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1.
A study of arsenic,iron and other dissolved ion variations in the groundwater of Bishnupur District,Manipur, India 总被引:1,自引:1,他引:0
Jayalakshmi Devi Oinam AL. Ramanathan Anurag Linda Gurmeet Singh 《Environmental Earth Sciences》2011,62(6):1183-1195
The presence of arsenic (As) in groundwater and its effect on human health has become an issue of serious concern in recent
years. The present study assessed the groundwater quality of the Bishnupur District, Manipur, with respect to drinking water
standards. Higher concentrations of pH, iron and phosphate were observed at several locations. Phosphate and iron levels were
highest in the pre-monsoon, followed by monsoon and post-monsoon seasons. The arsenic concentrations were highest during post-monsoon
(1–200 μg L−1) as compared to pre-monsoon (1–108 μg L−1) and monsoon (2–99 μg L−1). Kwakta and Ngakhalawai show higher levels of arsenic concentration as compared to the prescribed World Health Organization
(WHO) and Bureau of Indian Standards (BIS) norms. Arsenic showed a strong positive correlation with phosphate and negative
correlation with sulphate, suggesting a partial influence of anthropogenic sources. The study suggests that the Bishnupur
area has an arsenic contamination problem, which is expected to increase in the near future. 相似文献
2.
Munendra Singh Amit Kumar Singh Swati Nupur Srivastava Sandeep Singh A. K. Chowdhary 《Environmental Earth Sciences》2010,59(8):1703-1715
In the northern part of the Indian sub-continent, the Gomati River (a tributary of the Ganga River) was selected to study
the dynamics of Arsenic (As) mobilization in fluvial environment of the Ganga Plain. It is a 900-km-long, groundwater-fed,
low-gradient, alluvial river characterized by monsoon-controlled peaked discharge. Thirty-six water samples were collected
from the river and its tributaries at low discharge during winter and summer seasons and were analysed by ICP-MS. Dissolved
As and Fe concentrations were found in the range of 1.29–9.62 and 47.84–431.92 μg/L, respectively. Arsenic concentration in
the Gomati River water has been detected higher than in its tributaries water and characteristically increases in downstream,
attributed to the downstream increasing of Fe2O3 content, sedimentary organic carbon and silt-clay content in the river sediments. Significant correlation of determination
(r
2 = 0.68) was also observed between As and Fe concentrations in the river water. Arsenic concentrations in the river water
are likely to follow the seasonal temperature variation and reach the level of World Health Organization’s permissible limit
(10 μg/L) for drinking water in summer season. The Gomati River longitudinally develops reducing conditions after the monsoon
season that mobilize As into the river water. First, dissolved As enters into pore-water of the river bed sediments by the
reductive dissolution of Fe-oxides/hydroxides due to microbial degradation of sedimentary organic matter. Thereafter, it moves
upward as well as down slope into the river water column. Anthropogenically induced biogeochemical processes and tropical
climatic condition have been considered the responsible factors that favour the release of As in the fluvial environment of
the Ganga Plain. The present study can be considered as an environmental alarm for future as groundwater resources of the
Ganga–Brahmaputra Delta are seriously affecting the human–environment relationship at present. 相似文献
3.
Sudip Jyoti Sahu Bibhash Nath Sharmi Roy Biswapati Mandal Debashis Chatterjee 《Environmental Earth Sciences》2012,65(3):813-821
Groundwater contaminated with arsenic (As), when extensively used for irrigation, causes potentially long-term detrimental
effects to surface soils. Such contamination can also directly affect human health when irrigated crops, such as rice, vegetable
and fruits, are used for human consumption. Therefore, an understanding of the leaching behavior of As in surface soils is
of high importance, because such behavior may increase the bioavailability of As in the soil horizon. In this study, we have
investigated the role of phosphate ions in leaching and bioavailability of As in the soil horizon, where drinking groundwater
contains elevated levels of As (≥50 μg/L). Soil and groundwater samples were characterized in the laboratory and measured
for physical and chemical constituents. The soils are generally neutral to slightly alkaline in character (pH range 7.5–8.1)
with low to moderate levels of free Fe2O3, Al2O3, CaCO3, organic carbon, and clay content. The measured electrical conductivity (mean 599 μS/cm) of the soils demonstrates their
non-saline nature. The Eh values (range −37 to −151 mV) of the groundwater indicate anoxic condition with low to moderate
levels of bicarbonate (range 100–630 mg/L) and phosphate (range 0.002–4.0 mg/L). The arsenic content (range 50–690 μg/L; mean
321 μg/L) in groundwater has exceeded both WHO recommended guideline values (10 μg/L) and the National safe drinking water
limit (50 μg/L). Regression analyses demonstrate that the bioavailability of As in the soil horizon is mainly controlled by
the composition of free Fe2O3 and CaCO3 content of the soils. However, application of P could increase bioavailability of As in the soil horizon and become available
to plants for uptake. 相似文献
4.
