Ivermectin mobility in Delta del Paraná wetlands: influence of topography and soil geochemical features

Abstract

Grazing activities in wetlands ecosystems lead to the alteration of nutrients dynamics and the contamination of soils and waters with veterinary products, among other negative impacts. The objective of this work was to determine the presence and mobility of Ivermectin (IVM), an antiparasite compound used in livestock, in soils from three cattle fields located in the lower Delta del Paraná. Its mobility was correlated with the content of iron, different fractions of organic matter (OM) and clays. Results indicated that upper and middle zones of fields contained the highest content of clays and hematite (1.51 and 0.35 g/kg, respectively) and presented the highest amount of labile OM (3.70 and 2.93%, respectively), with 23.50 and 14.25 ppm of IVM, respectively. The low and anaerobic zone with high iron content (25 g/kg) and no hematite, presented 16 ppm of labile OM and 16.06 ppm of IVM. Results suggested a high mobility of IVM from upper to lower zones; and a high concentration of soluble IVM in the lower zones (2.87 ppm) compared to the upper topographies (0.45 and 1 ppm). The presence of this drug was strongly influenced by its interaction with the type of OM and the mineralogical composition of soils. This is the first time that IVM was reported to be associated to a mobile and soluble fraction of organic matter, representing a threatening situation to water courses. This study allowed to explain the occurrence and fate of the contaminant in wetlands accordingly to the physicochemical characterization of soils.