| 马莲河流域化学风化的季节变化和影响因素 |
| 摘要点击 2052 全文点击 814 投稿时间：2018-01-10 修订日期：2018-03-13 |
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| 中文关键词 马莲河 水化学 季节变化 蒸发岩 化学风化 |
| 英文关键词 Malian River hydrochemistry seasonal variation evaporite chemical weathering |
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| 中文摘要 |
| 为查明黄土高原马莲河流域不同季节河水化学的变化特征、来源及主要控制因子，2016年1~12月在流域下游雨落坪水文站采集时间序列水样40组，分析了主要离子组成并计算了化学风化速率.结果表明，河水总溶解固体（TDS）均值1154.0 mg·L-1，远高于长江、黄河和珠江.阳离子以Na+为主，均值202.8 mg·L-1，其次为Ca2+和Mg2+，阴离子以SO42-为主，均值431.2 mg·L-1.主要离子质量浓度的季节变化明显，总体规律是雨季前降低，雨季后增高，在融冰期和暴雨期分别突增和骤降.离子来源主要为岩石化学风化，蒸发岩、硅酸盐和碳酸盐贡献比例均值分别为67.1%、13.7%和19.2%.矿物含量和风化速率的不同决定了各风化作用对气候变化的差异响应：蒸发岩因其高风化速率对季风气候响应积极，雨季风化作用增强；雨季前期河水流量低，较长的水岩作用时间有利于硅酸盐风化进行；碳酸盐风化作用在雨季晚期和后期明显增强，可能因其在黄土中含量较高，雨季后降雨吸收了更多的土壤CO2形成H2CO3增进了碳酸盐的溶解.蒸发岩、碳酸盐风化速率和流量显著正相关，流量是控制流域化学风化的主要因素. |
| 英文摘要 |
| In order to discern temporal variations, sources, and controlling factors of river water chemistry in the Malian River Basin, time series samples were collected from the Yuluoping hydrological station in 2016. The compositions of major cations and anions were analyzed and a forward model was used to calculate the weathering rates of evaporite, silicate, and carbonate. Results showed that river water was brackish with average total dissolved solids of 1154.0 mg·L-1, indicating significant differences from other main rivers in China. Na+, Ca2+, Mg2+, and SO42- were the major ions present in water, with mean concentrations of 202.8, 86.0, 78.6, and 431.2 mg·L-1 respectively. Water chemistry exhibited distinct seasonal variations, with major ions gradually declining during the pre-monsoon period and increasing in the post-monsoon period. An abrupt rise in concentrations of major ions during the ice melting interval was observed, as well as a sharp drop during stormy events. Dissolved loads were mainly derived from chemical weathering, with the contribution ratios of evaporite, silicate, and carbonate being 67.1%, 13.7%, and 19.2% respectively. Chemical processes showed different responses to climate forcing, attributed to variations in mineral content in the watershed and dissolution kinetics. The dominant contribution of evaporite in the monsoon season was due to its rapid dissolution, while silicate weathering increased during the pre-monsoon period, with longer water rock interaction times when water discharge was lower. During the post-monsoon season, carbonate weathering was enhanced due to its high content in loess and due to more CO2 absorption by rain from soil. The average chemical weathering rates of evaporite, silicate, and carbonate were 30.6, 6.2, and 8.7 kg·(km2·d)-1, respectively. A strong correlation between evaporite weathering rates and river discharge was evident; a correlation was also observed between carbonate weathering rates and river discharge, indicating that water discharge played a dominant role in chemical weathering, rather than temperature or precipitation. |
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