Migration and Transformation Characteristics of Niclosamide in a Soil-Plant System

The molluscicide niclosamide is found in most of the wetlands of China. The migration and transformation pathways, and degradation kinetics of niclosamide in the plant-soil system was analyzed by with the use of potting experiment. Experimental results showed that degradation of niclosamide in rhizosphere soil fit the first-order kinetics, and microorganisms played an important role in the degradation of niclosamide. It was found that niclosamide degrades to form a series of aromatic intermediate products both in soil and plants. Niclosamide could be absorbed from soil to plant by the root and then migrate to the stem. At an initial concentration of niclosamide of 2.11 mg·kg^-1 in soil, the maximum residue of niclosamide in Artemisia somai aerial was 2.47 mg·kg^-1 after 10 days of cultivation. This value is close to the pollution maximum residue limit (3 mg·kg^-1) in rice, and niclosamide and its intermediates can remain about 43 days in plants. The experimental results demonstrate that the use of niclosamide in wetlands would have some risk in edible plants and was harmful for human health.