Assessment of the chemical components of Famenin groundwater,western Iran

The Faminin area in the semi-arid Hamadan state, western Iran is facing a serious deficiency in groundwater resources due to an increasing demand associated with rapid population growth and agricultural development. The chemical composition of 78 well samples throughout the Faminin area was determined with the aim of evaluating the concentration of the background ions and identifying the major hydrogeochemical processes that control the groundwater chemistry. The similarity between rock and groundwater chemistries in the recharge area indicates a significant rock-water interaction. The hydrochemical types Na–HCO₃ and Na–SO₄ are the predominate forms in the groundwater, followed by water types Ca–HCO₃ and Na–Cl. The high values of electrical conductivity and high concentrations of Na⁺, Cl⁻, SO₄²⁻ and NO₃⁻ in the groundwater appeared to be caused by the dissolution of mineral phases and would appeared to be caused by anthropogenic activities, such as intense agricultural practices (application of fertilizers, irrigation practice), urban and industrial waste discharge, among others.     

Use of environmental isotopes and hydrochemistry as indicators for the origin of groundwater resources in El Dabaa area,northwestern coastal zone of Egypt

The EI-Dabaa area is located on the northwestern coastal zone of Egypt and is considered to be one of the most important regions for land reclamation and agriculture. In addition, it has been selected as a potential site for constructing Egypt's first nuclear power plant.In April 1989, 14 groundwater samples were collected from the area as well as collecting samples from the Mediterranean sea and from local rainwater. These samples were subjected to chemical and environmental isotope analyses. The results of the analyses for stable isotopes (oxygen-18 and deuterium) indicate that the main recharge source of the groundwater in El-Dabaa is the local precipitation during the rainy season. Variation of the environmental tritium content as well as in the chemical composition of both major cations (Na,K,Ca,Mg) and major anions (Cl,SO₄,HCO₃) between different groundwaters in the studied area reflect the high degree of inhomogeneity of the aquifer and different recharging conditions due to permeability of the water bearing formation.The chemical water type of the El-Dabaa groundwater is sodium sulphate (Na₂SO₄) and the SAR values illustrate the suitability of these groundwaters for agricultural purposes.     

Suitability for human consumption and agriculture purposes of Sminja aquifer groundwater in Zaghouan (north-east of Tunisia) using GIS and geochemistry techniques

In Tunisia, the water resources are limited, partially renewable and unequally distributed between the wet north and the dry south of the country. The Sminja aquifer in Zaghouan city is located in north-east of Tunisia, between latitudes 36°38′ and 36°47′ and longitudes 9°95′ and 10°12′. This aquifer is used to satisfy the population needs for their domestic purposes and agricultural activities. Water analyses results are expressed by many methods, among which are geochemical methods combined with the geographic information system (GIS) (all schematic presentations of the diagram software (Piper, Riverside, Wilcox…), which can be used to assess the suitability of the Sminja aquifer groundwater for human consumption and irrigation purposes. A total of 23 wells were sampled in January 2013, and the concentrations of major cations (Na⁺, Ca²⁺, Mg²⁺ and K⁺), major anions (Cl^?, SO₄ ^2? and HCO₃ ^?), electrical conductivity and total dissolved solids were analysed. In the Sminja groundwater, the order of the cations dominance was Na > Ca > Mg > K and that of the anions was Cl > HCO₃ > SO₄. All of the analysed samples of the study area exceed chemical values recommended by the World Health Organisation guidelines and Tunisian Standards (NT.09.14) for potability but with different percentages. The aquifer spatial distribution of saturation indices reveals that all groundwater samples are under-saturated with gypsum, halite and anhydrite and are over-saturated with respect to calcite and dolomite based on water quality evaluation parameters for irrigation purposes; here, 87 % of samples in Sminja aquifer groundwater are suitable, whereas 13 % are unsuitable for irrigation uses.     

