Fate and effects of 3,4‐dichloroaniline in the laboratory and in outdoor ponds: I. fate

Abstract

AbstractProcess analysis and a mathematical model were used to evaluate and predict the fate of 3,4‐dichloroaniline (DCA) in 40‐m3 outdoor ponds. Six ponds were treated with DCA: three with a nominal concentration of 450 μg/L and three with a nominal concentration of 45 μg/L. These concentrations were maintained in the water by repeated applications during a period of 28 d. The predicted fate of DCA was compared with its observed fate.The dominant loss process was predicted to be direct phototransformation. Using the mathematical model SOLAR and an empirical correction for cloud cover, the rate constant for this process was calculated to be 0.12 to 0.20 d−1. Observed absorbance data for pond water were used to estimate the rate of indirect phototransformation to be 0.01 to 0.02 d−1. Evaporation, hydrolysis and biodegradation were predicted to be of minor importance. The partition coefficient of DCA between wet sediment and water was predicted to be near unity for the range of observed pH values. From this it was calculated that only 3% of the compound would be sorbed and that, therefore, this process could be neglected.The observed rate of loss of dissolved DCA from the ponds was 0.11 to 0.17 d−1, in good agreement with the predicted overall rate of loss, i.e., 0.13 to 0.22 d−1. It is concluded that the mathematical model SOLAR provided a reliable tool for predicting the rate of direct phototransformation of organic compounds in natural waters.