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1.
Groundwater arsenic survey in Cachar and Karimganj districts of Barak Valley, Assam shows that people in these two districts are drinking arsenic-contaminated (max. 350 μg/l) groundwater. 66% of tubewells in these two districts have arsenic concentration above the WHO guideline value of 10 μg/l and 26% tubewells have arsenic above 50 μg/l, the Indian standards for arsenic in drinking water. 90% of installed tubewells in these two districts are shallow depth (14–40 m). Shallow tubewells were installed in Holocene Newer Alluvium aquifers are characterised by grey to black coloured fine grained organic rich argillaceous sediments and are mostly arsenic contamination in groundwater. Plio-Pleistocene Older Alluvium aquifers composed of shale, ferruginous sandstone, mottle clay, pebble and boulder beds, which at higher location or with thin cover of Newer Alluvium sediments are safe in arsenic contamination in groundwater. 91% of tubewell water samples show significantly higher concentrations of iron beyond its permissible limit of 1 mg/l. The iron content in these two districts varies from 0.5 to as much as 48 mg/l. Most of the arsenic contaminated villages of Cachar and Karimganj districts are located in entrenched channels and flood plains of Newer Alluvium sediments in Barak-Surma-Langai Rivers system. However, deeper tubewells (>60 m) in Plio-Pleistocene Older Alluvium aquifers would be a better option for arsenic-safe groundwater. The arsenic in groundwater is getting released from associated Holocene sediments which were likely deposited from the surrounding Tertiary Barail hill range.  相似文献   

2.
High As contents in groundwater were found in Rayen area and chosen for a detailed hydrogeochemical study. A total of 121 groundwater samples were collected from existing tube wells in the study areas in January 2012 and analyzed. Hydrogeochemical data of samples suggested that the groundwater is mostly Na–Cl type; also nearly 25.62 % of samples have arsenic concentrations above WHO permissible value (10 μg/l) for drinking waters with maximum concentration of aqueous arsenic up to 25,000 μg/l. The reducing conditions prevailing in the area and high arsenic concentration correlated with high bicarbonate and pH. Results show that arsenic is released into groundwater by two major phenomena: (1) through reduction of arsenic-bearing iron oxides/oxyhydroxides and Fe may be precipitated as iron sulfide when anoxic conditions prevail in the aquifer sediments and (2) transferring of As into the water system during water–acidic volcanic rock interactions.  相似文献   

3.
The results of integral pumping tests (IPTs) performed in the city of Fabriano, Italy, are presented. The IPT methodology was developed by the European Union project INCORE, as a tool for groundwater investigation and source localization in contaminated areas. This methodology consists of a multiple-well pumping test in which the wells are positioned along a control plane downstream of suspected contaminant source zones and perpendicular to the mean groundwater flow direction. During the pumping, concentration time series of target contaminants are measured. In Fabriano, two control planes were realized to identify a chlorinated aliphatic hydrocarbon plume, to estimate the mass fluxes and draw up a ranked list of the main contamination sources. A numerical flow model was implemented to support the IPT design and to interpret the results. This study revealed low-level trichloroethylene contamination (concentration below 8 μg/l), tetrachloroethylene contamination (mean concentration up to 500 μg/l) and a mass flow rate of about 300 g/day. Through the application of the IPT method, the mean contaminant concentrations, the spatial distribution of concentration values along the control planes, and the total contaminant mass flow rates were evaluated, and the investigation area was reduced for further and deeper investigation activities.  相似文献   

4.
Problems on groundwater contamination in Japan are briefly summarized in this paper. Although normal physical conditions in Japan restrict the possibilities of groundwater contamination, human activities are threatening groundwater resources. A survey by the Environment Agency of Japan showed nationwide spreading of organic substances, such as trichloroethylene as well as nitrogen compounds. Synthetic detergents have also been detected even in rural areas and in deep confined aquifers, although their concentrations are not as high. Public awareness of agrichemical or pesticides abuse, especially from golf courses, is apparent. Other problems such as nitrate-nitrogen, leachate from landfills, and the leaking of underground storage tanks are also discussed.  相似文献   

