Modeling Uptake of Hydrophobic Organic Contaminants into Polyethylene Passive Samplers

Understanding the transfer of chemicals between passive samplers and water is essential for their use as monitoring devices of organic contaminants in surface waters. By applying Fick's second law to diffusion through the polymer and an aqueous boundary layer, the authors derived a mathematical model for the uptake of chemicals into a passive sampler from water, in finite and infinite bath conditions. The finite bath model performed well when applied to laboratory observations of sorption into polyethylene (PE) sheets for various chemicals (polycyclic aromatic hydrocarbons, polychlorinated biphenyls [PCBs], and dichlorodiphenyltrichloroethane [DDT]) and at varying turbulence levels. The authors used the infinite bath model to infer fractional equilibration of PCB and DDT analytes in field-deployed PE, and the results were nearly identical to those obtained using the sampling rate model. However, further comparison of the model and the sampling rate model revealed that the exchange of chemicals was inconsistent with the sampling rate model for partially or fully membrane-controlled transfer, which would be expected in turbulent conditions or when targeting compounds with small polymer diffusivities and small partition coefficients (e.g., phenols, some pesticides, and others). The model can be applied to other polymers besides PE as well as other chemicals and in any transfer regime (membrane, mixed, or water boundary layer-controlled). Lastly, the authors illustrate practical applications of this model such as improving passive sampler design and understanding the kinetics of passive dosing experiments.

“…The corresponding Laplace solutions for the concentration of performance reference compound and target analytes in PE can be derived by evaluating Equation as V W →∞ (Supplemental Data)

C_{target}^{PE} = C_{target}^{normalW} K_{PEW} \frac{1}{s^{\frac{3}{2}}} \frac{1}{\frac{K_{PEW}}{\sqrt{ψ}} \tanh true(- α \sqrt{\frac{s}{ψ}} true) - \coth true(\sqrt{s} true)}

C_{PRC}^{PE} = C_{PRC}^{PE, 0} true(\frac{1}{s} - \frac{1}{s^{\frac{3}{2}}} \frac{1}{\frac{K_{PEW}}{\sqrt{ψ}} \tanh true(- α \sqrt{\frac{s}{ψ}} true) - \coth true(\sqrt{s} true)} true)

where

C_{PRC}^{PE, 0}

is the initial concentration of a performance reference compound in the PE and

C_{target}^{normalW}

Section: Introductionsupporting

confidence: 76%

Section: Resultsmentioning

confidence: 89%

Modeling the transport of organic chemicals between polyethylene passive samplers and water in finite and infinite bath conditions

Tcaciuc

Apell

Gschwend

2015

“…Using Equations and 5 and the dissipation constants observed in the laboratory experiments from the present study, the δ w specific to the laboratory exposure was evaluated for each PAH. Although δ w is expected to be dependent on the diffusion of the chemicals, the results do not show a distinguishable trend with D w , most probably because it is insignificant regarding the uncertainty associated with the δ w values . Consequently, an average δ w is assigned for all the PAHs in a given sampler in the subsequent analysis.…”

Section: Resultsmentioning

confidence: 86%

Thickness and material selection of polymeric passive samplers for polycyclic aromatic hydrocarbons in water: Which more strongly affects sampler properties?

Belles

Alary

Mamindy-Pajany

2016

Three configurations of single-phase polymer passive samplers made of polyoxymethylene (POM), silicone rubber, and polyethylene (PE) were simultaneously calibrated in laboratory experiments by determining their partitioning coefficients and the POM diffusion coefficients and by validating a kinetic accumulation model. In addition, the performance of each device was evaluated under field conditions. With the support of the developed model, the device properties are discussed with regard to material selection and polymer thickness. The results show that a sampler's properties, such as its concentration-averaging period and ability to sample a large amount of polycyclic aromatic hydrocarbons, are widely affected by material selection. Sampler thickness also allows modulation of the properties of the device but with a much lower magnitude. Selection of the appropriate polymer and/or thickness allows samplers to be adapted either for quick equilibration or for the kinetic accumulation regime and promotes either membrane or water boundary layer control of the kinetic accumulation. In addition, membrane-controlled or equilibrated compounds are quantified with greater accuracy because they are not corrected by the performance reference compounds approach. However, the averaged concentrations cannot be assessed when compounds reach equilibrium in the sampler, whereas membrane-controlled devices remaining in the kinetic accumulation regime provide averaged concentrations without requiring performance reference compound correction; detection limits are then increased because of the higher mass transfer resistance of the membrane. Environ Toxicol Chem 2016;35:1708-1717. © 2015 SETAC.

“…A third method for modeling mass transfer has also been developed for both the sediments and the water column and accounts for compound‐specific diffusivities within both the sampler and the WBL or interstitial water (Fernandez et al , ; Apell and Gschwend ; Thompson et al ). The diffusion method is useful when uptake is controlled or partially controlled by the polymer, or if it is unclear how a compound's diffusion through the polymer will affect transfer kinetics.…”

Section: Introductionmentioning

confidence: 99%

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

Joyce

Burgess

2018

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.