MOBILIZATION OF MINING SOURCED TRACE ELEMENTS IN THE RIO GALA, ECUADOR

San Rafael, Canton Ponce Enriquez, Ecuador was once a thriving resort town for swimming and fishing only a few decades ago. However, long term artisanal gold mining in the San Gerardo mining district upstream of San Rafael has left the river brown and laden with tailings particles. Waste from the San Gerardo mining district flows into the Rio Chico which joins the Rio Gala north of the town of San Rafael. Residents of San Rafael bathe, swim, and eat fish from the Rio Gala. In the summer of 2014, a Learning Abroad class from the University of Utah collected filtered and unfiltered water samples from the Rio Chico and Rio Gala upstream of the confluence as well as downstream at the town of San Rafael. Groundwater samples from the primary well in San Rafael were also collected. Water samples were measured for trace elements and mercury (total and methyl). Human hair samples were collected in San Rafael along with human health surveys and measured for total mercury. Measured concentrations of aluminum, manganese, iron, arsenic, and antimony in river water of the Rio Gala exceed thresholds for ecosystem and human health. Additionally, a portion of the citizens show elevated Hg in hair with average concentrations (700 + 370 ng/g, n=9) approximately 70 times higher than the concentrations among Learning Abroad students (10.4 + 8.7 ng/g, n=10). Of the 10 residents surveyed in 2014, 70% relied on well water for their primary water source, with the remainder using bottled water. Little is known about the mobilization of trace elements from the contaminated Rio Gala to the surrounding alluvium where groundwater is used as a primary drinking supply. This summer, nested piezometers will be installed in the river banks of the Rio Gala and Rio Chico to understand the interactions between groundwater and surface water and to assess the potential mobility of contaminants.