Using performance reference compounds to compare mass transfer calibration methodologies in passive samplers deployed in the water column

Abstract

Performance reference compounds (PRCs) are often added to passive samplers prior to field deployments to provide information about mass transfer kinetics between the sampled environment and the passive sampler. Their popularity has resulted in different methods of varying complexity to estimate mass transfer and better estimate freely dissolved concentrations (C ) of targeted compounds. Three methods for describing a mass transfer model are commonly used: a first-order kinetic method, a nonlinear least squares fitting of sampling rate, and a diffusion method. Low-density polyethylene strips loaded with PRCs and of 4 different thicknesses were used as passive samplers to create an array of PRC results to assess the comparability and reproducibility of each of the methods. Samplers were deployed in the water column at 3 stations in New Bedford Harbor (MA, USA). Collected data allowed C comparisons to be performed in 2 ways: 1) comparison of C derived from one thickness using different methods, and 2) comparison of C derived by the same method using different thicknesses of polyethylene. Overall, the nonlinear least squares and diffusion methods demonstrated the most precise results for all the PCBs measured and generated C values that were often statistically indistinguishable. Relative standard deviations (RSDs) for total PCB measurements using the same thickness and varying model types ranged from 0.04 to 12% and increased with sampler thickness, and RSDs for estimates using the same method and varying thickness ranged from 8 to 18%. Environmental scientists and managers are encouraged to use these methods when estimating C from passive sampling and PRC data. Environ Toxicol Chem 2018;37:2089-2097. Published 2018 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Passive Sampler Exchange Kinetics in Large and Small Water Volumes Under Mixed Rate Control by Sorbent and Water Boundary Layer

“…Diffusion models may be useful for sampling the higher brominated PBDEs with LDPE at high flow velocities, but are not needed for sampling PAHs and PCBs. This is in line with a model comparison by Joyce and Burgess (2018) for PCB sampling by LDPE. Model results for POM also show that 1) sampling is likely WBL controlled for many compounds, 2) present practice of using K sw for calculating C w of the more hydrophobic compounds requires exposure times of a year or more, and 3) results for the less hydrophobic compounds reflect concentrations over the past few hours of POM deployments.…”

“…Equilibration times of compounds under sorbent‐controlled kinetics would be 4 times smaller ( t 63% proportional to L 2 ; Equation 24). As an example, Joyce and Burgess (2018) used LDPE with a thickness of 12.5 µm, corresponding to a (half)thickness 3 times smaller than listed in Table 1. Compounds from Table 1 would still be under WBL‐controlled kinetics ( Bi << 3), and equilibration times would decrease by a factor of 3 (71 d for PCB153).…”

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

“…These RSDs were then plotted against the compound's log K PEW to investigate trends (Figure 3). Previous reports suggest that PRC‐corrected C free values from passive sampling with polyethylene have an error of approximately 20 to 25% (Apell and Gschwend 2016; Joyce and Burgess 2018). In general, the RSD is >20% for the lighter PCBs and drops down for the midrange CBs with 4 chlorines, then starts to increase as log K PEW increases.…”

“…Extraction details followed Joyce and Burgess (2018). Briefly, polyethylene and blanks were spiked with recovery standards 13 C‐PCBs 9, 118, and 188 (12.5 µL; 20 µg/mL) and extracted by mixing on an orbital shaker in dichloromethane (~90 mL, overnight 2 times).…”

“…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). In the present study, we used PRCs to populate a diffusion‐based model to estimate f eq and calculated .…”