Impact of Simulated California Rice-Growing Conditions on Chlorantraniliprole Partitioning

Abstract

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) 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 K and ΔH and a batch equilibrium method following OECD 106 guidelines, respectively. K and ΔH were determined to be 1.69 × 10 - 2.81 × 10 atm·m·mol (15-35 °C) and 103.68 kJ·mol, respectively. Log(K) ranged from 2.59 to 2.96 across all soil and temperature treatments. Log(K) 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.

Nickel-Catalyzed Cross-Dehydrogenative Coupling of α-C(sp3)–H Bonds in N-Methylamides with C(sp3)–H Bonds in Cyclic Alkanes

“…Aryl amides and sulfonamides are privileged structural motifs that have found widespread application in agrochemicals, pharmaceuticals, natural products, dyes, polymers, and drugs . For example (Figure ), chlorantraniliprole ( 1 ) is an efficient insecticide and BMS-193884 ( 2 ) is a modulator of vascular tone, cell proliferation, and hormone production.…”

Quantum Yield for the Aqueous Photochemical Degradation of Chlorantraniliprole and Simulation of Its Environmental Fate in a Model California Rice Field

“…The dissipation of CAP from a California rice field was simulated using PFAM with parameters listed in the Supplemental Data, Table S2. Previous use of PFAM to simulate the partitioning of CAP estimated that approximately 87 and 12% would partition to the benthic and water compartments, respectively, after 100 d (Redman and Tjeerdema 2018). Our simulation (Figure 3), which integrates transformation and chemodynamic processes, predicts that the majority (>99%) of the insecticide will remain in the benthic compartment (Figure 3A), where it will degrade slowly (t 1/2,benthic flooded = 29 d; Figure 3C).…”

“…The overall environmental fate of CAP in a California rice field was simulated using the photochemical properties determined in the present study along with previously determined parameters for its partitioning (soil/water and air/water), degradation in California rice field soils, and hydrolysis as inputs for the pesticides in flooded applications model (PFAM; Young 2012; Redman and Tjeerdema 2018; Redman et al 2019a, 2019b). The rate constant for the photochemical degradation of CAP in natural sunlight ( j CAP,env ) was calculated by normalizing the photolysis rate constant determined in rice field water ( j CAP,FW ) to environmental conditions using the ratio of the experimentally determined photolysis rate constants for 2NB ( j 2NB,ref ) to the environmental photolysis rate constant ( j 2NB,env , 0.013 s −1 ) measured under natural sunlight in Davis at the summer solstice (21 June 2000) using Equation 11 (McGregor 2000): …”

“…The model rice field and CAP application rate were previously defined (Redman and Tjeerdema 2018). Briefly, a 1‐acre field with a flood depth of 15 cm and a benthic depth of 5 cm was used along with daily meteorological data for Sacramento (CA, USA) provided by the US Environmental Protection Agency (2017) to approximate summer growing season conditions.…”

“…Furthermore, it was detected in 72% of surface water samples collected along the California central coast region during 2013 and in 86% of samples collected in 2019 during surveys conducted by the California Department of Pesticide Regulation (Newhart and Kelley 2016; Deng 2019). This is likely a result of CAP's widespread urban and agricultural use in the state coupled with its low volatility (Henry's law constant 1.69 × 10 −16 – 2.81 × 10 −15 atm m 3 mol −1 ; 15–35 °C) and soil organic carbon/water partitioning coefficient (log K OC = 2.59–2.96; thermodynamic index of irreversibility 0.04–0.28; Redman and Tjeerdema 2018). Therefore, the degradation of CAP under California rice field conditions must be fully understood, to ensure the adoption of safe use practices and prevent its release into surrounding surface waters such as the Sacramento River system.…”