Effects of Salinization on Base Cation, Nutrient, Carbon, and Trace Metal Biogeochemistry in Human-Impacted Rivers in the Eastern US

Abstract

Urbanized watersheds in colder climates experience episodic salinization due to anthropogenic salt inputs and runoff from impervious surfaces. We conducted laboratory experiments and analyzed high-frequency sensor data to investigate the water quality impacts of freshwater episodic salinization across 12 watersheds draining two major metropolitan regions along the U.S. East Coast. Sediments from watersheds spanning land use gradients were incubated across a range of replicated salinity treatments (0–10 g/L sodium chloride). Our results suggested that episodic salinization can mobilize base cations, nutrients, and trace metals to streams through accelerated ion exchange and biogeochemical processes induced by shifting pH ranges and ionic strength. The response of dissolved carbon concentrations to experimental salinization varied between sites, and dissolved silica did not show any significant response. The growing impacts of freshwater salinization syndrome on nutrient mobilization, shifting acid–base status, and augmenting eutrophication warrant serious consideration in water quality management.