The Effects of Atmospheric Chemistry on Projected Ozone Concentrations in Response Emission Control Strategies in the South Coast Air Basin

Los Angeles's South Coast Air Basin (SoCAB) continues to experience ozone concentrations that exceed the National Ambient Air Quality Standards (NAAQS). Future control strategies include reductions in the emissions of nitrogen oxides (NOx) and volatile organic compounds (VOC) either separately or together. Air quality simulations were made with the Regional Atmospheric Chemistry Mechanism, version 2 (RACM2) in a chemical box model. These box model simulations are used to evaluate changes in the ozone concentrations in response to varying reductions of NOx and VOC. The modeling shows that ozone formation was VOC limited in the SoCAB for the base year 2008. Simulations made for the future year in 2030 predict a 10-20% higher peak ozone levels in the western and central basin compared to the 2008 base simulation. The simulations show that reductions in VOC or NOx emissions alone will not be the most effective ozone control strategy. Rather, reductions in both VOC and NOx emissions that retain low VOC to NOx ratios are more likely to be more effective in the SoCABt.