- The relative influences of trans-Pacific and regional atmospheric transport on measured concentrations of polycyclic aromatic hydrocarbons (PAHs), PAH derivatives [Nitro- (NPAH) and Oxy-(OPAH)], organic carbon (OC), and Particulate Matter (PM) less than 2.5 μm in diameter (PM₂.₅) were investigated in the Pacific Northwest, USA in 2010-2011. Ambient high volume PM₂.₅ air samples were collected at two sites in the Pacific Northwest: 1.) Mount Bachelor Observatory (MBO) in the Oregon Cascade Range (2763 m above sea level (asl)) and 2.) Confederated Tribes of the Umatilla Indian Reservation (CTUIR) in the Columbia River Gorge (CRG) (954 m asl). Nine trans-Pacific transport events (7 in 2010 and 2 in 2011) were identified at MBO and three of these days had direct acting mutagenicity greater than the negative control. 2-MNAP, 1-MNAP, 2,6-DMNAP, 1,3-DMNAP, 2-MPHE, 1-MPHE, NAP, ACY, ACE, CHR+TRI, and BenzANT, were identified as potential molecular markers for regional transport at MBO. While RET, BghiP, 9-NPH, 3,NPH, 1-NP, 1,8-DNP, and BcdPYRO were identified as potential molecular markers for trans-Pacific transport at MBO. At CTUIR, NOx, CO₂, and SO₂ emissions from a 585 MW coal fired power plant, in Boardman OR,
were found to be significantly positively correlated with PAH, OPAH, NPAH, OC, and PM₂.₅ concentrations. By comparing the Boardman Plant operational time frames when the plant was operating to when it was shut down, the plant was found to contribute a large percentage of the measured PAH (67%), NPAH (91%), OPAH (54%), PM₂.₅ (39%) and OC (38%) concentrations at CTUIR and the CRG prior to Spring 2011 and likely masked trans-Pacific atmospheric transport events to the CRG. Upgrades installed to the Boardman Plant in the spring of 2011 dramatically reduced the plant’s contribution to PAH and OPAH concentrations (by ~72% and ~40%, respectively) at CTUIR and the CRG but not NPAH, PM₂.₅ or OC concentrations. Sixteen days in 2010, and only one day in 2011, had direct acting mutagenicity greater than the negative control at CTUIR.