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排序方式: 共有1223条查询结果,搜索用时 124 毫秒
411.
Sanjay Singh B.K. Sapra Arshad Khan P.K. Kothalkar Y.S. Mayya 《Atmospheric environment (Oxford, England : 1994)》2010,44(6):795-802
In atmospheric aerosol studies, it is often required to use two different impactors, namely, the normal pressure and the low-pressure impactor, to measure the mass-size distribution over a wide size range. From the perspective of rendering the system compact for such measurements, it may be more advantageous to combine the two features in a single instrument. In an effort towards exploring this option, a variable configuration cascade impactor (VCCI) comprising of 7 normal pressure and 4 low-pressure stages has been designed and developed. In configuration-1, it operates as a low-pressure impactor, with a sampling flow rate of 10 L min?1 and classifies the particles from 0.1 to 21 μm in eleven size classes. In configuration-2, it operates as a normal pressure impactor, with a sampling flow rate of 45 L min?1, and classifies the particles from 0.53 to 10 μm in seven size classes. As part of performance evaluation of the system, the deposit patterns and the integral performance have been studied. For integral performance, a comparative mass-size distribution measurement between VCCI and standard Andersen impactor was carried out. Its performance was also evaluated against the GRIMM Scanning Mobility Particle Sizer (SMPS) in the common size range of both these instruments and against GRIMM Optical Particle Counter (OPC). In addition to this, VCCI was evaluated for its performance in the PMx configuration obtained by removing a few of the impactor stages sequentially and measuring corresponding size distribution for every stage removed. Changes in the distribution parameters due to spillover of the deposits of previous stage to remaining stages were within 10%. This variation is well within the generally accepted value for all environmental measurement related applications. 相似文献
412.
The animal, agro-wastes and water hyacinth (Eichhornia crassipes) are a serious problem for the society and ecosystem. The present study carried out the management of water hyacinth and observation of nutritional status like pH, electrical conductivity (EC), total organic carbon (TOC), total Kjeldahl nitrogen (TKN), C/N ratio, total phosphorus and total calcium (TCa) of liquid bio-fertilizer (vermiwash) before and after vermicomposting of feed materials of different combinations of buffalo dung (BD) with water hyacinth (WH) and gram bran (GB). After vermicomposting of different combinations of BD with WH and agro-wastes, significant decrease in level of pH, EC, TOC and C/N ratio was observed, whereas significant increase in TKN, TK, TAP and TCa level in vermiwash of final vermicompost with respect to initial feed material was observed. The pH of initial mixture in all combinations has tended to basic in nature, while in final vermicompost, it becomes neutral/basic. The significant increase was observed in the level of TKN, TK, TAP in BD + GB + WH (1:2:1) and TCa in BD + GB + WH (1:1:2) vermiwash of final vermicompost of combination, whereas decrease was observed in TOC, C/N ratio, pH and EC in BD + WH (1:1), BD + GB + WH (1:1:1), BD + GB + WH (1:2:1) and BD + GB (1:1), respectively. 相似文献
413.
A. K. Singh 《Russian Journal of Ecology》2016,47(3):310-314
Present study was carried out to determine pollinators’ diversity and their efficiency with modular approach; foraging behaviour, number of loose pollen adhered on their body and number of pollen deposited on the stigma. The observations explicitly indicate that Megachile spp., Xylocopa tenuiscopa, Amegilla zonata and Nomia sp. were true pollinators and out of these, Megachile spp. were key pollinators of pigeonpea. Among megachilids, Megachile lanata was the most efficient pollinator. Sufficient pollination meticulously accomplished in pigeonpea by true pollinators under this agro-ecological region. 相似文献
414.
Jay Krishna Thakur P. K. Srivastava S. K. Singh Zoltán Vekerdy 《Regional Environmental Change》2012,12(1):133-144
Wetland ecosystems are of global significance having productive, regulatory and informative function. These wetlands are crucial
for the long-term protection of water sources, as well as the survival of its unique biodiversity. Most of the wetlands of
Turkey are now facing serious threat from the anthropogenic sources and now near to the verge of extinction. This study has
been carried out to monitor vegetation dynamics and ecological status of wetlands of Koyna basin at spatial and temporal scale.
This study has involved MODerate-resolution Imaging Spectroradiometer (MODIS) images of the year 2000, 2004 and 2008 on daily
basis with spatial resolution of 1 km. The MODIS 16 days composite NDVI time series products of 250-m spatial resolution from
year 2000 to 2008 has been utilized to monitor the ecological status of the wetlands. The European Nature Information System
habitat classification map, meteorological data (precipitation, temperature) coupled with field data has been utilized to
validate NDVI values of nine habitats in the wetlands. The time series analyses of NDVI data values have been correlated with
the groundwater level depth from 1996 to 2004. The overall analysis has shown a declining trend of NDVI over the year 2000
to 2008, indicated a degraded wetland condition in span of 9 years. 相似文献
415.
