Characterization of representative ambient air ultrafine and nanoparticulate matter in the El Paso -Juarez metroplex: Morphology, chemical compositions, and speciation
There has been mounting evidence over the past few years that ultrafine (<100 >nm) and especially nanoparticulate (or nanoaerosols with mean diameter <50 >nm) fractions of ambient air particulate matter (PM) in the atmosphere are far more toxic than larger counterparts. Studies have indicated that they pose considerable health risks including mortality, respiratory complications, and chronic obstructive pulmonary diseases (COPD), especially among children, elderly people, and those with preexisting pathologies. Air pollutants in the same size range are also believed to lead to high incidence rates of cardiovascular diseases including ischemic heart diseases and stroke among certain groups of people, particularly those with compromised cardiovascular functions. ^ In this study, representative ambient air particles, of the submicron regime, have been collected in the El Paso-Juarez metroplex area on the U.S. and Mexico border using a device called a thermophoretic precipitator (TP) for two calendar years. The collected particles were examined by transmission electron microscopy (TEM) and physical and chemical characteristics including size, shape, and chemical composition of each collected air particle were studied. Identification of some individual particles, to a limited extent, was also attempted with available data from the particles collected. To maximize the validity of the qualitative information obtained from individual particles examined, carbon and/or formvar coated 3 mm copper or nickel grids have been used for TEM and scanning electron microscopy (SEM) studies. For each particle examined by TEM, Selected Area Electron Diffraction (SAED) patterns for crystalline analysis and the Energy Dispersive X-ray Spectrometry (EDS) for elemental analysis were also performed. ^ Approximately 800 individual air particles were examined for qualitative analysis from the air in El Paso-Juarez metroplex area and analyzed for characterization of representative particles in the air. About one fourth of these particles were fully tested for SAED and EDS databases. ^ Four qualitative observations were made: (1) The majority of the representative particles collected in the air of the El Paso-Juarez metroplex showed crystalline characteristics; (2) The major portion of the particles collected and observed were aggregates of smaller (ultrafine or nano) particles; (3) More than half of the examined particles have exhibited layered structures; (4) Most ambient air PM are mixtures of carbonaceous PM and micro or nanocrystals of different elements. The impacts of nanocrystalline aggregates, that haven't been examined much on human tissues including lung, may need further investigation in the near future. ^
Health Sciences, Public Health|Physics, Atmospheric Science|Environmental Sciences|Engineering, Environmental
Bang, John Jongchun, "Characterization of representative ambient air ultrafine and nanoparticulate matter in the El Paso -Juarez metroplex: Morphology, chemical compositions, and speciation" (2003). ETD Collection for University of Texas, El Paso. AAI3170283.