Environmental aging of polycyclic aromatic hydrocarbons on soot and its effect on source identification

• Published in: Chemosphere (Oxford) 2009-08, Vol.76 (8), p.1075-1081
• Main Authors: Kim, Daekyun, Kumfer, Benjamin M., Anastasio, Cort, Kennedy, Ian M., Young, Thomas M.
• Format: Article
• Language: English
• Subjects: Acenaphthenes - chemistry; Acenaphthenes - metabolism; Adsorption; Anthracene; Applied sciences; Carbon monoxide; Diagnostic systems; Environmental aging; Environmental Restoration and Remediation; Exact sciences and technology; Fluorenes - chemistry; Fluorenes - metabolism; Half-Life; Naphthalene; Naphthalenes - chemistry; Naphthalenes - metabolism; PAH; Phenanthrene; Pollution; Polyallylamine hydrochloride; Polycyclic Aromatic Hydrocarbons - chemistry; Polycyclic Aromatic Hydrocarbons - metabolism; Robustness; Soot; Soot - chemistry; Source apportionment; Sunlight; Time Factors; Two-phase degradation
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2009.04.031

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 3 h for naphthalene, acenaphthylene, acenaphthene, and fluorene and within 10 h 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.