Assessing the presence, concentrations, and potential ecological impacts of trace metal contamination in the Potomac River Test Range Complex middle danger zone

This study evaluated the presence, spatial distribution, and ecological risk of trace metal contamination in the Potomac River Test Range Complex (PRTR) middle danger zone, a heavily utilized military testing site with over a century of munitions activity. Surface water, near-bed water, and surficial sediment samples were collected from 21 sites and analyzed for trace metals (Al, As, B, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, and Zn) using inductively coupled plasma optical emission spectroscopy. Contamination levels were interpreted using the Heavy Metal Pollution Index (HPI) for water samples and the Geoaccumulation Index (Igeo) and Potential Ecological Risk Index (PERI) for sediments. Ward's multivariate cluster analysis with silhouette optimization was applied to assess spatial relationships between contamination patterns and historical projectile-density zones. Surface waters were generally low in contamination, whereas near-bed waters exhibited higher metal concentrations with multiple sites classified as critically polluted. Sediments showed widespread anthropogenic enrichment (Igeo Classes 1-3), with elevated ecological risks (PERI) concentrated in areas of dense historical munitions activity. Cluster analyses revealed clear spatial separation between high- and low-intensity use zones, supporting a linkage between munitions testing and localized contamination. These findings demonstrate that military activities contribute measurably to metal contamination superimposed on broader watershed inputs. This study represents one of the first field-based, multi-matrix assessments of contamination within the PRTR, advancing beyond prior evaluations that utilized modeling and screening approaches. This integrated framework provides improved resolution of contamination pathways and strengthens targeted monitoring, ecological risk assessment, and management of impacted aquatic systems.