Direct biomonitoring of pesticides degradation in biobeds: a visual index based on earthworms.

S. LAMMERTYN; F.V. MAGNI; A. DURAN; M.R. REPETTI; C. ZALAZAR; J.L. GODOY

Mar del Plata

Conferencia; VIII Congreso Argentino de la Sociedad de Toxicología y Química Ambiental. SETAC,; 2022

The biobeds are presented as an alternative for the good management of wastewaters with pesticides on farms. The design consists of a waterproof opening in the ground filled with a biologically active matrix (biomixture). Chemical analysis using gas or liquid chromatography coupled to mass spectrometry is commonly used to monitor pesticide degradation in biobeds. Nonetheless, the biodegradation process can generate metabolites as toxic or even more toxic than the parent compound, and their analysis is a difficult task. The monitoring of ecotoxicological changes using bioindicators from different taxonomic groups as earthworms and seeds could be adopted to evaluate the detoxification of these biomixtures. In this work, the avoidance test with Eisenia fetida and seed germination test with Lactuca sativa were applied to monitoring pesticides degradation in a biomixture polluted with five herbicides. Samples were taken on the initial day (after pesticide application) and days 30, 60, 90,150 and 210. Also, a new test was proposed based on the evaluation of visual injury in Eisenia fetida. The sensitivity and efficacy of these tests were evaluated and compared in a biomixture composed of wheat stubble, river waste and soil (50:25:25% in volume) during 210 days. The pesticides used were atrazine (50 mg/kg), prometryn (50 mg/kg), clethodim (25 mg/kg), haloxyfop-P-methyl (50 mg/kg) and dicamba (150 mg/kg). The results were compared with pesticide degradation data obtained by chromatographic - mass spectrometry (UHPLC-MS/MS). The injury index was reduced by 50% after 60 days. Pesticides showed high degradation rates at 60 days (> 98% for atrazine, clethodim, haloxyfop-P-methyl and prometryn, and > 95% for dicamba). Not injury was detected at day 150, while the avoidance response and germination index showed no toxicity at 210 days.The injury test showed a better correlation with pesticides degradation than the avoidance test and seed germination. This simple and inexpensive test has proved to be useful for in situ biomonitoring of biobeds.