Indicative Significance of Hydrogen and Oxygen Isotopic Composition of Water Bodies in the Fengpei Plain to Water Cycle and Evaporation
Fengpei Plain area includes Fengxian County,Peixian County and the northern part of Tongshan District.In recent years,groundwater overdraft and serious fluoride pollution have occurred in this area.In order to investigate the water cycle situation in the re-gion,a total of 28 samples of surface water and groundwater were collected,and the distribution pattern of hydrogen and oxygen isotope composition and its influencing factors were analyzed.The conversion relationship between shallow groundwater and surface water in the abundant plain area,as well as their respective evaporation loss ratios,were discussed.The research results indicate that the degree of secondary evaporation under clouds in atmospheric precipitation is relatively small,groundwater evaporate more strongly than nearby ar-eas.The isotope content of groundwater is gradually enriched along the direction of groundwater runoff,and there is a weak exchange interaction between 18O and CO2 in groundwater,leading to 18O depletion.Combined with the hydrological geological survey and hydro-gen and oxygen isotope characteristics,it is inferred that the groundwater in the middle and upper reaches of the river is more inclined to supply surface water,and the surface water in the lower reaches of the river leaks a lot to groundwater.It is calculated by the two end member method that the overall proportion of surface water recharged by groundwater recharge is about 20％-40％,even more than 60％at some areas.Most of the recharge ratio of the downstream river water to groundwater ranges from about 25％to 50％,with some points reaching up to 90％.Using the Rayleigh model under non equilibrium fractionation conditions to calculate the evaporation ratio,the evaporation ratio of river water is about 23％-28％,and the evaporation loss of groundwater is about 15％-20％.The results can provide scientific reference for water resource management in the Fengpei Plain area and similar surrounding areas.
hydrogen and oxygen isotopeswater cycleevaporationFengpei Plain areagroundwatersurface water
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