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1.
The hydrogeochemical parameters for groundwater samples of the Varanasi area, a fast-urbanizing region in India, were studied to evaluate the major ion chemistry, weathering and solute acquisition processes controlling water composition, and suitability of water quality for domestic and irrigation uses. Sixty-eight groundwater samples were collected randomly from dug wells and hand pumps in the urban Varanasi area and analyzed for various chemical parameters. Geologically, the study area comprises Quaternary alluvium made up of an alternating succession of clay, silty clay, and sand deposits. The Total dissolved solids classification reveals that except two locations, the groundwater samples are desirable for drinking, and all are useful for irrigation purposes. The cationic and anionic concentrations indicated that the majority of the groundwater samples belong to the order of Na > Ca > Mg > K and HCO3 > Cl > SO4 types, respectively. Geochemical classification of groundwater based on the Chadha rectangular diagram shows that the majority (81%) of groundwater samples belong to the calcium?Cbicarbonate type. The HCO3/ (HCO3 + SO4) ratio (0.87) indicates mostly carbonic acid weathering process due to presence of kankar carbonate mixed with clay/fine sand. The high nitrate concentration (>45?mg/l) of about 18% of the groundwater samples may be due to the local domestic sewage, leakage of septic tanks, and improper management of sanitary landfills. In general, the calculated values of sodium adsorption ratio, percent sodium, residual sodium carbonate, and permeability index indicate good to permissible use of water for irrigation, and only a few locations demand remedial measures for better crop yields.  相似文献   

2.
A part of the Gangetic Alluvial Plain covering 2,228 km2, in the state of Bihar, is studied for demarcating groundwater development potential zones. The area is mainly agrarian and experiencing intensive groundwater draft to the tune of 0.12 million cubic metre per square kilometres per year from the Quaternary marginal alluvial deposits, unconformably overlain northerly sloping Precambrian bedrock. Multiparametric data on groundwater comprising water level, hydraulic gradient (pre- and post-monsoon), aquifer thickness, permeability, suitability of groundwater for drinking and irrigation and groundwater resources vs. draft are spatially analysed and integrated on a Geographical Information System platform to generate thematic layers. By integrating these layers, three zones have been delineated based on groundwater development potential. It is inferred that about 48% of the area covering northern part has high development potential, while medium and low development potential category covers 41% of the area. Further increase in groundwater extraction is not recommended for an area of 173 km2, affected by over-exploitation. The replenishable groundwater resource available for further extraction has been estimated. The development potential enhances towards north with increase in thickness of sediments. Local deviations are due to variation of—(1) cummulative thickness of aquifers, (2) deeper water level resulting from localised heavy groundwater extraction and (3) aquifer permeability.  相似文献   

3.
This paper quantifies the allocation of ecosystem services value (ESV) associated with land use pattern and qualitatively examined impacts of land use changes and socio-economic factors on spatiotemporal variation of ESV in the Natural Wetland Distribution Area (NWDA), Fuzhou city, China. The results showed that total ESV of the study area decreased from 4,332.16?×?106 RMB Yuan in 1989 to 3,697.42?×?106 RMB Yuan in 2009, mainly due to the remarkable decreases in cropland (decreased by 55.3 %) and wetland (decreased by 74.2 %). Forest, water, and wetland played major roles in providing ecosystem services, accounting for over 90 % of the total ESV. Based on time series Landsat TM/ETM+ imagery, geographic information system, and historical data, analysis of the spatiotemporal variation of ESV from 1989 to 2009 was performed. It indicated that rapid expansion of urban areas along the Minjiang River resulted in significant changes in land use types, leading to a dramatic decline in ecosystem services. Meanwhile, because of land scarcity and unique ecosystem functions, the emergency of wetland and cropland protection in built-up area has become an urgent task of local authorities to the local government. Furthermore, there was still a significant negative correlation between ESV of cropland and wetland and the GDP. The results suggest that future planning of land use pattern should control encroachment of urban areas into cropland and wetland in addition to scientific and rational policies towards minimizing the adverse effects of urbanization.  相似文献   

