Uptake and Translocation of the Veterinary Pharmaceutical Monensin in Lactuca sativa Cultivated in Composted Soils

SANCHEZ URDAY, CAMILA D; ALONSO, LUCAS L; NAVARRO, MARCOS; URRUCHUA, FLORENCIA CAMILA; MARINO, DAMIAN J

Congreso; SETAC Latin America 14th Biennal; 2021

In recent decades, animal production has intensified and the use of veterinary antibiotics in animal husbandry has increased. Among the most widely used antibiotics in Argentina is monensin (MON). Since it is not completely metabolized by the animal, it is excreted and dumped together with the excreta (with or without treatment) in fields as a natural fertilizer. This practice raises questions about its destination, especially in soils and under the usual cultivation conditions. The objective of this work was to evaluate the potential incorporation and translocation of MON from the soil to a typical horticultural crop in the region. For this purpose, MON was impregnated on a local soil from a low anthropic activity (A° El Pescado area, Buenos Aires, Argentina), mixed with vermicompost at agronomic doses, to obtain nominal concentrations of 50 and 250 ug/kg. The treatments were fractionated in pots in which seedlings of lettuce (Lactuca sativa) were grown. Plants were maintained under controlled T, light, and irrigation conditions for 38 days. At the end of the trial, samples of plant tissue (leaves and roots), soil and irrigation leaching water were pre-treated, and extracts were analyzed by LC-MS/MS. A half-life of MON was observed in the study soil of 3.6 d, possibly due to the higher microbiological activity and organic matter in the compost. MON was not detected in leached water, evidencing its retention in the soil. Regarding growth, plants grown with the lowest dose tested had a greater leaf length growth compared to the other treatments, evidencing a hormesis effect, reported for other xenobiotics. As the test time elapsed, the concentration of MON increased significantly in the roots. The average root concentration range (3.2 -26.5 ug/kg) is on the order of those reported in cases of MON ingress from organic amendments. There were no significant differences in the root bioaccumulation factor (BFC) between treatments or times measured. Under the conditions tested, MON translocation to leaves was not observed, always obtaining values below the LOD (0.1 µg/kg). Under these conditions, no food safety risk associated with the consumption of lettuce was observed. However, their incorporation into roots highlights the need to explore these systems under conditions closer to real practices.