Computer codes, aquatic systems

Fate of Chemicals in Aquatic Systems Process Models and Computer Codes... 

In this paper, the volatilization of five organophosphorus pesticides from model soil pits and evaporation ponds is measured and predicted. A simple environmental chamber is used to obtain volatilization measurements. The use of the two-film model for predicting volatilization rates of organics from water is illustrated, and agreement between experimental and predicted rate constants is evaluated. Comparative volatilization studies are described using model water, soil-water, and soil disposal systems, and the results are compared to predictions of EXAMS, a popular computer code for predicting the fate of organics in aquatic systems. Finally, the experimental effect of Triton X-100, an emulsifier, on pesticide volatilization from water is presented. 

The most common approach used by geochemical modeling codes to describe the water-gas-rock-interaction in aquatic systems is the ion dissociation theory outlined briefly in chapter 1.1.2.6.1. However, reliable results can only be expected up to ionic strengths between 0.5 and 1 mol/L. If the ionic strength is exceeding this level, the ion interaction theory (e.g. PITZER equations, chapter 1.1.2.6.2) may solve the problem and computer codes have to be based on this theory. The species distribution can be calculated from thermodynamic data sets using two different approaches (chapter 2.1.4) ... 

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