SPATIAL ANALYSIS OF CONTAMINANT METAL TRAPPING ON FLOODPLAIN SURFACES OF THE SUSQUEHANNA RIVER IN NORTHEASTERN PENNSYLVANIA

Alluvial soils form in response to periodic deposition of sediment from fluvial systems. In areas with extensive industrial activity, such as mining, floodplains can capture eroded wastes from culm piles and mine tailings. Anthracite coal mining in Northeastern Pennsylvania has caused extensive degradation to both water and land resources of the region. While the introduction of environmental regulations has greatly improved the health of regional rivers, many polluted materials remain trapped within the system. Preliminary data suggest >2000 ha of floodplain landscapes within Susquehanna River basin may be contaminated with coal overwash, which typically has greater metal concentrations of As, Pb, and Cr compared to regional background levels. Chronic exposure to these metals can cause several diseases including birth defects and cancer.

The goals of our research were to evaluate how alluvial surfaces of the North Branch Susquehanna River (NBSR) vary in their ability to continue to capture coal-based sediments in regard to their geographic relationships to mining sites, evaluate trace metal concentrations, and determine the extent that these soils have been anthropogenically enriched with contaminants. Ten surface soil samples (0-10 cm depth) were collected from representative alluvial landscapes of the NBSR, including four river islands and four tributary deltas (80 total samples). Surface samples had between 1-11% coal grains as part of the sand fraction and all samples contained coal in the matrix. The surface alluvial soils had concentrations of As ranging from 4-14 mg/kg , Pb from 10-45 mg/kg, and Cr from 28-86 mg/kg. Geospatial analysis did not show strong correlation to modern land use or mining landscape variables, likely due to mixing and dilution of anthracite materials with agricultural sediments in floodwaters. However, elevated metal concentrations in floodplain surfaces suggest that alluvial landscapes in the NBSR basin are providing a water quality improvement function by removing these contaminants from the water system and slowing their flux to downstream waterways, such as the Chesapeake Bay.