DETERMINATION OF LOW-Z ELEMENTS IN ATMOSPHERIC AEROSOLS BY CHARGED-PARTICLE-INDUCED NUCLEAR REACTIONS

Nuclear reactions induced by charged particles are used to determine total carbon, nitrogen, and oxygen in atmospheric aerosols. These simple activation methods are quite sensitive, nondestructive, and require only a short amount of beam time (one minute in most cases) for each sample analysis. The method for determination of nitrogen in aerosols uses a proton beam to induce the /sup 14/N(p,..cap alpha..)/sup 11/C reaction. The detection system consists of a Ge(Li) gamma-ray spectrometer. A comparison of nitrogen found by the proton activation method with that found by an independent but destructive combustion method gave an average percent difference of 14% for 17 samples analyzed over a concentration range that spans two orders of magnitude. The sensitivity for detection of nitrogen is approximately 0.1 ..mu..g/cm/sup 2/. The method for determination of carbon in aerosols uses a deuteron beam to induce the /sup 12/C(d,n)/sup 13/N reaction. The results of the deuteron activation analysis of 15 samples were compared to the results of an independent combustion method. The comparison shows an average percent difference of 10%. The sensitivity for detection of carbon is approximately 0.5 ..mu..g/cm/sup 2/. Two methods were developed for determination of oxygen in atmospheric aerosols. One method uses a /sup 3/He beam to induce the /sup 16/O(/sup 3/He,p)/sup 18/F reaction. The second method uses a proton beam to induce the /sup 16/O(p,..cap alpha..)/sup 13/N reacton. The two methods were used to check one another. A comparison of the oxygen found in ten samples by /sup 3/He activation analysis with that found by proton activation analysis shows an average percent difference of 18%. The sensitivity for detection of oxygen is approximately 5 ..mu..g/cm/sup 2/ and is primarily limited by the rather large oxygen blank in the silver filter