[Heavy Metal Content and Risk Assessment of Sediments and Soils in the Juma River Basin].

The sediment and soil in the Juma River channel pose a risk of pollution to the downstream ecological environment of Beijing and Xiong'an New Area. To address this issue, sediments and soil samples were collected along the river from the source to the Zhangfang outlet. The samples were further divided into three types:main stream sediment (29 samples), riverbank soil (27 samples), and farmland soil (26 samples). Enrichment factor analysis and the potential ecological risk index were employed to investigate the ecological risk. The results showed that the average concentrations of Cd, Hg, Pb, Zn, and Cu in the river sediment and soil in the study area were higher than those in the Baiyangdian Lake sediment and the surface soil of Hebei Province, whereas the concentrations of As, Cr, and Ni were relatively lower. The ranking of heavy metal pollution levels from high to low were Cd > Hg > Pb > Zn > Cu > Cr > Ni > As. The comprehensive ecological risk index showed that farmland soil and riverbank soil were mainly at a slight risk, followed by a moderate risk. The potential ecological risk of the main stream sediment was mainly moderate, severe, and extremely severe, accounting for 35.5%, 24.1%, and 24.1%, respectively, and the main contributing factors of the risk were Cd and Hg. The results of multivariate statistical analysis indicated that the main pollution sources of Cd, Pb, Zn, and Cu were industrial and mining activities. Cr, Ni, and As were mainly controlled by the weathering of the parent rock, and As was also influenced by agricultural activities. Hg was controlled by composite pollution sources such as industrial and mining activities, parent rock weathering, and atmospheric dust fall. Overall, the risk of heavy metal in the soil of the research area was generally at a slight level. However, there was a significant enrichment of Cd and other heavy metal in the sediment of the Taiyu-Sigezhuang-Pengtou River. This river section should be the focus of environmental monitoring, river dredging, and governance.

[Formation Mechanism and Source Apportionment of Hydrochemical Components in Groundwater in the Yinchuan Plain].

Groundwater is one of the major water sources for production, living, and agricultural irrigation in the Yinchuan Plain. Owing to the influence of the regional environmental background and long-term effects of human activities, groundwater quality is generally inferior. To deeply analyze the formation mechanism and source of hydrochemical components in groundwater in the Yinchuan Plain, the traditional hydrochemical graphic method and mathematical statistics and principal component analysis-multivariate linear statistical model were used. Based on inorganic component contents of 100 phreatic water samples and 46 confined groundwater samples, the hydrochemical characteristics and quality status, spatial distribution of over-limit toxicological components, and contribution rate of hydrochemical components were analyzed. The results showed that the chemical components of groundwater were controlled by rock weathering and evaporation concentration. Dissolution-enrichment （F1）, original geological environment （F2）, and human activities（F3） were the principal factors that influenced groundwater hydrochemistry with the contribution rates of 73.67%, 14.45%, and 11.88%, respectively. The major over-limit toxicity indices in groundwater were NO3--N and F-. High NO3--N phreatic water was mainly influenced by agriculture activities, followed by the discharge of domestic sewage. Enrichment of groundwater F- was mainly caused by leaching of F-bearing minerals and cation exchange adsorption.

[Hydrochemical Characteristics and Pollution Source Identification of Groundwater in Plain Area of Barkol-Yiwu Basin].

Groundwater is an important water supply source for production and life in arid and semi-arid areas. This study revealed the hydrochemical characteristics of groundwater in the Barkol-Yiwu Basin of Xinjiang and analyzed the pollution sources, which is of great significance in the sustainable utilization of local groundwater. Four spring water samples, 20 unconfined groundwater samples, and 11 confined groundwater samples collected in August 2022 were analyzed using mathematical statistics, a graphic method, and the PCA-APCS-MLR model. The results showed that the chemical types of groundwater in the study area were complex and diverse. The spring water was mainly HCO3·SO4-Na·Ca type groundwater, the chemical types of unconfined groundwater were mainly HCO3·SO4-Na·Ca and HCO3·SO4-Ca, and the chemical types of confined groundwater were HCO3·SO4-Na·Ca and HCO3·Cl·SO4-Na·Ca. The hydrochemical type of confined water in unused land was single(Cl·SO4-Na·Ca), and the hydrochemical types of confined groundwater in cultivated land and urban and rural residential land were complex, indicating that groundwater was affected by human activities. The evolution process of groundwater was mainly affected by water-rock interactions and cationic exchange. The cation exchange from spring water to unconfined groundwater to confined groundwater was gradually enhanced, the weathering and dissolution of gypsum and anhydrite was gradually weakened, and the weathering and dissolution of rock salt was gradually strengthened. Leaching-enrichment(mainly the dissolution of evaporite), human activities(industrial, agricultural, and domestic pollution), and the primary geological environment were the main factors affecting groundwater in the study area.

