Abstracts

282 - Evaluating mining impacts on groundwater quality in Lake
Poopó basin, Bolivia using geochemical and isotope tracers
Sylvia Barroso 1 , Ronald Zapata 2 & Ramon Aravena 3
1
BC Ministry of Forests, Lands and Natural Resources, Nanaimo, British Columbia, Canada
2
Department of Engineering – University of San Francisco Xavier, Sucre, Bolivia
3
Department of Earth & Environmental Sciences – University of Waterloo, Waterloo,
Ontario, Canada
Historical and present mining activities have seriously impacted water quality in the Bolivian
Altiplano (High Plain). The environmental effects of mining in the Poopó River
and Antequera River sub-watersheds of the Lake Poopó Basin were considered, along
with physiography, geology, and mine waste management. Stable isotopes, 18 O and 2 H in
water, and 34 S and 18 O in sulfate complemented with chemical data were used to evaluate
the impacts of mine tailings in groundwater. In the Poopó River watershed, tailings leachate,
and slurry from the refinement of zinc and lead ore was held in a ~5 hectare tailings
impoundment situated at the apex of a colluvial fan, and isolated from the adjacent river.
In the Antequera River watershed, a >10 ha tailings reservoir was located within the river
channel, creating a dilute acidic (pH 2) mixture of precipitation and wastewater. As a result
of evaporation, the isotopic composition of water in the tailings impoundments was higher
than in groundwater and surface water. Springs, rivers, and shallow groundwater had an
average isotopic composition of -13‰, and -100‰ for δ 18 O and δ 2 H, respectively. Water
isotopes in groundwater from drilled wells were lower (median δ 18 O=-15‰, and δ 2 H=-
110‰), originating from recharge at higher elevation. Stable isotopes of sulfate combined
with geochemical data were useful indicators of mixing between polluted and ambient
waters. In comparison to other sources, tailings samples had a very negative sulfate isotope
composition with average values of -5‰ and -12‰ for δ 34 S and δ 18 O, respectively. Water
sources impacted by mine waste had lower sulfate isotope composition and higher concentrations
of cadmium and other trace metals. In Poopó impacts were evident in shallow
groundwater adjacent to the tailings pond. In Antequera, impacts of leachate from the
impoundment were noted at distance in down gradient groundwater and surface waters.
Options for provision of fresh water in this region are limited. Groundwater in drilled wells
contained elevated, naturally occurring, boron, aluminum and arsenic; while shallow dug
wells were contaminated by natural and anthropogenic pollutants, including tailings leachate
and evaporite salts. Sources of uncontaminated water were low temperature springs and
creeks at higher elevation, upstream of industrial activities and human settlements.
IAH-CNC 2015 WATERLOO CONFERENCE
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