The California-Mexico border region suffers from high levels of air pollution due to a large and expanding population, industrial growth, transportation and agriculture. In this project, researchers will investigate cross-border transport of pollutants and their impacts on regional air quality and climate through the collection and analysis of field data. The observational component of the work includes ground-based measurements along the California-Mexico border region, utilizing a combination of a central fixed site that will house state-of-the-science instruments to measure gases, aerosols, radiation and meteorological parameters and a mobile laboratory that can measure surface-atmosphere exchange fluxes using eddy covariance. The study will be complemented by measurements provided by Mexican colleagues at the fixed site and several mobile units for criteria pollutants and meteorological parameters. The main scientific objectives are to (1) characterize the emissions from major sources in the California-Mexico border regions, (2) determine the spatial and temporal variability in anthropogenic emissions of greenhouse gases and traditional air pollutants, and (3) elucidate the transport and transformation of these emissions and assess their impact on local and regional air quality and climate. A planned NOAA and California Air Resources Board study will provide additional data to aid in the analysis of these subjects.
The Intellectual Merit of the project is to assess the sources and processing of particulate matter and its precursors in the border region and their effects on regional air quality and climate. The analysis tasks will much better define the interplay of emissions and secondary particle formation, the diurnal evolution of fine particulate matter chemical composition under degraded air quality conditions, atmospheric processing of aerosols, particularly soot-containing particles, and their transport and transformation.
The Broader Impacts of the research include the direct involvement of graduate students and postdoctoral researchers in the tasks, and improved collaboration between U.S. and Mexican scientists and students. Results from the study will be directly presented to California and Mexican Government officials and will inform the development of air quality management strategies to reduce adverse human health, ecosystem, and climate impacts.
The scientific objectives for the Cal-Mex 2010 air quality study include characterization of gases and fine particulate matter (PM) to contribute to the understanding of their sources/transformation/impacts, which in turn will contribute to cost-effective mitigation strategies, investigation of the evolution and radiative properties of aerosols, including atmospheric aging of soot-containing particles, and modeling studies to assess the photochemical and meteorological processes characteristic of the Cal-Mex border region, to characterize the PM precursor and ozone chemistry and to examine the evolution of urban pollutants and regional transport, and the effects of air pollution on regional climate. The Texas A&M University (TAMU) team deployed several instruments to measure gases and particulate matter pollutants at the San Diego – Tijuana border area from 15 May to 30 June 2010. The major VOCs identified during the study included oxygenated VOCs and aromatics. Biogenic VOCs were scarce in this region due to the lack of vegetation in this arid area. Using an U.S. EPA positive matrix factorization model, VOCs together with other trace gases observed in this border region were attributed to four types of sources, i.e., local industrial solvent usage, gasoline vehicle exhaust, diesel vehicle exhaust, and aged plume due to regional background and/or long-range transport. Both gasoline and diesel engine emissions were associated with air masses passing through two busy cross-border ports. Aged plumes were strongly associated with NW wind, which might bring in aged air masses from the populated San Diego area. The results indicated that HCHO plays a dominant role in regulating the OH radical budget in the area. In addition, the results revealed that smaller particles contained dominantly fresh soot particles, while larger particles were mainly internally mixed of particles containing soot and inorganic/organic compounds in this region. The project provided training opportunities for two graduate students at TAMU, two visiting doctoral students from Mexico, and one visiting doctoral student from China, by conducting field measurements during the Cal-Mex 2010 air quality study or analyzing data collected from the field campaign.
