NMOC, ozone, and organic aerosol in the southeastern United States, 1999–2007: 1. Spatial and temporal variations of NMOC concentrations and composition in Atlanta, Georgia

Blanchard, Charles L.; Hidy, George M.; Tanenbaum, S.; Rasmussen, R. A.; Watkins, R.; Edgerton, Eric S.

doi:10.1016/j.atmosenv.2010.08.036

Cited by 31 publications

(25 citation statements)

References 20 publications

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“…Anthropogenic VOC mixing ratios have declined since 1999, but natural components such as isoprene and terpene mixing ratios have remained relatively constant ( Figure 6; Blanchard et al, 2010a;. Evidence suggests that O3 5 formation in the SEARCH region will move toward more NOx sensitive conditions with continued decreases in NOx emissions and more limited declines in anthropogenic VOC emissions, coupled with high levels of natural VOC emissions in the region.…”

Section: Future O3 Responsesmentioning

confidence: 99%

“…Annual mean isoprene mixing ratios were relatively constant, ~2.5 -3 ppbC, between 1998 and 2014. OH reactivity, computed as the product of concentration and kOH, indicates that biogenic VOCs, primarily isoprene, represent ~20% of the VOC reactivity at JST, ~30% at South Dekalb (SDK, located in metropolitan Atlanta ~16 km southeast of JST), and ~50% at YRK, averaged over all samples 15 collected between 1999 and 2007 (Blanchard et al, 2010a). Isoprene OH reactivity predominates at JST in summer but not in spring or fall (Figure 6).…”

Section: Seasonal Variations Of O3 Noy Noz Hno3 and Vocsmentioning

confidence: 99%

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Ozone Response to Emission Reductions in the Southeastern United States

Blanchard¹,

Hidy²

2017

Preprint

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Section: Future O3 Responsesmentioning

confidence: 99%

Section: Seasonal Variations Of O3 Noy Noz Hno3 and Vocsmentioning

confidence: 99%

Ozone Response to Emission Reductions in the Southeastern United States

Blanchard¹,

Hidy²

2017

Preprint

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“…All sites have measurements of meteorological parameters and gas-phase species (i.e., criteria pollutants, 24-hr ammonia [NH 3 ], commencing mid-2003 [Edgerton et al, 2007;Saylor, 2010], and nitric acid [HNO 3 ]). Nonmethane organic compound (NMOC) measurements were made by SEARCH at JST through 2008 and by U.S. EPA at YRK (Blanchard et al, 2010a). "NMOC" is used here to refer to ambient concentration measurements of lowmolecular-weight (C 2 -C 12 ), gas-phase, nonmethane organic compounds, whereas the term "volatile organic compound" (VOC) is reserved for emissions of gas-phase organic compounds as defined in U.S. EPA (1996).…”

Section: Search Network Descriptionmentioning

confidence: 99%

The Southeastern Aerosol Research and Characterization (SEARCH) study: Temporal trends in gas and PM concentrations and composition, 1999–2010

Blanchard¹,

Hidy²,

Tanenbaum³

et al. 2012

Journal of the Air & Waste Management Association

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The SEARCH study began in mid 1998 with a focus on particulate matter and gases in the southeastern United States. Eight monitoring sites, comprising four urban/nonurban pairs, are located inland and along the coast of the Gulf of Mexico. Downward trends in ambient carbon monoxide (CO), sulfur dioxide (SO 2 ), and oxidized nitrogen species (NO y ) concentrations averaged 1.2 AE 0.4 to 9.7 AE 1.8% per year from 1999 to 2010, qualitatively proportional to decreases of 4.7 to 7.9% per year in anthropogenic emissions of CO, SO 2 , and oxides of nitrogen (NO x ) in the SEARCH region. Downward trends in mean annual sulfate (SO 4 ) concentrations ranged from 3.7 AE 1.1 to 6.2 AE 1.1% per year, approximately linear with, but not 1:1 proportional to, the 7.9 AE 1.1% per year reduction in SO 2 emissions from 1999 to 2010. The 95th percentile of the March-October peak daily 8-hr ozone (O 3 ) concentrations decreased by 1.1 AE 0.4 to 2.4 AE 0.6 ppbv per year (1.5 AE 0.6 to 3.1 AE 0.8% per year); O 3 precursor emissions of NO x and volatile organic compounds (VOC) decreased at rates of 4.7 and 3.3% per year, respectively. Ambient particulate nitrate (NO 3 ) concentrations decreased by 0.6 AE 1.2 to 5.8 AE 0.9% per year, modulated in comparison with mean annual ambient NO y concentration decreases ranging from 6.0 AE 0.9 to 9.0 AE 1.3% per year. Mean annual organic matter (OM) and elemental carbon (EC) concentrations declined by 3.3 AE 0.8 to 6.5 AE 0.3 and 3.2 AE 1.4 to 7.8 AE 0.7% per year. The analysis demonstrates major improvements in air quality in the Southeast from 1999 to 2010. Meteorological variations and incompletely quantified uncertainties for emission changes create difficulty in establishing unambiguous quantitative relationships between emission reductions and ambient air quality.Implications: Emissions and secondary pollutants show complex relationships that depend on year-to-year variations in dispersion and atmospheric chemistry. The observed response of O 3 to NO x and VOC emissions in the Southeast implies that continuing reductions of precursor emissions, probably achieved through vehicle fleet turnover and emission control measures, will be needed to attain the National Ambient Air Quality Standard for O 3 . Reductions in fine particle concentrations have resulted from reductions of primary PM, especially EC and a portion of OM, and from reduction of gas precursors known to form particles, especially SO 4 from SO 2 . Continued reduction of PM 2.5 mass concentrations will require attention to organic constituents, which may be complicated by potentially unmanageable biogenic species present in the Southeast.

