Despite the fact that mercury is well known to be dominantly associated with particulates in aquatic systems, surprisingly little is known regarding how this influences mercury methylation and transport in aquatic systems. Mining-impacted areas in Ecuador provide unique opportunities to examine the role of colloids in mercury transport due to the high levels of mercury in unlined mining impoundments. This planning visit will lay a platform to explore the following science questions: 1) Does association with colloids significantly alter the transport distances of mercury in subsurface and surface aquatic systems? 2) Does association with colloids significantly alter the rate or extent of methylation of mercury in aquatic systems? Knowledge gained from this research may help to mitigate mercury contamination in both U.S. and international settings. The work will be carried out in collaboration with Dr. Ximena Diaz of Ecuador's National Polytechnic University, and will engage U.S. and Ecuadorian graduate students in project development activities. This planning visit will also support the development of two Ph.D. theses and one M.S. thesis by U.S. grad students.
Mining is the next big economic opportunity for Ecuador, with plans for major mine expansions in at least three areas of the country. However, little data and scant infrastructure exists to characterize (let alone manage) impacts to water quality. The public reaction to expanded mining in Ecuador includes strong negative sentiment based on the potential for adverse economic impacts. The negative perception is fueled by alarm in the absence of actual data on impacts. This project highlights the need for substantive information regarding mining impacts to water quality in Ecuador. Our goal in this preliminary project visit was to help Ecuadorian officials develop a fact-based understanding of mining impacts, and furthermore, to help develop a platform for a combined research and capacity building project to address the need for prudent decisions on mineral resource development and mitigation of environmental impacts. Both the Ecuadorian and U.S. participants benefited in terms of scientific training during this effort, which involved sampling of three river transects spanning above, within, and below mining areas in three mining zones of southern Ecuador. Characterization at these transects included measurement of field environmental parameters, as well as sampling for major ions, trace elements, and mercury. We found that trace element and mercury concentrations were strongly elevated in the mining-impacted portions of all three river transects, and that the up-gradient portions of the transects showed much lower concentrations of trace elements and mercury relative to the portions in the mining areas. Downstream of the mining areas, the rivers showed differing trends ranging from improved water quality (Quebrada Calixto in the Nambija area) to continued degradation (Rio Calera in the Zaruma area, Rio Siete in the Ponce Enriquez area). Sampling showed that mercury and other trace elements were dominantly associated with particles which, in the case of Quebrada Calixto, settled out of the water shortly downstream of the mining area. This suggests one simple way to mitigate impacts (via a settling pond). The Rio Siete showed conversion of total mercury to methyl mercury at its downstream portion. This is a concern, since methyl mercury is the highly neurotoxic form of mercury. Furthermore, this transformation occurs as the river flows into the organic-rich environment of the coastal banana plantations and shrimp farms, thereby raising concern for mercury uptake into food products. Another important impact of the project was the training and Development: The U.S. graduate students (One Ph.D. and one M.S.) received training on environmental sampling, field measurements, and chemical analyses. Also they and I gained knowledge regarding the fact and fiction driving negative perceptions of mining in Ecuador. Our Ecuadorian collaborators in the Ministry of Mining and the Ministry of Hydrology supported this project by providing vehicles, river discharge measurements, and sediment sampling and analyses. They are benefiting from valuable information regarding water quality in these rivers, which will help them to consider alternatives to mitigate these impacts. The field data, as well as trace element and mercury data, are now complete for the three river transects, each having 6 to seven sites long their length. This data is being synthesized with the river discharge measurements. The overall set of data will be made available to our Ecuadorian collaborators and any other interested parties. A collaborative publication will be developed during summer 2011 The extent of mercury and trace metal contamination of the three rivers examined is much improved as a result of this work, as is the extent of mercury methylation in these rivers. The U.S. State Department was very interested in the project. We were put in touch with officials at USAID to explore potential for growing the project into a research/capacity development project. Toward this effort I have received a $3000 grant from the University of Utah to develop a study abroad course to take undergraduate students to Ecuador in 2012 to examine the perceptions of mining impacts on water quality from the perspective of: 1) locals, 2) mine operators, 3) regulators, 4) indigenous population. These students will explore these perspectives, and will explore the availability of data regarding mining impacts, and will take samples to characterize impacts. We hope eventually to grow this project into a combined research/capacity building project to meet this need.
