I. Kinetics and mechanism of the ferrate oxidation of dimethyl sulfide in aqueous solution. II. A temporal profile of triazine and acetanilide herbicides in surface and ground water near Ashland, Nebraska

I. This work studies the reaction of ferrate with dimethyl sulfide (DMS). Reactants, intermediates, and products of this reaction were measured in a mechanistic study of this reaction. The source and destination of the oxygen atoms involved in this aqueous reaction were tracked using 18O-labeled water. This was accomplished by monitoring the masses of dimethyl sulfoxide (DMSO and DMS18O) by GC-MS. Information concerning intermediates was obtained by quenching the reaction at various times with hydroxylamine. The effect of different buffers and dissolved oxygen on the reaction were studied at pH 10.2 and found to have no significant influence on the kinetics or product distribution. Resolved rate constants were calculated to be 11sec−1 and 426sec−1 respectively for FeO42− and HFeO4− reacting with DMS. Isotope tracers using 18O-labeled water, GC-MS detection of the products and oxygen quantitation were used to provide evidence for an oxygen atom transfer from Fe(VI) to DMS being a step in the mechanism. It was also found that some solvent oxygen was incorporated into DMSO, probably from hydrogen peroxide or hydroxyl radical formed by oxidation of water by ferrate. II. Atrazine, cyanazine, alachlor, acetachlor and metolachlor were detected in the Platte River and surrounding ground water after the first thunderstorm following herbicide application. Maximum concentrations of atrazine in the Platte River vary from 2 ppb to 12 ppb in the years 1995 through 1998. Many tributaries intersect with the Platte River, but mixing of these waters is incomplete even miles downstream from their convergence. Induced recharge pulls surface water that may be contaminated with herbicides into the drinking water aquifer. Concentrations of analytes in the ground water near the Platte River in eastern Nebraska can be between 0 and 100% of the surface water concentrations. The lag time of this process has been estimated for wells at different distances from the Platte River. The lag times for analytes to enter production wells on an island in the river were between 5 and 9 days and to enter a monitoring well on the mainland were between 11 to 21 days. Because of these differences in lag times, analytes that degraded faster (acetanilides) were rarely detected in water samples taken from the mainland. Water samples taken from island wells regularly contained detectable concentrations of an the analytes