马莲河流域下游水体222Rn特征及指示意义

为揭示黄土高原典型流域地表水和地下水相互作用规律,以马莲河流域下游为例,应用氡同位素²²²Rn示踪方法分析了不同水体²²²Rn分布特征、影响因素以及河水和地下水转化关系,并利用氡同位素梯度指示河水和地下水作用强度。结果表明:马莲河下游不同水体²²²Rn活度差异较大,表现为白垩系地下水>黄土地下水>第四系地下水>河水。岩性是控制地下水中²²²Rn活度分布的首要因素,构造和氧化还原条件对其也有影响,河水²²²Rn活度主要受地下水补给的影响。马莲河下游各段²²²Rn同位素梯度分布表明R02—R03,R03—R04,R13—R14段地下水大量补给河水,其他区段地下水无补给或补给强度较低。

Characteristics and Implications of 222Rn in Water Body in the Lower Reach of Malian River

Radon isotope was utilized as a tracer to determine the river-groundwater interaction and explore the spatial variation and controlling factors of ²²²Rn activity in river water and groundwater in the lower reach of the Malian River. Isotope gradient was proposed as an indicator of the magnitude of river water and groundwater interaction. The results implied that ²²²Rn activity was considerably lower in river water than that in groundwater. The highest ²²²Rn activity in groundwater was found in the Cretaceous aquifer, followed by the loess aquifer, the quaternary aquifer, and river water in sequence. Moreover, ²²²Rn activity in groundwater was controlled by lithology, geological formation and redox conditions and lithology was the most important factor, whereas ²²²Rn activity in river water was influenced by groundwater discharge. The distribution of ²²²Rn isotopic gradient provided a detailed profile of river water and groundwater interaction. A positive index indicated that groundwater had entered surface water between those sites of R02-R03, R03-R04 and R13-R14, while a weaker interaction in other sites.