Bioavailability of bound residue derived from 14C-labeled chlorsulfuron in soil and its mechanism of phytotoxicity.

The bioavailability of bound residue (BR) derived from 14C-labeled chlorsulfuron in soil and effect of the main components of the BR on growth of rape (brassica napus) and rice (Oryza sativa L.) were investigated. The results showed that the BR with the concentration of 0.28 and 0.56 nmol/g air-dried soil, which was calculated by special radioactivity of 14C-labeled chlorsulfuron parent compound, resulted in significant depression effect on growth of rape seedling. It was assured that the main components (2-amino-4-methoxyl-6-methyl-1,3,5-triazine, 2-amino-4-hydroxyl-6-methyl-1,3,5-triazine, and 2-chloro-benzenesul-fonamide) of the BR did not inhibit the growth of rape and rice. LC-MS analysis demonstrated that the parent compound previously bound to the soil matrix could be again released and transformed into methanol-extractable residue during the course of rape growth. It was concluded that the molecular leading to the phytotoxicity to rape and rice in the BR is still the parent compound.