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排序方式: 共有460条查询结果,搜索用时 578 毫秒
411.
This paper describes a new method for the determination of nitrite in potable and polluted water, based on the reaction of nitrite with p-nitroaniline to form diazonium salt and its subsequent coupling with diphenylamine in acidic medium. The pink coloured dye formed obeys Beer's law in the range 0.16 to 0.56 μg/ml at λmax = 540 nm. The molar absorptivity and Sandell's sensitivity being 57.5 × 103 lmole?3cm?1 and 0.0008 μg/cm2, respectively. The optimum reaction conditions and other analytical parameters have been studied. Extraction of the dye with chloroform enhances the sensitivity considerably and makes 0.04 μg/ml of nitrite determinable. 相似文献
412.
A Dewan S K Gupta J P Jani S K Kashyap 《Journal of environmental science and health. Part. B》1980,15(4):395-402
The immunosuppressive effect of lindane was assessed in weanling rats over a period of 5 weeks. Agglutinin titres against S. typhi 'O' and 'H', S. paratyphi 'AH' and 'BR' antigens were determined following TAB vaccination in control and lindane-fed animals. The titres attained in non-treated controls were higher significantly than those in treated animals indicating a suppressive effect of lindane on humoral immune responses. 相似文献
413.
414.
Tillage and nutrient source effects on water quality and corn grain yield from a flat landscape 总被引:1,自引:0,他引:1
Beneficial effects of leaving residue at the soil surface are well documented for steep lands, but not for flat lands that are drained with surface inlets and tile lines. This study quantified the effects of tillage and nutrient source on tile line and surface inlet water quality under continuous corn (Zea mays L.) from relatively flat lands (<3%). Tillage treatments were either fall chisel or moldboard plow. Nutrient sources were either fall injected liquid hog manure or spring incorporated urea. The experiment was on a Webster-Canisteo clay loam (Typic Endoaquolls) at Lamberton, MN. Surface inlet runoff was analyzed for flow, total solids, NO(3)-N, NH(4)-N, dissolved P, and total P. Tile line effluent was analyzed for flow, NO(3)-N, and NH(4)-N. In four years of rainstorm and snowmelt events there were few significant differences (p < 0.10) in water quality of surface inlet or tile drainage between treatments. Residue cover minimally reduced soil erosion during both snowmelt and rainfall runoff events. There was a slight reduction in mineral N losses via surface inlets from manure treatments. There was also a slight decrease (p = 0.025) in corn grain yield from chisel-plow plots (9.7 Mg ha(-1)) compared with moldboard-plow plots (10.1 Mg ha(-1)). Chisel plowing (approximately 30% residue cover) alone is not sufficient to reduce nonpoint source sediment pollution from these poorly drained flat lands to the extent (40% reduction) desired by regulatory agencies. 相似文献
415.
Ram Gupta Ramesh Rudra Trevor Dkkinson 《Journal of the American Water Resources Association》1998,34(2):279-287
ABSTRACT: Physically-based models are extensively used to simulate the infiltration process under varied field conditions. Most models are based on the deterministic nature of input parameters related to the flow process (such as hydraulic conductivity). These models yield poor predictions of infiltration rates because they do not include the field-scale variations of flow parameters. The paper presents an approach for integrating the field-scale variability of hydraulic conductivity with an infiltration model to simulate infiltration under the rainfall conditions. A model describing the spatial structure of hydraulic conductivity has been developed using stochastic techniques. The stochastic structure of hydraulic conductivity was then incorporated in the Green-Ampt and Mein-Larson infiltration model. The model outputs on the instantaneous infiltration rates and cumulative infiltration were evaluated using the field infiltration data measured under simulated rainfall conditions. The results show that the combined model is capable of rep. resenting the instantaneous infiltration rates and cumulative infiltration of the study soils. The model may, therefore, be used to simulate the rainfall infiltration process for spatially-variable soils under the field conditions. 相似文献
416.
Photosynthesis inhibition of soybean leaves by insecticides 总被引:7,自引:0,他引:7
Field grown soybean cv. Williams-82 plants were sprayed with malathion or carbaryl formulations at 30, 60 and 90 days after planting. Net photosynthesis (PN) was measured in the control (water-sprayed) and pesticide-treated plants, 1, 3 and 7 days after treatment, with a LICOR 6200 Portable Photosynthesis System. The pesticide-treated plants showed a significant reduction (24% with malathion and 20% with carbaryl) in PN after the first application. After the 60-day spray treatment PN suppression on day 1 and day 3 after treatment was the same as after the first application; but PN reached the same level as that of the water-sprayed control 7 days after treatment. After the 90-day treatment no change in PN was observed with the pesticide-treated plants compared to the control. These data indicate that malathion and carbaryl formulations may exert a detrimental influence on soybean physiology. 相似文献
417.
Landslide hazard,vulnerability, and risk assessment (HVRA), Mussoorie township,lesser himalaya,India
Environment, Development and Sustainability - In the present study, landslide hazard, vulnerability and the risk assessment of the Himalayan township Mussoorie, located in the lower part of the... 相似文献
418.
Environment, Development and Sustainability - Prayagraj City is one the biggest cities in the State of Uttar Pradesh which has been selected as Smart City by Ministry of Housing and Urban Affairs,... 相似文献
419.
Kaushik K. Shandilya Mukesh Khare A. B. Gupta 《Environmental monitoring and assessment》2013,185(6):5251-5264
The organic matter of street dust is considered as one of the causes for high human mortality rate. To understand the association, the street dust samples were collected from four different localities (industrial, residential, residential–commercial, and commercial) situated in the greater Delhi area of India. The loss-on-ignition method was used to determine the organic matter (OM) content in street dust. The OM content, potassium, calcium, sulfate, and nitrate concentrations of street dust in Delhi, India is measured to understand the spatial variation. Correlation analysis, analysis of variance, and factor analysis were performed to define the sources. The dust OM level ranges from 2.63 to 10.22 %. It is found through correlation and factor analysis that OM is primarily contributed from secondary aerosol and vehicular exhaust. The OM levels suggest that the use of a residential–commercial site for commercial purposes is polluting the street dust and creating the environmental and human health problems. 相似文献
420.