Brian G. Katz James A. Kingsbury Heather L. Welch Roland W. Tollett 《Environmental Earth Sciences》2012,65(6):1759-1780
Groundwater chemistry and tracer-based age data were used to assess contaminant movement and geochemical processes in the
middle Claiborne aquifer (MCA) of the Mississippi embayment aquifer system. Water samples were collected from 30 drinking-water
wells (mostly domestic and public supply) and analyzed for nutrients, major ions, pesticides, volatile organic compounds (VOCs),
and transient age tracers (chlorofluorocarbons, tritium and helium-3, and sulfur hexafluoride). Redox conditions are highly
variable throughout the MCA. However, mostly oxic groundwater with low dissolved solids is more vulnerable to nitrate contamination
in the outcrop areas east of the Mississippi River in Mississippi and west Tennessee than in mostly anoxic groundwater in
downgradient areas in western parts of the study area. Groundwater in the outcrop area was relatively young (apparent age
of less than 40 years) with significantly (p < 0.05) higher dissolved oxygen and nitrate–N concentrations and higher detections of pesticides and VOCs compared to water
samples from wells in downgradient areas. Oxygen reduction and denitrification rates were low compared to other aquifers in
the United States (zero order rate constants for oxygen reduction and denitrification were 4.7 and 5–10 μmol/L/year, respectively).
Elevated concentrations of nitrate–N, and detections of pesticides and VOCs in some deep public supply wells (>50 m depth)
indicated contaminant movement from shallow parts of the aquifer into deeper oxic zones. Given the persistence of nitrate
in young oxic groundwater that was recharged several decades ago, and the lack of a confining unit, the downward movement
of young contaminated water may result in higher nitrate concentrations over time in deeper parts of the aquifer containing
older oxic water. 相似文献
5.
《Applied Geochemistry》2006,21(1):83-97
Groundwater in the Gwelup groundwater management area in Perth, Western Australia has been enriched in As due to the exposure of pyritic sediments caused by reduced rainfall, increased groundwater abstraction for irrigation and water supply, and prolonged dewatering carried out during urban construction activities. Groundwater near the watertable in a 25–60 m thick unconfined sandy aquifer has become acidic and has affected shallow wells used for garden irrigation. Arsenic concentrations up to 7000 μg/L were measured in shallow groundwater, triggering concerns about possible health effects if residents were to use water from household wells as a drinking water source. Deep production wells used for public water supply are not affected by acidity, but trends of progressively increasing concentrations of Fe, SO4 and Ca over a 30-a period indicate that pyrite oxidation products extend to the base of the unconfined aquifer. Falling Eh values are triggering the release of As from the reduction of Fe(III) oxyhydroxide minerals near the base of the unconfined aquifer, increasing the risk that groundwater used as a drinking water source will also become contaminated with high concentrations of As. 相似文献
6.
Groundwater arsenic contamination in Manipur,one of the seven North-Eastern Hill states of India: a future danger 总被引:1,自引:0,他引:1
Dipankar Chakraborti E. Jayantakumar Singh Bhaskar Das Babar Ali Shah M. Amir Hossain Bishwajit Nayak Sad Ahamed N. Rajmuhon Singh 《Environmental Geology》2008,56(2):381-390
Manipur State, with a population of 2.29 million, is one of the seven North-Eastern Hill states in India, and is severely
affected by groundwater arsenic contamination. Manipur has nine districts out of which four are in Manipur Valley where 59%
of the people live on 10% of the land. These four districts are all arsenic contaminated. We analysed water samples from 628
tubewells for arsenic out of an expected total 2,014 tubewells in the Manipur Valley. Analyzed samples, 63.3%, contained >10 μg/l
of arsenic, 23.2% between 10 and 50 μg/l, and 40% >50 μg/l. The percentages of contaminated wells above 10 and 50 μg/l are
higher than in other arsenic affected states and countries of the Ganga–Meghna–Brahmaputra (GMB) Plain. Unlike on the GMB
plains, in Manipur there is no systematic relation between arsenic concentration and the depth of tubewells. The source of
arsenic in GMB Plain is sediments derived from the Himalaya and surrounding mountains. North-Eastern Hill states were formed
at late phase of Himalaya orogeny, and so it will be found in the future that groundwater arsenic contamination in the valleys
of other North-Eastern Hill states. Arsenic contaminated aquifers in Manipur Valley are mainly located within the Newer Alluvium.
