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Bioaccumulation and Aquatic System Simulator (BASS) User’s Manual Version 2.3
Citation:
Barber, Craig. Bioaccumulation and Aquatic System Simulator (BASS) User’s Manual Version 2.3. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-01/035 2.3, 2018.
Impact/Purpose:
This report describes the theoretical development, parameterization, and application software of the BASSBioaccumulation and Aquatic System Simulator. This generalized, community-based simulation model is designed to predict the population and bioaccumulation dynamics of age-structured fish communities exposed to hydrophobic organic chemicals and class B and borderline metals that complex with sulfhydryl groups (e.g., cadmium, copper, lead, mercury, nickel, silver, and zinc). This report is not a case study on the application of BASS but a reference and user’s guide. The intended audience of this report includes EPA Program and Regional environmental engineers and scientists, technical staff in other state and federal agencies, and fisheries ecologists who routinely analyze and estimate the bioaccumulation of chemicals in fish for ecological or human health exposure assessments. Process-based models like BASS enable users to observe quantitatively the results of a particular abstraction of the real world. Moreover, such models can be argued to be the only objective method to make extrapolations to unobserved or unobservable conditions such as in the case of analyzing alternative management options for new or existing chemicals.
Description:
BASS (Bioaccumulation and Aquatic System Simulator) is a Fortran 95 simulation program that predicts growth, population, and bioaccumulation dynamics of age-structured fish assemblages exposed to hydrophobic organic pollutants and class B or borderline metals that complex with sulfhydryl groups (e.g., cadmium, copper, lead, mercury, nickel, silver, and zinc). The model’s bioaccumulation algorithms are based on diffusion kinetics and are coupled to a process-based model for the growth of individual fish. These algorithms consider both biological attributes of fishes and physico-chemical properties of the chemicals that together determine diffusive exchange across gill membranes and intestinal mucosa. Biological characteristics used by the model include the fish’s gill morphometry, feeding and growth rate, and proximate composition (i.e., its fractional aqueous, lipid, and structural organic content. Relevant physico-chemical properties include the chemical’s aqueous diffusivity, n-octanol / water partition coefficient (Kow), and, for metals, binding coefficients to proteins and other organic matter. BASS simulates the growth of individual fish using a standard mass balance, bioenergetic model (i.e., growth = ingestion - egestion - respiration - specific dynamic action - excretion). A fish’s realized ingestion is calculated from its maximum consumption rate adjusted for the availability of prey of the appropriate size and taxonomy. The community’s food web is delineated by defining one or more foraging classes for each fish species based on body weight, body length, or age. The dietary composition of each of these foraging classes is specified as a combination of benthos, incidental terrestrial insects, periphyton / attached algae, phytoplankton, zooplankton, and one or more fish species. Population dynamics are generated by predatory mortalities defined by the community’s food web and standing stocks, physiological mortality rates, maximum longevity of species, toxicological responses to chemical exposures, and dispersal. The model’s temporal and spatial scales are that of a day and of a hectare, respectively.