An exponential model based new approach for correcting aqueous concentrations of hydrophobic organic chemicals measured by polyethylene passive samplers

• Published in: The Science of the total environment Vol. 646; pp. 11 - 18
• Main Authors: Lao, Wenjian, Maruya, Keith A., Tsukada, David
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.01.2019
• Subjects: Calibration polyethylene (PE); Convective mass transfer; Exponential model; Hydrophobic organic compounds (HOCs); Non-equilibrium correction; Passive sampling; Convective mass transfer; Hydrophobic organic compounds (HOCs); Calibration polyethylene (PE); Exponential model; Passive sampling; Non-equilibrium correction
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2018.07.192

Although low density polyethylene (PE) passive samplers show promise for the measurement of aqueous phase hydrophobic organic chemicals (HOCs), the lack of a practical and unsophisticated approach to account for non-equilibrium exposure conditions has impeded widespread acceptance and thus application in situ. The goal of this study was to develop a streamlined approach based on an exponential model and a convection mass transfer principle for correcting aqueous concentrations for HOCs deduced by PE samplers under non-equilibrium conditions. First, uptake rate constants (k1), elimination rate constants (k2), and seawater-PE equilibrium partition coefficients (KPEWs) were determined in laboratory experiments for a diverse suite of HOCs with logKow range of 3.4–8.3. Linear relationships between log k2 and logKow, and between log KPEW and logKow were established. Second, PE samplers pre-loaded with 13C-labeled performance reference compounds (PRCs) were deployed in the ocean to determine their k2in situ. By applying boundary layer and convection mass transfer theories, ratio (C) of k2 values in field and laboratory exposures was estimated. This C value was demonstrated a constant that was only determined by water velocities and widths of PE strips. A generic equation with C and logKow as parameters was eventually established for extrapolation of non-equilibrium correction factors for the water boundary layer-controlled HOCs. Characterizing the hydrodynamic conditions indicated the sampler configuration and mooring mode should aim at sustaining laminar flow on the PE surface for optimal mass transfer. The PE estimates corrected using this novel approach possessed high accuracy and acceptable precision, and can be suited for a broad spectrum of HOCs. The presented method should facilitate routine utilization of the PE samplers. [Display omitted] •A new exponential model of non-equilibrium correction for HOCs.•Linkage of two exposure scenarios based on convection mass transfer principle.•Established relationships between rate constants or log KPEW and log Kow.•Incorporating hydrodynamics for optimization of PE sampler configuration.•The proposed method was validated showing close agreement with alternative method.