Water Resources Research Act Program

Details for Project ID 2006DC76B

Silica and Siliceous Surfaces as Host for Hazardous Metals in Water

Institute: District of Columbia
Year Established: 2006 Start Date: 2006-03-01 End Date: 2007-02-28
Total Federal Funds: $15,000 Total Non-Federal Funds: $9,300

Principal Investigators: Aaron Barkatt, April Pulvirenti

Project Summary: Ion exchange reaction on clay minerals and sorption by iron oxide minerals have long been regarded as the major reactions governing the fate and transport of metals in surface and ground waters, and in contaminated soils. In addition, silica gels can also bind metals by sorption and co-precipitation reactions. Our earlier sampling of tap water in the District of Columbia and of Potomac River water upstream of the water supply intakes (see below) suggests that silica-rich scales formed inside distribution pipes and shedding into consumed water can be a host for trace metals of health concern, such as lead (Pb) and copper (Cu). While some of the hazardous metal content may be present in metallic or metal oxide particles, hazardous metal species may be sorbed on, or co-precipitated with, silica. Radium, for instance, is known to adsorb on both quartz and silica gel (Ames et al., 1983; Nirdosh et al., 1987). Further work is necessary in order to evaluate the importance of sorption of hazardous metals on silica or their co-precipitation with silica in various aqueous environments, in particular those relevant to drinking water and environmental streams in geographical areas where widespread contamination with respect to lead and copper exists, such as the Washington, DC, area. Thus, in order to evaluate the potential of such contaminant retention systems to real-world conditions in urban settings with multiple contaminants present, the effects of variations in gel composition and solution composition need to be investigated. The overall objective of the proposed research project is to examine the effects of these parameters on the sorption of hazardous metals on siliceous surfaces.