Occurrence of 2,4,5‐T and Picloram in Subsurface Water in the Blacklands of Texas

Abstract

AbstractThis investigation was conducted to determine the concentration of 2,4,5‐T [(2,4,5‐trichlorophenoxy)acetic acid] and picloram (4‐amino‐3,5,6‐trichloropicolinic acid) in subsurface water after spray applications of the herbicides to the surface of a seepy area watershed and lysimeter in the Blacklands of Texas.A 1:1 mixture of the triethylamine salts of 2,4,5‐T + picloram was sprayed at 2.24 kg/ha every 6 months on the same area for a total of five applications. Herbicide content in the Houston Black clay during the study ranged from 0 to 162 ppb. Herbicide content on grass was high (28 to 113 ppm) immediately after spraying, but degraded rapidly after each treatment. Concentration of 2,4,5‐T and picloram in seepage and well water from the treated area was extremely low (<1 ppb) during the 3‐year study. No 2,4,5‐T was detected from 122 drainage samples from a field lysimeter sampled for 1 year after treatment with 1.12 kg/ha of 2,4,5‐T + picloram (1:1). Picloram was detected in small amounts (1 to 4 ppb) 2 to 9 months after treatment in lysimeter water.