Geochemical occurrences of arsenic and fluoride in bedrock groundwater: a case study in Geumsan County,Korea

Bedrock groundwaters in Geumsan County, Korea, were surveyed to investigate the distribution and geochemical behaviors of arsenic and fluoride, mobilized through geogenic processes. The concentrations were enriched up to 113 μg/L for arsenic and 7.54 mg/L for fluoride, and 16% of 150 samples exceeded World Health Organization drinking water guidelines for each element. Simple Ca-HCO₃ groundwater types and positive correlations with pH, Ca, SO₄, and HCO₃ were characteristics of high (>10 μg/L) As groundwaters. The oxidation reaction of sulfide minerals in metasedimentary rocks and locally mineralized zones seems to be ultimately responsible for the existence of arsenic in groundwater. Desorption process under high pH conditions may also control the arsenic mobility in the study area. High (>1.5 mg/L) F groundwaters were found in the Na-HCO₃ type and with greater depth. Fluoride seemed to be enriched by deep groundwater interaction with granitic rocks, and continuous supply to shallow Ca-HCO₃-type groundwater kept the concentration high. In the study area, drinking water management should include periodic As and F monitoring in groundwater.

     

Geochemistry and quality of groundwater of the Yarmouk basin aquifer,north Jordan

Quality of groundwater in the Yarmouk basin, Jordan has been assessed through the study of hydrogeochemical characteristics and the water chemistry as it is considered the main source for drinking and agriculture activities in the region. The results of the relationship between Ca²⁺ + Mg²⁺ versus HCO₃^? + CO₃^2?, Ca²⁺ + Mg²⁺ versus total cations, Na⁺ + K⁺ versus total cations, Cl^? + SO₄^2? versus Na⁺ + K⁺, Na⁺ versus Cl^?, Na⁺ versus HCO₃^? + CO₃^2?, Na⁺ versus Ca²⁺, and Na⁺: Cl^? versus EC describe the mineral dissolution mechanism through the strong relationship between water with rocks in alkaline conditions with the release of Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃^?, CO₃^2?, SO₄^2?, and F^? ions in the groundwater for enrichment. Furthermore, evaporation processes, groundwater depletion, and ion exchange contribute to the increased concentration of Na⁺ and Cl^? ions in groundwater. Anthropogenic sources are one of the main reasons for contamination of groundwater in the study area and for increasing the concentration of Mg²⁺, Na⁺, Cl^?, SO₄^2?, and NO₃^? ions. Results show the quality of groundwater in the study area is categorized as follows: HCO₃^? + CO₃^2? > Cl^? > SO₄^2? > NO₃^? > F^? and Na⁺ > Ca²⁺ > Mg²⁺ > K⁺. In conclusion, the results of TDS, TH, and chemical composition showed that 26% of the groundwater samples were unsuitable for drinking. About 28% of groundwater samples in the study area have a high concentration of Mg²⁺, Na⁺, and NO₃^? above the acceptable limit. Also, based on high SAR, 10% of the groundwater samples were not suitable for irrigation purposes.     

Tracing the factors responsible for arsenic enrichment in groundwater of the middle Gangetic Plain,India: a source identification perspective

Arsenic contamination in groundwater is of increasing concern because of its high toxicity and widespread occurrence. This study is an effort to trace the factors responsible for arsenic enrichment in groundwater of the middle Gangetic Plain of India through major ion chemistry, arsenic speciation, sediment grain-size analyses, and multivariate statistical techniques. The study focuses on the distinction between the contributions of natural weathering and anthropogenic inputs of arsenic with its spatial distribution and seasonal variations in the plain of the state Bihar of India. Thirty-six groundwater and one sediment core samples were collected in the pre-monsoon and post-monsoon seasons. Various graphical plots and statistical analysis were carried out using chemical data to enable hydrochemical evaluation of the aquifer system based on the ionic constituents, water types, hydrochemical facies, and factors controlling groundwater quality. Results suggest that the groundwater is characterized by slightly alkaline pH with moderate to strong reducing nature. The general trend of various ions was found to be Ca²⁺ > Na⁺ > Mg²⁺ > K⁺ > NH₄ ⁺; and HCO₃ ⁻ > Cl⁻ > SO₄ ²⁻ > NO₃ ⁻ > PO₄ ³⁻ > F⁻ in both seasons. Spatial and temporal variations showed a slightly higher arsenic concentration in the pre-monsoon period (118 μg/L) than in the post-monsoon period (114 μg/L). Results of correlation analyses indicate that arsenic contamination is strongly associated with high concentrations of Fe, PO₄ ³⁻, and NH₄ ⁺ but relatively low Mn concentrations. Further, the enrichment of arsenic is more prevalent in the proximity of the Ganges River, indicating that fluvial input is the main source of arsenic. Grain size analyses of sediment core samples revealed clay (fine-grained) strata between 4.5 and 7.5 m deep that govern the vertical distribution of arsenic. The weathering of carbonate and silicate minerals along with surface-groundwater interactions, ion exchange, and anthropogenic activities seem to be the processes governing groundwater contamination, including with arsenic. Although the percentage of wells exceeding the permissible limit (50 μg/L) was less (47%) than that reported in Bangladesh and West Bengal, the percentage contribution of toxic As(III) to total arsenic concentration is quite high (66%). This study is vital considering that groundwater is the exclusive source of drinking water in the region and not only makes situation alarming but also calls for immediate attention.     

