PMID- 26252366
OWN - NLM
STAT- MEDLINE
DCOM- 20160201
LR  - 20151010
IS  - 1096-2247 (Print)
IS  - 1096-2247 (Linking)
VI  - 65
IP  - 10
DP  - 2015 Oct
TI  - Precursor reductions and ground-level ozone in the Continental United States.
PG  - 1261-82
LID - 10.1080/10962247.2015.1079564 [doi]
AB  - 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 (NOx) 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 NOx 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 NOx 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 NOx 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 NOx 
      sensitivity with time (NMOC/NOx ratio increase), increase in O(3)production 
      efficiency at lower NOx concentrations (higher O(3)/NOy ratio), and the presence of 
      natural NOx 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 NOx 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.
FAU - Hidy, George M
AU  - Hidy GM
AD  - a Envair/Aerochem , Placitas , NM , USA.
FAU - Blanchard, Charles L
AU  - Blanchard CL
AD  - b Envair , Albany , CA , USA.
LA  - eng
PT  - Journal Article
PL  - United States
TA  - J Air Waste Manag Assoc
JT  - Journal of the Air & Waste Management Association (1995)
JID - 9503111
RN  - 0 (Air Pollutants)
RN  - 0 (Nitrogen Oxides)
RN  - 66H7ZZK23N (Ozone)
SB  - IM
MH  - Air Pollutants/*analysis
MH  - Air Pollution/*analysis/prevention & control
MH  - Environmental Monitoring
MH  - Models, Theoretical
MH  - Nitrogen Oxides/analysis
MH  - Ozone/*analysis
MH  - United States
EDAT- 2015/08/08 06:00
MHDA- 2016/02/02 06:00
CRDT- 2015/08/08 06:00
PHST- 2015/08/08 06:00 [entrez]
PHST- 2015/08/08 06:00 [pubmed]
PHST- 2016/02/02 06:00 [medline]
AID - 10.1080/10962247.2015.1079564 [doi]
PST - ppublish
SO  - J Air Waste Manag Assoc. 2015 Oct;65(10):1261-82. doi: 
      10.1080/10962247.2015.1079564.