Surface Changes in Well Casing Pipe Exposed to High Concentrations of Organics inAqueous Solution

摘要

This preliminary study was undertaken to assess how the surface structuralcharacteristics of four common well casing materials-polyvinyl chloride (PVC), Teflon (polytetrafluoroethylene, PTFE), stainless steel 304 (SS304) and stainless steel 316 (SS316)-are affected by exposure to an aqueous solution containing tetrachloroethylene, toluene, p-dichlorobenzene and 0-dichlorobenzene in concentrations near their solubility. Casing samples that had been exposed to a test solution for 1 week, 1 month and 6 months were examined with a scanning electron microscope (SEM) and compared with control samples placed in well water for an equivalent time period. Pieces of casing that had not been placed in any aqueous solution were also examined and are assumed to be representative of the initial structure of the casing's surface. These organics are of concern at hazardous waste sites, where they often occur in ground water. The observations indicate that the surface characteristics of PVC, SS316 and SS304 did not change when exposed to the organic aqueous solution. The surface variability and lack of distinguishing features at high magnification made it difficult to tell if the PTFE surface had changed. However, no obvious changes (swelling, pitting etc.) were seen. Keywords: Groundwater monitoring, Hazardous waste, Organic chemicals, Well casings, Hydrology. (jg)