Geological factors controlling occurrence and distribution of arsenic in groundwaters from the southern margin of the Duero Basin,Spain

Groundwater from springs and boreholes on the southern edge of the Cenozoic Duero Basin (DB) of Spain has concentrations of arsenic (As) which are commonly above the EC drinking-water limit of 10 μg/L and reach observed values up to 241 μg/L. Groundwater compositions within the sedimentary aquifer vary from Ca–HCO₃ type, variably affected by evaporation and agricultural pollution at shallow levels, to Na–HCO₃ compositions in deeper boreholes of the basin. Groundwater conditions are mainly oxidising, but reducing groundwaters exist in sub-basins within the aquifer, localised flow paths likely being influenced by basement structure. Arsenic concentrations are spatially variable, reaching up to 38 μg/L in springs of the Spanish Central System (SCS) basement aquifer and up to 62 μg/L in springs from the DB. Highest As concentrations are associated with the Na–HCO₃ compositions in deep boreholes (200–450 m depth) within the DB. These have high pH values (up to 9.6) which can give rise to associated elevated concentrations of V and U (up to 64 and 30 μg/L, respectively). In the deep borehole waters of the DB, oxidising flows derived from the mineralised igneous–metamorphic basement and discharging via major faults, and are considered the origin of the higher concentrations. Compositions are consistent with desorption of As and other anionic species from metal oxyhydroxides in an oxic environment. Under locally reducing conditions prevalent in some low-flow parts of the DB, an absence of detectable dissolved As is coincident with low or undetectable SO₄ concentrations, and consistent with loss via formation of authigenic sulphide minerals. Mitigation measures are needed urgently in this semi-arid region where provision of alternative sources of safe drinking water is logistically difficult and expensive.     

An incidence of skeletal fluorosis associated with groundwaters of the maritime carboniferous basin,Gaspé region,Quebec, Canada

Consumption of unusually high concentrations of F^– in groundwaters of the Maria area in the Gaspé peninsula of Quebec have resulted in symptoms of skeletal fluorosis in two members of the population. One of these individuals consumed approximately 50 mg of fluoride per day over a 6 year period before being hospitalized and later diagnosed with skeletal fluorosis. It is estimated that, until this case came to light, approximately 15–20% of the rural population (total approximately 1,600) in the area were consuming groundwaters with F^– levels between 5 and 28 mg L^–1 for at least 6 years. The high concentrations of F^– in well waters of the Maria area occur only in wells completed in Carboniferous sandstone-siltstone-conglomerate sediments that underlie a thick blanket of alluvial-colluvial-glacial overburden. These fluoriferous groundwaters exhibit high Na and HCO₃ ^– contents and low Ca and Mg concentrations compared to those associated with the overburden sediments. The high F levels greatly increase the risk for fluorotic diseases such as skeletal fluorosis and skeletal radiculomyopathy. Wells completed in overburden, although having suboptimal F^– levels are safer for the health of individuals in this region. Effective regulations for well drilling need to be formulated for regions underlain by Carboniferous formations in the Maritime provinces of Canada. In some regions, high F^– levels (10–25 mg L^–1) in groundwaters will seriously affect how, and to what extent, groundwater supplies can be developed for domestic use.To whom correspondence should be addressed.     

Hydrogeochemistry of the Coxilha das Lombas Aquifer, Brazil

The hydrogeochemical characterization of Coxilha das Lombas Aquifer, Brazil, was studied. Chemical characteristics from 23 groundwater samples and meteoric waters data from public registers were used. The ionic speciation and mineral dissolution/precipitation was calculated by EQ3/6 package software. The results showed low total dissolved solids (TDS) values and slightly acidic pH. The concentration of most abundant ions usually followed this trend Cl⁻>HCO₃ ⁺>SO₄ ²⁻>Na⁺. The characteristics of groundwaters and the chemistry similarity with the meteoric waters reflect their short residence time, due to high hydraulic conductivity, and low degree of water/rock interactions, due to sands composed mainly of quartz.     

