Identifying sources of ozone to three rural locations in Nevada, USA, using ancillary gas pollutants, aerosol chemistry, and mercury

• Published in: The Science of the total environment 2015-10, Vol.530-531 (C), p.483-492
• Main Authors: Miller, Matthieu B., Fine, Rebekka, Pierce, Ashley M., Gustin, Mae S.
• Format: Article
• Language: English
• Subjects: Aerosols - analysis; Air Pollutants - analysis; Air Pollution - statistics & numerical data; Criteria air pollutants; Environmental Monitoring; Long-range transport; Mercury - analysis; National Ambient Air Quality Standards; Nevada; Ozone - analysis; Particulate Matter - analysis; Wildfire emissions
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2015.03.146

Ozone (O3) is a secondary air pollutant of long standing and increasing concern for environmental and human health, and as such, the US Environmental Protection Agency will revise the National Ambient Air Quality Standard of 75ppbv to ≤70ppbv. Long term measurements at the Great Basin National Park (GBNP) indicate that O3 in remote areas of Nevada will exceed a revised standard. As part of the Nevada Rural Ozone Initiative, measurements of O3 and other air pollutants were made at 3 remote sites between February 2012 and March 2014, GBNP, Paradise Valley (PAVA), and Echo Peak (ECHO). Exceptionally high concentrations of each air pollutant were defined relative to each site as mixing ratios that exceeded the 90th percentile of all hourly data. Case studies were analyzed for all periods during which mean daily O3 exceeded the 90th percentile concurrently with a maximum 8-h average (MDA8) O3 that was “exceptionally high” for the site (65ppbv at PAVA, 70ppbv at ECHO and GBNP), and of potential regulatory significance. An MDA8≥65ppbv occurred only five times at PAVA, whereas this occurred on 49 and 65days at GBNP and ECHO, respectively. The overall correlation between O3 and other pollutants was poor, consistent with the large distance from significant primary emission sources. Mean CO at these locations exceeded concentrations reported for background sites in 2000. Trajectory residence time calculations and air pollutant concentrations indicate that exceedances at GBNP and ECHO were promoted by air masses originating from multiple sources, including wildfires, transport of pollution from southern California and the marine boundary layer, and transport of Asian pollution plumes. Results indicate that the State of Nevada will exceed a revised O3 standard due to sources that are beyond their control. •Air pollutant indicators allow identification of O3 sources to remote locations.•Ozone and other pollutants are only correlated during discreet pollution events.•Exceptionally high O3 events are caused by multiple sources.•Nevada will exceed a revised O3 standard due to external sources.