Oxyhydrogen Isotope Characteristics Of The River System In Western Sichuan Plateau

The Aba Autonomous Region, the rare endemic area of KBD, is located in the Northwest part of Sichuan Province. The cause of KBD is closely related to the hydrometrical-setting in that distinguish. In this region, surface water is the long term source of drinking water for local residents. Long term consumption of such water is likely cause KBD occurrence. This paper is based on the "the project of investigating underground water condition and the security water delivery" which the sub-name is "the survey of the ecological geochemistry in Aba Sichuan province (1212010913022)". Ascertaining the characteristic of hydro geochemistry, and the ox hydrogen isotope analysis combined with the factors on lithology, structure, hydrogeology, we discussed the different origin of different water, and its relationship.The main achievements as below:The δD and δ18O of rivers in study area are-107.5～-64.7and14.87～-9.68. Rivers of the study area is mainly supplied by meteoric water and the isotopic composition showing the characteristics of east to the west with obvious zonation. Because these rivers are mainly affected by the impact of the summer monsoon, the south-east Pacific and the South China Sea water vapor group, with obvious impact of the continental effect.The Western Sichuan Plateau is the common birthplace of both Changjiang River and Yellow River. The δD and δ18O of Changjiang River are-107.5～-64.7and-14.87～-9.68, which shows that Changjiang River in study area is mainly supplied by meteoric water and less evaporation. The δ18O and8D of Yellow River are-102.4～-79.7and-14.35～-10.03, whose deuterium excess parameter is lower than the Changjiang River, and the minimum is-0.250, which indicates the Yellow River is under a strong effect of evaporation.The characteristics of White River, Duke River, Suomo River and Jiaomuzu River is enrichment of light isotopes, yet the isotopic composition of their well water is more negative with high TDS, which means its supply source is from high-altituderegion, and after a long-distance migration; the cycle and the mutual supply between groundwater and rivers are not obvious. The analysis of water chemistry shows that the type of water is HCO3-Ca and HCO3-Ca·Mg. The water in study place is mostly middle alkalinity and light mineralization, and the value of TDS is between44.5-301.4mg/L.Spatial distribution of TDS shows the characteristics of the east to the west. The Baishuijiang River has the highest degree of mineralization, and the Zequ River’s TDS is the minimum. Duke River, Zequ River, Jiaomuzu River, Suomo River and White River is mainly affected by the supply of atmospheric precipitation, the value of TDS is less than150mg/L.The reason caused the difference of TDS is on the one hand, with the weathering of rocks under the strong erosion of river, ions are precipitated from rocks naturally; on the other hand, groundwater with much CO2supply which from soil rich in humic acids and organic matter, which dissolved carbonate minerals and silicate minerals..