Characterizing Sediment from Riverton, WY

Riverton, Wyoming is home to the seventh-largest Native American Reservation by area and a former uranium processing facility. Milling activities at this site have left the sediments and groundwater with elevated concentrations of uranium that occasionally disrupt water quality to the 12,000 residents of the reservation. The floodplain becomes seasonally wet and sometimes flooded from snowmelt that can be amplified by El Niño events. As a result, the sediments of this area experience periodic droughts and floods. There is concern that a decreased water stage can have major impacts on the geochemical makeup of this ecosystem as 1) a decreased water volume may result in an increase of pollutant concentrations and 2) a decreased water stage can have a significant impact the redox cycling within the subsurface and affect major biogeochemical cycles. This study addresses the need to understand current subsurface elemental distributions in Riverton, Wyoming. Overall, the project explores the sediment characteristics of several Riverton cores in response to drought and flood conditions. Samples for this study were taken over the course of twelve months - at three different time points. This summer, 105 Riverton sediment samples from August 2016 (the final time point) were geochemically characterized and compared to samples from dry conditions (August 2015) prior to the second largest flood on record at this location. We expect the sediments collected prior to the flood to vary greatly from the sediments collected after the flood because the activity of microbial communities is affected by differences in the physical structure of the soil. This data, along with an analysis of the microbial communities present in these sediments, will help the Francis Lab understand what factors shape the distribution and diversity of microbial communities present in order to better understand the subsurface biogeochemistry at Riverton