利用箱式模型研究PFCs的大气化学特征

Numerical Simulation on Atmospheric Chemical Reactions of Perfluoro Compounds Using a Box Model

全氟化合物(PFCs)是一种典型的新型持久性有机污染物(POPs),具有疏油、疏水耐高温等特性,化学稳定性强,近些年被广泛应用。由于其可以在环境中长期稳定存在并对生物体产生较大毒害作用,目前已经引起了全世界的关注。全氟调聚醇(FTOHs)在大气中的迁移和氧化并形成最终产物被认为是PFCs最终产物在全球分布的主要原因之一。全氟辛酸(PFOA)是一种重要的最终产物,而2-全氟辛基乙醇(8∶2 FTOH)是其主要的前体物。该研究基于加州理工大气化学机理(CACM)基础上开发了考虑PFCs的CACM_PFC机理,并基于CACM_PFC机理以8∶2 FTOH和N-乙基全氟正丁基磺酰胺(NEt FBSA)为主要前体物建立了箱式模型,模拟PFCs的前体物在大气中经过氧化最终转化成PFOA的一系列反应过程,分析气象因素和其他污染物对PFCs浓度变化的影响。结果表明:高温和高湿条件有利于8∶2 FTOH的转化和PFOA的生成。其他污染物如O_3能够促使PFCs向最终产物转化;NO_x对PFCs浓度的影响比较复杂,当NO_x浓度占主导时,NO_x会与CH_3O_2形成竞争抑制PFOA的生成,所以PFOA浓度较低;当CH_3O_2浓度占主导时PFOA浓度则较高。

Perfluoro compounds（PFCs）are considered to be the typical persistent organic pollutant with oleophobic and hydrophobic properties,thermo-stability and strong chemical stability.In recent years,PFCs have been widely used in industrial and civil sectors,being stable in the environment for a long time and producing toxic effects especially harmful to human health,so that have attracted worldwide concerns.It has been believed that transport and oxidation of fluorotelomer alcohols（FTOHs）generate a kind of end product,which is considered the main reason that PFCs have been widely distributed the world over.Perfluorooctanoic acid（PFOA）is an important end product,with 8∶2 FTOH beingits major precursor.In this paper,a box model was developed based on Caltech Atmospheric Chemical Mechanism（CACM）,taking into consideration the CACMPFC mechanism of PFCs’chemical reactions.The box model coupled with CACMPFC was applied to simulate PFOA formed by the oxidation of 8∶2 FTOH and NEt FBSA and the effects of meteorological fields and other pollutants on PFCs’concentration.Results of the simulation study showed that high temperature and high relative humidity were conducive to the formations of PFOA from 8∶2 FTOH;other pollutants such as O3 could promote PFCs’conversion to the end product.On the other hand,the impact on PFCs’concentration is complicated,and when NOx concentration was dominant it would compete with CH3O2 to inhibit PFOA’s accumulation,so that PFOA was low;however,when CH3O2 was the predominant constituent PFOA concentration would get high.