Enhancement of atrazine degradation by crude and immobilized enzymes in two agricultural soils

Contamination of soil, groundwater and surface water by atrazine is a worldwide concern. Arthrobacter sp. HB-5 is a high-efficiency atrazine degradation strain isolated by our laboratory. Crude enzyme extracted from HB-5 and immobilized enzyme made from crude enzyme on sodium alginate were introduced to atrazine-polluted soils to evaluate the degrading ability for practical use and to calculate the kinetics of atrazine degradation. Atrazine was applied at 10 mg/kg of soil. Brown soil or cinnamon soil samples with crude or immobilized enzyme were incubated at 25°C. Samples were collected every 24 h from 0 to 144 h to extract the residual atrazine and analyzed using gas chromatography. Results showed, at 144 h, that only about 10% of the initially applied amount of atrazine was left in the two soils, except in the control soil samples without crude or immobilized enzyme. Before 48 h of incubation, crude enzyme removed atrazine faster than the immobilized enzyme in each soil sample. However, after 120 h, degradation of atrazine reached a similar level with either treatment. Atrazine seemed to be removed more easily from cinnamon soil than from brown soil, and both crude and immobilized enzyme could be used. However, the immobilized enzyme is preferred for its stability.