Ms. Mariana Vasconcelos Barroca

Fluopyram (FL; C16H11CIF6N2O) is a broad-spectrum molecule belonging to the new generation of nematicides and also used for the control of several plant pathogens. The aim of this study was to quantify the adsorption and transport of FL in 3 soil textures. Initially, equilibrium adsorption isotherms were measured by batch method. Then, FL transport characteristics were quantified by flowthrough soil column experiments under saturated flow conditions. A pulse input of FL was given together with Bromide (Br), used as a conservative tracer. The flowthrough experiments were performed with loamy sand, loam and clayey soils under 3 flow rates (0.3, 1 and 4 ml min-1). The adsorption isotherms of FL exhibited constant partitioning for all soils, with distribution coefficient (Kd) ranging from 0.72 to 1.87 L Kg-1 for loam and clay, respectively. The established breakthrough curves (BTCs) obtained for bromide exhibited a symmetrical pattern, regardless of soil texture and flow rates, with an average of 100% of Br recovered, suggesting that physical equilibrium prevail in all soil columns. The FL BTCs exhibited sharp increase in concentration after the pulse input and long tailing during the leaching phase, not fully recovered even after leaching of 17 pore volumes. Our modeling effort implies that FL is undergoing fast adsorption and slow desorption kinetics.