5.
《Applied Geochemistry》2001,16(5):489-502
At the Monteponi Pb–Zn mine located in south-western Sardinia intensive dewatering has been carried out over about 100 a. A marked increase in the salinity and Hg concentration of deep groundwater occurred as the water table level was lowered from +15 to −160 m a.s.l. over this period. Closure of the mine implied the cessation of the expensive pumping system, and prompted the assessment of the contamination risk for the shallow groundwater system supplying Iglesias town. This study shows that deep water was mixed into the shallow aquifer as the water table level rose. An increase of salinity, mainly due to Na and Cl, has been observed in shallow groundwater. The input of Cl facilitates the dissolution of Hg. Moreover, the progressive mine flooding is causing an increase of other dissolved metals, mainly due to the weathering of primary sulphides and secondary minerals present in the ore, and remobilization of metals in the mine waste left in the galleries. A stratification process will allow the saline water at depth to settle, and this is expected to occur in a relatively short time (few years). The leaching of metals represents a greater concern for the quality of shallow groundwater, and the time necessary to clean up will be much longer (probably several decades) than that expected for the stratification of the water body.  相似文献   

6.
High arsenic levels in groundwater of the aquifers, belonging to the Pliocene terrestrial layers and Quaternary alluvial sediments, have become a significant problem for the inhabitants living in Sarkisla (Turkey). The main objective of this study was to determine the origin and arsenic contamination mechanisms of the Sarkisla drinking water aquifer systems. The highest arsenic concentrations were found in Pliocene layers and alluvial sediments with concentrations ranging from 2.1 to 155 mg/kg. These rocks are the main aquifers in the study area, and most of the drinking groundwater demand is met by these aquifers. Groundwater from the Pliocene aquifer is mainly Ca-HCO3 and Ca-SO4 water type with high EC values reaching up to 3,270 μS/cm, which is due to the sulfate dissolution in some parts of the alluvial aquifer. Stable isotope values showed that the groundwater was of meteoric origin. Tritium values for the groundwater were between 8.31 and 14.06 TU, representing a fast circulation in the aquifer. Arsenic concentrations in the aquifers were between 0.5 and 345 μg/L. The highest arsenic concentrations detected in the Pliocene aquifer system reached up to 345 μg/L with an average value of 60.38 μg/L. The arsenic concentrations of the wells were high, while the springs had lower arsenic concentrations. These springs are located in the upper parts of the study area where the rocks are less weathered. The hydrogeochemical properties demonstrated that the water–rock interaction processes in sulfide-bearing rocks were responsible for the remarkably high groundwater arsenic contamination in the study area. In the study area, the arsenic levels determined in groundwater exceeded the levels recommended by the WHO. Therefore, it is suggested that this water should not be used for drinking purposes and new water sources should be investigated.  相似文献   

7.
A groundwater arsenic (As) survey in Mirzapur, Varanasi, Ghazipur, Ballia, Buxar, Ara, Patna, and Vaishali districts of UP and Bihar shows that people from these districts are drinking As-contaminated groundwater (max. 1,300 μg/l). About 66 % of tubewells from Buxar to Mirzapur areas and 89 % of tubewells from Patna to Ballia areas have As?>?10 μg/l (WHO guideline). Moreover, 36 % of tubewells from Buxar to Mirzapur areas and 50 % of tubewells from Patna to Ballia areas have As above 50 μg/l. Most of the As-affected villages are located close to abandoned or present meander channels of the Ganga River. In contrast, tubewells located in Mirzapur, Chunar, Varanasi, Saidpur, Ghazipur, Muhammadabad, Ballia, Buxar, Ara, Chhapra, Patna, and Hazipur towns are As-safe in groundwater because of their positions on the Pleistocene Older Alluvium upland surfaces. The iron (Fe) content in tubewell water samples varies from 0.1 to 12.93 mg/l. About 77 % As-contaminated tubewells are located within the depth of 21 to 40 m in the Holocene Newer Alluvium aquifers. The potential source of As in sediments carried through the rivers from the Himalayas. Maximum As concentrations in the Older and Newer Alluvium sediments are 13.73 and 30.91 mg/kg, respectively. The Himalayas rivers, i.e. Yamuna, Ganga, Gomati, Ghaghara, Gondak, Buri Gandak, and Kosi rivers carrying suspended sediments have high content of As (max. 10.59 mg/kg).  相似文献   