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“…Rather than repeat the surveys of O 3 trends per se, we contribute to improving the understanding of O 3 trends in the continental United States by addressing the relationships between VOC and NO x emissions and ambient NMOC and NO 2 concentrations relative to O 3 changes. Currently there exist a limited number of concurrent sets of NO x and VOC emissions and both ambient precursor and O 3 data to make comparisons of trends at specific locations (e.g., Blanchard et al, 2010aBlanchard et al, , 2010bBlanchard et al, , 2014a. Although there are a large number of sites for O 3 measurement in the United States, the locations for measurement of NO x or NO y , total reactive nitrogen concentrations, are sparser; trend data for ambient NMOC are largely confined to the photochemical assessment measuring stations (PAMS) network comprising only 24 sites (Table S1).…”

Section: Introductionmentioning

confidence: 99%

Precursor reductions and ground-level ozone in the Continental United States

Hidy¹,

Blanchard²

2015

Journal of the Air & Waste Management Association

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Numerous papers analyze ground-level ozone (O 3 ) trends since the 1980s, but few have linked O 3 trends with observed changes in nitrogen oxide (NO x ) and volatile organic compound (VOC) emissions and ambient concentrations. This analysis of emissions and ambient measurements examines this linkage across the United States on multiple spatial scales from continental to urban. O 3 concentrations follow the general decreases in both NO x and VOC emissions and ambient concentrations of precursors (nitrogen dioxide, NO 2 ; nonmethane organic compounds, NMOCs). Annual fourth-highest daily peak 8-hr average ozone and annual average or 98th percentile daily maximum hourly NO 2 concentrations show a statistically significant (p < 0.05) linear fit whose slope is less than 1:1 and intercept is in the 30 to >50 ppbv range. This empirical relationship is consistent with current understanding of O 3 photochemistry. The linear O 3 -NO 2 relationships found from our multispatial scale analysis can be used to extrapolate the rate of change of O 3 with projected NO x emission reductions, which suggests that future declines in annual fourth-highest daily average 8-hr maximum O 3 concentrations are unlikely to reach 65 ppbv or lower everywhere in the next decade. Measurements do not indicate increased annual reduction rates in (high) O 3 concentrations beyond the multidecadal precursor proportionality, since aggressive measures for NO x and VOC reduction are in place and have not produced an accelerated O 3 reduction rate beyond that prior to the mid-2000s. Empirically estimated changes in O 3 with emissions suggest that O 3 is less sensitive to precursor reductions than is found by the CAMx (v. 6.1) photochemical model. Options for increasing the rate of O 3 change are limited by photochemical factors, including the increase in NO x sensitivity with time (NMOC/NO x ratio increase), increase in O 3 production efficiency at lower NO x concentrations (higher O 3 /NO y ratio), and the presence of natural NO x and NMOC precursors and background O 3 .Implications: This analysis demonstrates empirical relations between O 3 and precursors based on long term trends in U.S. locations. The results indicate that ground-level O 3 concentrations have responded predictably to reductions in VOC and NO x since the 1980s. The analysis reveals linear relations between the highest O 3 and NO 2 concentrations. Extrapolation of the historic trends to the future with expected continued precursor reductions suggest that achieving the 2014 proposed reduction in the U.S. National Ambient Air Quality Standard to a level between 65 and 70 ppbv is unlikely within the next decade. Comparison of measurements with national results from a regulatory photochemical model, CAMx, v. 6.1, suggests that model predictions are more sensitive to emissions changes than the observations would support.

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NMOC, ozone, and organic aerosol in the southeastern United States, 1999–2007: 1. Spatial and temporal variations of NMOC concentrations and composition in Atlanta, Georgia

Cited by 31 publications

References 20 publications

Ozone Response to Emission Reductions in the Southeastern United States

Ozone Response to Emission Reductions in the Southeastern United States

The Southeastern Aerosol Research and Characterization (SEARCH) study: Temporal trends in gas and PM concentrations and composition, 1999–2010

Precursor reductions and ground-level ozone in the Continental United States

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