In Manipur, the high rainfall and abundant surface water resources can be exploited to avoid repeating the mass arsenic poisoning
that has occurred on the GMB plains. 相似文献
7.
Manish Kumar Pankaj Kumar A.L. Ramanathan Prosun Bhattacharya Roger Thunvik Umesh K. Singh M. Tsujimura Ondra Sracek 《Journal of Geochemical Exploration》2010
Groundwater with high geogenic arsenic (As) is extensively present in the Holocene alluvial aquifers of Ghazipur District in the middle Gangetic Plain, India. A shift in the climatic conditions, weathering of carbonate and silicate minerals, surface water interactions, ion exchange, redox processes, and anthropogenic activities are responsible for high concentrations of cations, anions and As in the groundwater. The spatial and temporal variations for As concentrations were greater in the pre-monsoon (6.4–259.5 μg/L) when compared to the post-monsoon period (5.1–205.5 µg/L). The As enrichment was encountered in the sampling sites that were close to the Ganges River (i.e. south and southeast part of Ghazipur district). The depth profile of As revealed that low concentrations of NO3− are associated with high concentration of As and that As depleted with increasing depth. The poor relationship between As and Fe indicates the As release into the groundwater, depends on several processes such as mineral weathering, O2 consumption, and NO3− reduction and is de-coupled from Fe cycling. Correlation matrix and factor analysis were used to identify various factors influencing the gradual As enrichment in the middle Gangetic Plain. Groundwater is generally supersaturated with respect to calcite and dolomite in post-monsoon period, but not in pre-monsoon period. Saturation in both periods is reached for crystalline Fe phases such as goethite, but not with respect to poorly crystalline Fe phases and any As-bearing phase. The results indicate release of arsenic in redox processes in dry period and dilution of arsenic concentration by recharge during monsoon. Increased concentrations of bicarbonate after monsoon are caused by intense flushing of unsaturated zone, where CO2 is formed by decomposition of organic matter and reactions with carbonate minerals in solid phase. The present study is vital considering the fact that groundwater is an exclusive source of drinking water in the region which not only makes situation alarming but also calls for the immediate attention. 相似文献
8.
查明地下水中砷的时间变异性规律及机理是高砷地下水研究的难点和热点, 也是防控地下水砷污染的根本.选择在雨季前后对浅层潜水和孔隙承压水进行了动态监测.研究表明地下水砷含量和形态与地下水位波动存在明显的响应关系: 雨季开始后随着地下水位抬升, 地下水还原环境增强, As(Ⅴ)和Asp转化成As(Ⅲ), 颗粒态铁大幅降低, 导致水中溶解的砷和铁大幅增加, 地下水砷含量在雨季达到最高且As(Ⅲ)所占比例达到90%;雨季结束后随着水位逐渐降低, 地下水中As(Ⅲ)所占比例和溶解的砷含量下降.农业活动对浅层潜水砷形态季节性变化有明显的影响.孔隙承压水的砷形态分布变化较浅层潜水幅度大, 其变化与水位波动存在滞后效应.自然或人为活动引起的地下水位季节性变化改变了含水层的氧化还原环境, 补给水源与地下水之间的混合过程带来新的物质输入促进地下水系统中砷的迁移转化. 相似文献
9.
