三峡水库坝前水体水化学及溶解无机碳时空分布特征

Temporal and spatial variation of water chemistry and dissolved inorganic carbon isotope characterization in Three Gorges Reservoir

以三峡水库坝前水体为研究对象,分析了三峡水库蓄水至145m和172m水位时坝前垂向水体基本物理化学参数、主量元素、溶解无机碳(DIC)含量及其碳同位素(δ13CDIC)分布特征.研究结果表明,无论夏季还是冬季,坝前水体均没有出现水温分层现象,pH、电导、溶解氧也没有发生分层现象.坝前水体水化学组成主要受碳酸盐岩风化的控制,主量元素、溶解无机碳含量和三峡大坝截流前相比没有发生明显的变化.水体δ13CDIC值夏季(丰水期)低于冬季(枯水期),在垂向上变化不明显,与水库、湖泊δ13CDIC的时空变化特征相异而与自然河流的变化特征相似.目前,三峡水库坝前水体水化学特征主要表现出自然河流的特征,水库"湖沼学反应"还不明显.

Water samples upstream the Three Gorges Dam （TGD） were collected in July （summer） and December 2009 （winter） to determine the basic chemical and physical parameters, concentrations of major ions, and contents and isotopic values （ 813Cmc ） of dissolved inorganic carbon （DIC）. The results showed that the stratification of water temperature, pH, EC and dissolved oxygen has not been detected in the water column. The chemical composition of studied water samples in Three Gorges Reservoir was characterized by the dominance of Ca2 ~ and HCO3- , which is mainly controlled by weathering of carbonate rocks due to the widespread of these rocks in the upper Yangtze River catchment. Compared with the data in 2003 when the Three Gorges Dam was not fully completed, the concentrations of major ions and DIC in 2009 were not significantly varied. The ~13Cmc values of the water samples in summer were lower than those in winter, and didn＇t show significant variation with the increase of water depth, which is similar to the characteristics of natural rivers but different from the other reservoirs and lakes. At the present study, the hydrochemical characteristics of waters in the main river channel of Three Gorges Reservoir exhibited the feature of natural river rather than traditional reservoir.