Dual effects of precipitation and evaporation on lake water stable isotope composition in the monsoon region

We present the results of a 3-year monitoring programme of the stable isotope composition of lake water and precipitation at Taozi Lake, in the East Asian monsoon region of China. Our aims were to reveal the spatiotemporal pattern of variation of stable isotopes in a small closed-basin lake and to quantitatively determine the impacts of precipitation and evaporation on the stable isotope composition of lake water under a humid monsoon climate. In the time domain, the stable oxygen isotopic ratio of the lake water (delta O-18(L)) exhibited substantial seasonal and interannual variations, but the isotope variations between different precipitation events substantially exceeded seasonal and interannual variations. Compared with the stable isotopes in precipitation, delta O-18(L) was substantially positive and d(L) was negative. In the space domains, the lake water was homogeneously mixed. Indicated by statistic analyses, precipitation plays a dominant role in dynamic of the lake stable isotope during precipitation events of relatively large magnitude, whereas the effect of evaporation is dominant during smaller precipitation events. Results advance our understanding of the stable isotope change rule in the process of lake water evaporation, and it is helpful to identify the climatic significance recorded in stable isotopic compositions of lake bottom sediments.