THE MOBILITY OF [C-14] 3-CHLORO-P-TOLUIDINE HYDROCHLORIDE IN A LOAM SOIL-PROFILE

The movement of radiolabeled 3-chloro-p-toluidine hydrochloride (CPTH) in a loam soil was evaluated in a column leaching study. Twenty-five- gram portions of the soil were treated with about 30 mu g/g of uniform ly labeled [C-14]CPTH, and then incubated (aged) for 24 h under aerobi c conditions; this soil was applied to untreated soil columns, which w ere then leached with dilute aqueous calcium sulfate for a total leach ate volume equal to or greater than 50.8 times the cross-sectional are a, or about 450 to 600 ml. Results indicated that about 2% of the init ial radiolabeled compound leached through the soil profile, with the m ean apparent partition coefficient calculated to be 65 ml/g. The soil columns were separated into 6-cm sections and extracted with dilute aq ueous calcium sulfate, followed by 80% aqueous acetonitrile. About 90% of the [C-14]CPTH was sorbed to the uppermost 6 cm of soil. Following extraction, the residual soil was combusted, with these results indic ating that an average 77% of the parent compound and products present in the upper 6 cm were bound to the soil colloids. Approximately 1% of the applied radiolabeled compound volatilized during the soil aging a nd leaching processes. The mean mass balance based upon [C-14] analyse s was 102%. One major metabolite was detected in leachate fractions an d soil extracts, which was tentatively identified as N-acetyl-3-chloro -p-toluidine, based upon HPLC retention times. This same degradation p roduct was previously identified and confirmed using mass spectroscopy in CPTH aerobic soil biodegradation and fish accumulation studies. Th e extent to which CPTH was bound to the loam soil colloids, with only minimal movement through the soil profile, suggests a low potential fo r mobility of this pesticide in the soil environment.