Source characterization of major emission sources in the Imperial and Mexicali Valleys along the US Mexico border

Chemical profiles for particle emissions are needed for source apportionment studies using the chemical mass balance ŽCMB. receptor model. Source measurements of geological sources, motor vehicle exhaust, vegetative burning Že.g. asparagus, field burning, charbroil cooking., and industrial sources Že.g. oil-fueled glass plant, manure-fueled power plants. were acquired as part of the Imperial Mexicali Valley Cross Border PM10 Transport Study in 1992. Six different source sampling techniques Ži.e. hot- and diluted-exhaust sampling, ground-based source sampling, particle sweeping grab sampling, vacuum sampling, and laboratory resuspension sampling. were applied to acquire filter samples of PM2.5 and PM10 Žparticulate matter with aerodynamic diameters 2.5 and 10 m, respectively.. Filter samples were analyzed for mass by gravimetry, elements ŽNa to U. by X-ray fluorescence, anions ŽCl , NO 3 , SO4 . by ion chromatography, ammonium ŽNH 4 . by automated colorimetry, soluble sodium ŽNa . and potassium ŽK . by atomic absorption spectrophotometry, and organic and elemental carbon ŽOC, EC. by thermal optical reflectance. Concentration data were acquired for a total of 50 chemical species. Elevated abundances of crustal components ŽAl, Si, K, Ca, Fe. from geological material, carbon ŽOC, EC. and trace elements ŽBr, Pb. from vehicle exhausts, carbon ŽOC, EC. and ions ŽK , Cl . from vegetative burning, ions ŽSO4 , NH 4 , Na , K , Cl . and elements ŽCl, Se. from a manure-fueled power plants, and sulfur and trace elements ŽNa , Pb, Se, Ni, V. from an oil-fueled glass plant were found in the resulting source profiles. Abundances of crustal species Že.g. Al, Si, Ca. in the Imperial Mexicali Valley geological profiles are more than twice those found in central and southern California. Abundances of lead in motor vehicle exhausts indicate different vehicle fleets in border cities. Emission profiles from field burning and charbroil cooking specific to the border area show that a majority Ž 60%. of emissions are comprised of carbon, with high organic to total carbon ratios Ž0.93 to 0.97.. Abundances of sulfate and ammonium account for nearly 60% of the manure-fueled power plant’s emissions. Elevated levels of metals ŽNa , Pb, Cd, Se. and byproducts of petroleum combustion ŽS, Ni, V. were found in the oil-fueled glass plant’s emissions