Source apportionment and composition of precipitation and wet deposition in the Paso Del Norte airshed
Sonny P. Emmert, Univ. of Texas, El Paso, TX; and T. E. Gill
The composition of airborne particles scavenged by precipitation reflects the transport of materials from different air masses as well as inputs from local natural and anthropogenic sources. Air quality research in the El Paso, TX, U.S.A/Ciudad Juarez, Chihuahua, Mexico (Paso del Norte) metropolitan area has been traditionally limited to studies of local inputs of air pollution; no transition has yet been made to the scavenging, washout, and transport of pollutants by precipitation. The goal of this research is to identify local and transported pollutants in precipitation as well as to attempt a preliminary source apportionment of these contaminants. We are using a variety of analytical methods to investigate the biological, chemical, and geological constituents of precipitation samples collected in a central part of the Paso del Norte. Techniques include bacterial and fungal plate counts, gas chromatography/mass spectrometry, inductively coupled plasma/mass spectrometry, ion chromatography, transmission electron microscopy and scanning electron microscopy. Dozens of samples have been collected since October, 2004 and sampling will continue until 2006. Samples of precipitation are collected during every event so any air-mass or event-type differences in air mass biogeochemical compositions, depending upon their origin or other potential factors, can be evaluated. The samples are collected at a height of approximately 30 meters on the University of Texas at El Paso (UTEP) campus. A Texas Commission for Environmental Quality air monitoring station is located at UTEP approximately 0.5 km away from the precipitation sampling site. The TCEQ monitoring station provides hourly data for air quality parameters such as PM10, PM2.5, ozone, sulfur dioxide, nitric oxide, and nitrogen dioxide. The National Atmospheric Deposition Program (NADP) operates several sites in remote locations surrounding the region. The data from these air and precipitation monitoring stations are compared along with analyses of the precipitation samples to evaluate scavenging and partitioning of pollutant wet deposition. Samples collected to date have undergone preliminary analysis using a number of techniques. TEM and SEM revealed particles from both natural and anthropogenic sources. Particle sizes were found to be predominately in the fine fraction <1 micron suggesting mostly anthropogenic origin. Biological analysis has shown growth of both bacteria and fungi in the samples. .
Joint Session 5, Multi-media studies that address the effects of air pollution cycling in ecosystems (Joint between the 8th Conference on Atmospheric Chemistry and the AMS Forum on Managing our Physical and Natural Resources)
Wednesday, 1 February 2006, 1:30 PM-2:30 PM, A312
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