Neutron activation analysis of air-filters collected in Spokane, WA

More than 2200 atmospheric particulate matter filters were collected from 1995 through 2002 in the Spokane, WA area for the Spokane Air-Filters Project. The samples were sent to the US EPA in Research Triangle Park, NC for energy dispersive X-ray fluorescence (XRF) analysis and then delivered to the Washington State University Nuclear Radiation Center for neutron activation analysis (NAA). There were 28 elements of interest for the NAA portion of the project; however, due to detector efficiencies, background effects, and composition loading on each filter, only 15 of the 28 elements analyzed for produced valid results above the detection limit due to Compton background noise and blank subtraction. The 15 detectable elements with their six year average with associated 95% confidence interval concentrations in ng/m 3 are: As (0.384±0.88), K (50.0±194), La (0.051±0.251), Na (61.9±421), Sm (0.00928±0.072), Au (0.00154±0.149), Br (1.06±1.5), Ce (0.164±0.969), Co (0.0399±0.122), Cr (0.479±3.31), Fe (110±227), Sb (0.474±1.64), Sc (0.0197±0.00548), Th (0.011±0.0603), and Zn (12.4±32.6).