4.
As groundwater is a vital source of water for domestic and agricultural activities in Thanjavur city due to lack of surface water resources, groundwater quality and its suitability for drinking and agricultural usage were evaluated. In this study, 102 groundwater samples were collected from dug wells and bore wells during March 2008 and analyzed for pH, electrical conductivity, temperature, major ions, and nitrate. Results suggest that, in 90% of groundwater samples, sodium and chloride are predominant cation and anion, respectively, and NaCl and CaMgCl are major water types in the study area. The groundwater quality in the study site is impaired by surface contamination sources, mineral dissolution, ion exchange, and evaporation. Nitrate, chloride, and sulfate concentrations strongly express the impact of surface contamination sources such as agricultural and domestic activities, on groundwater quality, and 13% of samples have elevated nitrate content (>45 mg/l as NO3). PHREEQC code and Gibbs plots were employed to evaluate the contribution of mineral dissolution and suggest that mineral dissolution, especially carbonate minerals, regulates water chemistry. Groundwater suitability for drinking usage was evaluated by the World Health Organization and Indian standards and suggests that 34% of samples are not suitable for drinking. Integrated groundwater suitability map for drinking purposes was created using drinking water standards based on a concept that if the groundwater sample exceeds any one of the standards, it is not suitable for drinking. This map illustrates that wells in zones 1, 2, 3, and 4 are not fit for drinking purpose. Likewise, irrigational suitability of groundwater in the study region was evaluated, and results suggest that 20% samples are not fit for irrigation. Groundwater suitability map for irrigation was also produced based on salinity and sodium hazards and denotes that wells mostly situated in zones 2 and 3 are not suitable for irrigation. Both integrated suitability maps for drinking and irrigation usage provide overall scenario about the groundwater quality in the study area. Finally, the study concluded that groundwater quality is impaired by man-made activities, and proper management plan is necessary to protect valuable groundwater resources in Thanjavur city.  相似文献   

5.
The research was aimed at determining the depth to the watertable, aquifer thickness and subsurface geology of the studyarea thus revealing its groundwater distribution as well as its potential as a substitute to the surface water resources.Vertical electrical soundings were carried out in the study area with maximum electrode spread. The Schlumberger electrode configuration technique was adopted. VES data were processedusing Schlumberger analysis package. Lithologic logs of alreadyexisting boreholes in the study area were collected, evaluatedand comparison were carried out. The results reveal alternatinglayers of sands, sandstones, gravel and clay. The lithologiclogs revealed that the study area is underlain by coastal sands (Benin formation). The water table varies from 10–64 m and thickness of the aquifer ranges from 20–80 m. Results show that the study area is underlain by a thick extensive aquifer that has a transmissivity of 2.8 × 10-2m2 s-1 to 3.3 × 10-1m2 s-1 and storativity 1.44 × 10-4 to 1.68 × 10-3m s-1 values. The specific yield is about 0.31.The sandy component of the study area forms more than 90% ofthe sequence, therefore the permeability, the transmissivity andthe storage coefficient are high with an excellent source of groundwater resources.  相似文献   

6.
Groundwater recharge and available groundwater resources in Chithar River basin, Tamil Nadu, India spread over an area of 1,722 km2 have been estimated by considering various hydrological, geological, and hydrogeological parameters, such as rainfall infiltration, drainage, geomorphic units, land use, rock types, depth of weathered and fractured zones, nature of soil, water level fluctuation, saturated thickness of aquifer, and groundwater abstraction. The digital ground elevation models indicate that the regional slope of the basin is towards east. The Proterozoic (Post-Archaean) basement of the study area consists of quartzite, calc-granulite, crystalline limestone, charnockite, and biotite gneiss with or without garnet. Three major soil types were identified namely, black cotton, deep red, and red sandy soils. The rainfall intensity gradually decreases from west to east. Groundwater occurs under water table conditions in the weathered zone and fluctuates between 0 and 25 m. The water table gains maximum during January after northeast monsoon and attains low during October. Groundwater abstraction for domestic/stock and irrigational needs in Chithar River basin has been estimated as 148.84 MCM (million m3). Groundwater recharge due to monsoon rainfall infiltration has been estimated as 170.05 MCM based on the water level rise during monsoon period. It is also estimated as 173.9 MCM using rainfall infiltration factor. An amount of 53.8 MCM of water is contributed to groundwater from surface water bodies. Recharge of groundwater due to return flow from irrigation has been computed as 147.6 MCM. The static groundwater reserve in Chithar River basin is estimated as 466.66 MCM and the dynamic reserve is about 187.7 MCM. In the present scenario, the aquifer is under safe condition for extraction of groundwater for domestic and irrigation purposes. If the existing water bodies are maintained properly, the extraction rate can be increased in future about 10 % to 15 %.  相似文献   

