亚磷酸盐在硝酸根溶液中的光氧化过程及影响因素

摘要

亚磷酸盐(HPO32?,H2PO3?,+3价)是磷生物地球化学循环中的还原态形式,其在水环境中的光氧化过程可能是亚磷酸盐转化的重要途径之一.以300W汞灯为光源,研究了环境浓度(1μmol/L)的亚磷酸盐在NO3?溶液中的光氧化过程,探讨了NO3?浓度、溶液pH值、环境中普遍存在的离子(Cl?、SO42?、HCO3?、Fe3+、Mn2+)及腐殖酸对亚磷酸盐光氧化过程的影响.结果表明,亚磷酸盐在NO3?溶液中的光氧化反应符合准一级动力学规律,当NO3?浓度由0增至120μmol/L时,其速率常数由0.020h?1增至0.271h?1;酸性溶液(pH=4)有利于亚磷酸盐在硝酸根溶液中的光氧化,水环境中SO42?及Cl?对光氧化过程存在弱抑制,而HCO3?对光氧化过程产生较强的抑制作用.Fe3+促进了亚磷酸盐在NO3?溶液中光氧化过程,而Mn2+则是抑制作用.腐殖酸的加入对亚磷酸盐光氧化过程存在抑制作用.活性氧猝灭剂(异丙醇,叠氮化钠)的加入大大抑制了亚磷酸盐的光氧化过程,表明亚磷酸盐光氧化过程中,活性氧的产生对其光氧化起到关键作用.模拟太湖水样中亚磷酸盐的减少量与正磷酸盐的增加量一致,证明亚磷酸盐光氧化产物是正磷酸盐.%Phosphite (HPO32?, H2PO3?, +3valence) is a reduced form of phosphorus in the biogeochemical phosphorus cycle. Its photooxidation process can be an important path of its transformation in water environment. The photooxidation process of 1μmol/Lphosphite in nitrate solution was studied using 300W mercury lamp as light source. Experiments were carried out to study the influences of NO3? concentration, pH value and common ions in water (such as Cl?, SO42?, HCO3?, Fe3+, Mn2+) and humic acid, on the photooxidation of phosphite in NO3? solutions. The results demonstrate that the photooxidation of phosphite followed the pseudo-first-order kinetics and the photooxidation rate increased rapidly with increasing initial NO3? concentration. The kinetics constant changed from 0.020h?1 to 0.271h?1 with the concentration of NO3? increased from 0 to 120μmol/L. The kinetics constant decreased with the increase of pH and the addition of HCO3?. The addition of Cl? and SO42? slightly inhibited the photooxidation process. The addition of Fe3+ accelerated the photooxidation of phosphite in NO3? solution while Mn2+ inhibited the photooxidation. The addition of humic acid inhibited the photooxidation process. ROS (reactive oxygen species) were found to play an important role in the phosphite photooxidation reaction by using isopropanol and sodium azide (NaN3) as ROS quenchers. In the simulated Taihu Lake water experiment, the increased amount of phosphate coincided with the decreased amount of phosphite, which indicated that the photooxidation product of phosphite is phosphate.