Syed Hilal Farooq Pintu Prusty Raj Kumar Singh Subhajit Sen Dornadula Chandrasekharam 《Arabian Journal of Geosciences》2018,11(22):709
The contamination of aquifers by fluoride and arsenic is a major cause of concern in several parts of India. A study has thus been conducted to evaluate the extent and severity of fluoride contamination and also its seasonal variability. Two blocks (Purulia-1 and Purulia-2) were considered for this purpose. Twenty groundwater samples (in each season) were collected from tube wells during the pre-monsoon and post-monsoon seasons. In addition to fluoride, groundwater samples were also analyzed for major cations, anions, and other trace elements. The concentration of fluoride shows significant seasonal variation and ranges between 0.94–2.52 and 0.25–1.43 mg/l during the pre-monsoon and post-monsoon seasons, respectively. In pre-monsoon season, more than 40% of the water samples show fluoride concentrations higher than the WHO limit. However, during the post-monsoon season, none of the groundwater sample shows fluoride concentrations higher than the WHO limit. Lesser concentration during the post-monsoon season is attributed to the dilution effect by the percolating rainwater, which has also been reflected in the form of a decrease in concentrations of other elements. The petrographic studies of the rock samples collected from the study area show that the rocks are mainly composed of plagioclase, orthoclase, and quartz with abundant biotite. The weathering and dissolution of biotite plays an important role in controlling the fluoride concentrations in the groundwater of the study area. 相似文献
10.
Eva Pacioni Marco Petitta Ezio Burri Maria Fanelli Piero Mazzeo Fabrizio Ruggieri 《Environmental Earth Sciences》2010,61(1):201-216
This paper analyses flow and transport of pesticides from the unsaturated zone to groundwater so as to predict concentration
of those contaminants in the Fucino Plain’s groundwater, by site investigations and numerical simulations. Pesticides were
detected in surface water (peaks of 13 μg L−1) and groundwater (peaks of 0.37 μg L−1). Modelling tools made it possible to identify that pattern of precipitation, organic matter content, and root thickness
are the key factors involved in vertical seepage of pesticides. Numerical simulations indicated that a significant fraction
of contaminants is leached from the most surficial soil layers through runoff, while only a secondary fraction is mobilised
towards groundwater. Likelihood of contaminating deep groundwater is fairly low, whereas surface waters show higher susceptibility.
Results of the proposed conceptual hydrogeological model show that pesticides are more likely to be entrained by mixing of
stream water with shallow groundwater in periods of high water exploitation from shallow wells. 相似文献
11.
Movement of seasonal eddies in the Bay of Bengal (BOB) and its relation with cyclonic heat potential (CHP) and cyclogenesis
points have been investigated in this study using 6 years (2002–2007) of global ocean monthly analysis datasets based on the
Simple Ocean Data Assimilation (SODA) package (SODA v2.0.4) of Carton et al. (2005) and Indian Meteorological Department cyclogenesis points. The region dominated by anticyclonic eddies with CHP greater than
70 × 107 J/m2 as well as good correlations (>0.9) with sea surface height (SSH) and 26°C isothermal depth (D
26) can be a potential region of cyclogenesis. The region dominated by cyclonic eddies with CHP greater than 50 × 107 J/m2 and good correlation (>0.9) with both SSH and D
26 can serve as a potential region of high-level depression. Potential cyclogenesis regions are the southern BOB (5°N–12°N)
for the post-monsoon season and the head of BOB (north of 15°N) during southwest monsoon. Seven potential regions are identified
for the eddy formation for different seasons, which are consistent with the cyclogenesis points. The CHP distributions alone
are able to explain the cyclone tracks for the pre-monsoon and post-monsoon seasons but not for the monsoon season. 相似文献
12.