Hydrogeochemistry study and groundwater quality assessment in the north of Isfahan,Iran

This study presents the groundwater quality assessment in the north of Isfahan, Iran. In the study area, assessment and measurement of groundwater hydrochemical parameters such as pH, total dissolved solids (TDS), electrical conductivity (EC), sodium absorption ratio (SAR), total hardness, major cations (K⁺, Na⁺, Ca²⁺ and Mg²⁺) and major anions (Cl^?, \({\text{HCO}}_{ 3}^{ - } ,{\text{CO}}_{3}^{2 - }\) and \({\text{SO}}_{4}^{2 - }\)) concentrations were performed. Accordingly, the 66 water samples from different locations were collected during April and May 2015. Water samples collected in the field were analyzed in the laboratory for cations and anions using the standard methods. In this research, the analytical results of physiochemical parameters of groundwater were compared with the standard guideline values as recommended by the world health organization (WHO) for drinking and public health purposes. The pH values of groundwater samples varied from 7.05 to 8.95 with a mean of 7.78, indicating a neutral to slightly alkaline water. TDS values showed that 14% of the samples exceeds the desirable limit given by WHO. EC values varied from 213 to 4320 µS/cm, while 23% of the samples were more than the standard limit. Gibbs diagram had shown that 90% of the samples in the study area fall in the rock weathering zone, and this means that chemical weathering of rock-forming minerals is the main factor controlling the water chemistry in the study area. Irrigation suitability and risk assessment of groundwater are evaluated by measuring EC, %Na, SAR and RSC. According to the dominant cations and anions, five types of water were identified in the water samples: Ca-HCO₃, Ca-SO₄, Na-Cl, Na-HCO₃ and Na-SO₄. The results show that the majority of samples (30 samples, 45%) belongs to the mixed Na-SO₄ water type. Correlation analysis and principal component analysis was used to identify the relationship between ions and physicochemical parameters. Results indicated that 18 stations of the study area had the best quality and can be used for irrigation and drinking purposes in the future.     

Assessment of Groundwater Quality and Contamination from Uranium-Bearing Black Shale in Goesan–Boeun Areas, Korea

This study was initiated to identify the impact of metals and uranium enriched soil and black shale in groundwater quality and contamination. From a Piper diagram, groundwater was classified into four types as (Ca+Mg)–HCO₃ type, (Ca+Mg)–SO₄ type, the mixed type of these two and Na–HCO₃ type, reflecting the complicated nature of geology of the study area. Silicate weathering appeared to be the major water–rock interaction. In groundwater, metals including Cr, Pb, Cu and V, previously identified as being enriched in soils and black shale, were much lower in concentrations than Korean and US EPA drinking water guidelines. Instead, Fe and Mn caused major water-quality problems. In the artesian groundwater from an abandoned uranium mine, the uranium concentration was 21.3 µg L^–1, slightly higher than EPA guidelines of 20 µg L^–1. Heavy metals in groundwater appeared to be controlled mostly by sorptions on to Fe- and Mn-oxyhydroxides. They could be remobilised in groundwater with changes of pH and Eh conditions due to acid mine drainage from black shale or the recharge of fresh water. Uranium would be associated with carbonate and sulphate complexes in groundwater. Because of the remaining water-quality problems in the study area, we suggested containment of identified mine wastes, considering remedial measures for local problems with Fe and Mn, continuous monitoring of groundwater and developing groundwater from deep aquifers.     

Quality of tube well water intended for irrigation and human consumption with special emphasis on arsenic contamination at the area of Punjab,Pakistan

In the present study, the tube well water quality and the associated health risks, emphasizing on arsenic contamination, were investigated in rural and urban samples from Tehsil Mailsi located in Punjab, Pakistan. Arsenic concentrations (μg/L) were ranged from 12 to 448.5 and which exceeded the WHO recommended limit (10 μg/L) in all cases. The calculated average daily dose (3.3 × 10^?0.4 to 1.2 × 10^?0.2 mg/kg day) and hazard quotient (1.1–40) reflected the potential health risk to local population due to tube well water consumption as drinking purpose. Sodium percent (Na%), sodium absorption ratio, residual sodium carbonate, Kelly’s index and magnesium absorption ratio were also determined to assess the suitability of tube well water for irrigation purpose. The resulting piper plot revealed the Na–Ca–HCO₃ type water chemistry of the area and generally alkaline environment. The spatial distribution of arsenic in the tube well waters pinpoints the significant contribution of anthropogenic activities to arsenic pollution. Nevertheless, different statistical tools, including principal component analysis, hierarchical cluster analysis and correlation matrices, revealed the contribution of both natural and anthropogenic activities and alkaline type of aquifers toward the high level of arsenic contamination.     

