Department of Chemistry, University of Otago, Dunedin 9010, New Zealand.
Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322-1400, United States.
Environ Sci Technol. 2020 Jun 16;54(12):7302-7308. doi: 10.1021/acs.est.0c00964. Epub 2020 Jun 5.
A solid-phase fugacity meter was used to measure the soil-air partition coefficients of three semivolatile pesticides (chlorpyrifos, pyrimethanil, and trifluralin) in the absence of additional adjuvants (), as part of commercial formulations (), and as formulation mixtures with an additional spray adjuvant added (). Chlorpyrifos values were also measured over 15-30 °C, allowing for the change in internal energy of the phase transfer reaction (Δ) to be calculated and compared to the Δ for from the literature. Measured values were then used as input parameters in a pesticide volatilization model to understand how their variability affects pesticide volatilization rates under different conditions. Initial experiments conducted at ∼24 °C indicated that all pesticides volatilized more readily in the presence of adjuvants than in their absence and that the additional spray adjuvant had minimal impact. The Δ values were 328 and 90 kJ/mol for chlorpyrifos in the absence and presence of formulation adjuvants, respectively, suggesting that adjuvants may weaken or disrupt intermolecular attractions between pesticide molecules and soil. At temperatures below 24.5 °C, modeled chlorpyrifos volatilization rates were higher in the presence of adjuvants than in their absence; however, the opposite occurred at temperatures above 24.5 °C.
采用固相逸度计，在无额外助剂（）、作为商业制剂（）以及与额外喷雾助剂混合的制剂（）的情况下，测定了 3 种半挥发性农药（毒死蜱、嘧菌酯和氟乐灵）在土壤-空气间的分配系数。还在 15-30°C 下测定了氯吡硫磷的值，以计算相转移反应的内能变化（Δ），并与文献中的Δ值进行比较。测定的 值随后被用作农药挥发模型的输入参数，以了解其变异性如何影响不同条件下的农药挥发速率。在约 24°C 进行的初步实验表明，所有农药在有助剂存在时比在无助剂存在时更容易挥发，而额外的喷雾助剂的影响最小。在不存在和存在制剂助剂的情况下，氯吡硫磷的Δ值分别为 328 和 90 kJ/mol，这表明助剂可能削弱或破坏农药分子与土壤之间的分子间吸引力。在低于 24.5°C 的温度下，模型化的氯吡硫磷挥发速率在有助剂存在时高于无助剂存在时；然而，在高于 24.5°C 的温度下则相反。
