苯系物光催化开环降解产物低级醛类的健康效应

Health Effect of Volatile Aldehyde Compounds in Photocatalytic Oxidation of Aromatics Compounds

采用连续流配气系统,利用氮掺杂TiO2,在UV(4 W,254 nm)光照下光催化降解(PCO)室内甲苯和苯甲醛污染物,运用质子转移反应质谱仪实时检测气相中间产物,应用健康风险评估模型分析甲苯、苯甲醛光催化降解过程的健康效应.结果表明,甲苯和苯甲醛转化率和矿化率较高,但如乙醛和甲醛等低级醛类(VAs)中间产物形成潜在的健康风险,常规的转化率和矿化率指标不能全面表征苯系物的光催化过程的健康风险.乙醛极易在气相积累,是影响健康风险变化的关键;甲醛的摩尔分数稳定在较低水平,但其影响不可忽视.甲苯和苯甲醛降解过程的健康风险指数增大因子(η)随VAs积累而增大,最大值分别为8 499.68和21.43,VAs的贡献率为99.3%和98.3%;光催化降解稳定后η分别为236.09和2.30,VAs的贡献率为97.9%和97.8%;η平均值(30 min)分别为932.86和8.52,VAs的贡献率为98.5%和98.0%.由此提出了以低级醛类健康风险指数增大因子贡献值(ηVAs)表征苯系物光催化安全降解过程的特征评价指标.

Photocatalytic oxidation（PCO） of toluene and benzaldehyde in indoor air by N doped TiO2（N-TiO2） was conducted under UV irradiation of 254 nm.The intermediates were identified and monitored on real-time by proton transfer reaction-mass spectrometry.The health risks of PCO of toluene and benzaldehyde were assessed based on health risk influence index（η）.Results indicated that both the conversion rate and mineralization rate of toluene and benzaldehyde were relatively high,however,the volatile aldehyde compounds（VAs）,including acetaldehyde and formaldehyde generated from ring-opening,significantly influenced the health risks of PCO of toluene and benzaldehyde.Acetaldehyde played a crucial role on health risks,which was inclined to desorb from the surface of catalysts,accumulate in gas-phase,and increase the health risks of PCO of the aromatic compounds.The concentration of formaldehyde kept stable at a relatively low level,however its impact cannot be neglected.In the PCO process of toluene and benzaldehyde,η reached the maximum values of 8 499.68 and 21.43,with the ηVAs,contribution of VAs to the health risk influence index of outlet,reaching 99.3% and 98.3%,respectively.The average values of η in the PCO process of 30 min were 932.86 and 8.52,and for which ηVAs reached 98.5% and 98.0%,respectively.When PCO of toluene and benzaldehyde reached steady state,η were 236.09 and 2.30,and ηVAs reached 97.9% and 97.8%,respectively.Hence,ηVAs can be taken as a characteristic parameter in assessment of health risks of PCO of aromatic compounds.