Abstract
The degradation of mepanipyrim [N-(4-methyl-6-prop-1-ynylpyrimidin-2-yl)aniline] in two soils was studied under the laboratory conditions, using 14C-preparations labeled separately in the pyrimidine and the benzene rings. The half-lives of the parent compound in upland soils were 13 days and 3 months. The compound was degraded via pathways including elimination of the phenyl group, hydroxylation of the propynyl moiety, and hydroxylation at the benzene ring. The main degradation route was elimination of the phenyl group. The large portion of the resultant products was probably incorporated into the bound residues and a small part was further degraded to 14CO2. 14C-Carbon dioxide evolved in the soils treated with both 14C-preparations. Under the flooded condition mepanipyrim was degraded rapidly, and a larger amount of bound residues was formed compared with the upland condition. The main degradation route in the flooded condition was the serial changes of the propynyl moiety. Mepanipyrim was hardly degraded in the sterilized soils under the upland condition, suggesting that it was microbially degraded in the soils. It is also observed that mepanipyrim was slowly degraded even in the sterilized soils under the flooded condition, suggesting that non-biological degradation also was involved in causing the decrease of mepanipyrim.