7.
This paper is based on long-term monitoring data for soil water, salt content, and groundwater characteristics taken from shelterbelts where there has been no irrigation for at least 5 years. This study investigated the distribution characteristics of soil water and salt content in soils with different textures. The relationships between soil moisture, soil salinity, and groundwater level were analyzed using 3 years of monitoring data from a typical oasis located in an extremely arid area in northwest China. The results showed that (1) the variation trend in soil moisture with soil depth in the shelterbelts varied depending on soil texture. The soil moisture was lower in sandy and loamy shelterbelts and higher in clay shelterbelts. (2) Salinity was higher (about 3.0 mS cm?1) in clay shelterbelts and lower (about 0.8 mS cm?1) in sandy shelterbelts. (3) There was a negative correlation between soil moisture in the shelterbelts and groundwater level. Soil moisture decreased gradually as the depth of groundwater table declined. (4) There was a positive correlation between soil salinity in the shelterbelts and the depth of groundwater table. Salinity increased gradually as groundwater levels declined.  相似文献   

8.
Anekal Taluk lies in the southern part of the of Bangalore urban district, known for Bannerghatta wildlife sanctuary, Jigani industrial estate, silk industry, and the electronics city, the pride of India and hub of Bangalore's information technology. In the present study, evaluation of geochemistry of 28 representative bore wells samples from Anekal Taluk was undertaken. It was found that most of the samples (92.9%) belong to Ca(2+?)-Mg(2+?)-Cl(?-?) -SO2??water type with Ca-Mg-Cl and Ca-Cl hydrochemical facies. The groundwater sources were further categorized as normal chloride (32.14%) and normal sulfate (100%) water types based on Cl and SO(4) concentrations. Majority of the samples (64.3%) belong to C3-S1 water class, indicating water with high salinity and low sodium. Positive index of base exchange indicates the chloro-alkaline equilibrium in the study area. Groundwater potential zonation map for Anekal Taluk was generated using multiparametric and weighted overlay method using the spatial analyst tool in ArcGIS v9.2. Accordingly, five distinct classes corresponding to good(high), moderate (medium), moderate to poor (low), poor (very low), and poor to nil (very low) groundwater potential zones were identified in the region. Of this, 85.27% of the study area belongs to good/high to moderate/medium groundwater potential and only 14.73% belonging to moderate/poor to nil groundwater potential zones.  相似文献   

9.
Arsenic groundwater contamination exceeding 0.05 mg/l affecting the Newer Alluvial tracts of Patna and Bhojpur, the two worst affected districts located in the Middle Ganga Plain in the Bihar state, has been studied The area is underlain by two-tier Quaternary aquifer systems within a depth of 300 m below ground level, separated by a 15?C32-m-thick clay/sandy clay aquitard. The upper part (<50 m depth) of the shallow aquifer system is arsenic-contaminated. The deeper aquifer system (lying below 120?C130 m depth) exhibits low arsenic load (max 0.0035 mg/l), having hydraulic conductivity between 64.88 and 82.04 m/day. Groundwater in the deeper aquifer occurs under semi-confined to confined condition due to poor hydraulic conductivity of the middle clay (4.7 × 10???2???7.2 × 10???3 m/day). Hydraulic head of the deeper aquifer remains close to the surface than the shallow aquifer. The two aquifer systems in the Newer Alluvium are replaced by a thick single aquifer system in the adjoining Older Alluvium, within a depth of 330 m below ground. In the arsenic-contaminated area, deeper aquifer is protected by a middle clay, which may be developed for community drinking water supply by deep tube wells having a yield capacity of 150 m3/h.  相似文献   

