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911.
Vimal Kumar KG Dinesh Kumar PK Smitha BR Habeeb Rahman H Josia J Muraleedharan KR Sanjeevan VN Achuthankutty CT 《Environmental monitoring and assessment》2008,140(1-3):231-247
Seasonal variation of the hydrography along the southeast Arabian Sea is described using data collected onboard FORV Sagar
Sampada in September–October 2003 (later phase of Southwest monsoon, SWM) and March–April 2004 (Spring inter monsoon, SIM).
During the later phase of the SWM, upwelling was in the withdrawal phase and the frontal structure was clearer in the northern
sections (13 and 15°N lat) indicating strong upwelling in the area. The driving force of upwelling is identified as the combination
of alongshore wind stress and remote forcing with a latitudinal variability. Although a more prominent upwelling was found
in the north, a maximum surface Chlorophyll-a was found in the south (10°N). During the SIM, the area was characterized by oligotrophic water with relatively high Sea
Surface Temperature (>29°C) and low salinity (33.8 to 35.4). During March, the surface hydrography was found to be controlled
mainly by the intrusion of low-saline waters from the south, while during September by the high saline water from the north.
The presence of various water masses [Arabian Sea High Salinity Water (ASHSW), Persian Gulf Water (PGW), Red Sea Water (RSW)]
and their seasonal variations in the region is discussed and their decreasing influence towards the south is noted during
both periods of observation. During the SWM, the dynamic topography showed the equator-ward flow of the West India Coastal
Current (WICC) at the surface and a pole-ward coastal under current at sub-thermocline depth. During the SIM, surface circulation
revealed the WICC flowing pole-ward north of 13°N, but equator-ward flow in the south, with a clockwise circulation around
the Lakshadweep High. 相似文献
912.
Sharma KK Kalpana Sharma V Gupta P Jaya M Kumar A Singh B 《Environmental monitoring and assessment》2008,137(1-3):179-184
Fipronil termiticide belongs to phenyl-pyrazole class of chemical compounds. It has broad-spectrum activity particularly against
house hold pests such as cockroaches, mosquitoes, locusts, ticks, and fleas at both larval and adult stages. At high dosage
it can be used to control subterranean termites in building foundations. To evaluate long term efficacy against termites the
persistence and vertical distribution of fipronil was studied under natural weather conditions of Dehradun, India. Fipronil
was applied at four concentrations i.e. 0.05, 0.1, 0.25 and 0.5% a.i ha−1 by drenching 17 × 17 in.2 plot prepared as per modified ground board test. Soil samples were collected after 22, 38 and 56 months of treatment up to
the depth of 75 cm. The soil core was cut into five distinct sections i.e. 0–15, 15–30, 30–45, 45–60 and 60–75 cm depth. The
residues were extracted by shaking 20 g soil sample with acetone. The acetone extract was concentrated and cleaned-up over
florisil column. Fipronil residues were estimated on GLC at 220, 260, and 300°C oven, injector and detector temperature respectively.
Fipronil was found to persist beyond 56 months after application. Two metabolites viz. desulfinyl and sulfide-fipronil were
detected in sampling after 22 months of application that also dissipated with time. Fipronil residues were found up to 60 cm
depth. The residues in deeper layers dissipate slowly with time and after 56 months of treatment residues were detected only
up to 30 cm depth. 相似文献
913.
M. Berlin G. Suresh Kumar Indumathi M. Nambi 《Environmental Modeling and Assessment》2014,19(4):283-299
Nitrogen pollution in groundwater resulting from wastewater application to land is a common problem, and it causes a major threat to groundwater-based drinking water supplies. In this study, a numerical model is developed to study the nitrogen species transport and transformation in unsaturated porous media. Further, a new mass transfer module for dissolved oxygen (DO) is incorporated in the one-dimensional numerical model for nitrogen species transport to describe the fate and transport of nitrogen species, dissolved oxygen, dissolved organic carbon (DOC), and biomass. The spatial and temporal variation of dissolved oxygen is incorporated in the model through the mass transfer from gaseous phase to water phase in an unsaturated porous system. The numerical results of the water flow model and single species and multispecies transport model in an unsaturated zone developed for this purpose have been validated with the available analytical/numerical solution. The developed model is applied in clay loam, silt, and sand soils to analyze the transport behavior of nitrogen species under unsaturated condition. The numerical results suggest that the high rate of oxygen mass transfer from the air phase to the water phase positively increases the dissolved oxygen in the applied wastewater and enhances the nitrification process. Because of this high oxygen mass transfer, the nitrate nitrogen concentration significantly increases in the unsaturated zone and the same is transported to a larger depth at higher simulation period. On the other hand, the low rate of oxygen mass transfer implicitly enhances the denitrification process and finally reduces the nitrate nitrogen concentration in the unsaturated zone. The numerical results also show that the nitrate nitrogen transport is rapid in sandy soil when compared with clay loam and silty soils under high oxygen mass transfer rate. In essence, the high oxygen mass transfer rate significantly increases the nitrate nitrogen in the unsaturated zone, especially at a greater depth at larger time levels and eventually affects the groundwater quality. 相似文献
914.
