Science of the Total Environment 530–531 (2015) 453–454
Contents lists available at ScienceDirect
Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv
The Nevada Rural Ozone Initiative: A framework for developing an understanding of factors contributing to elevated ozone concentrations in rural and remote environments
Health impacts associated with air pollution are one of the most critical environmental issues we face today. The World Health Organization estimates that one in eight deaths worldwide in 2012 could be attributed to elevated levels of ambient and indoor pollutants (WHO, 2014). While much of this impact is due to particulate matter (PM), ozone also is a significant contributor to the negative consequence. Reducing ozone concentrations is a complex problem since it is a secondary pollutant that is not directly emitted from sources, but rather is formed by chemical reactions in the atmosphere. Hence, in order to improve air quality, there is a critical need to develop a better understanding of the factors leading to elevated concentrations of ozone in the atmosphere. The U.S. National Ambient Air Quality Standard (NAAQS) for ozone is currently 75 ppbv, and the proposed lowered NAAQS ozone standard will be between 60 and 70 ppbv—to be implemented October 1, 2015. Previous studies indicate that remote/rural locations likely would be out of compliance with the new standard. However, in rural/remote locations – such as those common in the State of Nevada, US, – anthropogenic emissions are limited, thus baseline concentrations (or those measured in areas remote from sources) of ozone are an important contributor to the observed elevated values. Because of the rural nature, high elevation, and complex terrain of the State measurements made at appropriate locations in Nevada were hypothesized to be representative of baseline ozone concentrations for the continental U.S. and understanding these would enhance our knowledge of the factors leading to elevated ozone in other similar regions. This special section contains seven papers focused on improving our understanding of the sources of ozone, with particular emphasis on the Western US Ozone, aerosol, and other trace gas measurements were made at 13 locations in Nevada as part of the Nevada Rural Ozone Initiative (NVROI) initiated in 2011, and funded by the Nevada Division of Environmental Protection. Results obtained through this research provide valuable insight into ozone pollution in rural areas and are important for developing policies to protect human and ecosystem health in the Western U.S. and other regions around the world. The first paper by Gustin et al., “The Nevada Rural Ozone Initiative (NVROI): Insights to Understanding Air Pollution in Complex Terrain,” lays the foundation for the other papers. It provides an overview of the project, includes sampling locations, and compares concentrations measured during the first year of the project with those measured at upwind locations in California. This paper provides insight into understanding meteorology in complex terrain and demonstrates how sampling location affects observations. An important conclusion is that measured concentrations are regularly above the threshold reported
http://dx.doi.org/10.1016/j.scitotenv.2015.05.071 0048-9697/© 2015 Elsevier B.V. All rights reserved.
for causing a reduction in growth or yield, or visible injury for plants (40 ppbv), and sustained exposure at high elevation locations in the western U.S. may be detrimental for ecosystems. The second paper by Fine et al., “Variability and sources of surface ozone at rural sites in Nevada, USA: Results from two years of the Nevada Rural Ozone Initiative,” demonstrates how the Great Basin National Park (GBNP) located in eastern Nevada is out of compliance with the current Maximum Daily 8-h Average (MDA8) NAAQS. This analysis demonstrates that GBNP is an excellent sentinel site, ideally positioned to intercept pollution from regional and global sources. For the two-year period considered, MDA8 ozone at GBNP was an average of 3.1 to 12.6 ppbv higher than at other rural sites. This finding indicates that interstate and international cooperation may be necessary to meet a more stringent ozone NAAQS as hemispheric background concentrations increase. The paper, “Identifying sources of ozone to three rural locations in Nevada, USA, using ancillary gas pollutants, aerosol chemistry, and mercury,” by Miller et al. describes ozone, carbon dioxide, nitrogen oxides, mercury, and particulate matter concentrations measured at three sites. Events were chosen for periods during which mean daily ozone exceeded the 90th percentile concurrently with an MDA8 ozone concentration that was both unusually large for the site and of potential regulatory significance. The overall correlation between ozone and other pollutants at these remote sites was generally poor, consistent with their great distance from any significant primary emission sources. This work also demonstrates that background carbon monoxide concentrations are increasing and ozone exceedances of the revised NAAQS in Nevada will need to be addressed in conjunction with regulatory bodies outside of the State. The manuscript, “Investigating the influence of long-range transport on surface O3 in Nevada, USA using observations from multiple measurement platforms,” by Fine et al. reports on data collected in Nevada and on board the NASA Ames Alpha Jet Atmospheric eXperiment (AJAX) that began making routine aircraft measurements of ozone and other greenhouse gases over Nevada in 2011. The availability of aircraft and surface measurements in a relatively rural, remote setting in the Intermountain West presented a unique opportunity to investigate sources contributing to the O3 observed in Nevada. The analyses indicated that stratosphere-to-troposphere transport, long-range transport of Asian pollution, and regional emissions from urban areas and wildfires influenced surface observations. “Identification of sources contributing to PM2.5 and ozone at elevated sites in the western U.S. by receptor analysis: Lassen Volcanic National
