STERILE AND NONSTERILE DEGRADATION OF CARBON-14-PRIMISULFURON IN SOILFROM 4 DEPTHS

The degradation of C-14-primisulfuron -pyrimidinyl]amino]carbonyl]amin o]sulfonyl]benzoic acid) was monitored for 2 mo using soil microcosms under sterile and nonsterile conditions. Both chemical and biological degradation was detected. The half-life was 2.1 wk for nonsterile samp les from 0 to 5 cm, and 3.4 wk for nonsterile samples from 20 to 25 cm . After 7 wk, bound residues accounted for 48 and 27% of the recovered radioactivity in these samples, respectively. For sterile samples fro m the same depths, the half-life was >7 wk and bound residues accounte d for 7% of the recovered radiolabel. Disappearance and bound residue formation of primisulfuron were similar for both sterile and nonsteril e samples from deeper in the profile (45-75 cm) indicating little biol ogical degradation occurred in these subsurface samples. Chemical and microbial degradation of primisulfuron appeared to differ; the same me tabolites were produced but at different times and in different amount s. Very little (14)C0(2) (<3%) was produced from any sample. These res ults indicate that initial hydrolyzation of the sulfonylurea bridge oc curs both chemically and biologically, but does not occur readily in t he subsoil. This may have implications for the prevention of groundwat er contamination and for the bioremediation of contaminated soils.