8.
Arsenic occurrence in groundwater near the Cimino-Vico volcanoes (central Italy) was analysed considering the hydrostratigraphy and structural setting and the shallow and deep flows interacting within the Quaternary volcanics. Groundwater is the local source of drinking water. As documented in the past, arsenic in the groundwater has become a problem, and the European maximum allowable contaminant level was recently lowered to 10 μg/L. Chemical analyses of groundwater were conducted, sampled over an area of about 900 km2, from 65 wells and springs representative of the volcanic aquifer and thermal waters. Considering the type of aquifer, the nature of the aquifer formation and its substratum, the hydrochemical data highlight that the arsenic content of the groundwater is mainly connected with the hydrothermal processes in the volcanic area. Thermal waters (54–60°C) fed from deep-rising fluids show higher arsenic concentrations (176–371 μg/L). Cold waters sampled from the volcanic aquifer are characterized by a wide variability in their arsenic concentration (1.6–195 μg/L), and about 62% exceed the limit of 10 μg/L. Where the shallow volcanic aquifer is open to deep-rising thermal fluids, relatively high arsenic concentrations (20–100 μg/L) are found. This occurs close to areas of the more recent volcano-tectonic structures.  相似文献   

9.
Arsenic in groundwaters of the alluvial aquifer of Bardsir plain, SE Iran   总被引:1,自引:1,他引:0  
Bardsir plain is located in the central part of Kerman Province of Iran. The relative prevalence of arsenic-related cancers, the high concentration of arsenic in nearby plains, as well as the recharge of this aquifer through the mountains composed of high-sulfide volcanic rocks have been motivations of the authors to study the concentration of this element in Bardsir plain. Arsenic concentration was measured in 63 groundwater samples using inductively coupled plasma mass spectrometry method. The results were evaluated through iso-concentration maps, correlation diagrams, and multivariate statistical methods. Accordingly, the concentration of arsenic ranges from 1.3 to 464.5 μg/l with an average value of 134.2 μg/l. So, the groundwaters are enriched with arsenic to much higher levels than permitted for than drinking water acceptable level (10 μg/l). The high arsenic levels in groundwaters of Bardsir plain are ascribed to joint influence of decomposition of sulfides present in mountainous volcanic rocks and the mixing with hydrothermal waters in some locations. Supposedly, the prevalence of higher than 8 pH values has enhanced the release of arsenic from Fe-hydroxides generated during sulfide weathering process.  相似文献   

10.
Polycyclic aromatic hydrocarbon (PAH) and nitrated PAH (NPAH) products are toxic. Thus, determination of their concentrations is of great interest to researchers of soil and water pollution control. In this work, soil samples, surface water samples, and groundwater samples were collected, and the concentrations of 16 priority PAHs and 15 NPAHs were determined using an HPLC-ultraviolet detector. Results showed that the total PAH concentrations ranged within 489.69–1,670.11 ng/g (average = 905.89 ng/g) in soil samples, 4.00–23.4 μg/l (average = 9.84 μg/l) in surface water samples, and 2.14–22.3 μg/l (average = 8.37 μg/l) in groundwater samples. The NPAH concentrations were one to two orders of magnitude lower than the PAH concentrations and ranged within 22.72–128.70 ng/g (average = 63.88 ng/g) in soil samples. 2-Nitropyrene and 6-nitrochrysene were the most abundant compounds, accounting for about 14.3 and 26.5 %, respectively. Source analysis revealed that most PAHs originated from coal combustion around the study area, whereas NPAH studies suggested that the primary emission of gasoline engines and daytime OH reactions were the dominant sources of these compounds.  相似文献   