To study arsenic(As) content and distribution patterns as well as the genesis of different kinds of water, especially the different sources of drinking water in Guanzhong Basin, Shaanxi province, China, 139 water samples were collected at 62 sampling points from wells of different depths, from hot springs, and rivers. The As content of these samples was measured by the intermittent flowhydride generation atomic fluorescence spectrometry method(HG-AFS). The As concentrations in the drinking water in Guanzhong Basin vary greatly(0.00–68.08 μg/L), and the As concentration of groundwater in southern Guanzhong Basin is different from that in the northern Guanzhong Basin. Even within the same location in southern Guanzhong Basin, the As concentrations at different depths vary greatly. As concentration of groundwater from the shallow wells(50 m deep, 0.56–3.87 μg/L) is much lower than from deep wells(110–360 m deep, 19.34–62.91 μg/L), whereas As concentration in water of any depth in northern Guanzhong Basin is 10 μg/L. Southern Guanzhong Basin is a newly discovered high-As groundwater area in China. The high-As groundwater is mainly distributed in areas between the Qinling Mountains and Weihe River; it has only been found at depths ranging from 110 to 360 m in confined aquifers, which store water in the Lishi and Wucheng Loess(Lower and Middle Pleistocene) in the southern Guanzhong Basin. As concentration of hot spring water is 6.47–11.94 μg/L; that of geothermal water between 1000 and 1500 m deep is 43.68–68.08 μg/L. The high-As well water at depths from 110 to 360 m in southern Guanzhong Basin has a very low fluorine(F) value, which is generally 0.10 mg/L. Otherwise, the hot springs of Lintong and Tangyu and the geothermal water in southern Guanzhong Basin have very high F values(8.07–14.96 mg/L). The results indicate that highAs groundwater in depths from 110 to 360 m is unlikely to have a direct relationship with the geothermal water in the same area. As concentration of all reservoirs and rivers(both contaminated and uncontaminated) in the Guanzhong Basin is 10 μg/L. This shows that pollution in the surface water is not the source of the high-As in the southern Guanzhong Basin. The partition boundaries of the high- and low-As groundwater area corresponds to the partition boundaries of the tectonic units in the Guanzhong Basin. This probably indicates that the high-As groundwater areas can be correlated to their geological underpinning and structural framework. In southern Guanzhong Basin, the main sources of drinking water for villages and small towns today are wells between 110–360 m deep. All of their As contents exceed the limit of the Chinese National Standard and the International Standard(10 μg/L) and so local residents should use other sources of clean water that are 50 m deep, instead of deep groundwater(110 to 360 m) for their drinking water supply. 相似文献
13.
Spatial assessment of salinity and nitrate pollution in Amman Zarqa Basin: a case study 总被引:1,自引:0,他引:1
Mustafa Al Kuisi Mohammed Al-Qinna Armin Margane Taiseer Aljazzar 《Environmental Earth Sciences》2009,59(1):117-129
Intensive use of land resources in arid and semi-arid regions exert serious pressures on groundwater resources and jeopardize
further socio-economical developments. The Amman-Zarqa Basin (AZB), the most vital basin in Jordan, is facing recent groundwater
deterioration due to a very large increase in water demands for domestic, agricultural, and industrial uses. The objectives
of this paper were to quantify the degree of contamination in the basin by evaluating the characteristics, distribution and
seasonal variations of two pollution indicators (nitrate concentration and salinity) and to determine the impacts of human
activities (land use) on groundwater quality. Based upon long-term data (1970–2005) of groundwater samples collected from
538 wells across the AZB, spatial analyses indicated that both indicators have a strong spatial dependence and are anisotropically
distributed. Prediction maps of Ordinary Kriging and Indicator Kriging provided detailed indications of the major and minor
sources of pollution in the basin. Inefficient wastewater treatment plants, industrial activities and agricultural practices
were responsible for 91, 85, and 25% salinization of nearby wells, respectively. Nitrate pollution had reached 73% above threshold
(50 mg/L) in some cases. The temporal analyses estimated the salinity buildup rate to be around 8 × 10−2 μS/cm per day, while nitrate buildup rate was estimated to be around 6 × 10−2 mg/L per day. Remote sensing and spatial analyses helped greatly in groundwater quality assessment not only in providing
the environmental status of the AZB but also in delineating the potential of contamination risk zones and their correlation
to human activities. Furthermore, the paper suggests some environmental protection strategies that should be adopted to protect
the vital groundwater resources of the basin from further deterioration. 相似文献
14.
The aquifer system of the Upper Triassic Keuper Sandstone, an important source of drinking water in northern Bavaria, is
affected by elevated arsenic concentrations. Within the study area of 8000 km2, no evidence exists for any artificial source of arsenic. Data from about 500 deep water wells show that in approximately
160 wells arsenic concentrations are 10–150 μg/L. The regional distribution of arsenic in the groundwater shows that elevated
arsenic concentrations are probably related to specific lithofacies of the aquifers that contain more sediments of terrestrial
origin. Geochemical measurements on samples from four selected well cores show that arsenic has accumulated in the rocks.
This indigenous arsenic is the source of arsenic in the groundwater of certain facies of the middle unit of the Keuper Sandstone.
Received, June 1998 / Revised, January 1999, May 1999 / Accepted, June 1999 相似文献
15.
