Trace element cycling in Great Salt Lake wetlands, Wasatch snowpack, and mining-impacted streams of southern Ecuador

This work examines trace element cycling in four contexts: 1) diel variability in trace element concentrations in Great Salt Lake wetlands; 2) spatial variability in surface water, pore water, and sediment chemistry of Great Salt Lake wetlands; 3) dust-mediated loading of trace elements to Wasatch snowpack; and 4) trace element concentrations and loads in mining-impacted streams of southern Ecuador. Each project is briefly summarized below.;1) In the freshwater wetlands of Great Salt Lake, we observed diel trends in concentrations of anion-forming elements (selenium, antimony, vanadium, and uranium) that were positively correlated with pH, whereas the cation manganese displayed an opposite trend. The opposing trends in aqueous concentrations of anions and cations were attributed to pH-driven changes in sorption to bottom sediment. Surface complexation modeling was used to provide a mechanistic basis for the observed trends.;2) We examined surface water, pore water, and sediment chemistry of Great Salt Lake wetlands. The wetlands contained variable amounts of trace elements, nutrients, and salinity, reflecting different sources of groundwater and surface water runoff. Plant health metrics showed negative correlations with metal concentrations in sediment, indicating that sediment chemistry plays a very important role in wetland plant health.;3) We sampled snowpack across the Wasatch Mountains prior to snow melt and found that spring dust events are the primary vector of trace and major element loading to Wasatch Mountain snowpack. The implication of this work is that increasing dust emission due to climate change, changes in land use, or other factors may have a negative effect on snowmelt runoff chemistry, which is a major water source to metropolitan areas downstream.;4) We measured trace element concentrations and loads in streams that are affected by different modes of artisanal mining. This study has provided the basis for future work in southern Ecuador that will deal with more specific problems such as groundwater contamination from leaky tailings ponds, and the effects of toxic metals on humans and biota.