Evaluation of the influence of different cations on the mobility and performance of dicamba-based ionic liquids

Abstract

Herbicidal ionic liquids are considered as an alternative to commercial crop protection products, however current research is mainly concerned with their physicochemical properties and biological activity. In our study, we decided to comprehensively evaluate the fate of selected herbicidal ionic liquids after they enter the soil environment through comprehensive sorption, mobility and leaching studies. The studies were carried out for two herbicidal ionic liquids containing cation: betaine or choline and anion dicamba. The phytotoxicity studies conducted indicate a protective effect of betaine and choline cations for root growth of monocotyledonous plants, thus offsetting the toxic effects of dicamba anion present in the soil. Moreover, the analyzed herbicidal ionic liquids do not show any toxic effect on soil microorganisms. The results also indicate that in the soil profile the hydrophilic betaine cation is not sorbed and moves quickly through the soil profile. The choline cation, on the other hand, is sorbed about 40% (depending on the soils), but is leached. On the other hand, the analysis of sorption and mobility of the dicamba anion, from the HILs, did not show significant differences to the migration of dicamba anion from the sodium form. Our results give a first insight into the fate of ionic liquids in the environment indicating that the cations and anions act as independent chemical molecules when entering the soil ecosystems.