Assessment of groundwater contamination using geographic information systems

In this study two sites were selected in order to investigate groundwater contamination and spatial relationships among groundwater quality, topography, geology, landuse and pollution sources. One site is the Asan area, an agricultural district where pollution sources are scattered and which is mainly underlain by granite of Cretaceous age. The other site is the Gurogu area of Seoul city, an industrial district where an industrial complex and residential areas are located and which is mainly underlain by gneiss of Precambrian age. Groundwater samples collected from these districts were analysed for chemical constituents. An attribute value files of chemical constituents of groundwater and the spatial data layers were constructed and pollution properties were investigated to establish out spatial relationships between the groundwater constituents and pollution sources using geographic information systems (GIS).Relatively high contents of Si and HCO₃ ^– in the groundwater from the Asan area reflect the effect of water–rock interaction whereas high contents of Cl^–, NO₃ ^– and Ca²⁺ in the groundwater from the Gurogu area are due to the pollution of various sources. The significant seasonal variation of SiO₂, HCO₂ ^– and Ca²⁺ contents, and that of Ca²⁺ content were observed in the Asan and the Gurogu areas, respectively. Seasonal variation of pollutants such as Cl^–, NO₃ ^– and SO₄ ^2– was not observed in either area. Pollution over the critical level of the Korean drinking water standard has been investigated from 15 sampling sites out of 40 in the Asan area, and 33 sampling sites out of 51 in the Gurogu area. Pollution by NO₃ ^–, Cl^–, Fe²⁺, Mn²⁺, SO₄ ^2– and Zn²⁺ in the groundwater from the industrial district (Gurogu area) and that of NO₃ , SO₄ ^2– and Zn²⁺ in the groundwater from the agricultural district (Asan area) were observed. The principal pollutant in both areas is NO₃ ^–. Deep groundwater from the Asan area is not yet contaminated with NO₃ ^– except for one site, but most of the shallow groundwater site occurring near the potential point sources is seriously contaminated. From the result of buffering analysis, it seems clear that factories and stock farms are the principal pollution sources in the Asan area. The groundwater from the Gurogu area has already been seriously polluted considering the fact of NO₃ ^– contamination of deep groundwater. Chlorine pollution of shallow groundwater in the Gurogu area was also observed. Spatial relationship between pollution level and its source was clarified in this study by using GIS, which will be applicable to the effective management of groundwater quality.     

Using hydrochemical signatures to characterize the long-period evolution of groundwater information in the Dagu River Basin,China

• The long-period groundwater evolution was identified by hydrochemical signatures. • The dominant processes in the groundwater evolution were verified. • Groundwater quality in the coastal areas was susceptible to deterioration due to SI. • Groundwater contamination arose from fertilizer, livestock manure & domestic sewage. The evolution of hydrochemical compositions influenced by long-period interactions between groundwater and the geo-environment is a fundamental issue for exploring groundwater quality and vulnerability. This study systematically investigated the hydrochemical processes and anthropogenic interference occurring in the river basin by bivariate plots, Gibbs diagrams, saturation index, and the major ions ratios. Apparent changes in groundwater hydrochemistry have been observed in the study area, illustrating the origins of major ions are affected by various internal and external factors. Results highlighted that TDS varied from freshwater to brackish water, ranging between 187.90 and 2294.81 mg/L. Ca²⁺ and HCO₃⁻ are the dominant ions in the studied samples. The results gained by Gibbs diagrams, bivariate plots, saturation index, and the major ions ratios demonstrated that minerals dissolution/precipitation, cation exchange, and human inputs play crucial roles in the unconfined aquifers. Moreover, the overuse of nitrogen fertilizer, livestock manure, and industrial/domestic sewage led to nitrate and nitrite contamination and brought significant challenges to the surrounding hydrogeo-environment. The present study could make an unambiguous identification of natural processes and anthropogenic interventions influencing groundwater hydrochemistry’s long-period evolution and create a preliminary strategy for groundwater resources management.     

