Atmospheric distribution of gas- and particle-phase quinones in Southern California

Quinones are reactive organic compounds known to initiate reactions associated with a host of toxicological events. Their presence in different atmospheres has been demonstrated although their sources remain uncertain. As a result of their reactivity and instability during chemical analysis, only a limited number of studies have reported on atmospheric concentrations of quinones in ambient air. Furthermore, besides the limited information on quinones associated with particulate matter, no previous studies have quantified vapor-phase quinones. We report vapor- and particle-phase concentrations of 1,2- and 1,4-naphthoquinones (1,2-NQ, 1,4-NQ), 9,10-phenanthraquinone (9,10-PQ), and 9,10-anthraquinone (9,10-AQ), measured over a 5-year period in Southern California. The results showed that vapor-phase concentrations of the target quinones were in general higher than those in the particle-phase. Vapor-phase concentrations ranged from 80 pg/m3 for the AQ to 1747 pg/m3 for the 1,4-NQ, and the particle-phase concentrations between 13 pg/m3 for the 1,2-NQ and 250 pg/m3 for 9,10-AQ. The target quinones were found to be distributed between vapor- and particle-phase, with the exception of 9,10-PQ found only in the particle-phase. The differences observed in the concentrations among sites and seasons suggest different source contributions; source sites were dominated by primary sources, while downwind locations showed a high contribution from photochemical activity.