11.
A logistic regression model for the probability of arsenic exceeding the drinking water guidelines (10 μg/L) in bedrock groundwater was developed for a selected county in Korea, where arsenic occurrence and release reactions have been investigated. Arsenic was enriched naturally by the oxidation of sulfide minerals in metasedimentary rocks and mineralized zones, and due to high mobility in alkaline pH conditions, concentrations were high in groundwater of the county. When considering these reactions of arsenic release and water quality characteristics, several geological and geochemical factors were selected as influencing variables in the model. In the final logistic regression model, geological units of limestone and metasedimentary rocks, the concentrations of nitrate and sulfate, and distances to closed mines and adjacent granite were retained as statistically significant variables. Predicted areas of high probability agreed well with known spatial contamination patterns in the county. The model was also applied to an adjacent county, where the groundwater has not previously been tested for the presence of arsenic, and a probability map for arsenic contamination was then produced. Through the analysis of arsenic concentrations at the wells of high probability, it was determined that the applied model accurately indicated the arsenic contamination of groundwater. The logistic regression approach of this study can be applied to predict arsenic contamination in areas of similar geological and geochemical conditions to the county used in this model.  相似文献   

12.
Large numbers of As-enriched geothermal springs are distributed at the southern Tibetan Plateau, and their influence on river water is still not clear. Lhasa River and its tributary, Duilong Qu located at downstream of the largest geothermal spring of the Tibetan Plateau, were selected for sampling during monsoon and non-monsoon seasons. Dissolved trace elements (B, Cr, Ni, Cu, Zn, As, Cs, Ba and U) were measured in river water samples by ICP-MS. The results show that due to contribution of geothermal spring, As levels of Duilong Qu (205.6 μg/L) and Lhasa River (12.7 μg/L) were higher during non-monsoon season than that of WHO guideline for drinking water (10 μg/L). Accordingly, As level of river water was lower during the monsoon season than that of the non-monsoon season due mainly to dilution process. Therefore, although Tibetan rivers are generally considered as free of contamination, geothermal springs cause As contamination of river water at some local regions and may harm the local residents. Further research is needed in other parts of the plateau to determine whether As level of groundwater of the related region is high.  相似文献   

13.
The concentrations of uranium, iron and the major constituents were determined in groundwater samples from aquifer containing uranyl phosphate minerals (meta-autunite, meta-torbernite and torbernite) in the Köprüba?? area. Groundwater samples from wells located at shallow depths (0.5–6 m) show usually near neutral pH values (6.2–7.1) and oxidizing conditions (Eh = 119–275 mV). Electrical conductivity (EC) values of samples are between 87 and 329 μS/cm?1. They are mostly characterized by mixed cationic Ca dominating bicarbonate types. The main hydrogeochemical process is weathering of the silicates in the shallow groundwater system. All groundwater in the study area are considered undersaturated with respect to torbernite and autunite. PHREEQC predicted UO2(HPO4) 2 2? as the unique species. The excellent positive correlation coefficient (r = 0.99) between U and PO4 indicates the dissolved uranium in groundwater would be associated with the dissolution of uranyl phosphate minerals. The groundwater show U content in the range 1.71–70.45 μg/l but they are mostly lower than US EPA (2003) maximum contaminant level of 30 μg/l. This low U concentrations in oxic groundwater samples is attributed to the low solubility of U(VI) phosphate minerals under near neutral pH and low bicarbonate conditions. Iron closely associated with studied sediments, were also detected in groundwater. The maximum concentration of Fe in groundwater samples was 2837 μg/l, while the drinking water guidelines of Turkish (TSE 1997) and US EPA (2003) were suggested 200 and 300 μg/l, respectively. Furthermore, iron and uranium showed a significant correlation to each other with a correlation coefficient (r) of 0.94. This high correlation is probably related to the iron-rich sediments which contain also significant amounts of uranium mineralization. In addition to pH and bicarbonate controlling dissolution of uranyl phosphates, association of uranyl phosphates with iron (hydr) oxides seems to play important role in the amount of dissolved U in shallow groundwater.  相似文献   

