硫和氧同位素示踪黄河及支流河水硫酸盐来源

Sources of riverine sulfate in Yellow River and its tributaries determined by sulfur and oxygen isotopes

  • 摘要: 为了准确识别河水硫酸盐受自然风化和人为活动影响的过程,做好地表水资源管理,选择黄河小浪底水库以下干流和支流河水为主要研究对象,分期采集河水样品,采用硫酸盐硫和氧同位素,结合水化学组成及潜在硫酸盐来源硫和氧同位素范围,判定黄河及支流河水硫酸盐的来源及混入比例。结果表明:① 研究区黄河河水硫酸盐主要来源于第四纪黄土中易溶硫酸盐,干流河水SO42-含量均值为2.23 mmol/L,δ34SSO4和δ18OSO4均值分别为+8.9‰和+10.4‰;② 研究区沁河丰水期河水硫酸盐24%来源于大气降水,61%来源于土壤硫酸盐溶解,15%来自于石膏溶解;平水期河水硫酸盐39%来源于大气降水,36%来源于土壤硫酸盐溶解,25%来源于石膏溶解。沁河河水SO42-含量均值为2.44 mmol/L,δ34SSO4和δ18OSO4均值分别为+9.8‰和+9.7‰;③ 研究区洛河河水硫酸盐受生活污水影响较大,伊河河水硫酸盐受到土壤硫酸盐溶解和化学肥料溶解的共同影响,伊洛河河水SO42-含量均值为1.27 mmol/L,δ34SSO4和δ18OSO4均值分别为+10.4‰和+6.5‰。蒸发盐类矿物溶解以及土壤硫酸盐溶解等自然风化过程是控制区域河水硫酸盐来源的重要过程,人为活动对伊洛河河水硫酸盐的贡献不容忽视。

     

    Abstract: Determining the cycle of riverine sulfate, affected by natural weathering and anthropogenic activities, is necessary for surface water management. Mainstream and tributaries of Yellow River from Xiaolangdi Reservoir, including Qinhe River and Yiluo River, were selected. River water samples were collected during different seasons, and dual isotopes of dissolved sulfate were measured, together with hydrochemical compositions of surface water and isotopic compositions of potential sources. Based on these, sources of dissolved sulfate in Yellow River and its tributaries with the mixing ratios of different sources in Qinhe River could be identified. The results indicate that: ① dissolved sulfate in Yellow River mainly derived from Quaternary loess, and the mean sulfate content was 2.23 mmol/L, with the mean δ34SSO4and δ18OSO4 values of +8.9‰ and +10.4‰, respectively; ② during flood season, 24% of dissolved sulfate in Qinhe River derived from rain water, 61 percent of dissolved sulfate derived from soil, and 15 percent of dissolved sulfate derived from gypsum dissolution. During temperate season, the mixing ratios of rain water, soil and gypsum were 39%, 36% and 25%, respectively. The mean sulfate concentration was 2.44 mmol/L, and mean δ34SSO4and δ18OSO4 values were +9.8‰ and +9.7‰, respectively; and, ③ dissolved sulfate in Luohe River more derived from sewage water and that in Yihe River was mainly controlled by soil and fertilizer. The mean sulfate concentration in Yiluo River was 1.27 mmol/L, and mean δ34SSO4and δ18OSO4values were +10.4‰ and +6.5‰, respectively. Dissolved sulfate in local river water was mainly controlled by natural weathering processes, such as dissolution of evaporites minerals and soil sulfate. At the same time, it should not be ignored that anthropogenic activities had altered the hydrochemical composition of the water Yiluo River, which should be paid more attention by local surface water managers.

     

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