Degradation study of mesotrione and other triketone herbicides on soils and sediments

Triketone compounds are considered to be less stable in the ecosystems in comparison with other herbicides. However, their degradation processes in environment are under investigation as both parents and degradation products can exhibit toxicity on non-target organisms. The objective of this research was to investigate the degradation of triketone herbicides: mesotrione, sulcotrione, and tembotrione, as well as their degradation products in soils and sediments. The degradation studies were conducted in soil and sediment samples with different physicochemical properties. All experiments were conducted under standard experimental conditions; therefore, it was possible to assess the influence of pH, organic carbon (OC) content of soils and sediments, and the sunlight on the stability of triketones and their degradation products. The conditions of extraction and chromatographic determination were optimized for the determination of triketones and their degradation products in laboratory-spiked sediment and soil samples. The triketone degradation products exhibited higher stability in soil and sediment samples in comparison with parent herbicides. Soil microorganisms accelerated the degradation of all investigated compounds. In alkaline soil and sediments, all analytes exhibited higher stability in comparison with the acidic sorbents. The influence of OC content in sorbents was not evident. Photodegradation was the main path of triketones decomposition in soils and sediments. Since the stability of triketone herbicides may be significant, depending on the environmental conditions, the monitoring of the concentration of these compounds and in particular their degradation products should be conducted under the field conditions.