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:11/19/2016)... Securus Technologies, a leading provider of civil and criminal ... monitoring, announced today that it has offered a challenge ... technology judge determine who has the largest and best ... platform, and the best customer service. "ICSolutions ... we do – which clearly is not the case ...
(Date:11/15/2016)... 2016  Synthetic Biologics, Inc. (NYSE MKT: SYN), ... the gut microbiome, today announced the pricing of ... its common stock and warrants to purchase 50,000,000 ... to the public of $1.00 per share and ... the offering, excluding the proceeds, if any from ...
(Date:6/27/2016)... , June 27, 2016 Research and Markets ... America 2016-2020" report to their offering. ... North America to grow at a CAGR of 12.28% ... prepared based on an in-depth market analysis with inputs from industry ... over the coming years. The report also includes a discussion of ...
Breaking Biology News(10 mins):
(Date:11/30/2016)... 30, 2016  GenomOncology today announced the appointment of ... Affairs.  Dr. Coleman will oversee clinical content ... knowledge-enabled platform. The GenomOncology software suite empowers molecular pathologists with ... and clinical decision support, from quality control through reporting. ... , , ...
(Date:11/30/2016)... 2016  The Allen Institute for Cell Science ... publicly available collection of gene edited, fluorescently tagged ... cellular structures with unprecedented clarity. Distributed through the ... are a crucial first step toward visualizing the ... makes human cells healthy and what goes wrong ...
(Date:11/30/2016)... BILLERICA, Massachusetts , 30. November 2016 ... und Technologieunternehmen, hat heute die Unterzeichnung einer ... gegeben. Diesen zufolge wird Evotec AG Screeningleistungen ... und shRNA-Bibliotheken bereitstellen. Der Zugriff auf diese ... Bereich Screening eröffnet einen schnelleren Weg zur ...
(Date:11/30/2016)... , ... November 30, 2016 , ... ... for advanced technology applications, introduces the 5th generation, ultra-bright, Laser-Driven Light Source, the ... Laser-Driven Light Source (LDLS™) technology, the EQ-77 offers higher radiance and irradiance from ...
Breaking Biology Technology: