Duirk Stephen E, Collette Timothy W
National Exposure Research Laboratory, Office of Research and Development, US Environmental Protection Agency, Athens, Georgia 30605, USA.
Environ Sci Technol. 2006 Jan 15;40(2):546-51. doi: 10.1021/es0516615.
Chlorpyrifos (CP) was used as a model compound to develop experimental methods and prototype modeling tools to forecast the fate of organophosphate (OP) pesticides under drinking water treatment conditions. CP was found to rapidly oxidize to chlorpyrifos oxon (CPO) in the presence of free chlorine. The primary oxidant is hypochlorous acid (HOCl), kr = 1.72 (+/-0.68) x 10(6) M(-1)h(-1). Thus, oxidation is more rapid at lower pH (i.e., below the pKa of HOCl at 7.5). At elevated pH, both CP and CPO are susceptible to alkaline hydrolysis and degrade to 3,5,6-trichloro-2-pyridinol (TCP), a stable end product. Furthermore, hydrolysis of both CP and CPO to TCP was shown to be accelerated in the presence of free chlorine by OCl-, kOCl,CP = 990 (+/-200) M(-1)h(-1) and kOCl,CPO = 1340 (+/-110) M(-1)h(-1). These observations regarding oxidation and hydrolysis are relevant to common drinking water disinfection processes. In this work, intrinsic rate coefficients for these processes were determined, and a simple mechanistic model was developed that accurately predicts the temporal concentrations of CP, CPO, and TCP as a function of pH, chlorine dose, and CP concentration.
毒死蜱（CP）被用作模型化合物，以开发实验方法和原型建模工具，用于预测饮用水处理条件下有机磷（OP）农药的归宿。研究发现，在游离氯存在的情况下，CP会迅速氧化为毒死蜱氧磷（CPO）。主要氧化剂是次氯酸（HOCl），反应速率常数kr = 1.72（±0.68）×10⁶ M⁻¹h⁻¹。因此，在较低pH值（即低于HOCl的pKa值7.5）下氧化更快。在较高pH值下，CP和CPO都易受碱水解作用，并降解为稳定的终产物3,5,6-三氯-2-吡啶醇（TCP）。此外，在游离氯存在下，OCl⁻会加速CP和CPO水解为TCP的过程，kOCl,CP = 990（±200）M⁻¹h⁻¹，kOCl,CPO = 1340（±110）M⁻¹h⁻¹。这些关于氧化和水解的观察结果与常见的饮用水消毒过程相关。在这项工作中，确定了这些过程的本征速率系数，并开发了一个简单的机理模型，该模型能够准确预测CP、CPO和TCP的瞬时浓度随pH值、氯剂量和CP浓度的变化。
