FORMATION AND TRANSPORT OF DEETHYLATRAZINE AND DEISOPROPYLATRAZINE INSURFACE-WATER

Field disappearance studies and a regional study of nine rivers in the Midwest Corn Belt show that deethylatrazine (DEA; 2-amino-4-chloro-6- isopropylamino-s-triazine) and deisopropylatrazine (DIA; 2-amino-4-chl oro-6-ethylamino-s-triazine) occur frequently in surface water that ha s received runoff from two parent triazine herbicides, atrazine 2-chlo ro-4-ethylamino-6-isopropylamino-s-triazine) and cyanazine thylamino-6 -methyl-propionitrileamino-s-triazine). The concentration of DEA and D IA in surface water varies with the hydrologic conditions of the basin and the timing of runoff, with maximum concentrations reaching 5 mug/ L (DEA + DIA). Early rainfall followed by a dry summer will result in an early peak concentration of metabolities in surface water. A wet su mmer will delay the maximum concentrations of metabolites and increase their runoff into surface water, occasionally resulting in a slight s eparation of the parent atrazine maximum concentrations from the metab olite maximum concentrations, giving a ''second flush'' of triazine me tabolites to surface water. Replicated field dissipation studies of at razine and cyanazine indicate that DIA/DEA ratios will vary from 0.4 /- 0.1 when atrazine is the major triazine present to 0.6 +/- 0.1 when significant amounts of cyanazine are present. A comparison of transpo rt time of DEA and DIA from field plots to their appearance in surface water indicates that storage and dilution are occurring in the alluvi al aquifers of the basin.