长江下游竹林小流域土壤水同位素时空分布探究

Temporal and Spatial Distribution of Soil Water Isotopes in Small Bamboo Watershed in Lower Reaches of Yangtze River

为揭示长江下游竹林小流域的林内降水和土壤水同位素的空间变化规律,通过分析2017年梅雨期和睦桥小流域中游时段林外降水和林内降水及不同采样点的日林内降水和日土壤水同位素变化规律,发现雨强较大情况下,林内降水同位素相对于林外降水贫化,主要由于竹林内雾气的出现加强了雨水与周围贫化水汽的交换作用;各采样点土壤水同位素对于降水同位素的响应具有一定的滞后性,滞后时间大约为2 d;土壤水中δ^(18)O与土壤含水率存在明显的负相关关系,说明了土壤蒸发作用对于土壤水同位素具有一定的影响。

In order to reveal the spatial variation of stable isotopes in throughfall and soil water in the small bamboo watershed in the lower reaches of the Yangtze River, this paper analyzed the stable isotopes data of hourly throughfall and precipitation in the middle reach of the watershed during the Meiyu period in 2017, as well as the daily throughfall and soil water isotopes data at different sampling points. It is found that under the relatively heavy rain intensity conditions, the isotopes composition of throughfall is relative depleted than that of precipitation, the appearance of fog in the bamboo forest strengthens the exchange effect between the rainwater and the surrounding water vapor with depleted isotopes. The response of soil water isotopes at each sampling point to precipitation isotopes has obvious hysteresis property, and the lag time is about 2 days. There is an obvious negative correlation between δ^(18)O in soil water and soil water moisture, which indicates that soil evaporation has a significant impact on soil water isotopes.