Uttam Kumar Sarkar Vineet Kumar Dubey Atul Kumar Singh Brij Kishor Gupta Ajay Pandey Rupali Kumar Sani Wazir Singh Lakra 《The Environmentalist》2012,32(4):476-484
We record here the recent occurrence, abundance and distribution of six exotic fish species, viz. Oreochromis mossambicus, Cyprinus carpio, Hypopthalmicthys molitrix, Ctenopharyngodon idellus, Clarias gariepinus, and Pterygoplichthys disjunctivus (a new exotic in India) distributed through the four important tributaries of river Ganga basin in India. From the total catch, the abundance index of all exotic species in different rivers ranged from 1.1 to 14.5?% with highest value in River Gomti. The relative abundance of the exotic species in all the four tributaries demonstrated that a single species C. carpio contributed a considerable abundance (43.3?C83?%) than that of the remaining exotic fishes. The Common Carp, C. carpio, was ubiquitous in all the four tributaries of Ganges basin studied and had the highest local distribution (52.63?%). Smaller size groups of endangered (Chagunius chagunio, Chitala chitala, and Tor tor) and migratory species (Bagarius bagarius, Ompok pabda, Wallago attu, and Sperata aor) in the four tributaries were recorded, and the increasing appearance of Common Carp and other exotic fishes is signaling biological invasion. Possible threats to the indigenous fish fauna, as a result of the invasion and proliferation of these exotics, are discussed. 相似文献
416.
The purpose of this study is to conduct a long-term site-specific risk assessment for zinc (Zn) susceptibility of bivalves, green mussel Perna viridis and hard clam Ruditapes philippinarum, based on published experimental data by linking the biologically-based damage assessment model with the subcellular partitioning concept. A comprehensive risk modeling framework was developed to predict susceptibility probability of two bivalve species exposed to waterborne Zn. The results indicated that P. viridis accumulates more Zn toxicity, whereas both toxic potency and the recovery rate of Zn are higher for R. philippinarum. We found that negative linear correlations exist in elimination-recovery and elimination-detoxification relationships, whereas a positive linear correlation was observed in recovery-detoxification relationships for bivalves exposed to waterborne Zn. Simulation results showed that the spatial differences of susceptibility primarily resulted from the variation of waterborne Zn concentration under field conditions. We found that R. philippinarum is more susceptible of Zn than P. viridis under the same exposure condition. Results also suggested that Zn posed no significant susceptibility risk to two bivalve species in Taiwan. We suggested that these two species can be used to biomonitor the water quality on Taiwan coastal areas. 相似文献
417.
Effect of active molluscicidal components of Sapindus mukorossi and Terminalia chebula on the acetylcholinesterase (AChE), acid and alkaline phosphatase (ACP/ALP) activity in the nervous tissue of freshwater snail Lymnaea acuminata were studied. In vivo and in vitro exposure of saponin (active component of S. mukorossi pericarp) and tannic acid (active component of T. chebula) significantly inhibited the AChE, ACP and ALP activity in the nervous tissue of L. acuminata. The inhibition kinetics of these enzymes indicate that saponin and tannic acid caused competitive and competitive-non-competitive inhibition of AChE, respectively. Saponin also caused competitive and competitive-non-competitive inhibition of ACP and ALP, respectively, whereas tannic acid caused competitive-non-competitive inhibition of ACP and ALP. Thus the inhibition of AChE, ACP and ALP by saponin and tannic acid in the nervous tissue of L. acuminata may be the cause of molluscicidal activity of S. mukorossi and T. chebula. 相似文献
418.
Chlorpyrifos degradation by the cyanobacterium <Emphasis Type="Italic">Synechocystis</Emphasis> sp. strain PUPCCC 64 总被引:1,自引:0,他引:1
Singh DP Khattar JI Nadda J Singh Y Garg A Kaur N Gulati A 《Environmental science and pollution research international》2011,18(8):1351-1359
Background, aim, and scope
Indiscriminate use of insecticides leads to environmental problems and poses a great threat to beneficial microorganisms. The aim of the present work was to study chlorpyrifos degradation by a rice field cyanobacterium Synechocystis sp. strain PUPCCC 64 so that the organism is able to reduce insecticide pollution in situ. 相似文献419.
Optimization of nitrate reduction by EDTA catalyzed zero-valent bimetallic nanoparticles in aqueous medium 总被引:2,自引:0,他引:2
Kunwar P. Singh Arun K. Singh Shikha Gupta 《Environmental science and pollution research international》2012,19(9):3914-3924
The present study aims to investigate the EDTA catalyzed reduction of nitrate (NO 3 ? ) by zero-valent bimetallic (Fe?CAg) nanoparticles (ZVBMNPs) in aqueous medium and to enumerate the effect of temperature, solution pH, ZVBMNPs dose and EDTA concentration on NO 3 ? reduction. Batch experimental data were generated using a four-factor Box?CBehnken design. Optimization modeling was performed using the response surface method for maximizing the reduction of NO 3 ? by ZVBMNPs. Significance of the independent variables and their interactions were tested by the analysis of variance and t test statistics. The model predicted maximum reduction capacity (340.15?mg?g?1 NO 3 ? ) under the optimum conditions of temperature, 60?°C; pH?4; dose, 1.0?g?l?1; and EDTA concentration, 2.0?mmol?l?1 was very close to the experimental value (338.62?mg?g?1) and about 16?% higher than the experimentally determined capacity (291.32?mg?g?1). Study demonstrated that ZVBMNPs had higher reduction efficiency than Fe0 nanoparticles for NO 3 ? . EDTA significantly enhanced the NO 3 ? reduction by ZVBMNPs. The EDTA catalyzed reduction of NO 3 ? by ZVBMNPs can be employed for the effective decontamination of water. 相似文献
420.
Singh KP Singh AK Gupta S Rai P 《Environmental science and pollution research international》2012,19(6):2063-2078