Navigation Links
Ground-level ozone falling faster than model predicted
Date:3/11/2013

There is good news and better news about ground-level ozone in American cities. While dangerous ozone levels have fallen in places that clamp down on emissions from vehicles and industry, a new study from Rice University suggests that a model widely used to predict the impact of remediation efforts has been too conservative.

Particularly in Northeastern cities, ozone levels dropped even beyond what was anticipated by cutting emissions of nitrogen oxides (NOx) from 2002 to 2006. The study published online by the journal Atmospheric Environment suggests the Community Multiscale Air Quality (CMAQ) model misjudged the reduction in ozone by 20 to 60 percent.

"The models have been underpredicting how much benefit we get from controlling NOx emissions in some instances," said Daniel Cohan, an assistant professor of civil and environmental engineering and an author of the study with Rice graduate student Wei Zhou and Sergey Napelenok, a scientist in the Environmental Protection Agency's Atmospheric Modeling and Analysis Division.

"Following major controls of NOx, ozone has come down more quickly than anticipated," Cohan said. "This is good news. But it also poses a challenge because states rely upon models to predict whether they'll attain ozone standards in the future. If the models have key uncertainties that affect their responsiveness, that can affect the states' control strategies."

Ozone is not emitted directly but instead forms near the ground from precursor emissions of NOx and hydrocarbons. Modeling of this complex chemistry is important to help states comply with federal standards for ozone, which now stand at 75 parts per billion (ppb) and may be tightened by the Obama administration. A recent Rice study showed a positive correlation between high ozone levels and cardiac arrest.

In 2002, the EPA implemented a cap-and-trade program known as the NOx SIP Call to curtail emissions of ozone-forming NOx from industries in Eastern states. The dramatic reduction in emissions over the subsequent four years provided a real-world experiment for the researchers to test how well computer models predict improvements in air quality.

"We found that even when we tried to model things with the best available emissions and the best available meteorology, we still had a gap, especially in the Northeast states, that couldn't be explained," he said.

In the SIP Call regions, the researchers found the simulated drop in ozone was 4.6 ppb, while the observed drop was 8 ppb, a significant difference. Faster-than-expected reductions in NOx emissions may explain some but not all of that gap. The remaining gap may result from inaccuracies in how the model represents the chemistry and transport of air pollutants, Cohan said.

"How ozone responds to changes in NOx and hydrocarbons is a nonlinear chemistry," Cohan said. "So it's certainly possible that even the best models could be slightly inaccurate in defining those relationships. It tells us that, as modelers, we need to revisit the formulations, especially the chemistry."

While it may be preferable for models to be a bit conservative rather than too aggressive in predicting ozone improvements, Cohan said, the models are intended to represent air pollution as accurately as possible. A study by Cohan's research group last year showed that regulatory modeling by states tended to slightly under-predict the ozone reductions that were actually achieved.

"The goal of everyone in the process is to reach attainment in the most cost-effective manner possible, and we need accurate models to inform those decisions," Cohan said.


'/>"/>
Contact: David Ruth
david@rice.edu
713-348-6327
Rice University
Source:Eurekalert

Related biology news :

1. Ozone treated water v. lethal microbial material
2. Houston Clean Air Network offering real-time online ozone report
3. Ozones impact on soybean yield: Reducing future losses
4. University of Illinois receives grant to study ozone resistance in corn
5. Ozone levels have sizeable impact on worker productivity
6. 2 climate scientists win 2012 Vetlesen Prize for work on ozone hole, ice cores
7. Oceans acidifying faster today than in past 300 million years
8. From scourge to saint: E. coli bacteria becomes a factory - to make cheaper, faster pharmaceuticals
9. Tiny electrical sensors could signal faster MRSA diagnosis
10. Athletic frogs have faster-changing genomes
11. What does a tree growing faster than its neighbor look like from outer space?
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:2/3/2016)... -- Vigilant Solutions announces today that the ... solved two recent hit-and-run cases with the ... Solutions. Brian Wenberg explains, "I was ... out of a convenience store and witnessed an elderly male back out ... his vehicle and leaving the scene.  In his statement ...
(Date:2/2/2016)... , Feb. 2, 2016 Checkpoint ... that Rising Market Are you interested in ... forecasts revenues for checkpoint inhibitors. Visiongain,s report gives ... submarket, product and national level. Avoid falling ... what progress, opportunities and revenues those emerging cancer ...
(Date:2/1/2016)... -- Rising sales of consumer electronics coupled ... gesture control market size through ... electronics coupled with new technological advancements to drive global ... through 2020   --> Rising ... to drive global touchfree intuitive gesture control market ...
Breaking Biology News(10 mins):
(Date:2/9/2016)... , Feb. 9, 2016 This market ... the current and future prospects of the market in ... report include companies engaged in the manufacture of microbiology ... executive summary with a market snapshot providing the overall ... of this report. This section also provides the overall ...
(Date:2/9/2016)... , February 9, 2016 Three-Year ... Enables Children to Take Part in Life-Changing Camp ... new initiative designed to positively affect the lives of children born ... care. --> SHPG ) is announcing a new initiative ... diseases, as well as the future of rare disease care. ...
(Date:2/9/2016)... LONDON , Feb. 9, 2016 /PRNewswire/ ... (PTP1B) Inhibitors-Pipeline Insights, 2016", report provides in ... their development activities around the Protein-Tyrosine Phosphatase ... the product profiles in various stages of ... Phase II, Phase III and Preregistration. Report ...
(Date:2/8/2016)... 2016 Should antibiotic bone cement products be ... prevent infection after standard total hip or knee replacement ... Institute have been fielding a lot lately. ... Line?" --> "Antibiotic Bone Cement: ... --> While there isn,t a simple answer, ...
Breaking Biology Technology: