报告人介绍：威廉.约翰逊（William Paul Johnson）为美国犹他大学地质和地理学系教授，矿业和地球科学院副院长，犹他大学学术理事会主席，环境领域权威期刊EST-L编委会成员。1993年获得科罗拉多大学博士学位，2000和2011分别获得犹他大学优秀教师科研奖。主持科研项目17项，项目经费达到245万美元。发表SCI论文101篇，总被引4216次，HI指数35。
Contaminant Removal and Precious Metal Recovery
by Lateral Channel Filtration in Mining-Impacted Rivers
William P Johnson, University of Utah
Artisanal or small-scale mining impacts on water quality occur globally, with greater impacts occurring in developing countries, often in remote and/or lesser-developed regions of South America, Africa, and Asia. Alluvial mining is a common practice downstream of mined areas to recover particle-bound precious metals not recovered by upstream mining/processing activities. Alluvial mining involves excavation and processing of streambed alluvium, exacerbating turbidity and contaminant loads, and leaving behind a constructed channel that is typically linear and not meandering, such that contaminants are directly transmitted to downstream water bodies without the beneficial contaminant removal processes that are facilitated by hyporheic exchange in meandering and braided channels.The strong economic incentives that drive alluvial mining requires development of solutions that minimize environmental impacts while maximizing economic benefit from alluvial mining.Potential solutions must harness local materials in these typically lesser-developed settings, and must work under dramatic seasonal shifts in flow, both of which limit options for remediation infrastructure.
The utility of hyporheic transport to remove particle-bound contaminants has been long recognized. Following this idea, a case study in Southern Ecuador explored whether excavating channels lateral to the impacted stream in the alluvial floodplain coaxes streamflow laterally through the alluvium and enhances filtration-driven deposition of particle-bound contaminants and precious metals for subsequent recovery.The advantage of lateral channel filtration is that lateral flow is forced without built infrastructure, and without constraining longitudinal flow, thereby minimizing damage in response to seasonal flooding.The case study explores whether alluvial mining be better managed to attenuate particle-bound contaminants and improve water quality while increasing economic benefit.