砷浓度、形态及碳酸氢盐对蜈蚣草吸收砷的影响

为了探讨超富集植物蜈蚣草在处理高砷地下水方面的可行性,研究了水培条件下砷的浓度、形态和碳酸氢盐(HCO-3)对超富集植物蜈蚣草吸收砷的影响。实验中使用了浓度为0.1～100mg·L-1的As(III)和As(V)溶液。HCO-3处理中,HCO-3浓度范围为0.5～20mmol·L-1,As(III)或As(V)的浓度为5mg·L-1。结果表明,在水培条件下,蜈蚣草具有明显的耐高砷特征。当介质砷含量高达100mg·L-1时,砷的去除率可达到80%,且对As(III)的吸收效率高于As(V)。植物体内砷形态研究表明,蜈蚣草体内2种形态砷的含量与外源砷形态有一定的关系,As(V)处理条件下,植物体中的As(V)比例较As(III)处理高。高浓度的HCO-3(20mmol·L-1)处理对蜈蚣草地上部分生物量没有明显影响,但是抑制了地下部分的生长,并且对砷的吸收表现出明显的抑制作用。     

砷浓度、形态及碳酸氢盐对蜈蚣草吸收砷的影响

大同盆地是典型的高砷地下水分布区。利用从地方性砷中毒严重病区山阴县采集的高砷地下水样品,用稀释培养法实验研究了外加砷源对地下水中微生物数量的影响;同时基于生物学可培养法和16S rDNA序列比对法,选取代表性高砷水样,研究了耐砷菌的种群特征。结果表明,外加砷源对地下水中微生物数量影响显著,高浓度砷会抑制大部分微生物生长,使微生物数量减少;低浓度砷对微生物生长具有一定促进作用。通过多次分离、纯化从3个不同砷含量地下水样中分离到多株砷抗性菌,经鉴定属于主要为Bacillus、Pseudomonas、Paenibacillus、Aeromonas、Enterobacter5个属。从RDP(Ribosomal Database Project)分析显示3个水样可培养微生物组成不同,都有生存能力强能够耐低浓度NaAsO₂的Bacillales,优势耐砷菌是γ-proteobacteria,其中Enterbacter具有耐高浓度NaAsO₂的能力。     

Lithological and hydrochemical controls on distribution and speciation of uranium in groundwaters of hard-rock granitic aquifers of Madurai District,Tamil Nadu (India)

Uranium is a radioactive element normally present in hexavalent form as U(VI) in solution and elevated levels in drinking water cause health hazards. Representative groundwater samples were collected from different litho-units in this region and were analyzed for total U and major and minor ions. Results indicate that the highest U concentration (113 µg l^?1) was found in granitic terrains of this region and about 10 % of the samples exceed the permissible limit for drinking water. Among different species of U in aqueous media, carbonate complexes [UO₂(CO₃) ₂ ^2? ] are found to be dominant. Groundwater with higher U has higher pCO₂ values, indicating weathering by bicarbonate ions resulting in preferential mobilization of U in groundwater. The major minerals uraninite and coffinite were found to be supersaturated and are likely to control the distribution of U in the study area. Nature of U in groundwater, the effects of lithology on hydrochemistry and factors controlling its distribution in hard rock aquifers of Madurai district are highlighted in this paper.     

Hydrogeochemical processes identification and groundwater pollution causes analysis in the northern Ordos Cretaceous Basin,China