[Assessment of Groundwater Contamination Risk in the Plain Area of Southern Turpan Basin].

Groundwater contamination risk assessment is an effective tool for groundwater pollution prevention and control. The evaluation system mainly includes three parts:groundwater contamination source load assessment, groundwater vulnerability assessment, and groundwater function value evaluation. Taking the plain area of southern Turpan Basin as an example, based on the survey data and land use data, point source pollution and non-point source pollution were divided to evaluate the load of groundwater pollution sources, the classical DRASTIC model was selected to evaluate the vulnerability of groundwater, and the functional value of groundwater was evaluated from the point of view of water quality and quantity. The three factors were weighted and superimposed via GIS platform to generate the risk zoning map of groundwater contamination. The results showed that the overall risk of groundwater contamination in the study area was low. The area of high-risk and relatively high-risk areas accounted for 15.5% of the total study area, which were mainly distributed in L1, L2, and L3 of the study area. L1 was mainly affected by high pollution source load and high groundwater vulnerability. L2 was mainly the result of the joint action of high groundwater function value and domestic non-point source pollution. Non-point source pollution dominated by agricultural activities and high functional value of groundwater were the main reasons for the high risk of groundwater pollution in the L3 area. The results of the groundwater contamination risk assessment serve as an important reference for decision-makers to delineate the prevention and control area of groundwater pollution.

[Hydrochemical Characteristics and Possible Controls of Groundwater in the Xialatuo Basin Section of the Xianshui River].

In order to study the characteristics of groundwater chemistry and groundwater flow system in the Xianshui River fault zone, samples of precipitation, surface water, groundwater, and hot spring samples in the Xialatuo Basin were collected and tested. Through the test data, the main ions and the sources of recharge were analyzed by means of ionic relations, correlation analysis, Gibbs plot, Piper triangular diagrams, and saturation index. The groundwater recharge sources in the basin were studied using combined hydrogen and oxygen isotope information. Results show that all the water samples in the study area were weakly alkaline. The predominant cations were Ca2+, Mg2+, and Na+. Among these, Ca2+ accounted for 2.6%-53.6%, with an average value of 28.84%, Mg2+ accounted for 2.7%-57%, with an average value of 40.6%, and Na+ accounted for 6.2%-93.1%, with an average value of 28.6%. The anions were mainly HCO3-, accounting for 82.4%-98% of the total anions and with an average value of 89.6%. HCO3- and Na+ accounted for most of the ions with 93.1% and 98%, respectively, in the Zhanggu hot spring. The total dissolved solids (TDS) of the groundwater ranged from 116.11 to 372.75 mg·L-1, and with an average value of 281.91 mg·L-1. The hydrogeochemical type of groundwater was HCO3-Mg·Ca and HCO3-Ca·Mg. It is controlled by carbonatite dissolution with a circulatory depth range in dozens of meters. The hot springs are controlled by the fault zone and are mainly distributed along the main stem of the Xianshui River fault. Their water is of the HCO3-Na type. The hydrogeochemical process is controlled by silicate dissolution with a circulatory depth range in thousands of meters.

[Seasonal Variations in River Water Chemical Weathering and Its Influence Factors in the Malian River Basin].

In order to discern temporal variations, sources, and controlling factors of river water chemistry in the Malian River Basin, time series samples were collected from the Yuluoping hydrological station in 2016. The compositions of major cations and anions were analyzed and a forward model was used to calculate the weathering rates of evaporite, silicate, and carbonate. Results showed that river water was brackish with average total dissolved solids of 1154.0 mg·L-1, indicating significant differences from other main rivers in China. Na+, Ca2+, Mg2+, and SO42- were the major ions present in water, with mean concentrations of 202.8, 86.0, 78.6, and 431.2 mg·L-1 respectively. Water chemistry exhibited distinct seasonal variations, with major ions gradually declining during the pre-monsoon period and increasing in the post-monsoon period. An abrupt rise in concentrations of major ions during the ice melting interval was observed, as well as a sharp drop during stormy events. Dissolved loads were mainly derived from chemical weathering, with the contribution ratios of evaporite, silicate, and carbonate being 67.1%, 13.7%, and 19.2% respectively. Chemical processes showed different responses to climate forcing, attributed to variations in mineral content in the watershed and dissolution kinetics. The dominant contribution of evaporite in the monsoon season was due to its rapid dissolution, while silicate weathering increased during the pre-monsoon period, with longer water rock interaction times when water discharge was lower. During the post-monsoon season, carbonate weathering was enhanced due to its high content in loess and due to more CO2 absorption by rain from soil. The average chemical weathering rates of evaporite, silicate, and carbonate were 30.6, 6.2, and 8.7 kg·(km2·d)-1, respectively. A strong correlation between evaporite weathering rates and river discharge was evident; a correlation was also observed between carbonate weathering rates and river discharge, indicating that water discharge played a dominant role in chemical weathering, rather than temperature or precipitation.