大气颗粒物表面液态水中典型多环芳烃光解的模拟研究

Photolysis of selected polycyclic aromatic hydrocarbons in simulated particles liquid water

大气颗粒物在老化过程中表面液态水含量与组成发生改变,导致液态水中多环芳烃(PAHs)的光解行为也会相应改变,影响其大气寿命。构建大气颗粒物不同液态水环境,对3种典型PAHs(蒽(Ant)、菲(Phe)和芘(Pyr))在液态水环境中的光解行为进行研究。结果表明,纯水体系中的光解速率为Ant>Phe>Pyr,酸度增大有助于Pyr光解;酸化条件下增加Fe^(3+)浓度能够促进PAHs的光解,但草酸对3种PAHs光解的影响并不一致,导致草酸-铁混合体系对PAHs光解的促进作用出现差异。与纯水体系相比,PAHs在大气细颗粒物(PM_(2.5))水提取液体系中的光解受到抑制,但水溶性有机碳(WSOC)质量浓度较高(1 mg/L)时能促进Pyr的光解;大气PM_(2.5)水提取液中添加Fe^(3+)产生的光解促进作用弱于纯水体系。不同液态水环境中Phe的主要光解产物均为9,10-菲醌,大气PM_(2.5)水提取液中9,10-菲醌的寿命最长。

The particles surface liquid water content and chemical compositions varied with the aging degree of atmospheric particles.As a result,the photolysis behavior of polycyclic aromatic hydrocarbons(PAHs)in particles liquid water would change and then affect the atmospheric lifetime of PAHs.In this study,PAHs including anthracene(Ant),phenanthrene(Phe)and pyrene(Pyr)were selected to study their photolysis kinetics in various simulated liquid water.The results showed that the photolysis rates were as follows:Ant>Phe>Pyr in pure aqueous solution,and the increase of acidity was benefit to Pyr photolysis.Addition of Fe^(3+)could accelerate the PAHs photolysis in acidified aqueous solution.However,the effect of oxalate addition varied with the type of PAHs,leading to the photolysis differences of PAHs in the mixture of oxalate and Fe^(3+)solution.The photolysis of PAHs in the water extracts of atmospheric fine particles(PM_(2.5))was inhibited in comparison with those in pure aqueous solution,but the photolysis of Pyr was accelerated when the water soluble organic(WSOC)mass concentration exceeded 1 mg/L.In comparison with the pure aqueous solution with Fe^(3+),the effects of Fe^(3+)addition into atmospheric PM_(2.5)water extracts on the photolysis of PAHs were relatively weak.The major photolysis product of Phe was 9,10-phenanthraquinone in different liquid water systems,and 9,10-phenanthraquinone was found to have the longest lifetime in atmospheric PM_(2.5)water extracts.