10.
The sorption of carbon tetrachloride, ethylene dibromide, and trichloroethylene in two silty clay loam soils and aluminium (Al3+) or calcium (Ca2+) saturated montmorillonite clay was studied. When the adsorbents were exposed to environmental levels of these chemicals (10 to 1000 ppb in water) the amounts of each of the chemicals sorbed were 6% or less of that available except for a 17% sorption of trichloroethylene by Al-saturated clay. In the case of the Ca-saturated clay, there was no apparent sorption of carbon tetrachloride or trichloroethylene. When soil sorption was normalized based on the soil organic carbon content (K oc) a correlation was found between the K oc, water solubility, and octanol/water partitioning coefficients of the chemicals. However, carbon tetrachloride did not behave according to with the predicted relationships.  相似文献   

11.
甘家湖湿地边缘带土地荒漠化演变中土壤颗粒分形特征   总被引:1,自引:0,他引:1  
采用分形理论,研究了甘家湖湿地边缘带不同景观变化类型土壤颗粒体积分形维数的特征。结果表明,(1)从芦苇湿地边缘、胡杨林土、梭梭灌木林土、芦苇湿地、耕地周边、耕地到盐化草甸土的土壤粒径变化可以看出:湿地边缘带土壤荒漠化演变中砂粒含量在逐渐上升,粉粒、粘粒含量逐渐下降。这表明湿地边缘带人为的放牧、开垦、牛羊践踏对土壤产生了...  相似文献   

12.
Untreated sewage and agriculture are the most important sources of contamination. The study was carried out by conducting a short-term surface water and groundwater pollution survey of the Owerri Urban area and its environs, in order to establish the current levels of pollution. An attempt has been made to show the relationships between pollution levels, population density, industrial and agricultural activities. The spatial distribution of pollutants due to a poor land use system and to human activities was investigated. This emphasises integrated planned development as a preventive measure for arresting pollution levels in fast growing urban centres. The total groundwater stored in the area amounts to 7.87 × 109 m3. Twenty five percent of this is released as base flow into the adjacent rivers (Otamiri and Nworie). The annual groundwater recharge is 3.4 × 109 m3. The enormous volume of groundwater stored and the comparatively low cost of development makes groundwater an excellent alternative supply source for the area (Uma et al., 1984).  相似文献   

13.
Some wetland plant species are adapted to growing in the areas of higher metal concentrations. Use of such vegetation in remediation of soil and water contaminated with heavy metals is a promising cost-effective alternative to the more established treatment methods. Throughout the year, composite industrial effluents bringing various kinds of heavy metals contaminate our study site, the East Calcutta Wetlands, a Ramsar site at the eastern fringe of Kolkata city (formerly Calcutta), India. In the present study, possible measures for remediation of contaminated soil and water (with elements namely, Ca, Cr, Cu, Pb, Zn, Mn, and Fe) of the ecosystem had been investigated. Ten common regional wetland plant species were selected to study their efficiency and diversity in metal uptake and accumulation. Results showed that Bermuda grass (Cynodon dactylon) had the highest total Cr concentration (6,601 ± 33 mg kg???1 dw). The extent of accumulation of various elements in ten common wetland plants of the study sites was: Pb (4.4?C57 mg kg???1 dw), Cu (6.2?C39 mg kg???1 dw), Zn (59?C364 mg kg???1 dw), Mn (87?C376 mg kg???1 dw), Fe (188?C8,625 mg kg???1 dw), Ca (969?C3,756 mg kg???1 dw), and Cr (27?C660 mg kg???1 dw) indicating an uptake gradient of elements by plants as Ca>Fe>Mn>Cr>Zn>Cu>Pb. The present study indicates the importance of identification and efficiency of metal uptake and accumulation capabilities by plants in relation to their applications in remediation of a contaminated East Calcutta Wetland ecosystem.  相似文献   