Erik Espinosa María Aurora Armienta Olivia Cruz Alejandra Aguayo Nora Ceniceros 《Environmental Geology》2009,58(7):1467-1477
High arsenic (As) groundwater is widely distributed in northwestern Hetao Plain, an arid region with sluggish groundwater
flow. Observed As concentration in groundwater from wells ranges from 76 to 1,093 μg/l. Most water samples have high total
dissolved solids, with Cl and HCO3 as the dominant anions and Na as the dominant cation. The major hydrochemical types of most saline groundwaters are Na–Mg–Cl–HCO3 and Na–Mg–Cl. By contrast, fresh groundwaters generally belong to the Na–Mg–HCO3 type. High concentrations of arsenic in shallow aquifers are associated with strongly reducing conditions, as evidenced by
high concentrations of dissolved organic carbon, ammonium, as well as dissolved sulfide and Fe, dominance of arsenite, relatively
low concentrations of nitrate and sulfate, and occasionally high content of dissolved methane (CH4). High As groundwaters from different places at Hetao Plain experienced different redox processes. Fluoride is also present
in high As groundwater, ranging between 0.40 and 3.36 mg/l. Although fluorosis poses an additional health problem in the region,
it does not correlate well with As in spatial distribution. Geochemical analysis indicates that evapotranspiration is an important
process controlling the enrichment of Na and Cl, as well as trace elements such as As, B, and Br in groundwater.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
16.
Assessment of groundwater quality and contamination problems ascribed to an abandoned uranium mine (Cunha Baixa region,Central Portugal) 总被引:2,自引:0,他引:2
The assessment of groundwater quality and its environmental implications in the region of the abandoned Cunha Baixa uranium
mine (Central Portugal) was carried out from 1995 to 2004. Shallow groundwater is the major water supply source for irrigation
in the neighbourhood of Cunha Baixa village. Water samples from the mine site as well as from private wells were collected
in order to identify the mining impact on water composition, the extent of contamination and the seasonal and temporal groundwater
quality variations. Some of the sampled private wells contain waters having low pH (<4.5–5) and high values of EC, TDS, SO4, F, Ca, Mg, Al, Mn, Ni, U, Zn and 226Ra. The wells located through the ESE–WSE groundwater flow path (1 km down gradient of the mining site) display the most contaminated
water. In the summer season, the levels of SO4, Al, Mn, and U were 50–120 times higher than those registered for uncontaminated waters and exceeded the quality limits for
irrigation purposes, presenting soil degradation risks. Nevertheless, this study indicates that groundwater contamination
suffered a small decrease from 1999 to 2004. The bioaccumulation of toxic metals such as Al, Mn, and U within the food chain
may cause a serious health hazard to the Cunha Baixa village inhabitants. 相似文献
17.
Environmental and health risk assessment in abandoned mining area, Zlata Idka, Slovakia 总被引:1,自引:0,他引:1
The Zlata Idka village is a typical mountainous settlement. As a consequence of more than 500 years of mining activity, its environment has been extensively affected by pollution from potentially toxic elements. This paper presents the results of an environmental-geochemical and health research in the Zlata Idka village, Slovakia. Geochemical analysis indicates that arsenic (As) and antimony (Sb) are enriched in soils, groundwater, surface water and stream sediments. The average As and Sb contents are 892 mg/kg and 818 mg/kg in soils, 195 mg/kg and 249 mg/kg in stream sediments, 0.028 mg/l and 0.021 mg/l in groundwater and 0.024 mg/l and 0.034 mg/l in surface water. Arsenic and Sb concentrations exceed upper permissible limits in locally grown vegetables. Within the epidemiological research the As and Sb contents in human tissues and fluids have been observed (blood, urine, nails and hair) in approximately one third of the village’s population (120 respondents). The average As and Sb concentrations were 16.3 μg/l and 3.8 μg/l in blood, 15.8 μg/l and 18.8 μg/l in urine, 3,179 μg/kg and 1,140 μg/kg in nails and 379 μg/kg and 357 μg/kg in hair. These concentrations are comparatively much higher than the average population. Health risk calculations for the ingestion of soil, water, and vegetables indicates a very high carcinogenic risk (>1/1,000) for as content in soil and water. The hazard quotient [HQ=average daily dose (ADD)/reference dose (RfD)] calculation method indicates a HQ>1 for groundwater As and Sb concentrations. 相似文献
18.
