Monitoring of smog aerosols with elemental analysis by accelerator beams
The California Air Resources Board has operated an aerosol monitoring network of up to 15 stations since January 1973, using impactors to collect size segregated samples and ion-excited x-ray emission to perform the subsequent elemental analyses. Two-stage Lundgren-type rotary drum impactors with afterfilters collect particles in the 0.1 to 0.6 ..mu..m, 0.6 to 5 ..mu..m, and 5 to 20 ..mu..m size ranges. 18-MeV alpha beams from an isochronous cyclotron are used to excite x-rays in the aerosol samples, which are then detected by a Si(Li) x-ray detector. On-line data collection and reduction codes generate aereal densities for elements between sodium and uranium, with sensitivities in the nanogram per cubic meter range for most elements. During the first year of operation, about 12,000 analyses were performed; each analysis included 15 to 25 elements. Extensive studies with real aerosols were required before the problem of bounce-off for dry, silicious aerosols was solved by coating the drums with 530 ..mu..g/cm/sup 2/ mylar upon which was deposited about 50 ..mu..g/cm/sup 2/ paraffin. Penetration of the Nuclepore final filter contributed important corrections to the smallest size range, based upon the work of Spurney and Lodge. Operation of the collection system was verified through extensive comparisons on an element by element basis with high-volume filter samplers, and a nominal collection error of +-15% was assigned from these causes.
- Research Organization:
- Univ. of California, Davis
- OSTI ID:
- 7321673
- Journal Information:
- Natl. Bur. Stand. (U.S.), Spec. Publ.; (United States), Journal Name: Natl. Bur. Stand. (U.S.), Spec. Publ.; (United States) Vol. 2; ISSN XNBSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400104* -- Spectral Procedures-- (-1987)
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54 ENVIRONMENTAL SCIENCES
AEROSOLS
ALPHA BEAMS
BEAMS
CHEMICAL ANALYSIS
COLLOIDS
DISPERSIONS
HELIUM 4 BEAMS
ION BEAMS
NONDESTRUCTIVE ANALYSIS
SMOG
SOLS
X-RAY EMISSION ANALYSIS