Surface runoff of herbicides: a study on slope, soil type and risks for the aquatic matrix

• Grant number: 24/14071-1
• Support Opportunities: Scholarships in Brazil - Master
• Start date: July 01, 2025
• End date: April 30, 2027
• Field of knowledge: Agronomical Sciences - Agronomy - Crop Science
• Principal Investigator: Valdemar Luiz Tornisielo
• Grantee: Camila de Werk Pinácio
• Host Institution: Centro de Energia Nuclear na Agricultura (CENA). Universidade de São Paulo (USP). Piracicaba , SP, Brazil

Abstract

When herbicides are applied, they can undergo transport processes, such as surface runoff. Where, after precipitation, according to their physical-chemical characteristics, they can be transported with the water flow, in free form or adhered to soil particles. This transport is responsible for the direct contamination of water bodies, which can cause damage to non-target organisms. Therefore, the objective of this project will be to quantify the surface runoff of herbicides with different physical-chemical characteristics (metribuzin, diclosulam and propisochlor), in two types of soils, on different slopes, considering the presence or absence of straw, to investigate the risks of this transport of these herbicides into the aquatic matrix and, consequently, their impacts on non-target aquatic organisms. To this end, three stages will be carried out, the first involves studies of sorption, desorption, and leaching, following OECD guidelines, characterizing the herbicides in these processes, and helping to understand surface runoff. The second stage is the study of surface runoff, where microcosms will be made to evaluate how the type of soil, the slope (0, 5, and 10%), the presence or absence of sugarcane straw (15 t ha-1) affect the transport of herbicides in a condition of extreme rain (200 mm in 48 hours). Based on these results, the final stage of the project, which consists of acute and chronic tests on daphnia (Daphnia magna), considering the quantities of herbicides drained from the soil in stage II of the project, also under OECD guidelines. This way, a method for studying surface runoff using radiometric techniques and microcosms is expected to be standardized. Furthermore, it will be possible to complement the data on the behavior of herbicides in the environment, mainly about surface runoff, and assist in understanding the environmental risks for non-target aquatic organisms through this transport under extreme rainfall conditions.