Impact of Simulated California Rice-Growing Conditions on Chlorantraniliprole Partitioning.

Chlorantraniliprole (3-bromo-N-[4-chloro-2-methyl-6-(methylcarbamoyl)phenyl]-1-(3-chloro-2-pyridine-2-yl)-1H-pyrazole-5-carboxamide, CAP; water solubility 1.023 mg·L-1) was recently registered for application on California rice fields. Air- and soil-water partitioning of CAP were investigated under simulated California rice field conditions through calculation of KH and ΔawH and a batch equilibrium method following OECD 106 guidelines, respectively. KH and ΔawH were determined to be 1.69 × 10-16 - 2.81 × 10-15 atm·m3·mol-1 (15-35 °C) and 103.68 kJ·mol-1, respectively. Log(Koc) ranged from 2.59 to 2.96 across all soil and temperature treatments. Log(KF) ranged from 0.61 to 1.14 across all soil, temperature, and salinity treatments. Temperature and salinity increased sorption significantly at 35 °C (P < 0.05) and 0.2 M (P < 0.0001), respectively, while soil properties impacted sorption across all treatments. Overall results, corroborated using the Pesticides in Flooded Applications Model, indicate that volatilization of CAP is not a major route of dissipation and sorption of CAP to California rice field soils is moderately weak and reversible.