A radioactive tracing technique was used to estimate the environmental safeness of a weedicide （bensulfuron-methyl）. It was revealed that different kinds of waterlogged soil have different speeds of degradation for 14C-bensulfuron-methyl applied under a dark culture condition indoor. The degradation in alkaline soil is slower than that in neapal soil

e.g. in neutral yellow brown end the residual half-life is 62 dsys

whereas that in alkaline yellow fluvo-aquiv earth is 129 days.The bound residue of 14 C-be nsulfuron-methyl in waterlogged soil is evident and increases with time. For example

on the 104th day

the bound residue is 34.15% of primitive activity while that on the 165th day is 46.45%.