CHARACTERISTICS OF OXYGEN ISOTOPIC COMPOSITION OF THE LAKES ALONG THE MID-LOWER REACHES OF THE YANGTZE RIVER

Pollution and eutrophication are the severe environmental problems lakes along the mid-lower reaches of the Yangtze River are faced with. Recently oxygen isotope of the water bodies has been widely applied to tracing the evolution and sources of the water bodies, transformation among precipitation, surface water and ground water and sources of pollutions.
Based on the analysis of δ¹⁸O in 45 lakes along the mid-lower reaches of the Yangtze River, the evolution process of lake waters was studied. The results show that δ¹⁸O shifts in lake waters reflect the variations of water sources of the lakes, and the relations of alternative evolution between lake waters during flood season and dry season of the Yangtze River. δ¹⁸O values for Chaohu Lake and Shitang Lake in Anhui Province,which lie in the middle mid-lower reaches of the Yangtze River are relatively high, whereas those of Poyang and Taihu Lakes that respectively lie in the upper and lower reaches are much lower due to the influence of water changes in seasons. Therefore, the Yangtze River has much greater effect on the lake water exchanges in the upper and lower reaches than in the middle. By the comparison of δ¹⁸O values in lakes, we conclude that the influence of the Yangtze River on the lakes is obvious during summer months, but lake waters are stable during autumn and winter months. The broad range of δ¹⁸O shifts of Huanggai Lake and Daye Lake during summer and autumn is directly related to the fluctuation of water level of the Yangtze River. The lakes are connected to the Yangtze River during its flood season, whereas they are separated from the river during dry season. Moreover, the great transformation of δ¹⁸O in Xuanwu Lake is caused by artificial water exchange.