It is necessary to identify the hydrogeochemical processes and analyze the causes of groundwater pollution due to the lack of knowledge about the groundwater chemical characteristics and the endemic diseases caused by groundwater pollution in the northern Ordos Cretaceous Basin. In this paper, groundwater chemical facies were obtained using the piper trilinear diagram based on the analysis of 190 samples. The hydrogeochemical processes were identified using ionic ratio coefficient, such as leaching, evaporation and condensation. The causes and sources of groundwater pollution were analyzed by correspondence analysis, and the spatial distribution and enrichment reasons of fluoride ion were analyzed considering the endemic fluorosis emphatically. The results show that leaching, evaporation and condensation, mixing, and anthropogenic activities all had significant impact on hydrogeochemical processes in the study area. However, cation exchange and adsorption effects were strong in the S2 and S3 groundwater flow systems, but weak in S1. Groundwater is mainly polluted by Mn and COD_Mn in the study area. The landfill leachate, domestic sewage, and other organic pollutants, excessive use of pesticides and fertilizers in agriculture, and pyrite oxidation from long-term and large-scale exploitation of coal are the sources of groundwater pollution. The S1 has the highest degree of groundwater pollution, followed by S2 and S3. High concentration of fluoride ion is mainly distributed in the north and west of study area. Evaporation and condensation and groundwater chemistry component are the most important causes of fluoride ion enrichment. The results obtained in this study will be useful for understanding the groundwater quality for effective management and utilization of groundwater resources and assurance of drinking water safety.     

Evaluation of groundwater quality in the Xinjiang plain area

Groundwater is the main source of drinking water for the urban and rural residents in the plain area of the Xinjiang Uygur Autonomous Region, China. The quality of groundwater has a direct relationship with human health. Thus, 386 groundwater samples collected from April to August in 2003 were analyzed. The samples were collected in basic evaluation units which are determined on the basis of watersheds. Total dissolved solids, total hardness, pH value, NH₃-N, C₆H₅OH, Chemiluminescence detection of permanganate index (COD_Mn) and intestinal germ group were evaluated according to the guidelines of Groundwater Quality Standard (GB/T14848-93). The quality of the groundwater in each evaluation unit was classified by using the One Veto Method (a unified approach stipulated by the Ministry of Water Resources). The results indicate that the groundwater in the mainstream area of the Tarim Basin and the Yerqiang River Sub-basin belongs to Category V; the groundwater in the Wulungu River Sub-basin, the Kaidu-Kongque River Sub-basin, the Kashgar River Sub-basin, the Cherchen River Sub-basin and the Hotan River Subbasin belongs to Category IV; the groundwater in the Aibi Lake System belongs to Category II, and the groundwater of other evaluation units belongs to Category III. The causes of water quality formation were concisely analyzed. The results can be useful for the evaluation and management of water resources in the Xinjiang Plain Area.     

Variations in heavy metal contamination of stream water and groundwater affected by an abandoned lead–zinc mine in Korea

This study evaluated variations in heavy metal contamination of stream waters and groundwaters affected by an abandoned lead–zinc mine, where a rockfill dam for water storage will be built 11 km downstream. For these purposes, a total of 10 rounds of stream and groundwater samplings and subsequent chemical analyses were performed during 2002–2003. Results of an exploratory investigation of stream waters in 2000 indicated substantial contamination with heavy metals including zinc (Zn), iron (Fe) and arsenic (As) for at least 6 km downstream from the mine. Stream waters near the mine showed metal contamination as high as arsenic (As) 8,923 μg L⁻¹, copper (Cu) 616 μg L⁻¹, cadmium (Cd) 223 μg L⁻¹ and lead (Pb) 10,590 μg L⁻¹, which greatly exceeded the Korean stream water guidelines. Remediation focused on the mine tailing piles largely improved the stream water qualities. However, there have still been quality problems for the waters containing relatively high concentrations of As (6–174 μg L⁻¹), Cd (1–46 μg L⁻¹) and Pb (2–26 μg L⁻¹). Rainfall infiltration into the mine tailing piles resulted in an increase of heavy metals in the stream waters due to direct discharge of waste effluent, while dilution of the contaminated stream waters improved the water quality due to mixing with metal free rain waters. Levels of As, Cu and chromium (Cr) largely decreased after heavy rain but that of Pb was rather elevated. The stream waters were characterized by high concentrations of calcium (Ca) and sulfate (SO₄), which were derived from dissolution and leaching of carbonate and sulfide minerals. It was observed that the proportions of Ca and SO₄ increased while those of bicarbonate (HCO₃) and sodium and potassium (Na+K) decreased after a light rainfall event. Most interestingly, the reverse was generally detected for the groundwaters. The zinc, being the metal mined, was the most dominant heavy metal in the groundwaters (1758–10,550 μg L⁻¹) near the mine, which far exceeded the Korean standard of 1000 μg L⁻¹ for drinking water. The decreases in the heavy metals contents in the groundwaters associated with reduced rainfall were quite different from the increases observed for the stream waters, which is not clearly understood at this time and warrants further investigation.