14.
Constructed wetland (CW) and constructed pond (CP) are commonly utilized for removal of excess nutrients and certain pollutants from stormwater. This study characterized shallow groundwater quality for pre- and post-CW and CP system conditions using data from monitoring wells. Results showed that the average concentrations of groundwater phosphorus (P) decreased from pre-CW to post-CW but increased from pre-CP to post-CP. The average concentrations of groundwater total Kjeldahl nitrogen and ammonium ( $ {\mathrm{NH}}{_4^{ + }} $ ) increased from pre-CW (or CP) to post-CW (or CP), whereas the average concentrations of groundwater arsenic (As), chromium, nickel, and zinc (Zn) decreased from pre-CW to post-CW regardless of the well locations. Variations of groundwater cadmium, copper, and Zn concentrations were larger in pre-CP than in post-CP and had a tendency to decrease from pre-CP to post-CP. In general, the average concentrations of groundwater aluminum and manganese decreased and of groundwater calcium, iron, magnesium, and sodium increased from pre-CP to post-CP. The average values of water levels (depth from the ground surface), redox potential, and conductance decreased and of chloride and sulfate ( $ {\mathrm{SO}}{_4^{{ - 2}}} $ ) increased after the wetland and pond were constructed regardless of the well locations. Results further revealed that there were significant differences (α?=?0.05) between the pre- and post-CW (or CP) for redox potential, water level, and As. This study suggests that the CW–CP system had discernible effects on some of the shallow groundwater quality constituents. This information is very useful for fully estimating overall performance of stormwater treatment with the CW–CP system.  相似文献   

15.
Monitoring and assessment of the coastal aquifers are becoming a worldwide concern for the need of additional and sustainable water resources to satisfy demographic growth and economic development. A hydrochemical and geoelectrical investigation was conducted in the El-Omayed area in the northwestern coast of Egypt. The aim of the study was to delineate different water-bearing formations, provide a general evaluation of groundwater quality, and identify the recharge sources in aquifers. Thirty-seven water samples were collected and chemically analyzed from the sand dune accumulations and oolitic limestone aquifers. Fifteen profiles of vertical electrical soundings (VESs) were obtained in the oolitic limestone aquifer to examine the variations of subsurface geology and associated groundwater chemistry. The groundwater reserves in the El-Omayed area are mainly contained in sand dune accumulations and oolitic limestone aquifers. The aquifer of sand dune accumulations contains freshwater of low salinity (average total dissolved solids (TDS)?=?974 mg/l). Groundwater of oolitic limestone aquifer is slightly brackish (average TDS?=?1,486 mg/l). Groundwater of these aquifers can be used for irrigation under special management for salinity control, and regular leaching as indicated by electrical conductivity and sodium adsorption ratio. Results of VES interpretation classified the subsurface sequence of oolitic limestone aquifer into four geoelectric zones, with increasing depth, calcareous loam, gypsum, oolitic limestone, and sandy limestone. Oolitic limestone constitutes the main aquifer and has a thickness of 12–32 m.  相似文献   

16.
Wybong Creek discharges salts into the agriculturally and industrially important Hunter River in New South Wales, Australia. Abrupt increases in salinity occur periodically in the mid-Wybong Creek catchment. In order to understand the processes which cause these abrupt increases, changes in surface and groundwater were investigated. It is shown that salinity increases can be attributed to highly discrete groundwater discharge directly into the river from below. Hourly electrical conductivity data measured in the river showed regular, diurnal electrical conductivity fluctuations of up to 350 μS cm?1. These fluctuations could not be attributed to barometric pressure, temperature, or evapotranspiration. Instead, a similar periodicity in surface water electrical conductivity and groundwater height in nearby groundwater wells was found. Fluctuations were of similar periodicity to the orthotides which cause fluctuations in surface water height and are induced by Earth tides. The geology in the mid-catchment area indicates conditions are optimal for Earth tides to impact groundwater. The reporting of orthotidal changes in water chemistry in this article is believed to be the first of its kind in the scientific literature, with the large fluctuations noted having important implications for water monitoring and management in the catchment. Further research investigating Earth-tide-induced phases of groundwater heights will better constrain the relationships between surface water chemistry and groundwater height.  相似文献   

