Potential of terracing to reduce glyphosate and AMPA surface runoff on Latosol

Abstract

Purpose: Glyphosate is the world’s most used herbicide and monitoring glyphosate in the environment is a relevant topic. The present study aims to develop a methodology to extract glyphosate from the soil and sediments, and assess the potential of the terracing system to mitigate contamination by glyphosate and AMPA in soil and water. Materials and methods: Collections were performed on a weekly basis in two different periods of the agricultural calendar, totaling 24 Latosol soil samples, 12 sediment samples, and 10 water samples. The sampling was performed in two distinct areas: in the cultivation area where the lots with and without terrace were installed (soil and water of the reservoirs) and in the creek (sediment) present in the middle of the property. The analytes were extracted from the soil and sediment samples using alkaline extraction with KH2PO4 and NH4OH. The supernatant resulting from the extraction and the water samples were submitted to the derivatization (FMOC-Cl) and solid-phase extraction steps. The samples were then analyzed by high-performance liquid chromatography equipped with fluorescence detector (HPLC-FD). Results and discussion: The soil samples showed AMPA content in all samples ranging from 0.50 to 1.11 μg g−1 of soil. Glyphosate could be quantified in 37.5% of the samples, and the concentrations ranged from 0.21 to 0.49 μg g−1. High concentrations of glyphosate were detected in the water samples (20.74 and 31.24 μg L−1) in the first rain events after application, decreasing significantly in the following rainfall events. The concentrations found were similar for both lots, but the volume of runoff water was higher in the lot without terrace, thus a greater mass of analyte was transported. None of the analytes under investigation could be quantified in the analysis of riverbed sediments. Glyphosate and AMPA, however, were detected in 50 and 75% of the sediment samples respectively. Conclusions: The results indicate the presence of analytes in the cultivation areas and prove the effectiveness of the terracing system in agricultural areas, limiting the dumping of the material originated from the surface runoff into water bodies and reducing the risk of contamination.