Toxiwasp

TOXIWASP combines most of the kinetic structure of EXAMS 2 with the transport capabilities of WASP (Water Analysis Simulation Program). TOXIWASP uses variable chemical degradation rates from chemical properties and the environmental conditions of the aquatic ecosystem. These rates are reduced from pseudo first-order rates to first-order rates including the processes hydrolysis, biotransformation, phototransformation, oxidation, and volatilisation. Assuming ultimate local equilibrium, and using a chemical dependent partition coefficient as well as spatially varying environmental carbon fractions, sorption onto sediments and biomass is calculated. Environmental alternations could be specified in any time scale by providing monitoring data. TOXIWASP generates total sediment and chemical concentrations every time step in every segment, including surface water, subsurface water, surface bed and subsurface bed. Advection, dispersion, mass loading, sedimentation, and scour affect sediment concentration in the water column and in the bed sediment concentrations depend on burial and erosion. In addition chemical concentrations are influenced by degradation, sediment-water dispersion, and percolation. Lateral transport of chemical within the bed is neglected and transport data are not calculated in the program. TOXIWASP is developed to model stratified lakes reservoirs, large rivers, estuaries, and coastal waters. As for EXAMS 2 (Burns et al²) the TOXIWASP user has to accept the model’s inability to connect the water body to a chemically contaminated atmosphere.