Products of the Photolysis of 3,6-Dichloropicolinic Acid (the Herbicide Lontrel) in Aqueous Solutions

We studied the composition of products of the photochemical degradation of 3,6-dichloropicolinic acid (DCPA), the active principle of Lontrel, a herbicide broadly used in agriculture. Ultraviolet irradiation (mimicking the natural sunlight action) did not degrade DCPA completely to environmentally safe products. The rate of DCPA degradation was notably lower when distilled water was replaced by river water and even lower in sea water. Chromatomass spectrometry revealed 9 compounds among the photolysis products, in addition to undegraded DCPA.