A review and comparison of models for predicting dynamic chemical bioconcentration in fish

Abstract

Over the past 20 years, a variety of models have been developed to simulate the bioconcentration of hydrophobic organic chemicals by fish. These models differ not only in the processes they address but also in the way a given process is described. Processes described by these models include chemical diffusion through the gill's interlamellar water, epithelium, and lamellar blood plasma; advective chemical transport to and from the gill by ventilation and perfusion, respectively; and internal chemical deposition by thermodynamic partitioning to lipid and other organic phases. This article reviews the construction and associated assumptions of 10 of the most widely cited fish bioconcentration models. These models are then compared with respect to their ability to predict observed uptake and elimination rates using a common database for those model parameters that they have in common. Statistical analyses of observed and predicted exchange rates reveal that rates predicted by these models can be calibrated almost equally well to observed data. This fact is independent of how well any given model is able to predict observed exchange rates without calibration. The importance of gill exchange models and how they might by improved are also discussed.

Foodweb modeling for polychlorinated biphenyls (PCBs) in the Twelvemile Creek Arm of Lake Hartwell, South Carolina, USA

“…For all fishes and invertebrates, diet uptake exceeded gill uptake; the ratio of gill:diet uptake was in the range of 5%, which is consistent with similar studies (Barber, 2003). Fish and invertebrates lost PCB through mortality and depuration; invertebrates also lost PCB through washout and predation.…”

“…Fish biomass in AQUATOX was initialized with data collected by the GADNR. A wet:dry biomass ratio of 5 was used to convert dry weight biomass predicted by AQUATOX to wet weight values measured by GADNR (Barber, 2003). To calibrate the model, values of half-saturation parameters for all three fish species were adjusted so that mean biomass for each fish species in mid-August stabilized in the range of the values measured by the GADNR.…”

Mathematical relationships between metrics of chemical bioaccumulation in fish

“…The bioconcentration factor (BCF) is defined here as the nondimensional ratio of the volumetric concentrations in fish C F (mol/m 3 ) and in water C W (mol/m 3 ). The BCF is then deduced as C F /C W after prolonged exposure when a steady state is reached.…”

“…As part of this initiative, various kinds of bioaccumulation data and metrics are used to determine whether and to what extent chemicals are bioaccumulative. Extensive literature exists on bioaccumulation from scientific and regulatory perspectives, examples being the reviews by Barber [3,4], Mackay and Fraser [5], Arnot and Gobas [6], Ehrlich et al [7], Burkhard et al [8], and Gobas et al [9], the latter summarizing the conclusions of a SETAC-sponsored workshop held in 2008. These and other reviews have pointed out the existence of several metrics of bioaccumulation that differ in definition, in regulatory application, and in adoption by the scientific community.…”

“…A 4.7-log-unit concentration increase from water to organism 1 was caused by bioconcentration, then only a subsequent 0.8 log unit increase in concentration in fish 4 occurs because of both bioaccumulation and biomagnification. On the contrary, viewing bioaccumulation from a linear concentration perspective suggests that for chemical D bioconcentration causes only an increase from 1 in water to 50 000 g/m 3 in organism 1 at the base of the food web, whereas the increase from organism 1 to organism 4 is 270 000 mg/m 3 . Depending on which perspective is adopted, bioconcentration or biomagnification may be viewed as the more important process contributing to the overall concentrations, fugacities, and resulting exposures throughout the food web.…”