient diet. The Na+‐K+ and mitochondrial (Oligomycin‐sensitive) Mg2+ATPase activities in brain and liver of rats fed with iron‐deficient diets were decreased significantly. However, the ATPase activities in these tissues from rats fed with cobalt mixed with iron‐sufficient diets were not altered. 相似文献
346.
Geochemistry of the suspended sediment in the estuaries of the Mandovi and Zuari rivers, central west coast of India 总被引:1,自引:0,他引:1
Pratima M. Kessarkar R. Shynu V. Purnachandra Rao Feng Chong Tanuja Narvekar Jing Zhang 《Environmental monitoring and assessment》2013,185(5):4461-4480
The geochemistry of the suspended particulate matter (SPM) collected during the monsoon was determined to identify the sources of SPM and to understand the physicochemical processes in the Mandovi and Zuari river estuaries. The concentrations of SPM decrease seaward in both estuaries, but are relatively high at bay stations. Kaolinite is the most dominant clay mineral in the upstream of both rivers. Smectite increases seaward in both estuaries and is abundant in the bay. Upstream stations of Mandovi, where ore deposits are stored on the shore, exhibit high Fe, Mn, total rare earth elements (∑REE), and middle REE- and heavy REE-enriched patterns. Channel stations of both estuaries exhibit middle REE- and light REE-enriched patterns, which gradually changed seaward to middle REE- and heavy REE-enriched patterns. Canal stations exhibit the highest concentrations of major and trace metals. High metal/Al ratios occur at stations in the upstream of Zuari and at the confluence of canals in the Mandovi estuary. Enrichment factors of metals indicate that Mn is significantly polluted while other metals are moderately polluted. The δ 13C and δ 15N of organic matter indicate that the terrigenous organic matter at the upstream is diluted seaward by marine organic matter. Organic matter at bay stations is largely marine and altered-type. The compositions of SPM are controlled by the particulates from ore dust, the geology of the drainage basins, and the physicochemical processes in the estuaries. Particulates resuspended from the bay are dominated by ore dust, which are advected into the channels of both estuaries during the lull periods of the monsoon. 相似文献
347.
V. Sivakumar F. Chandrasekaran G. Swaminathan P.G. Rao 《Journal of Cleaner Production》2009,17(1):101-104
Studies on ultrasound-assisted processes are gaining importance due to its effectiveness and facilitating green method in processing. Degreasing of skin/hide prior to tanning process is an important unit operation. Presence of large amounts of natural fat at the interior of skin/hide matrix makes degreasing process a challenging one. Conventionally, organic solvent and/or detergent based degreasing process are employed leading to environmental problems. In the present paper, the use of power ultrasound in aqueous degreasing process has been studied and compared with different degreasing systems. Glutaraldehyde pre-tanning has also been employed for carrying out the degreasing process at ultrasonic bath temperature. The results indicate that there is a significant increase in the degreasing efficiency due to the application of ultrasound. About 2-fold increase in fat removal has been observed due to the use of ultrasound as compared to control under the given process conditions. Comparing the degreasing efficiencies of the solvent with aqueous based ultrasonic processes, about 80% of the solvent degreasing efficiency could be obtained for aqueous degreasing process. This novel ultrasonic process helps in making aqueous degreasing process a viable option, which is eco-friendly even dispensing with temperature control measures. 相似文献
348.
349.
The Hponkanrazi Wildlife Sanctuary, North Myanmar and three contiguous protected areas, comprise some of the largest expanses
of natural forest remaining in the region. Demand for wildlife products has resulted in unsustainable exploitation of commercially
valuable species resulting in local extirpation of vulnerable species. Camera trap, track and sign, and questionnaire-based
surveys were used to examine (a) wildlife species targeted by hunters, (b) the importance of wild meat for household consumption,
and (c) the significance of hunting as a livelihood activity for resident villages. Certain commercially valuable species
highly preferred by hunters were either completely absent from hunt records (tiger, musk deer and otter) or infrequently obtained
during actual hunts (bear, pangolin). Species obtained by hunters were commonly occurring species such as muntjacs with low
commercial value and not highly preferred by hunters. Fifty eight percent of respondents (n = 84) indicated trade, 27% listed subsistence use and 14% listed human-wildlife conflict as the main reason for hunting (n = 84). Average amount of wild meat consumed per month is not significantly higher during the hunting season compared to the
planting season (paired t-test, P > 0.05). Throughout the year, the average amount of fish consumed per month was higher than livestock or wild meat (Friedman
test, P < 0.0001). Hunting is driven largely by trade and wild meat, while not a critical source of food for a large number of families
could potentially be an important, indirect source of access to food for hunting families. Findings and trends from this study
are potentially useful in helping design effective conservation strategies to address globally prevalent problems of declining
wildlife populations and dependent human communities. The study provides recommendations to reduce illegal hunting and protect
vulnerable species by strengthening park management through enforcement, increasing the opportunity costs of poaching, establishing
no-take zones and research to determine the economic significance of hunting for livelihoods. 相似文献
350.
James M. Godowitch George A. Pouliot S. Trivikrama Rao 《Atmospheric environment (Oxford, England : 1994)》2010,44(24):2894-2901
An investigation of the concentrations of nitrogen oxides (NOX) from an air quality model and observations at monitoring sites was performed to assess the changes in NOX levels attributable to changes in mobile emissions. This evaluation effort focused on weekday morning rush hours since urban NOX concentrations are strongly influenced by the significant loading of emissions associated with heavy commuter traffic. On-road vehicle NOX emissions generated by the MOBILE6 model revealed a steady decline with an overall decrease of 25% for 2002–2006. In this study, a dynamic model evaluation was undertaken that entails an assessment of the predicted concentration response of the Community Multiscale Air Quality (CMAQ) model due to changes in NOX emissions as well as to meteorological variability spanning 3-month summer periods over five consecutive years (2002–2006) against observed concentration changes at NOX monitoring sites located primarily in urban areas of the eastern United States. Both modeled and observed hourly NOX concentrations exhibited maximum values that coincided with the morning peak NOX emissions. The notable results, based on 3-h average (6–9 AM local time) NOX concentrations, derived between the 50th and 95th percentiles of cumulative concentration distributions, revealed that modeled changes at these elevated NOX levels generally tracked the year-to-year variations in the observed concentration changes. When summer 2002 values were used as a reference, both modeled and observed results also showed definitive decreases in weekday morning urban NOX concentrations over this multi-year period, which can be primarily attributed to the reductions in mobile source emissions. Whereas observed NOX concentrations have declined by about 25% over this period consistent with the decline in the modeled mobile emission sector, modeled NOX concentration changes were close to the decreases exhibited in all (mobile + other sectors) surface NOX emissions whose overall decline was about 15% over this multi-year period. 相似文献