喀什噶尔河下游平原区地下水咸化特征及成因分析

为了揭示新疆喀什噶尔河下游平原区地下水咸化的分布特征和形成机制，综合运用数理统计、Duorv图、PCA-APCS-MLR模型、离子比值和水文地球化学模拟等方法，对2018年采集的69组地下水样品进行分析.结果表明，研究区地下水总体呈弱碱性，TDS的变化范围为573.0~16700.0 mg ·L^-1，地下水化学类型主要为HCO₃·SO₄·Cl、SO₄和SO₄·Cl型；咸化系数计算结果表明，从潜水至深层承压水咸化程度呈现出逐渐增加的规律；蒸发浓缩作用和溶滤作用是导致研究区地下水咸化的主要因素，从潜水至深层承压水碳酸盐岩、硅酸盐岩的风化溶解和阳离子交换作用逐渐减弱，而蒸发盐岩的风化溶解持续加强，也是导致深层地下水咸化程度大于浅层地下水的首要因素；人类活动对研究区地下水咸化也产生了一定的影响；相邻含水层咸水的越流补给加剧了研究区地下水的咸化.

Characteristics and Causes of Groundwater Salinization in the Plain Area of the Lower Kashgar River

This study revealed the distribution characteristics and formation mechanism of groundwater salinization in the plain area of the lower Kashgar River in Xinjiang, which can provide scientific basis for a local sustainable groundwater exploitation plan and practical significance for local water supply security and social stability. Fifteen phreatic water samples, 38 shallow confined groundwater samples, and 16 deep confined groundwater samples were collected in September 2018. Mathematical statistics, a Duorv diagram, PCA-APCS-MLR model, ion ratios, and hydrogeochemical simulations were comprehensively used for sample analysis. The results showed that groundwater was weakly alkaline in general (pH ranged between 6.48 and 8.60 with an average of 7.57), with total dissolved solids (TDS) ranging from 573.0 to 16700.0 mg·L^-1. Groundwater was mainly composed of Cl^-, SO₄^2-, Na⁺, and Ca²⁺. The main groundwater hydrochemical types included were HCO₃·SO₄·Cl, SO₄, and SO₄·Cl. No brine was observed in the study area, phreatic water was mainly composed of brackish water and saline water, and confined groundwater was mainly composed of saline water. The salinization coefficient calculation results showed that the salinization degree gradually increased from phreatic water to deep confined groundwater. Evaporation concentration and lixiviation were the main factors leading to the salinization of groundwater. The dissolution and cation exchange of carbonate and silicate rocks gradually weakened from phreatic water to deep confined groundwater, whereas the dissolution of evaporite rock always dominated and was gradually strengthened, which was also the primary factor that caused the salinity of deep groundwater to be higher than that of shallow groundwater. Human activities such as agricultural fertilization, unreasonable use of surface water for irrigation, and improper treatment of domestic sewage had a certain impact on groundwater salinization. The leaking recharge of salt water from adjacent aquifers aggravated the groundwater salinization.