Effect of Heavy Metals on Bacterial Attachment in Soils

The presence of both heavy metals and bacteria is frequently reported in urban storm water runoff. Adsorption and complexation of metals onto bacteria and soil takes place as storm water runoff infiltrates into the subsurface, potentially changing both bacterial and mineral surfaces, and altering the attachment of bacteria onto soil surfaces. Scanning electron microscopy and energy dispersive X-ray spectroscopy analyses were performed on soil samples equilibrated with synthetic storm water amended with copper, lead, and zinc to determine changes in the elemental content of soil. Sets of batch sorption experiments of Escherichia coli onto soil were conducted under different conditions by varying solution composition and soil exposure history. E. coli attachment increases in synthetic storm water with elevated heavy metals concentrations (Kd=0.0229 mL/mg) as opposed to nutrient buffer (Kd=0.0100 mL/mg) for the same untreated soil. For E. coli both suspended in nutrient buffer, Kd is higher when equilibrated with metals-treated soil (Kd=0.0119 mL/mg) in comparison with untreated soil (Kd=0.0100 mL/mg). Results indicate that the presence of heavy metals in solution increases bacterial attachment to soil surfaces.