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A. Gertler, J. Bennett / Science of the Total Environment 530–531 (2015) 453–454
Park, California, and Great Basin National Park, Nevada” by VanCuren and Gustin reports on the use of ozone and PM2.5 composition at Great Basin and Lassen National Parks to assess sources of these pollutants. Positive matrix factorization and neural net regression were used to link aerosol chemistry and ozone. Combustion-derived secondary sulfate was a major contributor to particle mass, along with biomass burning and Asian dust. “Unraveling the sources of ground level ozone in the Intermountain Western United States using Pb isotopes” by Christensen et al. combined back-trajectory analysis coupled with Pb isotopic measurements of aerosols to distinguish the observed sources of ozone. Regional sources (Los Angeles/Las Vegas) are currently the most significant contributors of surface ozone at Great Basin National Park. Data analyses demonstrate, however, that ozone from Asia (China) significantly increased during the period of the study at such a rate that this source will exceed the contribution from Los Angeles/Las Vegas in the next decade. The final paper by Fine et al., “Development of a statistical model to identify spatial and meteorological drivers of elevated O3 in Nevada and its application to other rural mountainous regions,” used three years of data measured at sites throughout rural Nevada to develop a readily comprehensible Categorical and Regression Tree (CART) model to identify spatial and meteorological characteristics that led to elevated baseline O3. The results indicate that transport, rather than local production, influenced observed O3 concentrations and that high elevation sites in
rural Nevada are representative of baseline conditions in the Intermountain Western US. Overall, the papers contained in this Special Section of Science and the Total Environment present a comprehensive approach to monitoring and assessing the factors contributing to elevated ozone concentrations in rural/remote regions. The detailed measurement, modeling, and analysis techniques presented in these seven papers can serve as useful tools to develop reduction strategies that are needed to protect ecosystem and human health in the Western US and other regions around the world. References World Health Organization, 2014. 7 million premature deaths annually linked to air pollution. http://www.who.int/mediacentre/news/releases/2014/air-pollution/en/ (25 March).
Alan Gertler Guest Editor James Bennett Overseeing Editor
Contents lists available at ScienceDirect
Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv
The Nevada Rural Ozone Initiative: A framework for developing an understanding of factors contributing to elevated ozone concentrations in rural and remote environments
Health impacts associated with air pollution are one of the most critical environmental issues we face today. The World Health Organization estimates that one in eight deaths worldwide in 2012 could be attributed to elevated levels of ambient and indoor pollutants (WHO, 2014). While much of this impact is due to particulate matter (PM), ozone also is a significant contributor to the negative consequence. Reducing ozone concentrations is a complex problem since it is a secondary pollutant that is not directly emitted from sources, but rather is formed by chemical reactions in the atmosphere. Hence, in order to improve air quality, there is a critical need to develop a better understanding of the factors leading to elevated concentrations of ozone in the atmosphere. The U.S. National Ambient Air Quality Standard (NAAQS) for ozone is currently 75 ppbv, and the proposed lowered NAAQS ozone standard will be between 60 and 70 ppbv—to be implemented October 1, 2015. Previous studies indicate that remote/rural locations likely would be out of compliance with the new standard. However, in rural/remote locations – such as those common in the State of Nevada, US, – anthropogenic emissions are limited, thus baseline concentrations (or those measured in areas remote from sources) of ozone are an important contributor to the observed elevated values. Because of the rural nature, high elevation, and complex terrain of the State measurements made at appropriate locations in Nevada were hypothesized to be representative of baseline ozone concentrations for the continental U.S. and understanding these would enhance our knowledge of the factors leading to elevated ozone in other similar regions. This special section contains seven papers focused on improving our understanding of the sources of ozone, with particular emphasis on the Western US Ozone, aerosol, and other trace gas measurements were made at 13 locations in Nevada as part of the Nevada Rural Ozone Initiative (NVROI) initiated in 2011, and funded by the Nevada Division of Environmental Protection. Results obtained through this research provide valuable insight into ozone pollution in rural areas and are important for developing policies to protect human and ecosystem health in the Western U.S. and other regions around the world. The first paper by Gustin et al., “The Nevada Rural Ozone Initiative (NVROI): Insights to Understanding Air Pollution in Complex Terrain,” lays the foundation for the other papers. It provides an overview of the project, includes sampling locations, and compares concentrations measured during the first year of the project with those measured at upwind locations in California. This paper provides insight into understanding meteorology in complex terrain and demonstrates how sampling location affects observations. An important conclusion is that measured concentrations are regularly above the threshold reported
http://dx.doi.org/10.1016/j.scitotenv.2015.05.071 0048-9697/© 2015 Elsevier B.V. All rights reserved.
