Application of passive sampling technology in HOCS contaminated sediment management and remediation
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Passive sampling technology is an emerging approach of using sorbents to obtain freely dissolved concentrations of target compounds in air or aquatic environment. This research focuses on using passive sampling technology to determine and monitor hydrophobic organic contaminants (HOCs) in sediment porewater using solid phase micro-extraction (SPME) with polydimethylsiloxane (PDMS) fibers. The traditional way to obtain porewater concentrations is to convert bulk sediment concentrations. Compared to conventional techniques, passive sampling technology has several advantages. It’s efficient and easy to process. It has less impacts on the surroundings and it can provide lower detection limits. More importantly, passive sampling method can directly obtain sediment porewater concentration which is regarded as a good indicator of bioaccumulation and chemical activity. Therefore, it is essential for risk management. In addition, passive samplers have the capability to capture the concentrations that change over time and don’t need to be corrected for organic carbon or lip species on a temporal or spatial scale. Due to the above advantages, passive sampling approach is a promising method to monitoring pollutants in aquatic environment, especially in contaminated sediment management and remediation. In this dissertation, three applications of passive sampling technologies in HOCs contaminated sediment management were explored based on in situ pilot studies. The SPME PDMS method was employed at two different polychlorinated biphenyl (PCB) contaminated sediment sites, Hunter’s Point Navy Shipyard (San Francisco, CA) and Columbia Slough (Portland, OR). The spatial representativeness of passive sampling method was explored and compared with bulk sediment measurement by developing spatial semivariogram models. The SPME PDMS fibers were used to monitor the concentration change with time after application of activated carbon to the sediment surface as an in situ treatment at the Hunter’s Point site. The ability of passive sampling to assess site transport conditions was also explored. An analytical model was developed to estimate groundwater upwelling velocities and effective diffusion coefficients using the rate of release of performance reference compounds. The results indicate that passive sampling approach is a viable and promising tool for evaluating exposure and risk of HOC contaminated sediment management, the effectiveness of in situ remediation and for characterizing site transport characteristics.