Understanding the Spatial Distribution of Mercury- Contaminated Sediment Along the Androscoggin River

Keywords: river contamination, contaminant spatial analysis, GIS
Abstract Type: Guided Poster Abstract

Abstract

Contamination and subsequent leakage of mercury (Hg) from a former chlor-alkali facility along the Androscoggin River (Berlin, NH, USA) provides an opportunity to investigate the processes controlling the spatial distribution of floodplain storage of Hg. We hypothesize that the distribution of floodplain Hg is controlled by changes in the downstream gradient in stream power which previous work has shown controls the erosion and deposition of fluvial sediment. To test this hypothesis, we collected floodplain soil core samples across five transects within the first 10 km downstream of the source. Along each transect samples were collected up to 30 cm depth at locations along the floodplain corresponding to the 2-, 5-, and 10-year flood recurrence intervals. If the distribution of floodplain mercury is controlled by the gradient in stream power, we expect that results will show: (1) elevated Hg concentrations within the first 10km that fluctuate at the local-scale, having higher Hg inventories along reaches with decreasing stream power (depositional reaches) and lower Hg inventories along reaches with increasing stream power (erosional reaches), (2) Hg inventories will be highest at the 2- year flood recurrence interval, and (3) Hg concentrations will peak within 5cm- 20cm depths. As stream power gradients can be mapped using GIS tools, results from this study will allow for the a priori prediction of locations of higher and lower floodplain Hg concentrations which can inform environmental remediation designs and has applications towards analyses of environmental justice in riverine environments.