Abstract Summary/Description
Elevated concentration of inorganic contaminants in urban streams is a widespread issue that must be addressed to ensure sustainable and equitable development. Heavy metals (HMs) are one such contaminant, typically sourced from the poor management of industrial and domestic waste. Past studies have revealed that the mobility of HMs is constrained by the movement of nanoparticles known as colloids. Herein, we present an investigation of the concentration of HMs in the South River, a perennial urban stream located in East Point, Georgia. The headwaters of the river lie immediately downstream of a class 1 designated hazardous waste site, whose groundwater and soil are known to be contaminated with copper, lead, nickel, and zinc, among several other pollutants. Six sampling points were selected in collaboration with local community members to evaluate the spatial extent of HM contamination, beginning where the river first daylights 0.4 miles away from the hazardous site and adjacent to public housing property. Following their collection, the samples were fractionated into < 415 nm, < 260nm, and < 35nm size fractions using differential centrifugation and a final “dissolved” < 3kDa fraction using ultrafiltration. HM concentrations were quantified using an inductively coupled plasma-mass spectrophotometer. The colloid’s physiochemical characteristics in the different size fractions were assessed using scanning electron microscopy and energy-dispersive X-ray spectroscopy. Preliminary results show a uniform distribution of relative HM concentrations across the fractions, with decreased concentrations moving downstream. Knowledge of the preferential fraction and chemical characteristics of the colloids HMs are sorbed onto will help inform more effective remediation techniques.