14.
The groundwater in the karst region of northeastern Vietnam is found in various structural zones such as the Ha Lang, Song Hien, Hon Gai, Song Lo, Song Gam, and Hoang Lien Son Zones, etc. Results from this study show that groundwater in this region is at different depths: ~120 m deep at Quang Ninh, ~100 m at Lang Son, ~80 m at Cao Bang (The most water-abundant depth observed at Cao Bang varies from 40 to 45 m) while it varies from 18–25 to 80 m deep at Quan Ba (Ha Giang), especially at Meo Vac (Ha Giang), where groundwater is observed at 700–800 m deep (equivalent to local base level of the Nho Que River). Overall, groundwater in the region is fresh with total minerals varying from 250 to 400 mg/l; except for the coastal area of Quang Ninh, where groundwater is characterized by much higher total minerals (M = 3–18 g/l) due to the mixing with the saline sea water. The chemistry of water in the region demonstrates that the water is mainly bicarbonate with a [HCO3 ?] concentration varying from 150 to 265 mg/l, pH is of 6.5–8.1, and its hardness is of 3.7–6.0 meq/l.  相似文献   

15.
Groundwater pumped from the semi-confined Complex Terminal (CT) aquifer is an important production factor in irrigated oases agriculture in southern Tunisia. A rise in the groundwater salinity has been observed as a consequence of increasing abstraction from the aquifer during the last few decades. All sources of contamination were investigated using hydrochemical data available from the 1990s. Water samples were taken from wells tapping both the CT and the shallow aquifers and analyzed with regard to chemistry tracers. Hydrochemical and water quality data obtained through a sampling period (December 2010) and analysis program indicate that nitrate pollution can be a serious problem affecting groundwater due to the use of nitrogen (N) fertilizers–pesticides in agriculture. The concentration of nitrate in an groundwater-irrigated area in Gafsa oases basin was studied, where abstraction from an unconfined CT aquifer has increased threefold over 25 years to 34 million m3/year; groundwater levels are falling at up to 0.7 m/year; and groundwater is increasingly mineralised (TDS increase from 500 to 4,000 mg/L), with nitrate concentrations ranging from 16 to 320 mg/L.  相似文献   

16.
Nitrate is a common pollutant in surface water and groundwater of agricultural areas. It is essential to monitor this pollutant in groundwater, especially when it is used for drinking purposes without treatment. The present study was carried out in an intensively irrigated area which forms a part of Nalgonda district, Andhra Pradesh, India where groundwater meets all the water needs of the rural population living in this area. The objective was to assess the spatiotemporal variation in the concentration of nitrate in groundwater and soil. Based on the analysis of 496 groundwater samples collected from 45 wells over a period of 2 years from March 2008 to January 2010 by sampling every 2 months, it was observed that groundwater in 242 km2 of the total 724 km2 area had nitrate above the maximum permissible limit of 45 mg/l for drinking purposes. Nitrate concentration in groundwater showed a positive relation with potassium, chloride, and sulfate, indicating their source from fertilizers. Reasons for the high concentration of nitrate in domestic areas were the dumping of animal wastes and leakage from septic tanks. The pH of the soil samples showed that most of the area had basic soil. Apart from pH, organic carbon, available phosphorous, available potassium, ammoniacal nitrogen, and nitrate nitrogen were also analyzed in the 97 soil samples.  相似文献   

17.
There is an urgent need for characterization of leachate arising from waste disposal to ensure a corresponding effective leachate management policy. Field and laboratory studies have been carried out to investigate the impact of municipal landfill leachate on the underlying groundwater at a site in West Malaysia. The solid waste was disposed of directly onto an unprotected natural soil formation. This situation was made worse by the shallow water table. The hydrochemical composition of groundwater in the vicinity of the site (background) is a dilute mixed cation, bicarbonate water. The high ionic balance error of ~13.5% reveals that the groundwater body underneath the site was a highly contaminated leachate rather than contaminated groundwater. Elevated concentration of chloride (355.48 mg/L), nitrate (10.40 mg/L as NO3), nitrite (14.59 mg/L), ammoniacal-N (11.61 mg/L), sodium (227.56 mg/L), iron (0.97 mg/L), and lead (0.32 mg/L) measured downgradient indicate that the contamination plume has migrated further away from the site. In most cases, the concentration of these contamination indicators, together with the ranges of sodium percentage (66.3–89.9%) and sodium adsorption ratio (10.1–19.7%), were found to be considerably higher than the limit values of safe water for both domestic and irrigation purposes, respectively.  相似文献   

