Concentration of Picloram in Runoff Water

Runoff water was sampled over a 2-year period from an 8-ha site that had been treated and retreated with 4-amino-3,5,6-trichloropicolinic acid (picloram) at the rate of 1.12 kg/ha in the spring of 1969 and 1970. Runoff water was sampled adjacent to the plots and in two creek systems up to 2.0 km from the plots. Samples taken adjacent to the plots declined to less than 10 ppb by 10 to 12 weeks after application. Eight days after application, water sampled 1.2 km from the plots contained less than 1 ppb of picloram. Less than 1.0 ppb levels were occasionally detected 1.6 km from the plots 8 months after treatment.