The dynamic behavior of tetrachloroethene (PER), atrazine, and nitrilotriacetate (NTA) in a small lake in Switzerland has been evaluated quantitatively using field data and a simulation software (MASAS) for modeling organic pollutants in lakes. For PER, atrazine and NTA, the input and the seasonal variation in the vertical distribution could be described successfully by applying simple box models as well as a one-dimensional vertical model. In the case of PER, it was possible to reconstruct the input history for a long time period (9 years), and it was found that the stagnant boundary layer model was well suited for estimating the average gas exchange rate of this volatile compound between the lake and the atmosphere. Atrazine showed, except for a short time period during the summer, a very conservative behavior in the lake. For NTA, an average in situ rate constant of 0.035 d(-1) was determined for its elimination from the water column. The elimination was attributed primarily to biodegradation. The results of this study demonstrate nicely the power of the combined use of mathematical models, including computer simulations, and field measurements for assessing the environmental behavior of organic pollutants.