Priyanka Chaudhary Harmesh Sahay Richa Sharma Alok Kumar Pandey Shashi Bala Singh A. K. Saxena Lata Nain 《Environmental monitoring and assessment》2015,187(6):391
Polyaromatic hydrocarbons (PAHs) utilizing bacteria were isolated from soils of seven sites of Mathura refinery, India. Twenty-six bacterial strains with different morphotypes were isolated. These strains were acclimatized to utilize a mixture of four polycyclic aromatic hydrocarbons, i.e., anthracene, fluorene, phenanthrene, and pyrene, each at 50 mg/L concentration as sole carbon source. Out of total isolates, 15 potent isolates were subjected to 16S rDNA sequencing and identified as a member of diverse genera, i.e., Bacillus, Acinetobacter, Stenotrophomonas, Alcaligenes, Lysinibacillus, Brevibacterium, Serratia, and Streptomyces. Consortium of four promising isolates (Acinetobacter, Brevibacterium, Serratia, and Streptomyces) were also investigated for bioremediation of PAH mixture. This consortium was proved to be efficient PAH degrader resulting in 40–70 % degradation of PAH within 7 days. Results of this study indicated that these genera may play an active role in bioremediation of PAHs. 相似文献
915.
Enteric methane mitigation technologies for ruminant livestock: a synthesis of current research and future directions 总被引:2,自引:0,他引:2
Patra AK 《Environmental monitoring and assessment》2012,184(4):1929-1952
Enteric methane (CH4) emission in ruminants, which is produced via fermentation of feeds in the rumen and lower digestive tract by methanogenic
archaea, represents a loss of 2% to 12% of gross energy of feeds and contributes to global greenhouse effects. Globally, about
80 million tonnes of CH4 is produced annually from enteric fermentation mainly from ruminants. Therefore, CH4 mitigation strategies in ruminants have focused to obtain economic as well as environmental benefits. Some mitigation options
such as chemical inhibitors, defaunation, and ionophores inhibit methanogenesis directly or indirectly in the rumen, but they
have not confirmed consistent effects for practical use. A variety of nutritional amendments such as increasing the amount
of grains, inclusion of some leguminous forages containing condensed tannins and ionophore compounds in diets, supplementation
of low-quality roughages with protein and readily fermentable carbohydrates, and addition of fats show promise for CH4 mitigation. These nutritional amendments also increase the efficiency of feed utilization and, therefore, are most likely
to be adopted by farmers. Several new potential technologies such as use of plant secondary metabolites, probiotics and propionate
enhancers, stimulation of acetogens, immunization, CH4 oxidation by methylotrophs, and genetic selection of low CH4-producing animals have emerged to decrease CH4 production, but these require extensive research before they can be recommended to livestock producers. The use of bacteriocins,
bacteriophages, and development of recombinant vaccines targeting archaeal-specific genes and cell surface proteins may be
areas worthy of investigation for CH4 mitigation as well. A combination of different CH4 mitigation strategies should be adopted in farm levels to substantially decrease methane emission from ruminants. Evidently,
comprehensive research is needed to explore proven and reliable CH4 mitigation technologies that would be practically feasible and economically viable while improving ruminant production. 相似文献
916.
Spatial variability and temporal changes in the trace metal content of soils: implications for mine restoration plan 总被引:1,自引:0,他引:1
Rachna Chandra B. Anjan Kumar Prusty P. A. Azeez 《Environmental monitoring and assessment》2014,186(6):3661-3671
Trace metals in soils may be inherited from the parent materials or added to the system due to anthropogenic activities. In proposed mining areas, trace metals become an integral part of the soil system. Usually, researchers undertake experiments on plant species selection (for the restoration plan) only after the termination of mining activities, i.e. without any pre-mining information about the soil-plant interactions. Though not shown in studies, it is clear that several recovery plans remain unsuccessful while carrying out restoration experiments. Therefore, we hypothesize that to restore the area effectively, it is imperative to consider the pre-mining scenario of metal levels in parent material as well as the vegetation ecology of the region. With these specifics, we examined the concentrations of trace metals in parent soils at three proposed bauxite locations in the Eastern Ghats, India, and compared them at a spatio-temporal scale. Vegetation quantification and other basic soil parameters accounted for establishing the connection between soil and plants. The study recorded significant spatial heterogeneity in trace metal concentrations and the role of vegetation on metal availability. Oxidation reduction potential (ORP), pH and cation exchange capacity (CEC) directly influenced metal content, and Cu and Ni were lithogenic in origin. It implies that for effective restoration plant species varies for each geological location. 相似文献
917.
Ground level ozone is responsible for the formation ofsmog, and for a variety of adverse effects on bothhuman and plant life. High concentrations of groundlevel ozone occur during the summer months. This paperdescribes the development of a model to forecast themaximum daily concentration of ozone as a function ofthe maximum surface temperature, for ozonenon-attainment regions in Ohio. The model wasdeveloped by statistical analysis of existing data.Site-specific models were developed initially. Theverification and evaluation of the performancecriteria of the model at each site were explored bycomparing the model with an independent datasetcollected from that site. A generalized statewidemodel was developed from the site-specific models. Theperformance criteria of this model were verified andevaluated by employing the same independent datasetsemployed for the site-specific models. An exceedencemodel to predict the occurrence of ozone exceedencesover 100 ppb has also been presented. 相似文献
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