The Degradation and Migration of Cyclanilide in Soil and Sediment in China

The environmental fate of a plant growth regulator cyclanilide was studied in this paper. The degradation, adsorption, and migration behaviors of cyclanilide were detailly measured in the laboratory. The results showed that the DT₅₀ of cyclanilide degradation in the Jiangxi red, Taihu paddy, Changshu wushan, Shaanxi tide, and Dongbei black soils was 42.3 d, 31.9 d, 14.4 d, 30.4 d as well as 27.4 d under aerobic conditions and 32.3 d, 37.4 d, 29.3 d, 48.9 d as well as 27.0 d under water anaerobic conditions, respectively, with the main metabolite being 2,4-dichloroaniline (2,4-D). The DT₅₀ of 2,4-D ranged from 5.26 to 27.1 days under aerobic conditions, and from 10.6 to 54.1 days under anaerobic conditions. The adsorption of cyclanilide by the soils was well fitted by the empirical linear adsorption isotherm, and the adsorption constant (K_{d, H}) values in the Jiangxi red, Taihu paddy, Changshu wushan, Shaanxi tide, and Dongbei black soils were 7.08, 4.49, 4.05, 3.20, and 1.41, respectively. The results of a mobility test showed that cyclanilide had strong mobility in the most test soils. Furthermore, soil pH is the dominant element affecting the adsorption of cyclanilide in the soils. Under aerobic environment, the DT₅₀ of total cyclanilide in river and lake water-sediment systems were 30.7 d and 34.0 d, respectively; under anaerobic environment, their DT₅₀ were 30.8 d and 31.4 d, respectively. In water-sediment systems, 2,4-D mainly exists in aqueous phase and the DT₅₀ ranged from 5.23 to 8.76 days. This work demonstrated that cyclanilide has the potential risk to contaminate environment and attention should be paid to its application.