18.
The geochemical processes controlling chemical composition of groundwater are studied using hydrochemical and isotopic data in Abdan-Dayer coastal plain, south of Iran. The salinity of groundwater in the coastal plain ranges from 1,000, a fresh end-member, to more than 50,000 μS cm?1, a saline end-member. Groundwater salinity increases from the recharge area toward areas with a shallow water table close to the Persian Gulf coast due to direct evaporation and sea water intrusion as confirmed by mixing binary diagrams, stable isotope content, and Br?/Cl? ratio. Groundwater flow pattern in the study area has been modified due to over-pumping of groundwater in recent years which resulted in further saline water migration toward fresh water and their mixing. The maximum mixing ratio is estimated about 15% in different parts of the study area according to chloride concentration.  相似文献   

19.
Knowledge of the baseline of groundwater nitrate is essential for water quality management. As large-scale anthropogenic activities, especially utilization of chemical fertilizers began from the 1950s in most countries, such as China, the baseline of groundwater nitrate can be determined from pre-modern water using tritium and statistical analysis. In the (semi)arid northern China, the median values of nitrate baseline for the three large regions (Tarim river basin, TRB; Loess Plateau of China, LPC; North China Plain, NCP) range from 2 to 9 mg/L (as NO3). Several main factors control nitrate content in the unsaturated zone moisture and in groundwater, e.g., nitrate input, sediment moisture movement (direction and rate), and depth of water table at the macroscopic scale in (semi)arid areas, where nitrate loss by denitrification can be limited. Sixteen unsaturated zone profiles (638 sediment samples in total) with depths ranging from 5 to 18.25 m were sampled to demonstrate how those factors affect groundwater nitrate. As sediment moisture moves upward from the water table in the TRB case, a large inventory of nitrate in the unsaturated zone with evapo-transpired origin would never enter groundwater and groundwater nitrate contents remain at the baseline level. On the contrary, in the LPC and NCP, nitrate from fertilizers may pass through the unsaturated zone and eventually reach the water table to pollute groundwater. It is also noticed that there is a time lag between land-use change and groundwater quality response, due to the buffering capacity of the thick unsaturated zone, to which attention should be paid regarding water quality management.  相似文献   

20.
Concentrations of trace elements such as As, Ba, Co, Cr, Cu, Ni, Pb, Rb, Sr, V, Y, Zn and Zr were studied in soils to understand metal contamination due to agriculture and geogenic activities in Chinnaeru River Basin, Nalgonda District, India. This area is affected by the geogenic fluoride contamination. The contamination of the soils was assessed on the basis of geoaccumulation index, enrichment factor (EF), contamination factor and degree of contamination. Forty-four soil samples were collected from the agricultural field from the study area from top 10–50 cm layer of soil. Soil samples were analyzed for trace elements using X-ray fluorescence spectrometer. Data revealed that soils in the study area are significantly contaminated, showing high level of toxic elements than normal distribution. The ranges of concentration of Ba (370–1,710 mg/kg), Cr (8.7–543 mg/kg), Cu (7.7–96.6 mg/kg), Ni (5.4–168 mg/kg), Rb (29.6–223 mg/kg), Sr (134–438 mg/kg), Zr (141.2–8,232 mg/kg) and Zn (29–478 mg/kg). The concentration of other elements was similar to the levels in the earth’s crust or pointed to metal depletion in the soil (EF < 1). The high EFs for some trace elements obtained in soil samples show that there is a considerable heavy metal pollution, which could be due to excessive use of fertilizers and pesticides used for agricultural or may be due to natural geogenic processes in the area. Comparative study has been made with other soil-polluted heavy metal areas and its mobility in soil and groundwater has been discussed. A contamination site poses significant environmental hazards for terrestrial and aquatic ecosystems. They are important sources of pollution and may result in ecotoxicological effects on terrestrial, groundwater and aquatic ecosystems.  相似文献   

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