Photodecomposition of Organic Phosphorus in Aquatic Solution under Solar Irradiation with Nitrate: Kinetics and Influencing Water Parameters

摘要

The transformation of organic phosphorus plays an important role in the phosphorus cycle in the natural environment. In this study, a series of laboratory-based experiments were conducted to address the influence of nitrate (NO~-_3photochemical activity on the transformation of methyl parathion under solar irradiation. It is demonstrated that the photodecomposition of methyl parathion by NO~-_3, obeys pseudo-first-order reaction kinetics, with the photodecomposition rate increasing with NO~-_3 concentration. The photodecomposition rates of methyl parathion by NO~-_3 were strongly influenced by pH, concentration of humic acid and Fe~(3+) . Higher concentrations of Fe~(3+) and lower concentrations of humic acid accelerated the photodegradation induced by NO~-_3. Moreover, compared to alkaline media the acidic media can enhance the rate of methyl parathion degradation. Formation of the hydroxyl radical (• OH) was identified through the measurement of photoluminescence spectra (PL) using ter-ephthalic acid as the trapping molecule. The primary transformation pathways of methyl parathion in the presence of NO~-_3 under solar irradiation were proposed through the qualitative and quantitative analysis of byproducts. Intermediates, such as paraoxon, 4-nitrophenol and orthophosphate, were identified, and a mineralization pathway from methyl parathion to orthophosphate was proposed.