Geochemical and isotopic characteristics of shallow groundwater within the Lake Qinghai catchment, NE Tibetan Plateau
Geochemical and isotopic characteristics of shallow groundwater within the Lake Qinghai catchment, NE Tibetan Plateau
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青藏高原东北部青海湖流域浅层地下水地球化学和同位素特征
DOI：
10.1016/j.quaint.2013.05.033
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发表时间：
2013-11
影响因子：
2.2
通讯作者：
肖军
中科院分区：
文献类型：
--
作者：
肖军
通过对青海湖流域浅层地下水主要离子、锶同位素（87 Sr/86 Sr）、氢同位素（δD）和氧同位素（δ 18 O）的分析，揭示了青海湖流域浅层地下水的空间变化、控制因素、溶质来源和补给来源。该地区浅层地下水呈微碱性，97%为优质淡水，但布哈和湖滨地下水中硝酸盐和硫化物浓度较高。大部分浅层地下水为Ca 2 +-HCO 3 −型，而湖泊（LS）周围的部分地下水则为Na+-Cl−型湖水（QHL）。地下水地球化学受区域岩性组合、离子交换和矿物沉淀的控制。溶解态Sr浓度和87 Sr/86 Sr比值分别为1.0 ~ 15.6 μmol/L和0.709859 ~ 0.715779。第一次定量计算在地下水中使用的前向模型表明，40%的溶解Sr来自碳酸盐风化，33%来自蒸发岩溶解，17%来自硅酸盐风化，其余来自大气输入的整个流域。在沙柳（SL）、哈尔盖（HG）和布哈（BH）样品中，碳酸盐风化作用占主导地位，而在LS和道塘（DT）样品中，蒸发岩溶解作用占主导地位。δD和δ 18 O数据表明，雨水是青海湖流域河水和浅层地下水的主要补给源。青海湖水具有布哈型水的特征，但由于碳酸盐沉淀，其Sr地球化学特征与浅层地下水不同。虽然浅层地下水贡献了溶解Sr的QHL的0.5%，地下水必须考虑到湖水的化学和预算的特点。
Major ions, isotopic ratios of strontium (87Sr/86Sr), hydrogen (δD) and oxygen (δ18O) of groundwater samples were analyzed to decipher spatial variation, controlling factors, solute sources, and the recharge source of shallow groundwaters within the Lake Qinghai catchment. Shallow groundwaters in this area are slightly alkaline, with 97% being fresh water of good quality, though there are high concentrations of nitrate and sulfide in Buha and lakeside groundwaters. Most of the shallow groundwaters are of the Ca2+–HCO3−type, whereas part of groundwaters surrounding the lake (LS) belongs to the Na+–Cl−type as lake water (QHL). Groundwater geochemistry is controlled by regional lithological association, ion exchange, and mineral precipitation. The dissolved Sr concentrations and87Sr/86Sr ratios vary from 1.0 to 15.6 μmol/L, and from 0.709859 to 0.715779, respectively. The first quantitative calculation in groundwater using a forward model shows that 40% of dissolved Sr is from carbonate weathering, 33% from evaporite dissolution, 17% from silicate weathering, and the remainder from atmospheric input for the whole catchment. Carbonate weathering dominates groundwater geochemistry in Shaliu (SL), Hargai (HG) and Buha (BH) samples, while evaporite dissolution dominates LS and Daotang (DT) samples. δD and δ18O data show that rain water is the major recharge source of both river water and shallow groundwater within the Lake Qinghai catchment. Qinghai Lake water is characterized by Buha-type water, but its Sr geochemistry is different from the shallow groundwater due to carbonate precipitation. Although shallow groundwater contributes ∼5% of the dissolved Sr to the QHL, groundwater must be taken into account when the chemistry and budget of lake water are characterized.
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