Groundwater quality assessment using a new integrated-weight water quality index (IWQI) and driver analysis in the Jiaokou Irrigation District, China.

Groundwater is an important water resource in arid and semi-arid regions. The impact of human activities on groundwater is increasing. After 60 years running, the groundwater quality and its formation mechanism are imperative questions needed to be answered in Jiaokou Irrigation District, Guanzhong Basin, China. In this study, the quality of groundwater in Jiaokou Irrigation District was assessed by a new integrated-weight water quality index (IWQI), and the groundwater chemistry is studied through integrated statistical, geostatistical and hydrogeochemical approaches. The patterns for the average anion and cation concentrations were HCO3- > SO42- > Cl- > NO3- > CO32- > NO2-, and Na+ > Mg2+ > Ca2+ > K+ > NH4+, respectively. Statistics showed that the major water chemistry types were HCO3-Na, SO4·Cl-Na, and Cl·SO4-Na. A new integrated-weight water quality index (IWQI) was proposed based on the entropy-weighted method and CRITIC method and showed excellent performance for explaining and evaluating the groundwater quality. The IWQI results show 65.33% of groundwater, mainly distributed in the central and western parts of this study area, was unsuitable for drinking. Furthermore, SO42－, HCO3－, Cl－, NO3－, and Na+ had more important effects on groundwater quality. The weathering process affecting groundwater quality in the study area is carbonate dissolution, followed by silicate weathering and evaporite dissolution, whereas the major geochemical processes include the dissolution and precipitation of calcite, as well as the dissolution of dolomite and gypsum (anhydrite). Cation exchange also plays an important role in the hydrogeochemical evolution of groundwater with a long residence time. Anthropogenic activities affecting groundwater quality included long-term irrigation infiltration and excessive use of fertilizers. The findings and the results of the study can improve understanding of the processes driving groundwater chemistry in Jiaokou Irrigation District, and can be used for reference to other similar regions in the world.

Hydrogeochemistry and fluoride contamination in Jiaokou Irrigation District, Central China: Assessment based on multivariate statistical approach and human health risk.

Too little and too much fluorine are potentially hazardous for human health. In the Jiaokou Irrigation District, ionic concentrations, hydrogeochemistry, and fluoride contaminations were analyzed using correlation matrices, principal component analysis (PCA), and health risk assessment. The patterns for the average cation and anion concentrations were Na+ > Mg2+ > Ca2+ > K+ and SO42- > HCO3- > Cl- > NO3- > CO32-. The fluoride concentrations ranged between 0.29 and 8.92 mg/L (mean = 2.4 mg/L). 5% of the samples displayed lower than the recommended limit of 0.5 mg/L fluoride content, while 69% exceeded the allowable limits of 1.5 mg/L for drinking. The low F- content is distributed in a small part of the southeast, while elevated F- mainly in the central area of the study region. The PCA results indicated three principal components (PC), PC1 having the greatest variance (45.83%) and affected by positive loadings of TDS, Cl-, SO42-, Na+, and Mg2+, PC2 accounting for 17.03% and dominated by Ca2+, pH, HCO3-, and K+, and PC3 representing 12.17% and mainly comprising of CO32-. High fluoride groundwater is of the SO4-Cl-Na type, followed by HCO3-Na type. Evaporation and ion exchange play important roles in producing high fluoride groundwater. Furthermore, saturation index and anthropogenic activities also promote the high fluoride concentrations. The values of the total hazard quotient of 93% groundwater samples were greater than 1 for infants, followed by 85% for children, 68% for teenagers, and 57% for adults. Non-carcinogenic health risks to infants may occur over the entire study area, while for adults, health risks are mainly found in Weinan and Pucheng. High fluorine may have a potential negative influence on neurodevelopment, especially for infants and children. Adults in this region have serious dental fluorosis and skeletal fluorosis because of long-term drinking of high fluoride groundwater. Therefore, measures, including using organic fertilizers, strengthening defluoridation process, and optimizing water supply strategies, are necessary in this area.

