title: Towards an improved understanding of processes controlling absorption efficiency and biomagnification of organic chemicals by fish.
abstract: Dietary exposure is considered the dominant pathway for fish exposed to persistent, hydrophobic chemicals in the environment. Here we present a dynamic, fugacity-based three-compartment bioaccumulation model that describes the fish body as one compartment and the gastrointestinal tract (GIT) as two compartments. The model simulates uptake from the GIT by passive diffusion and micelle-mediated diffusion, and chemical degradation in the fish and the GIT compartments. We applied the model to a consistent measured dietary uptake and depuration dataset for rainbow trout (n=215) that is comprised of chlorinated benzenes, biphenyls, dioxins, diphenyl ethers, and polycyclic aromatic hydrocarbons (PAHs). Model performance relative to the measured data is statistically similar regardless of whether micelle-mediated diffusion is included; however, there are considerable uncertainties in modeling this process. When degradation in the GIT is assumed to be negligible, modeled chemical elimination rates are similar to measured rates; however, predicted concentrations of the PAHs are consistently higher than measurements by up to a factor of 20. Introducing a kinetic limit on chemical transport from the fish compartment to the GIT and increasing the rate constant for degradation of PAHs in tissues of the liver and/or GIT are required to achieve good agreement between the modelled and measured concentrations for PAHs. Our results indicate that the apparent low absorption efficiency of PAHs relative to the chemicals with similar hydrophobicity is attributable to biotransformation in the liver and/or the GIT. Our results provide process-level insights about controls on the extent of bioaccumulation of chemicals.
authors.affiliation: Department of Environmental Science and Analytical Chemistry, Stockholm University, Svante Arrhenius väg 8, SE-11418 Stockholm, Sweden; Institute of Environmental Engineering, School of Metallurgy and Environment, Central South University, Changsha 410083, China. Electronic address: xiao.53@csu.edu.cn.
authors.forename: Ruiyang
authors.initials: R
authors.lastname: Xiao
authors.affiliation: ARC Arnot Research & Consulting, 36 Sproat Avenue, Toronto, Ontario M4M 1W4, Canada; Department of Physical and Environmental Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario M1C 1A4, Canada.
authors.forename: Jon A
authors.initials: JA
authors.lastname: Arnot
authors.affiliation: Department of Environmental Science and Analytical Chemistry, Stockholm University, Svante Arrhenius väg 8, SE-11418 Stockholm, Sweden.
authors.forename: Matthew
authors.initials: M
authors.lastname: MacLeod
mesh_terms: D000818:Animals; D001711:Biotransformation; D065569:Gastrointestinal Absorption; D041981:Gastrointestinal Tract / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D008954:Models, Biological; D017686:Oncorhynchus mykiss / Q000378:metabolism*; D009930:Organic Chemicals / Q000737:chemistry / Q000493:pharmacokinetics*; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000493:pharmacokinetics*
chemical_list: D009930:Organic Chemicals; D014874:Water Pollutants, Chemical
keywords: Biotransformation; Dietary absorption; Gastrointestinal tract; Micelle-mediated diffusion