萨旺尼河溶解性有机质对5-MeO-BDE-47光解影响研究

Insight into the Photodegradation of 5-MeO-BDE-47 with Different Dissolved Organic Matter from the Suwannee River

近年来,新型溴代有机污染物甲氧基多溴联苯醚(MeO-PBDEs)已在多种水环境中被检出.由于该类污染物可能具有类二噁英效应,因此引起广泛关注.为评价MeO-PBDEs的水环境风险,有必要对其水环境转化行为展开研究.已有研究表明,光化学降解是水环境中MeO-PBDEs的一条重要消除途径.作为水环境中普遍存在,且是污染物间接光解重要参与者的溶解性有机质(DOM),其对MeO-PBDEs的光解影响尚不清楚.基于此,选取水环境中经常检出的5-MeO-BDE-47作为模型化合物,考察模拟太阳光照条件下,三种DOM(包括萨旺尼河富里酸、腐殖酸和天然有机质)对其光解动力学的影响,并分析了影响机理.结果表明,三种DOM均抑制5-MeO-BDE-47光解,其中DOM光屏蔽作用的相对抑制贡献率为44%～88%,静态淬灭要比动态淬灭抑制作用更大.DOM替代物实验表明,5-MeO-BDE-47可以被激发三线态DOM(~3DOM~*)替代物氧化降解,但对于真正的DOM分子,由于其分子中含有酚类结构,能起到抗氧化剂作用,从而有效抑制~3DOM~*氧化降解5-MeO-BDE-47.

In recent years,MeO-PBDEs have frequently been detected in various aquatic systems.Due to their dioxin-like effects,MeO-PBDEs have obtained mounting concern.To better assess the environmental risks of MeO-PBDEs in water,it is essential to investigate their environmental transformation behaviors.Previous studies have proved that MeO-PBDEs can undergo direct and self-sensitized photolysis,however,knowledge on indirect photolysis of MeO-PBDEs is still scarce.As the ubiquitous species existed in aquatic environment,dissolved organic matter(DOM) plays a crucial role in the indirect photolysis of various pollutants.To date,no information on DOM-initiated indirect photolysis of MeO-PBDEs can be retrieved.In this study,5-MeO-BDE-47 and three DOM from the Suwannee River including fulvic acid(FA),humic acid(HA) and natural organic matter(NOM) are selected as the targets.Simulated sunlight experiments indicate that each DOM can inhibit the photodegradation of 5-MeO-BDE-47.The effects of light screening and quenching as the crucial factors to hinder the photodegradation were considered.Light screening plays a major role in slowing 5-MeO-BDE-47 photodegradation with the relative contribution to be 44%~88%.Static quenching makes a larger contribution than dynamic quenching.DOM surrogate experiments imply the oxidation of 5-MeO-BDE-47 by photo-excited triplet DOM(~3DOM~*) surrogate,but the presence of phenol moieties(as antioxidant) on genuine DOM molecules can sufficiently impede the oxidation of 5-MeO-BDE-47 by ~3DOM~*.