长江颗粒(类)金属元素分布、来源和向海输送

基于对长江干流与主要支流丰水期的调查和下游一个水文年的综合观测，结合多元数理统计手段和历史观测数据，对悬浮颗粒物中元素的时空变化、控制因素和来源等进行了解析，探讨了流域自然和人为因素对元素输送的影响.结果表明，大多颗粒物携带的元素在涪陵至宜昌河段存在下降趋势，这和三峡水库对颗粒物的滞留有关.多个元素在人口活动密集的下游地区出现高值，为人类活动和流域地质背景共同作用的结果.统计表明，硼（B）、钪（Sc）、镓（Ga）、锶（Sr）、钛（Ti）、锆（Zr）和铌（Nb）元素主要来源于岩石风化和土壤侵蚀等自然过程；锰（Mn）、铜（Cu）、锌（Zn）、镍（Ni）、钴（Co）、铅（Pb）、镉（Cd）和铬（Cr）元素主要受人类活动影响.尽管颗粒物中各元素入海通量差异大，但大多在丰水期的输送通量占全年的比例最高，且颗粒态元素的输送通量远高于溶解态.长江悬浮颗粒物中重金属元素含量在全球河流处于中等浓度水平.长江输沙量因筑坝发生了较大的变化，悬浮颗粒物中金属元素的输送源汇格局因此正在发生改变，并可能对河流和河口环境产生深远的影响.

Distribution, Sources, and Export of the (Sub-) Metal Elements in the Changjiang River

Based on the observations of 16 stations in the main stream and the major tributaries during flood season and the monthly observations in the lower stream at Jiangyin station in the Changjiang (Yangtze) River for one year, we discussed the content, distribution, and source of metal elements associated with suspended particulate matter and explored the influence of natural and human factors on the transport of metal elements associated with suspended particulate matter in the Changjiang River, combined with multivariate mathematical statistics. The results showed that almost all elements had downward trends in the reach from Fuling to Yichang, largely relating to the retention effect of the Three Gorges Reservoir. Furthermore, most elements had high values in the lower reaches of the Changjiang River, which was the result of human disturbance and the geological setting in the basin. Statistical analysis showed that the sources of B, Sc, Ga, Sr, Ti, Zr, and Nb were mainly derived from natural processes including rock weathering and soil erosion. Mn, Cu, Zn, Ni, Co, Pb, Cd, and Cr were mainly controlled by human activity. There were large ranges in export fluxes of metal elements in the Changjiang River, and the share during flood season contributed the largest part to the annual load. Compared with that in other large rivers around the world, the abundance of heavy metal elements in the Changjiang River was at a moderate level. Due to the huge amount of sediment transported by the Changjiang River, the export of metal elements associated with suspended particulate matter had been altered by the change in suspended sediment, thereby having a profound effect on the riverine and estuarine environment.