Thursday, 13 February 2003: 8:45 AM
Natural Radioactivity in Aerosols and What It Can Tell Us
Natural radioactivity can be a useful tool in determining transport and residence times of aerosols. This paper will outline (1) the use of naturally occurring 7Be for tracing and assessment of the impacts of upper air parcels and (2) the use of 210Pb and its daughters, 210Bi and 210Pb, to estimate submicron aerosol residence times. We will also discuss how 7Be data can be used to address problems with sampling on the network scale for PM-2.5 measurements. High-volume measurements to determine mass loadings of aerosols are often of uncertain reliability. Errors can be large if sampling volumes are not determined accurately. Power loss, filter loading leading to reduction in air flow, and a variety of other problems in city aerosol networks can lead to inaccurate assessment of aerosol distributions. The 7Be values, which should be reasonably consistent on network scales, can identify problems and allow for correction of data.
Our past measurements of 210Pb and its daughters have been made by using slower flow cascade impaction systems. We will present data taken with higher-volume slotted cascade impactors that allow one-day measurements of apparent ages. The use of 210Po to address soil aerosol sources will be presented and discussed in light of data taken in recent studies.