Chapter 13 Passive diffusion samplers to monitor volatile organic compounds in ground-water

Abstract

Publisher Summary Diffusion samplers (DSs) have been useful in examining volatile organic compounds (VOC) concentrations at the groundwater/ surface-water interface and in monitoring wells. This chapter discusses the types of DSs used to examine VOCs in ground-water that have been divided into sorption devices and equilibrium DSs. Sorption devices for measuring VOC concentrations in ground-water typically consist of a semi-permeable membrane enclosing a sorptive medium. This type of DS has been used successfully to map the zone of VOC-contaminated ground-water beneath a tidal pond where the contaminated ground-water was discharging to surface-water. Equilibrium-type DSs typically consist of a closed receptacle composed of a semi-permeable or permeable membrane containing vapor or water free of the target analytes. When these types of DSs are deployed in VOC-contaminated water, equilibrium begins to develop between VOC concentrations in the ambient water and in the water or air of the DS. Passive DSs have been used to examine ground-water VOCs primarily in two types of applications. The first type of application involves obtaining VOC concentrations in ground-water immediately prior to its discharge to surface-water. The second type of application involves deploying DSs in wells for well monitoring. Confirmation of the appropriateness for use of DSs in particular wells is typically done by comparing DS results with historical or with pumped sample results collected soon after recovering the DSs.