Assessment of Groundwater Quality and Human Health Risk (HHR) Evaluation of Nitrate in the Central-Western Guanzhong Basin, China.

To investigate the quality of domestic groundwater and assess its risk to inhabitants of the Guanzhong Basin, China, 191 groundwater samples were collected to analyze major ions, nitrate, pH, total dissolved solids (TDS), total hardness (TH), and electrical conductivity (EC). The physiochemical parameters, hydrochemical facies, and sources of major ions were analyzed using Durov diagrams, bivariate diagrams, and chloro-alkaline indices (CAI-I and CAI-II). The suitability of groundwater for drinking, the nitrate distribution, and human health risk (HHR) for different age groups were evaluated. The results showed that the relative abundance of cations in the groundwater samples was K++Na+ > Ca2+ > Mg2+, while that of anions was HCO3- > SO42- > Cl- > NO3-. Groundwater samples mainly contained HCO3-Na and HCO3-Ca, which were introduced mainly by rock weathering and ion exchange. The groundwater in the Guanzhong Basin contained mainly good and medium water, and the groundwater in the southern part of the Wei River was better than that north of the Wei River. Areas containing high nitrate concentrations were mainly located in the central and western parts of the Guanzhong Basin. The percentages of low risk (<45 mg/L), high risk (45-100 mg/L), and very high risk (>100 mg/L) of nitrate pollution in the study area were 90.58%, 8.9%, and 0.52%, respectively. The HHR assessment results indicated that people in the 6-12 month age group were more likely to suffer from health complications due to a higher nitrate concentration, followed by 6-11 years, 21-65 years, 18-21 years, ≥65 years, 11-16 years, and 16-18 years age groups, which was mainly due to the different exposure parameters. The results of this study will be useful in regional groundwater management and protection.

Hydrogeochemical Characterization and Irrigation Quality Assessment of Shallow Groundwater in the Central-Western Guanzhong Basin, China.

Groundwater is the major water resource for the agricultural development of the Guanzhong Basin, China. In this study, a total of 97 groundwater samples (51 from the North Bank of the Wei River (NBWR) and 46 from the South Bank of the Wei River (SBWR)) were collected from the central-western Guanzhong Basin. The aim of this study was to investigate the hydrogeochemical characteristics of the basin and to determine the suitability of shallow groundwater for irrigation. The groundwater of the entire study area is alkaline. The groundwater of the SBWR is fresh water, and the NBWR groundwater is either freshwater or brackish water. The average concentration of ions (except for Ca2+) in SBWR samples is lower than in NBWR samples. HCO3- is dominant in the groundwater of the study area. Ca2+ is dominant in the SBWR while Na+ is dominant in the NBWR. The SBWR groundwater is mainly of the HCO3-Ca·Mg type, and has undergone the main hydrogeochemical processes of rock weathering-leaching. The hydrochemical facies of the majority of the NBWR groundwater samples are the HCO3-Na type with several minor hydrochemical facies of the HCO3-Ca·Mg, SO4·Cl-Na, and SO4·Cl-Ca·Mg types. Its chemistry is mainly controlled by rock weathering, cation exchange, and evaporation. Salinity hazard, sodium percentage, sodium adsorption ratio, residual sodium carbonate, magnesium hazard, permeability index, Kelley's ratio, potential salinity, synthetic harmful coefficient, and irrigation coefficient were assessed to evaluate the irrigation quality of groundwater. The results of the comprehensive consideration of these indicators indicate that the percentage of NBWR water samples suitable for irrigation purposes ranges between 15.7% and 100% at an average level of 56.7%. Of the SBWR water samples suitable for irrigation, the percentage ranges from 78.3% to 100% with an average of 91.8%. Land irrigated with such water will not be exposed to any alkali hazard, but will suffer from a salinity hazard, which is more severe in the NBWR. Thus, most of the water in the NBWR can be used for soils with good drainage conditions which control salinity.