民勤绿洲灌区地下水水化学特征及其演化驱动机理

通过分析民勤绿洲灌区55个地下水样的相关水化学指标,探讨该区地下水水化学特征及其演化驱动机理。结果表明:研究区地下水阳离子以Na~+和Mg~(2+)为主,阴离子以SO_4~(2-)和Cl~-为主;其中K~+、Na~+、Mg~(2+)、CO_3~(2-)、Cl~-、SO_4~(2-)表现为强变异性,而Ca~(2+)和HCO_3~-则表现为中等变异。研究区地下水水化学类型以SO_4-Mg型、Cl-Mg型、SO_4-Na型和Cl-Na型为主,沿着地下水流方向(坝区→泉山区→湖区),阳离子中Na~+逐渐取代了Mg~(2+)的主导地位,而阴离子中SO_4~(2-)一直占主导地位,但Cl~-的比重在不断增加。研究区地下水水化学组分主要来自岩盐、石膏等蒸发岩、碳酸盐矿物以及硅铝酸盐矿物的风化溶解。地下水水化学演化是由蒸发浓缩、阳离子交换和溶滤共同作用的结果。该研究结果可为民勤绿洲地下水资源评价、合理利用及其保护提供科学依据与决策指导。

Hydrochemical Characteristics and Evolution Mechanism of Groundwater in the Minqin Oasis

Groundwater hydrochemical characteristics and their driving mechanism of evolution in the Minqin Oasis were explored based on the data of total 55 groundwater samples.The results showed that the dominant cations were Na + and Mg2+,and the main anions were SO42-and Cl-.The variability of concentrations of K +,Na +,Mg2 +,CO32-,Cl-and SO42-was strong,but that of Ca2 + and HCO3-was moderate.The main hydrochemical types of groundwater in the study area were SO4-Mg,Cl-Mg,SO4-Na and Cl-Na.Along the direction of groundwater flow (Baqu→ Quanshan→Huqu),the dominant component Mg2 + was gradually replaced by Na +,SO24-was always the dominant anion,but the proportion of Cl-was gradually increased.The chemical composition of groundwater originated mainly in the weathering dissolution of evaporites,such as rock salt,gypsum,carbonate minerals and aluminosilicate minerals.Evolution of groundwater hydrochemical characteristics was jointly affected by evaporation,concentration,cation exchange and lixiviation.The results of this study could provide the scientific basis and decision-making guidance for evaluating,rationally utilizing and conserving groundwater resources in the Minqin Oasis.