Keywords: Central composite design, model quality root mean square error, regression coefficient, degradation pathway

Abstract

Carbofuran has been banned by the European Union in 1999, however, this insecticide continues to be widely used in Asia, Australia and South America, including Malaysia. The degradation of carbofuran under the effects of pH (4 - 7), moisture (30 - 70%) and temperature (30 – 70 ºC) were studied using response surface methodology. Sterilized soil was incubated according to the inscribed central composite design with a total of 24 experiments. The percentage of carbofuran loss was calculated and fitted according to linear, interaction and quadratic models. The model quality was measured based on the root mean square error (RMSE) and regression coefficient, R2. Linear model was the best model to describe the degradation of carbofuran with the lowest RMSE. All the three factors were found to correlate positively to the loss of carbofuran with pH demonstrating a significant effect (p < 0.05). This suggests that hydrolysis is the major pathway controlling the degradation of carbofuran. The model was experimentally verified revealing an error of 5.82%.