MDA8 O3 Values at Rural Surface Sites in Nevada, USA: Results from Two Years of the Nevada Rural Ozone Initiative (NVROI)

Friday, 19 December 2014
Mae Sexauer Gustin1, Rebekka Fine2, Matthieu B Miller2, Joel D Burley3, Daniel A Jaffe4, R. Bradley Pierce5 and Meiyun Lin6, (1)University of Nevada-Reno, Reno, NV, United States, (2)University of Nevada Reno, Natural Resources and Environmental Science, Reno, NV, United States, (3)Saint Marys College California, Walnut Creek, CA, United States, (4)University of Washington Bothell Campus, Bothell, WA, United States, (5)NOAA/NESDIS, Center for Satellite Application and Research, Madison, WI, United States, (6)Princeton University, Program in Atmospheric and Oceanic Sciences, Princeton, NJ, United States
Local anthropogenic emissions are limited in Nevada (USA); however, data collected at Great Basin National Park (GBNP), which is located in rural eastern Nevada, indicate that ozone (O3) routinely exceeds the threshold proposed for a more stringent National Ambient Air Quality Standard (NAAQS). Here, we focused on data collected between July 2011 and June 2013. For this period, the maximum daily 8-h average (MDA8) O3 at GBNP exceeded the current NAAQS threshold (75 ppb) 7 times. Our analyses indicate that a combination of sources including emissions from regional wildfires and urban areas of southern California as well as stratospheric intrusions and long-range transport of Asian pollution contributed to elevated O3 observed at GBNP. Although MDA8 O3 measured at GBNP was well correlated with that measured at 5 other rural Nevada sites during this period, MDA8 O3 was 3.1 to 12.6 ppb greater at GBNP than at these other rural sites which emphasizes the need for spatially detailed measurements particularly in areas of complex terrain. The maximum MDA8 O3 at these 6 rural NV sites ranged from 68 to 80 ppb. GBNP was the only rural site to exceed the current NAAQS threshold during the period considered; however, when lower thresholds were considered the spatial and temporal extent of exceedances in rural Nevada increased indicating that interstate and international cooperation will be necessary to reduce ambient O3 concentrations in rural Nevada. MDA8 O3 at rural Nevada sites were significantly correlated with measurements at urban Nevada (r = 0.64 to 0.82; p < 0.05) and rural California (r = 0.61 to 0.83; p = 0.00) sites suggesting that common mechanisms influence O3 observed throughout the region.