Evaluation of passive sampling polymers and nonequilibrium adjustment methods in a multiyear surveillance of sediment porewater PCBs

Abstract

Polymeric passive sampling devices are increasingly used to measure low‐level, freely dissolved concentrations of hydrophobic organic contaminants in environmental waters. A range of polymers have been used for this purpose, and several different methods of accounting for nonequilibrium using performance reference compounds (PRCs) have been proposed. The present study explores the practical impacts of these decisions in an applied context using results from a multiyear passive sampling surveillance of polychlorinated biphenyl concentrations in sediment porewater at a contaminated marsh amended with activated carbon (AC) sorbent materials. In a series of 5 sampling events spanning almost 2 yr, we deployed polyoxymethylene and polyethylene samplers and calculated porewater concentrations with 5 different PRC adjustment methods. The results provide a basis for evaluating amendment performance by showing reductions of 34 to 97% in amended sediment porewater concentrations. They also provide a quantitative underpinning for discussions of the differences between sampling polymers, selection of PRCs, generation of high‐resolution vertical profiles of porewater concentrations, and a comparison of PRC adjustment methods. For unamended sediment, older methods based on first‐order kinetics agreed well with a recently developed method based on diffusion into and out of sediment beds. However, the sediment diffusion method did not work well for the sediments amended with AC.