Collaborative Research: Quantifying Human Forcing of Legacy Sediment and Metal Contamination Dynamics on the Yunnan Plateau of Southwestern China

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Globally, metal contamination from past human activities hinders human management of environmental systems, particularly soils (agriculture) and aquatic systems (drinking water). One of the universal challenges in the management of these historical contaminants is that they can be transported by both the wind and in water (generally attached to sediments in water). Clarification of the relative importance of these transport pathways is fundamental to the successful management of contaminated soils and prevention of future soil degradation worldwide. In many cases, there are substantial delays in the water-sediment pathway, and these delays create challenges in risk evaluation of recent contamination. Further, more recent activities such as urbanization can remobilize historical contamination. This project focuses on the Yunnan region of China, a region with multiple historical periods of metal extraction and purification. Reconstruction of the long history of interactions between the airborne and waterborne contaminant transport in the Yunnan allows examination of the environmental implications of substantial global metal contamination that has occurred with the industrial revolution and the influence of land use changes on contaminant mobilization. This research aims to develop a longer-term perspective of sediment dynamics in southwestern China and assess the timing, magnitude, rate, and source of metal accumulation in lake environments. In particular, the project links three goals: 1) Quantitatively estimate the amount of metal contaminants stored in watershed soils and attribute their source using geochemical mixing models; 2) Identify the controls on erosion, transport, accumulation, and redistribution of these metal contaminants, particularly human controls by examination of historical events recorded in sediments; and 3) Document the influences of natural climate variability versus human activity on metal accumulation in lake systems. When combined, these goals provide the means to measure the risks of contamination stored in the landscape to all modern human systems and enhance our understanding of how cumulative watershed impacts influence our Earth system.This award is cofunded by the Geomorphology and Land-use Dynamics Program, the Experimental Program to Stimulate Competitive Research, and the Office of International Science and Engineering.