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. Environ Toxicol Chem 2018;37:2487-2495. © 2018 SETAC.

Persistent reductions in the bioavailability of PCBs at a tidally inundated Phragmites australis marsh amended with activated carbon

“…In the 5‐ to 7.5‐cm depth interval, significant reductions in Σ C pw were only observed in plot A, where they were significant at all sampling events ( t test, p < 0.05). This finding is discussed at greater length separately (Sanders et al ).…”

“…Each K d value is calculated from an average concentration in sediment ( C sed ) value ( n = 5) for the 0‐ to 5‐cm horizon and an average adjusted porewater concentration ( C pw ′) value ( n = 5) for the 0‐ to 2.5‐cm horizon. The C pw value was adjusted with the k e – K ps performance reference compound method (Sanders et al ). Orange line: organic carbon model; black line: organic carbon and black carbon model (see text for descriptions).…”

“…Because C sed was measured in the upper 5 cm of sediment whereas C pw 0 represented only the upper 2.5 cm in that sampling event, the resulting K d values should be interpreted with care, particularly in the amended plots. The discrepancy is less relevant for plot B, where no significant vertical trend in C pw was found in subsequent high-resolution measurements (Sanders et al 2018). In all plots, PCB K d exhibited a log-log correlation with the octanol-water partitioning constant (K OW ; Hawker and Connell 1988) across individual congeners ( Figure 5).…”

Interlaboratory Study of Polyethylene and Polydimethylsiloxane Polymeric Samplers for Ex Situ Measurement of Freely Dissolved Hydrophobic Organic Compounds in Sediment Porewater

“…It is well established that the use of PRCs contributes to the uncertainty of estimating C free , especially for poorly equilibrated PRCs (Jonker et al, 2018, 2020; Joyce et al, 2020). Uncertainty associated with the use of poorly equilibrated PRCs (see Jalalizadeh & Ghosh, 2017; Sanders et al, 2018) may have contributed to the higher interlaboratory variability for the more hydrophobic compounds we observed. When selecting polymer sampler deployment methods, those that result in higher fractional loss of PRCs and a closer approach to equilibrium have been shown to result in lower uncertainty (i.e., higher accuracy; Jalalizadeh & Ghosh, 2017) and should be employed whenever feasible.…”

In Situ Investigation of Performance Reference Compound‐Based Estimates of PCB Equilibrated Passive Sampler Concentrations and Cfree in the Marine Water Column

“…In contrast to laboratory, or ex situ, deployments where conditions can be controlled to favor achieving equilibrium, PRCs are of particular value in field deployments of passive samplers (i.e., in situ), where equilibrium cannot be assumed or determined. Several studies have used PRCs in water column and sediment in situ deployments to estimate C free (Smedes 2007; Tomaszewski and Luthy 2008; Fernandez et al 2009, 2012; Perron et al 2013a, 2013b; Estoppey et al 2014; Burgess et al 2015; Joyce et al 2015; Apell and Gschwend 2016; Apell et al 2018; Sanders et al 2018). In a previous study, we suggested that using a sampling rate approach (Booij and Smedes 2010) or a diffusion‐based approach (Thompson et al 2015) to determine C free often resulted in statistically indistinguishable results in a field deployment (Joyce and Burgess 2018).…”