Ibticem Chamtouri Habib Abida Hafedh Khanfir Salem Bouri 《Environmental Geology》2008,55(5):1123-1133
Groundwater in Sfax City (Tunisia) has been known since the beginning of the century for its deterioration in quality, as
a result of wastewater recharge into the aquifer. An average value of 12 × 106 m3 of untreated wastewater reaches the groundwater aquifer each year. This would result not only in a chemical and biological
contamination of the groundwater, but also in an increase of the aquifer piezometric level. Quantitative impacts were evaluated
by examining the groundwater piezometric level at 57 surface wells and piezometers. The survey showed that, during the last
two decades, the groundwater level was ever increasing in the urban area with values reaching 7 m in part; and decreasing
in Sidi Abid (agricultural area) with values exceeding −3 m. Groundwater samples for chemical and microbial analysis were
collected from 41 wells spread throughout the study area. Results showed significantly elevated levels of sodium, chlorides,
nitrates and coliform bacteria all over the urban area. High levels (NO3: 56–254 mg/l; Na >1,500 mg/l; Coliforms >30/100 ml) can be related to more densely populated areas with a higher density
of pit latrine and recharge wells. Alternatively results showed a very variable chemical composition of groundwater, e.g.
electrical conductivity ranges from 4,040 to19,620 μs/cm and the dry residual varies between 1.4 and 14 g/l with concentrations
increasing downstream. Furthermore a softening of groundwater in Set Ezzit (highly populated sector) was observed. 相似文献
19.
Geochemical study of arsenic and other trace elements in groundwater and sediments of the Old Brahmaputra River Plain,Bangladesh 总被引:1,自引:1,他引:0
Faruque Ahmed M. Hawa Bibi Hiroaki Ishiga Takehiko Fukushima Teruyuki Maruoka 《Environmental Earth Sciences》2010,60(6):1303-1316
The geochemical study of groundwaters and core sediments from the Old Brahmaputra plain of Bangladesh was conducted to investigate
the distribution of arsenic and related trace elements. Groundwaters from tube wells are characterized by pH of 6.4–7.4, dissolved
oxygen (DO) of 0.8–1.8 mg/l, Ca contents of 5–50 mg/l, and Fe contents of 0.2–12.9 mg/l. Arsenic concentrations ranged from
8 to 251 μg/l, with an average value of 63 μg/l. A strong positive correlation exists between As and Fe (r
2 = 0.802; p = 0.001) concentrations in groundwater. The stratigraphic sequences in the cores consist of yellowish silty clays at top,
passing downward into grayish to yellowish clays and sands. The uppermost 3 m and lower parts (from 13 to 31 m) of the core
sediments are oxidized (average oxidation reduction potential (ORP) +170 and +220 mV, respectively), and the ORP values gradually
become negative from 3 to 13 m depths (−35 to −180 mV), indicating that anoxic conditions prevail in the shallow aquifers
of the Brahmaputra plain. Age determinations suggest that clay horizons at ~10 m depth were deposited at around 2,000 and
5,000 years BP (14C ages) during the transgressive phase of sea-level change. Elevated concentrations of As, Pb, Zn, Cu, Ni, Cr, and V are present
in the silts and clays, probably due to adsorption onto clay particles. Significant concentrations of As occur in black peat
and peaty sediments at depths between 9 and 13 m. A strong positive correlation between As and Fe was found in the sediments,
indicating As may be adsorbed onto Fe oxides in aquifer sediments. 相似文献
20.
Nitrate contamination of groundwater in an agroecosystem in Zhangye Oasis,Northwest China 总被引:5,自引:2,他引:3
In order to assess the extent of groundwater contamination by nitrate (NO3
−–N) and to provide information about the deterioration of the groundwater quality in Zhangye Oasis, Northwest China, a study
was conducted in this area. The mean value of NO3
−–N concentrations in groundwater samples was 10.66 ± 0.19 mg l−1. NO3
−–N concentrations exceeding 10 mg l−1 (the threshold for drinking water set by the World Health Organization) were found in 32.4% of 71 wells, and were 13, 33.3,
52.4 and 50.0% in the groundwater samples from drinking wells, irrigation wells, hand-pumping wells and groundwater table
observation wells, respectively. The result showed that the groundwater samples that had NO3
−–N concentrations exceeding the threshold for drinking water were mostly collected from a depth of less than 20 m. Groundwater
NO3
−–N concentrations in areas used for the cultivation of vegetables, seed maize and intercropped maize were significantly higher
than those in urban or paddy areas. NO3
−–N contamination of groundwater in areas with sandy soil was more severe than in those with loam soil. 相似文献