for causing a reduction in growth or yield, or visible injury for plants (40 ppbv), and sustained exposure at high elevation locations in the western U.S. may be detrimental for ecosystems. The second paper by Fine et al., “Variability and sources of surface ozone at rural sites in Nevada, USA: Results from two years of the Nevada Rural Ozone Initiative,” demonstrates how the Great Basin National Park (GBNP) located in eastern Nevada is out of compliance with the current Maximum Daily 8-h Average (MDA8) NAAQS. This analysis demonstrates that GBNP is an excellent sentinel site, ideally positioned to intercept pollution from regional and global sources. For the two-year period considered, MDA8 ozone at GBNP was an average of 3.1 to 12.6 ppbv higher than at other rural sites. This finding indicates that interstate and international cooperation may be necessary to meet a more stringent ozone NAAQS as hemispheric background concentrations increase. The paper, “Identifying sources of ozone to three rural locations in Nevada, USA, using ancillary gas pollutants, aerosol chemistry, and mercury,” by Miller et al. describes ozone, carbon dioxide, nitrogen oxides, mercury, and particulate matter concentrations measured at three sites. Events were chosen for periods during which mean daily ozone exceeded the 90th percentile concurrently with an MDA8 ozone concentration that was both unusually large for the site and of potential regulatory significance. The overall correlation between ozone and other pollutants at these remote sites was generally poor, consistent with their great distance from any significant primary emission sources. This work also demonstrates that background carbon monoxide concentrations are increasing and ozone exceedances of the revised NAAQS in Nevada will need to be addressed in conjunction with regulatory bodies outside of the State. The manuscript, “Investigating the influence of long-range transport on surface O3 in Nevada, USA using observations from multiple measurement platforms,” by Fine et al. reports on data collected in Nevada and on board the NASA Ames Alpha Jet Atmospheric eXperiment (AJAX) that began making routine aircraft measurements of ozone and other greenhouse gases over Nevada in 2011. The availability of aircraft and surface measurements in a relatively rural, remote setting in the Intermountain West presented a unique opportunity to investigate sources contributing to the O3 observed in Nevada. The analyses indicated that stratosphere-to-troposphere transport, long-range transport of Asian pollution, and regional emissions from urban areas and wildfires influenced surface observations. “Identification of sources contributing to PM2.5 and ozone at elevated sites in the western U.S. by receptor analysis: Lassen Volcanic National
454
A. Gertler, J. Bennett / Science of the Total Environment 530–531 (2015) 453–454
Park, California, and Great Basin National Park, Nevada” by VanCuren and Gustin reports on the use of ozone and PM2.5 composition at Great Basin and Lassen National Parks to assess sources of these pollutants. Positive matrix factorization and neural net regression were used to link aerosol chemistry and ozone. Combustion-derived secondary sulfate was a major contributor to particle mass, along with biomass burning and Asian dust. “Unraveling the sources of ground level ozone in the Intermountain Western United States using Pb isotopes” by Christensen et al. combined back-trajectory analysis coupled with Pb isotopic measurements of aerosols to distinguish the observed sources of ozone. Regional sources (Los Angeles/Las Vegas) are currently the most significant contributors of surface ozone at Great Basin National Park. Data analyses demonstrate, however, that ozone from Asia (China) significantly increased during the period of the study at such a rate that this source will exceed the contribution from Los Angeles/Las Vegas in the next decade. The final paper by Fine et al., “Development of a statistical model to identify spatial and meteorological drivers of elevated O3 in Nevada and its application to other rural mountainous regions,” used three years of data measured at sites throughout rural Nevada to develop a readily comprehensible Categorical and Regression Tree (CART) model to identify spatial and meteorological characteristics that led to elevated baseline O3. The results indicate that transport, rather than local production, influenced observed O3 concentrations and that high elevation sites in
rural Nevada are representative of baseline conditions in the Intermountain Western US. Overall, the papers contained in this Special Section of Science and the Total Environment present a comprehensive approach to monitoring and assessing the factors contributing to elevated ozone concentrations in rural/remote regions. The detailed measurement, modeling, and analysis techniques presented in these seven papers can serve as useful tools to develop reduction strategies that are needed to protect ecosystem and human health in the Western US and other regions around the world. References World Health Organization, 2014. 7 million premature deaths annually linked to air pollution. http://www.who.int/mediacentre/news/releases/2014/air-pollution/en/ (25 March).
Alan Gertler Guest Editor James Bennett Overseeing Editor
