Kim Daekyun, Kumfer Benjamin M, Anastasio Cort, Kennedy Ian M, Young Thomas M
University of California, Davis, 95616, USA.
Chemosphere. 2009 Aug;76(8):1075-81. doi: 10.1016/j.chemosphere.2009.04.031. Epub 2009 May 13.
Soot-associated PAHs were exposed to simulated sunlight to investigate disappearance rates under environmental aging conditions and to examine the robustness of diagnostic ratios for PAH source apportionment. Naphthalene, acenaphthylene, acenaphthene, and fluorene showed an obvious two-phase disappearance in all experiments while phenanthrene and anthracene exhibited this behavior for all but the highest soot loading. The first phase loss is 5-40 times faster than the second phase loss and occurred within 3h for naphthalene, acenaphthylene, acenaphthene, and fluorene and within 10h for phenanthrene and anthracene. Two-phase disappearance was not observed for any of the higher molecular weight PAHs with 4-6 rings. Each PAH has a unique loss rate via photodegradation and volatilization and these rates of some PAHs were affected by soot loadings; phenanthrene and anthracene showed similar rates in the first phase and increased loss rates in the second phase as soot loading increased. In the absence of light, the loss of PAHs was related to both temperature and molecular characteristics. Due to differences in disappearance rates of individual PAHs under illumination over extended times, prolonged exposure to sunlight could change the interpretation of some diagnostic ratios used previously for PAH source identification. This result indicates that more consistent and accurate methods that take into consideration the longevity of particulate PAHs are needed for reliable source apportionment.
将与煤烟相关的多环芳烃暴露于模拟阳光下，以研究环境老化条件下的消失速率，并检验用于多环芳烃源分配的诊断比值的稳健性。在所有实验中，萘、苊烯、苊和芴均呈现出明显的两阶段消失现象，而菲和蒽除了在最高煤烟负载量时外，在所有实验中也表现出这种行为。第一阶段的损失比第二阶段的损失快5至40倍，萘、苊烯、苊和芴在3小时内发生，菲和蒽在10小时内发生。对于任何具有4至6个环的较高分子量多环芳烃，均未观察到两阶段消失现象。每种多环芳烃通过光降解和挥发都有独特的损失率，其中一些多环芳烃的这些速率受煤烟负载量的影响；菲和蒽在第一阶段显示出相似的速率，并且随着煤烟负载量的增加，在第二阶段损失率增加。在无光条件下，多环芳烃的损失与温度和分子特性都有关。由于在长时间光照下各个多环芳烃消失速率的差异，长时间暴露于阳光下可能会改变先前用于多环芳烃源识别的一些诊断比值的解释。这一结果表明，为了进行可靠的源分配，需要更一致、准确的方法来考虑颗粒态多环芳烃的持久性。
