A Sediment Pore Water Diffusion Sampler (“Peeper”) for Compound Specific Isotope Analysis of Chlorinated Aromatic Hydrocarbons

摘要

Background/Objectives. The widespread use of chlorinated aromatic hydrocarbons has resulted in several hundreds of contaminated sites throughout North America. Their persistence and toxicity has led to an increased interest in the development of techniques to track and understand their fate in the environment. Compound Specific Stable Isotope Analysis (CSIA) has proven effective to identify and quantify in situ biodegradation of many organic contaminants in groundwater. Recently, CSIA has shown promise to distinguish between aerobic and anaerobic degradation of chlorinated aromatic hydrocarbons. To date, CSIA has mostly been applied to groundwater; whereas, connection between anaerobic groundwater and aerobic surface water is common and generally takes place through bottom sediments of surface hydrosystems (e.g., river, lake). At this groundwater–sediment pore water interface, changes in hydrologic regime affect oxidation-reduction conditions and contaminant reaction mechanisms and hence the contaminant mass flux discharged to surface waters. Carbon isotope fractionation has been shown to be an important tool in identifying the effects of degradation and differentiating between different degradation mechanisms. To evaluate such changes in the field, a sampling technique allowing for a fine vertical resolution is required and can be achieved using passive diffusion (“peepers”) sediment pore water samplers. Results from the co-implementation of CSIA and peepers at a major contaminated field site will be presented.