An environmental scoping study in the Lower Rio Grande Valley of Texas .2. Assessment of transboundary pollution transport and other activities by air quality monitoring

This paper examines ambient air monitoring results conducted as part of a multi-media study known as the Lower Rio Grande Valley Environmental Scoping Study. Monitoring was performed at a ''central'' and a ''border'' site in the Brownsville, TX, air shed in the spring and summer of 1993. This study provided a preliminary assessment of transboundary pollution transport and possible anthropogenic activities in the Lower Rio Grande Valley. Overall (compared to other studies), low or comparable concentrations of trace elements, acidic gases, volatile organic compounds (VOCs), pesticides, and polycyclic aromatic hydrocarbons (PAHs) were found, Analysis of airborne particulate matter showed elevated coarse mass concentrations; also, the fine and coarse fractions were dominated by crustal elements associated with resuspended soil and dust. In addition, high fine- and coarse-particle chlorine levels, as well as silicates enriched with sulfur, were associated with sea salt from the nearby Gulf of Mexico. The prevailing winds during both spring and summer were predominantly from the east to the southeast of Brownsville and greatly limited the ability to assess transport of pollutants from neighboring Matamoros, Mexico. Carbon and VOC concentrations were higher in the spring phase than in the summer phase and may be the result of seasonal activities (i.e., residential heating) or waste and field burning. Although the Brownsville vicinity is dominated by agricultural activity, pesticide concentrations were low or comparable to other studies. PAHs were also comparable. Published by Elsevier Science Ltd.