Alpine watersheds ultimately support the drinking, agricultural, and industrial water needs for most of the western United States, and are critical sources of water worldwide. A key concern in many alpine watersheds is metal contamination, either from abandoned mining operations or from natural sources. In order to design and prioritize useful water management and remediation strategies, we need to identify important metal sources and understand how metal loads change over different spatial and temporal scales. We will attack this problem in a new way - by using the emerging tools of Fe and Zn isotopes to fingerprint metal sources and to identify metal transport processes in mountain catchments impacted by acidic, metal-rich waters. We have framed this investigation to advance scientific understanding in three main areas: 1) Distinguishing between Fe and Zn loads that are attributable to groundwater discharge to surface-water as opposed to surface runoff, 2) Distinguishing between anthropogenic and natural sources of Fe and Zn, and 3) Correlating seasonal changes in Fe and Zn isotopes with hydrogeochemical changes. We will complete our project by integrating our findings into a conceptual model for evaluating metal contamination in alpine waters. Our research plan includes targeted field sampling of waters (both dissolved and suspended loads) and rocks in Prospect and Handcart Gulches in Colorado, and complementary lab experiments with sulfide-rich mineral separates. Both field sites are contaminated with metals and include remarkable access to groundwater through existing networks of monitoring wells. We will also take advantage of differences in metal sources (anthropogenic vs. natural) and in dissimilar groundwater-surface water relationships in these watersheds to test our hypotheses. Our proposal is collaborative, combining the expertise and resources within the U. S. Geological Survey with PI Borrok and students in the Department of Geological Sciences at the University of Texas at El Paso (UTEP). Our work will specifically broaden participation from underrepresented students already at UTEP. UTEP is the only research-intensive doctoral university in the U.S. with a Mexican-American majority student population. To further enhance educational opportunities, we have partnered with the Mountain Studies Institute, an independent research/education institution and alpine field station in Silverton, Colorado. We will utilize the MSI?s boarding, field laboratory, and educational facilities for our field work in Prospect Gulch. Partnerships with the USGS and MSI will allow students at UTEP access to cutting-edge equipment/facilities and to participate in a broad range of research experiences.
