U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings of the Technical Meeting, Colorado Springs, Colorado, September 20-24, 1993, Water-Resources Investigations Report 94-4015

Use of Static Column Experiments to Identify Factors Affecting Bacterial Attachment in Contaminated Aquifer Sediments From Cape Cod, Massachusetts

Abstract

The mineralogy of, sediment in, and geochemistry of, ground water from the Cape Cod contaminated aquifer have been found to affect bacterial attachment and transport through aquifer sediments. Static column experiments, under simulated aquifer conditions, were used to identify chemical factors (for example, pH, the concentration of dissolved organic carbon [DOC], the presence and concentration of divalent ions and other competing ligands, and ionic strength) which can affect bacterial transport in the subsurface. pH strongly affected bacterial attachment in uncontaminated sediments; an increase in pH from 5.8 to 7.9 resulted in a 70 percent drop in fractional bacterial attachment. Also, attachment of bacteria to aquifer sediments was substantially affected by changes in the amount and type of DOC from both contaminated and uncontaminated ground water. Finally, ionic strength and divalent ions, such as sulfate, were found to affect bacterial attachment. The experiments indicate that competitive and (or) synergistic interactions can operate under different pH conditions. Thus, different geochemical conditions can affect cell-grain surface interactions by competing with bacteria for binding sites and (or) by modifying grain or cell-surface characteristics.