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 UCSD part of this interdisciplinary project investigated cross-border transport of particulate matter (PM) pollutants and their impacts on regional air quality and climate along the Cal-Mex border region by characterization of fine PM organic mass fragments (AMS), organic functional groups (FTIR, STXM-NEXAFS), and black carbon size distributions (SP2). There are three peer-reviewed publications led by the Russell group supported by this project [Takahama et al., 2012, Atmos. Environ., and two additional manuscripts in preparation], in addition to multiple collaborative papers led by other groups. Our primary findings relevant to air quality and climate policy in the Tijuana region are: (1) A substantial fraction of submicron particles in northern Tijuana are transported from the Los Angeles - Long Beach region [Takahama et al., 2012]. This fraction includes secondary organic components formed by photochemical oxidation of fossil fuel combustion emissions from shipping, trucking, and other transportation activities. (2) At the Cal-Mex Supersite in Tijuana, there are two substantial sources of black carbon (BC), the first associated with vehicle emissions and the second associated with burning of biofuel as well as trash [Takahama et al., in preparation]. The distinction between the two types was evident in the organic mass fragments that co-varied with BC during May and June of 2010. Further, the size distribution of BC was smaller (modal mean diameter below 100 nm) for vehicular BC (modal mean diameter 200-300 nm). Vehicular BC appeared to be fresh from local sources and correlated with traffic patterns with highs on weekday mornings. Burning BC did not have an observed cycle, with some of the highest concentration events occurring between 10 pm and 3 am (local time). The latter suggests a substantial contribution from off-hour residential or industrial waste removal by uncontrolled, open-air combustion. (3) The Cal-Mex regional particle concentrations during CalMex were representative of typical seasonal mean concentrations during other years over the last decade [Guzman-Morales et al., 2012]. As part of collaborative capacity building, L. Russell, S. Takahama, and A. Johnson worked with Guillermo Rodriguez from the Universidad Autónoma de Baja California Tijuana (Faculty of Chemical Science and Engineering) and trained several students (Ruben Duran, Aldo Cortez, Bianca Puckita) in the measurement and analysis of atmospheric particles. These students gained the competency to operate and calibrate instruments during the field campaign and played a large role in the success of the project. G. Rodriguez and active students remain involved in the post-analysis and interpretation of the environmental measurements. In addition to these capacity-building activities, the project hired Janin Guzman-Morales from the Autonomous University of Mexico in Mexico City (UNAM) as a research assistant. Using the training she received working on Cal-Mex measurements, Janin applied to the Scripps graduate program and was accepted to begin graduate studies as a PhD student at Scripps in Fall 2011.
