湟水河河床沉积物元素含量及化学风化分析

选择湟水河流域湟源至乐都段为研究区段,采集并分析了湟水河及支流北川河、南川河河道不同地点25个河床泥沙样品的常量元素地球化学特征。结果表明:富集Si、Al、Ca和Fe;而贫K、Na、Mg、Ti和Mn,说明主要沉积有硅酸盐和碳酸盐。通过化学风化指数(CIA)计算,发现从湟源-湟中(多巴)-西宁市-平安-乐都段,化学风化强度具有不同的变化特征。西宁市及周边地区CIA最低,湟源县-多巴镇、平安-乐都以及北川河CIA明显较高,具有更强的风化侵蚀过程,并得到聚类分析结果的验证。利用CIA与现代观测气象数据(降水量变差系数)对比,发现CIA与降水量变差系数呈正相关分布,说明流域强降水(如暴雨、大雨)侵蚀了周围覆盖的第四纪黄土,并富含Ca/Mg碳酸盐。

Chemical alternation index and element geochemistry of riverbed sediments from Huangshui river

Twenty-five riverbed sediments from Huangyuan to Ledou in Huangshui river were collected and its tributary(such as Beichuan river and Nanchuan river),their trace element contents were measured by XRF(X-Ray Fluorecence).The results indicate that these sediments enrich in Si,Al,Ca and Fe;while poor in K,Na,Mg,Ti and Mn,which shows that they are mainly silicate and carbonate.Similarly,we found that chemical index of alternation(CIA) of these sediments in different sites are varied based on mathematics calculation,cluster analysis and factor analysis.The value is the lowest in Xining city and surrounding region,and it is much higher in Huangyuan county,Pingan county,Ledu county and Beichuan river.In addition,we also compared CIA with weather data(precipitation coefficient of variation) in observatory,and found that CIA is positive correlation with precipitation coefficient of variation.The result shows that strong precipitation maybe eroded surface loess sediments overlaid river terraces and bring much Ca or Mg into riverbed sediments.