淮北平原区氢氧同位素水文实验研究

Hydrological Experiments on Oxygen and Hydrogen Isotopic Variations in Precipitation,Groundwater and Riverwater in Huaibei Plain,Anhui Province

运用氢氧稳定同位素18O2、H结合Ca2+及电导率等方法对淮北平原区五道沟径流试验场一次降雨径流过程进行了水文示踪实验研究,分别对降雨、地表水及地下水进行采样。通过现场测试与实验分析结果表明,次降雨过程中的1δ8O及δ2H的变幅较大并随雨强的降低而增大;#1、#6井中地下水的1δ8O及δ2H变化不大,接受降雨补给量极小,与补给区水源的氢氧同位素组成有关,对本次降雨入渗补给的响应较慢,有明显的滞后效应;浅层#3井对本次降雨同位素信号的响应较快,井水中的钙离子含量也迅速升高,有来自土壤水的补给;IR自记井及S4井由于受抽水灌溉等人类活动的持续影响,δ18O(或2δH)明显偏负,有来自深层潜水的补给;流域出口断面河水的1δ8O(或2δH)变幅远小于本次降雨的δ18O(或2δH)变幅,与降雨量及平原流域较强的均化作用有关。

A hydrologic tracing experiment was conducted for a precipitation event in the Wudaogou Hydrological Experimental Catchment （WHEC） located in north Anhui Province of China. Precipitation, groundwater and streamflow were sampled and analyzed for Calcium, EC,18O and 2 H, The results of the analysis show that the isotopic composition values of precipitation are influenced by rainfall intensity and vary in a very large range during the experimental period. The values increase when rainfall intensity decreases. δ18O and δ2H values for groundwater from holes #1, #3 and #6 are related to the oxygen-18 and deuterium composition of the groundwater recharge sources and precipitation in the area. There exists time lag effect between phreatic water in the three holes and atmospheric precipitation, so the oxygen and hydrogen isotope signal of groundwater in the holes reflects slowly that of precipitation. Wells IR and $4 are continuously influenced by agricultural pumping and irrigation, in which groundwater appears to be an abrupt negative shift, which indicates that there are some recharge sources from deep phreatic water. It was found that the variation range of δ18O and δ2H values of streamflow is smaller than that of precipitation, we attribute this case to the total rainfall amount and the uniformization effect of catchment, which makes the variation of original isotopic or chemical composition of rainfall become small or even overridden as waters move along long flowpaths through subsurface soil layers and finally come to the outlet of the catchment.