基于水化学和环境同位素的准格尔煤田地下水循环特征

Characterization of groundwater circulation in the Jungar coalfield based on water chemistry and environmental isotopes

为揭示准格尔煤田地区地下水循环特征,运用水化学技术、水汽轨迹模型和环境同位素等方法分析不同水体水化学特征、环境同位素特征、大气降水主要来源、地表水及地下水转化关系。结果表明:地表水矿化度低,呈弱碱-偏碱性,水化学类型以HCO_(3)·SO_(4)·Cl-Ca型水为主;地下水整体矿化度低,偏弱碱性,主要以HCO_(3)-Na·Ca型、Cl-Na型、HCO_(3)-Ca·Mg型、HCO_(3)·Cl-Na型水为主;黄河水δ(D)平均值为-79.6‰、δ(^(18)O)平均值为-10.47‰,第四系地下水δ(D)平均值为-66.25‰、δ(^(18)O)平均值为-9.1‰,白垩系地下水δ(D)值为-70.6‰、δ(^(18)O)值为-9.3‰,石炭-二叠系地下水δ(D)平均值为-77.07‰、δ(^(18)O)平均值为-9.9‰,寒武-奥陶系地下水δ(D)平均值为-75.73‰、δ(^(18)O)平均值为-10.06‰;大气降水受极地气团和季风影响,主要来源为西风带水汽、地表水和地下水水汽蒸发再循环;断层带、褶皱轴部裂隙带为不同含水层间主要导水通道,大气降水和黄河为地下水主要补给来源;高承压水头寒武-奥陶系岩溶裂隙水越流补给第四系松散孔隙水和砂岩裂隙水,第四系松散孔隙水通过地层间不整合接触面裂隙发育带向下补给石炭-二叠系砂岩裂隙水,黄河水对寒武-奥陶系地下水的补给比例受地质构造发育的影响较大。

The Jungar coalfield is one of the major coal resource mining sites in northwest China.Water damage at the bottom of the coal seam has become an important factor that is limiting the development of the local economy and society.Therefore,it is important to identify the recharge relationship and circulation characteristics between atmospheric precipitation,surface water,and groundwater in the Jungar coalfield to provide a theoretical basis for the scientific development of coal resources and the effective restoration of groundwater resources in the area.Environmental isotope method,water chemistry analysis methods,and HYSPLIT applied to the groundwater of the Jungar coalfield.Through historical data collection,field survey sampling,and indoor analysis,the water chemistry composition and environmental isotope characteristics of atmospheric precipitation,surface water and groundwater,the main sources of atmospheric precipitation,surface water and groundwater transformation relationships were analyzed.The results show that:(1)Surface water has low mineralization and is weakly alkaline,and the water chemistry type is mainly HCO_(3)·SO_(4)·Cl-Ca type water.The overall mineralization of groundwater is low and weakly alkaline,and the water chemistry type is mainly HCO_(3)-Na·Ca type,Cl-Na type,HCO_(3)-Ca·Mg type,and HCO_(3)·Cl-Na type water.(2)The average value ofδ(D)of Yellow River water is-79.6‰,and theδ(^(18)O)is-10.7‰,respectively.The average value ofδ(D)of Quaternary water is-66.25‰,and theδ(^(18)O)is-9.1‰,respectively.The average value ofδ(D)of Cretaceous water is-70.6‰,and theδ(^(18)O)is-9.3‰,respectively.The average value ofδ(D)of Carboniferous-Permian water is-77.07‰,and theδ(^(18)O)is-9.9‰,respectively.The average value of Cambrian-Ordovician waterδ(D)average value is-75.73‰,δ(^(18)O)is-10.06‰.Atmospheric precipitation is influenced by polar air masses and southeastern monsoons,and the principal sources are westerly water vapor,surface water,and groundwater vapor evaporation recirculation.(3)The fourth system water has high tritium content,the presence of nuclear explosive tritium,and excellent groundwater runoff conditions.The Cretaceous water has low tritium content and is a mixture of groundwater recharged before 1952 and recently recharged water.The Carboniferous-Permian water contains a wide range of tritium content,including groundwater recharged before 1952 and modern water.The Cambrian-Ordovician water contains a wide range of tritium content,including groundwater recharged before 1952,modern water,and mixed water.(4)The recharge ratio of atmospheric precipitation to Cambrian-Australian water ranges from 0.98%to 91.7%,with an average recharge rate of 61.2%.The recharge ratio of surface water(referred to as Yellow River water)to Cambrian-Ordovician water ranges from 0.83%to 90.2%,with an average recharge rate of 38.8%.Among them,the recharge ratio of Yellow River water to Cambrian-Ordovician water is larger in Longwanggou,Suancigou,and Huangyuchuan well field,which is influenced by the development of geological structures.The fault zone and the fracture zone of the fold axis are the main water-conducting channels between different aquifers.Atmospheric precipitation and the Yellow River are the principal sources of groundwater recharge.The precipitation vapor sources are mainly westerly water vapor,surface water,and groundwater vapor evaporation recirculation.Highly pressurized head Cambrian-Ordovician karst fracture water cross-flow recharges the Fourth Series and sandstone fracture water.The pore water of the Fourth Series recharges the fracture water of the Carboniferous-Permian sandstone downward through the fracture development zone of the unconformity contact surface between the strata.The recharge ratio of the Yellow River to Cambrian-Australian water is influenced by the development of geological structures.In Longwanggou,Suancigou,and Huangyuchuan well field,the proportion of recharge of the Yellow River water to Cambrian-Ordovician water is larger.