排序方式： 共有34条查询结果，搜索用时 187 毫秒
1.
The aim of this study is to determine the acoustic characteristics of sailfin sandfish over a wide frequency range. The acoustic survey was conducted in Fe 相似文献
2.
A method to estimate stream conveyance losses, including stream bank seepage and evapotranspiration from riparian areas, was developed for the Truckee River in California and Nevada (USA). Aquifer diffusivity is the primary variable required to compute aquifer head and seepage. Head and seepage conceptual models developed in previous studies were calibrated using stream stage and aquifer head at five sites along the Truckee River. The equations for head require numerical convolution to solve. It was found that head is insensitive to diffusivity and a single value for diffusivity provides good results at all study sites. Also, because releases from storage are usually prescribed as a step increase in flow for a given period of time followed by a step decrease in flow, an analytic solution for volume of seepage can be used in place of numerical convolution. Under typical operating conditions, seepage volume represents a small fraction of the total reservoir releases. Uncertainty in seepage estimates can be reduced with increased accuracy in hydraulic conductivity. This work demonstrates a valuable technique to estimate conveyance losses under natural and managed stream flow. 相似文献
3.
WU Rina CONG Weiwei LI Yonghua LI Siyao WANG Dongfang JIA Zhiqing WANG Feng 《资源与生态学报(英文版)》2019,10(2):196-201
The dryland ecosystem is the dominant component of the global terrestrial ecosystem since arid regions occupy 45% of the earth’s land area and feed 38% of the world's population. The stability and sustainable development of the dryland ecosystem are critical for achieving the millennium development goal (MDG) in the arid and semiarid areas. However, there is still no scientific guideline for measuring and conserving the health and productivity of dryland ecosystems. Therefore, the purpose of this study is to develop the scientific conceptual framework of defining, monitoring and evaluating the ecological quality of dryland ecosystems. The ecological quality of dryland ecosystems is represented by a system of comprehensive indicators that are each extracted from the ecological elements, and structural and functional indices of the ecosystem. These indicators can be monitored by integrating satellites and unmanned aerial vehicles with ground-based sensor networks at the scale of either observational sites or regional scales. Finally, the ecological quality can be evaluated by evaluation models based on the normalized index values and their thresholds. This paper presents a conceptual framework for monitoring and evaluating the ecological quality of drylands, which provides a way of advancing the monitoring, diagnosis, and evaluation of the ecological quality of the dryland ecosystems. 相似文献
4.
Chander Kumar Singh Rina Kumari Neha Singh Javed Mallick Saumitra Mukherjee 《水文研究》2013,27(17):2462-2474
The groundwater is the only source of drinking water in the Jaisalmer district of Rajasthan, India. The study area is a part of the Thar Desert. It has low and scattered population and no industries; hence, the possibility of anthropogenic input of fluoride is almost negligible. Thus, the enrichment of fluoride is only possible due to geochemical processes taking place in the groundwater of the region. A total of 100 groundwater samples, 34 samples from Jaisalmer and 66 samples from the Pokharan administrative blocks, were collected. It was observed that the concentration of fluoride ranged from 0.08 mg/l to 4.56 mg/l in the groundwater of Jaisalmer and from 0.56 mg/l to 6.60 mg/l in the samples of the Pokharan block. The alkaline condition (average pH, 7.7 ± 0.22 and 8.01 ± 0.25 in Jaisalmer and the Pokharan administrative block, respectively) in the region favours fluorite dissolution. Ion exchange, dissolution of calcite, semi‐arid climate, alkaline conditions and weathering are responsible for fluoride enrichment in the groundwater of the study area. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
5.
Chandrashekhar Azad Vishwakarma Ratan Sen Neha Singh Priyadarshini Singh Vikas Rena Kumari Rina Saumitra Mukherjee 《Journal of the Geological Society of India》2018,92(6):753-763
This paper focuses on the suitability of spring water for drinking and irrigation purposes in a part of eastern Himalaya, south Sikkim. There are many anthropogenic and geogenic factors contributing as a source of major cations and anions in the spring water. The spring water chemistry show a variation in EC, pH, TDS, Temperature, Na+, K+, Mg2+, Ca2+, Fe2+, Pb, Mn, Cu, HCO3-, Cl-, PO43-, NO3-, F- and SO42-. Mainly two types of water quality indexing has been used, one for suitability of spring water for drinking purposes and the other for irrigation purposes. For drinking purposes, Piper diagram used for determination of water type, water quality index (WQI) for quality monitoring and saturation index for mineral dissolution in water. % Na, RSC (Residual Sodium Carbon) and SAR (sodium absorption ratio) have been used for irrigation suitability. Piper diagram shows that CaHCO3 type of water was dominant in the study area. The WQI depicted excellent category and SAR, percent sodium and RSC (Residual Sodium Carbon) depict excellent, good and permissible category for irrigation purposes. Principle component analysis (PCA) was used to determine the major influencing factor responsible for the variability in the parameters analysed of spring water. 相似文献
6.
