溶质势对地表蒸发速率的影响

Contribution of osmotic potential on bare soil evaporation rate

针对盐碱化土壤地表蒸发速率研究的不足,以表层土壤为研究对象,采用土壤蒸发试验和数学模型相结合的方法分析了溶质势对地表蒸发速率的影响。结果表明:当土壤中盐分没有沉淀结晶时,溶质势是盐分引起地表蒸发速率降低的主要原因;溶质势越低,蒸发速率下降比例越大,该下降比例与溶质势有近似线性关系,但同时还受到空气温度与相对湿度、土壤温度以及土壤基质势等因素的影响;当表层土壤存在水盐补给时,地表蒸发速率总是变化趋向于水分补给速率,但含盐土壤蒸发速率变化较慢,而且若补给水分中含盐,那么其稳定蒸发速率会低于水分补给速率。

A combined approach of evaporation experiment and mathematical modeling is used to analyze the influ- ence of osmotic potential on the bare soil evaporation rate. The result shows that the osmotic potential is proven to be the main reason for the decline of evaporation rates in saline soils when no salt precipitation occurs. The rate decline is almost linearly proportional to the decrease in osmotic potential, and is also affected by air temperature, air relative humidity, soil temperature, and soil matrix potential. When a constant water flux is supplied to the topsoil, the evapo- ration rate would always tend to be the constant value. However, the evaporation rate in saline soils is rather slower if the saline water is supplied to the topsoil, and the steady evaporation rate would tend to be a bit slower than the water supply rate.