Estimation of air emissions from non-road mobile sources in a coastal urban airshed

Emissions of air pollutants continue to play a central role in a number of air quality issues. A recent EPA trend analysis study found that emissions from all sources are decreasing, except for non-road sources. A major study was undertaken for this research to estimate emissions for criteria pollutants from mobile non-road sources in Corpus Christi urban airshed (CCUA) for 1999, 2002 and 2005. CCUA covers Aransas, San Patricio and Nueces counties. There are twelve non-road emission source categories and emissions from nine of them were computed in this study using the NONROAD (2005). The other three non-road source categories included marine vessels, locomotives and aircrafts operations. Estimates for marine vessels and locomotives followed EPA recommended methodologies and aircraft operations emissions were computed using Emission and Dispersion Modeling System (EDMS) model. Comparison of past inventory estimates for 1999 with the emissions from the current study using NONROAD (2005) model for also for 1999 highlighted a significant reduction in the emission estimates by 1,124 tons/year for NOx, 1,863 tons/year for CO and 1,870 tons/year for VOC.; The major sources of NOx emission in CCUA for 2005 were identified to be marine vessels, locomotives and agricultural equipments, while majority of CO and VOC emissions were due to pleasure crafts, commercial and recreational equipment, residential lawn and garden equipments, and aircraft operations. The marine ships and barges together contributed to 41% of total non-road NOx emissions, while locomotives and agricultural equipment emitted 37 and 12 percent of NOx emissions, respectively. Commercial equipment and residential lawn and garden were responsible for about 58 percent of the total CO non-road emissions. Pleasure crafts and aircrafts operations together emitted 46% of VOC. It is anticipated that a refinement of local data on activities of military aircrafts anticipated in a future study would further increase the contribution of VOC emissions from aircrafts and allied operations to a larger fraction within the non-road sources.; In addition, an evaluation of the use of fuel and engine technologies for reduction in the NOx emissions from major diesel engine sources such as marine vessels, locomotives and agricultural equipment was undertaken in this study. Implementing various cost-effective control technologies in the CCUA could potentially result in a net reduction of NOx emissions from non-road sources by around 2,456 to 3,950 tons/year.