Geochemical characterization and heavy metal contamination of groundwater in Satluj River Basin 总被引：1，自引：0，他引：1
Chander Kumar Singh Kumari Rina Ravi Prakash Singh Saumitra Mukherjee 《Environmental Earth Sciences》2014,71(1):201-216
Groundwater, a renewable and finite natural resource, vital for man’s life, social and economic development and a valuable component of the ecosystem, is vulnerable to natural and human impacts. The aim of present study is to evaluate hydrogeochemical parameters and heavy metals in groundwater and to study their spatial distribution in the Rupnagar District of Punjab. The spatial distribution of physico-chemical parameters were studied using Arc GIS 9.2. It was observed that the concentration of parameters, such as NO3, Cd, Cr, Mn and Pb was above permissible limit (World Health Organization, WHO) in southern part of the study area. The heavy metal pollution index (HPI) was calculated for all sampling locations and it was found much above the critical limit of pollution. Geochemical reaction models of selected water groups were constructed using Phreeqc. Geochemical modeling suggests that sodium has source other than halite-albite and calcium has alternate source other than gypsum-carbonate or silicates. It also suggests that evaporites, ion exchange, dissolution along with anthropogenic activities are controlling the hydro-geochemistry of groundwater in the region. Various indices, such as heavy metal pollution index, permeability index, sodium adsorption ratio, were studied to verify suitability of groundwater for drinking and irrigation. 相似文献
7.
Kumari Rina Chander Kumar Singh P. S. Datta Neha Singh S. Mukherjee 《Environmental Earth Sciences》2013,69(7):2377-2391
In semi-arid/arid regions, groundwater is the major source of irrigation, drinking and industrial requirements, water salinity and shortage are major problems of concern. North Gujarat, India, is one such area where highly saline groundwater is generally ascribed to rapid increase of population, agriculture and industries induced decline in water table by unplanned abstraction of groundwater. However, no effort has been made to discriminate the natural and anthropogenic influences on groundwater salinity. In this brief background, the present study attempts to identify the factors and processes controlling the groundwater salinity in the area, based on ionic ratios in integration with various graphical methods, saturation indices and geographical information system. Na+/Ca2+ > 1 indicates the deficiency of Ca2+ possibly due to CaCO3 precipitation or ion exchange process. Na+/Cl? > 1 and $ {\text{SO}}_{4}{}^{2 - } /{\text{Cl}}^{ - } \gg 0.05 $ suggest salinization is mainly due to wastewater infiltration and/or due to irrigation water return flow. Sea water intrusion in coastal parts, vertical and lateral mixing of water and anthropogenic inputs are also responsible for salinization of groundwater. USSL diagram, Na%, sodium adsorption ratio, residual sodium carbonate and magnesium hazard indicate unsuitability of groundwater for irrigation purposes. To prevent groundwater salinization, appropriate measures need to be taken to control further indiscriminate exploitation of groundwater for irrigation. 相似文献
9.
Zhang Peng Rina Zuraida Yuan Honglin Xu Jian Gao Lianfeng Zhang Zhenguo Yang Ce 《地球科学进展》2016,31(5):494-502
Laser Ablation-Inductively Coupled Plasma-Mass Spectrometer (LA-ICP-MS) provides an opportunity for us to perform in-situ microanalysis for depth profiling of elements and trace elements/Calcium ratios in calcite foraminiferal shells. In this study, Globigerinoides ruber shells were investigated with a total of 173 ablating positions from a total of 11 core top sediment samples that retrieved from the Indonesian Seas. The results showed changing compositions of Magnesium and Calcium from the inside to the outside surface for both of intra-test and inter-test. Subsequently, Mg/Ca ratios from the LA-ICP-MS microanalysis were compared with Mg/Ca ratios based on regular analyses, suggesting that LA-ICP-MS microanalysis may provide a comparatively safe and convenient way for investigating Mg/Ca ratio of planktonic foraminiferal shells with considerable reliability and accuracy. 相似文献
10.
Rina Argelia Andersson Philip Meyers Edward Hornibrook Peter Kuhry Carl‐Magnus Mörth 《第四纪科学杂志》2012,27(6):545-552
A peat deposit from the East European Russian Arctic, spanning nearly 10 000 years, was investigated to study soil organic matter degradation using analyses of bulk elemental and stable isotopic compositions and plant macrofossil remains. The peat accumulated initially in a wet fen that was transformed into a peat plateau bog following aggradation of permafrost in the late Holocene (～2500 cal a BP). Total organic carbon and total nitrogen (N) concentrations are higher in the fen peat than in the moss‐dominated bog peat layers. Layers in the sequence that have lower concentrations of total hydrogen (H) are associated with degraded vascular plant residues. C/N and H/C atomic ratios indicate better preservation of organic matter in peat material dominated by bryophytes as opposed to vascular plants. The presence of permafrost in the peat plateau stage and water‐saturated conditions at the bottom of the fen stage appear to lead to better preservation of organic plant material. δ15N values suggest N isotopic fractionation was driven primarily by microbial decomposition whereas differences in δ13C values appear to reflect mainly changes in plant assemblages. Positive shifts in both δ15N and δ13C values coincide with a local change to drier conditions as a result of the onset of permafrost and frost heave of the peat surface. This pattern suggests that permafrost aggradation not only resulted in changes in vegetation but also aerated the underlying fen peat, which enhanced microbial denitrification, causing the observed 15N‐enrichment. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献