Variability of Dissolved Trace Elements in Rivers and Streams: Seasonal Redox Effects

9508199席勒最近的实验室工作表明，密西西比河中溶解的微量元素浓度存在季节性变化，其他河流系统经历类似季节性变化的证据有限。这种变化最好的解释是季节性变化减少了对河流系统的投入。这项研究的目标是1)更好地了解密西西比河水系中季节性溶解微量元素变异性的来源，2)在其他较小的河流和水系中寻找类似的变异性，3)为未来的微量元素工作奠定基础，这些工作将侧重于侵蚀状况、岩石成分和溶液化学对溪流中溶解微量元素的影响，以及4)验证过滤方法。将收集密西西比河及其支流以及密西西比州和加利福尼亚州其他河流的季节性样本，以更好地定义季节性影响，并确定这种现象的普遍程度。此外，还将进行实验，以检测锰氧化物的依赖温度的氧化--这一过程可能在季节性循环中发挥作用。研究人员还将验证过滤方法，并开发一种更容易的注射器过滤方法，供其他为研究收集样本的工作人员使用。河样将用原子吸收、流动注射和电感耦合等离子体质谱进行分析。确定季节变化的性质是了解河流中溶解的微量元素浓度的重要组成部分。这一研究结果将对了解河流溶解微量元素的某些控制因素、设计和解释其他旨在了解河流溶解微量元素地球化学、设计水质方案和解释水质数据的基础研究具有重要意义。***

9508199 Shiller Recent laboratory work has shown that there is a seasonal variation in the concentrations of dissolved trace elements in the Mississippi River, and limited evidence that other river systems undergo similar seasonal variations. This variation can best be explained by seasonal changes reducing inputs to the river system. The goals of this research are to 1) better understand the origin of the seasonal dissolved trace element variability in the Mississippi River system, 2) look for similar variability in other smaller river and stream systems, 3) lay the groundwork for future trace element work which will focus on the effects of erosional regime, rock composition, and solution chemistry on dissolved trace elements in streams, and 4) verify filtration methods. Seasonal samples of the Mississippi River and its tributaries, as well as other rivers in Mississippi and California, will be collected to better define the seasonal effect and determine how widespread the phenomena is. Also, experiments will be performed to detect temperature-dependent oxidation of manganese oxides -- a process which may play a role in the seasonal cycle. Researchers will also verify filtration methods and develop an easier syringe filtration method which could be used by other workers collecting samples for the research. River samples will be analyzed by atomic absorption, flow injection, and ICP-MS. Characterizing the nature of seasonal variability is a vital component of understanding the concentrations of dissolved trace elements in rivers. The results of this research will be important for understanding some of the controls on fluvial dissolved trace elements, designing and interpreting other basic research aimed at understanding fluvial dissolved trace element geochemistry, designing water quality programs, and interpreting water quality data. ***