关键词: ²²²Rn, 地下水补给, 水循环, 质量平衡, 柴达木盆地

Abstract:

Water resources are scarce in the arid region in Northwest China， and the ecological environment is fragile. In the context of global climate change and human activity interference， the use of isotope methods to conduct fine-scale surface water-groundwater interaction studies is a basic requirement for exploring local water cycle changes and water resources management. Research of water cycle and runoff variation has always been a difficult issue of assessment of water resources in arid basins. In May and August， 2019， samples of river water and groundwater had taken， then ²²²Rn concentration of these samples were measured and river runoff were also gauged. Then spatial and temporal characteristics of ²²²Rn concentrations in river water and groundwater had analyzed， together with interactions between them. The results show that （1） ²²²Rn concentration of river water in mountains are high， with a mean value of 948.72 Bq·m^-3， indicating that groundwater coming out of bedrock fissure water is an important source of river water in the mountains， especially near a tectonic faults； （2） ²²²Rn concentration of river water in the alluvial floodplain with less groundwater recharge are low， 76.71 Bq·m^-3 in^{average； （3） 222Rn concentration rises to average 676 Bq·m-3 in the transitional zone of alluvial floodplain and low-lying plain， where groundwater recharges to the river as spring. Toward downstream low plain， 222Rn concentration of river water go down again； （4） temporally， compared to May， 222Rn concentration of river water is relatively low in August， showing a decline of groundwater recharge； （5） 222Rn concentration of groundwater is 2-3 orders of magnitude higher than river water and demonstrate a spatial variation of high in the middle whereas low in the east and west； （6） in S1~S2， two concurrent processes of groundwater discharging to river and river water leaking to groundwater dominate the surface-groundwater interaction. A mass balance method was used to calculate the exchange flux which indicates accumulated river leakage flux in May and August is 3.87 m3?s-1 and 0.9 m3?s-1， separately， while 0.51 m3?s-1 and 0.47 m3?s-1 for groundwater discharge flux. River leakage is more powerful than river discharge and the flow flux between surface and groundwater varies noticeably in different sections and different time.}

Key words: ²²²Rn, groundwater recharge, water cycle, mass balance, Qaidam basin