Chemical Characteristics and Transformation Relationship of Groundwater and Surface Water in Fenghe River Basin at the Northern Foot of Qinling Mountains,China
The Fenghe River is one of the"Eight Waters of Chang'an",and in-depth research on the status quo of its water environment,influencing factors,and the relationship between surface water and groundwater transformation is the key to the ecological restoration of the river.Based on 62 groundwater samples and 17 surface water samples collected in Fenghe River Basin in July 2022,the chemical characteristics and influencing factors of groundwater and surface water were analyzed by mathematical statistics,Piper diagram,Gibbs diagram,ion ratio method and hydrogen and oxygen isotopes,and the transformation relationship between groundwater and surface water was explored.The results show that ① the groundwater in the study area is weakly alkaline,about 50％is extremely hard water,25％is hard water,and the total dissolved solids(TDS)is large,the maximum value is as high as 1 916 mg·L-1,and NO3-concentration is high;surface water is weakly alkaline,soft or slightly hard water,with less TDS and more organic matter;the cations of surface water and groundwater are mainly Ca2+,the anions are mainly HCO3-,and the surface water is basically HCO3-Ca water;the main chemical types of groundwater are HCO3-Ca,HCO3·SO4-Ca,HCO3-Ca Mg and HCO3·SO4-Ca·Mg types accounted for 24.19％,24.19％,16.13％and 9.68％,respectively,and the spatial variation of water chemistry type is large.② The water chemical characteristics of the study area are mainly controlled by rock weathering,and evaporation concentration and atmospheric precipitation are also affected;in addition to the dissolution of rock salt,Na+in water should also be affected by silicate weathering,and Ca2+,Mg2+and HCO3-mainly come from the weathering and dissolution of carbonates such as calcite and dolomite;the alternating adsorption of cations in groundwater is common,which has a great impact on Ca2+and Na+concentrations;human activities have increased the concentrations of SO42-,NO3-and Cl-in some groundwaters,while surface water is less affected by human activities.③ The surface water is mainly used to recharge groundwater in the alluvial fan top-middle in the study area,and the recharge ratio is 46.62％;the leading edge of the alluvial fan is mainly recharged by groundwater for surface water,and the recharge ratio is 13.62％;the lower plain is mainly recharged by surface water to groundwater,with a recharge ratio of 38.39％.
water chemistryinfluencing factortransformation relationshipgroundwater-surface waterion ratiorecharge ratiohydrogen and oxygen isotopesWeihe River Basin
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