Model AQUATOX

In the following example, the AQUATOX model is run in its simplest form (without biota) for a pond that is 1 m deep, with surface area 400 m2, a DOC of 10 mg/L, and 1.2 kg/m2 organic matter in the sediment layer. On day one, a total amount of 50 pg/L of the insecticide chlorpyrifos is added to the water phase of this imaginary water body. The model results are presented in Figures 2.6 and 2.7. From these... 

FIGURE 2.6 Results of an AQUATOX model run specifying the fate of chlorpyrifos over time after a onetime addition of 50 pg/L to a small pond. 

FIGURE 2.7 AQUATOX model run showing the modeled differences in the density of species with and without the normal application pattern of esfenvalerate to a small pond adjacent to a cornfield. 

The extrapolation methods related to differences in media and matrices are mainly governed by sorption processes. Therefore, uncertainty analysis should try to address toxicant properties related to sorption (KD, A"ow, Ka, etc.) and matrix-specific characterization of sorption sites (qualitative and quantitative). Some of the computerized models for exposure and effects assessment explicitly include options for treating key variables as probability distributions (e.g., AQUATOX). 

Computer models that simulate the dynamics of food webs might be used to extrapolate results of model ecosystem experiments to systems differing in size and ecological complexity. In principle, food-web models such as IFEM (Bartell et al. 1988), AQUATOX (Park 1999), and C-COSM (Traas 2004) can be adapted to do this, at least when detailed information on the ecology and ecotoxicology of the species and functional groups of concern is available. 

Park RA] US Environmental Protection Agency. 1999. AQUATOX for Windows a modular toxic effects model for aquatic ecosystems [computer program], Washington (DC) US Environmental Protection Agency, http //www.epa.gov/ost/models/aquatox/ (accessed December 28, 2007). 

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