17.
The water quality of the Akyatan Lagoon was characterized using hydrochemical methodology. The lagoon is located on the Mediterranean coast and is the largest wetland ecosystem in Turkey. In addition, the lagoon is classified as a hyper-salinity wetland. Water samples were collected monthly between December 2007 and November 2008. Eleven stations within the lagoon were determined, and triplicate grab samples were obtained from each station to characterize water quality as follows: T °C, pH, total alkalinity (TAlk), dissolved oxygen (DO), total dissolved solids (TDS), salinity, electrical conductivity (EC), and main anions, including chloride (Cl?), nitrates (NO3 ?), and sulfate (SO4 2?). Results from selected stations indicated varying TDS, EC, salinity, and Cl? concentrations, from 20,892 to 175,824 mg/L, from 35.7 to 99.6 mS/cm, from 22.3 to 71.0 ppt, and from 14,819 to 44,198 mg Cl?/L, respectively. Data indicated that the spatial distribution of water quality parameters was significantly affected by freshwater input via the constructed drainage channels which collect water from a catchment area and discharge water into the lagoon as a point source, thus preventing drainage water to reach the lagoon as a nonpoint source.  相似文献   

18.
Steady- and transient-state simulations of groundwater flow and particle movement in the sub-watershed of the river Labe in Dě?ín town was carried out using Visual MODFLOW software. The simulations were performed for calibration and for the scenarios that the change in the water level of the river Labe was undergoing. Steady-state simulation was carried out for the sake of calibration of model outputs. For transient simulation, two different scenarios were considered in order to investigate the response of the aquifer system to the stresses applied on surface water of the river. The simulation results have shown that the surface water and groundwater interactions, and the subsequent particle movement were affected by the stresses applied on the surface water in the river Labe. The first scenario involved the rapid recharge of surface water to the aquifer in the vicinity of the river while particles still move towards the river at the places far away from the river. At the end of the second scenario, particles still tend to move towards the river slowly and finally tend to stay within the aquifer as equilibrium of hydraulic gradient is reached between the surface and groundwater levels. The time series graphs of hydraulic heads at all observation wells show that the groundwater level in the surrounding aquifer rises significantly as a result of recharges from the river. The local water balance of the study area was calculated and expressed as the rates of water entering and leaving the system. At the end of the second scenario, the difference between the rate of flow into and out of the model area was 0.73 m3 day?1.  相似文献   

19.
The availability of Landsat data allows improving the monitoring and assessment of large-scale areas with land cover changes in rapid developing regions. Thus, we pretend to show a combined methodology to assess land cover changes (LCCs) in the Hamoun Wetland region (Iran) over a period of 30-year (1987–2016) and to quantify seasonal and decadal landscape and land use variabilities. Using the pixel-based change detection (PBCD) and the post-classification comparison (PCC), four land cover classes were compared among spring, summer, and fall seasons. Our findings showed for the water class a higher correlation between spring and summer (R2?=?0.94) than fall and spring (R2?=?0.58) seasons. Before 2000, ~?50% of the total area was covered by bare soil and 40% by water. However, after 2000, more than 70% of wetland was transformed into bare soils. The results of the long-term monitoring period showed that fall season was the most representative time to show the inter-annual variability of LCCs monitoring and the least affected by seasonal-scale climatic variations. In the Hamoun Wetland region, land cover was highly controlled by changes in surface water, which in turn responded to both climatic and anthropogenic impacts. We were able to divide the water budget monitoring into three different ecological regimes: (1) a period of high water level, which sustained healthy extensive plant life, and approximately 40% of the total surface water was retained until the end of the hydrological year; (2) a period of drought during high evaporation rates was observed, and a mean wetland surface of about 85% was characterized by bare land; and (3) a recovery period in which water levels were overall rising, but they are not maintained from year to year. After a spring flood, in 2006 and 2013, grassland reached the highest extensions, covering till more than 20% of the region, and the dynamics of the ecosystem were affected by the differences in moisture. The Hamoun wetland region served as an important example and demonstration of the feedbacks between land cover and land uses, particularly as pertaining to water resources available to a rapidly expanding population.  相似文献   

20.
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