Sorption and Leaching of Trace-Level Metals by Polymeric Well Casings

摘要

The most commonly used well casing materials (polyvinyl chloride (PVC),polytetrafluoroethylene (PTFE) and stainless steel) cannot be used for all monitoring applications. Therefore, a series of experiments was conducted to compare three alternative polymeric well casing materials fluorinated ethylene propylene (FEP), fiberglass-reinforced epoxy (FRE) and fiberglass-reinforced plastic (FRP) with PVC and PTFE. These studies were conducted to determine the overall suitability of these materials for use in groundwater monitoring wells. Previous studies compared these materials for sorption of dilute organic solutes, leaching of organic constituents, and resistance to degradation by chemicals, especially organic solvents. This particular study focuses on sorption and leaching of metals. This study shows that the fiberglass materials were more apt to leach metal contaminants than PVC, FEP, and PTFE. Leached concentrations, with one exception (Pb leaching from FRP), were below maximum allowable limits set by the US EPA for drinking water. With respect to sorption, none of the polymers sorbed the anions tested, but all of them sorbed the cations tested. FEP and PTFE were much less sorptive than the other materials. These results and those from our previous studies can be used, along with other considerations, to select a casing material that is best suited for the intended monitoring application and conditions in the well.