Radioactivity associated with airborne particulates was monitored continuously by 17 ESER Program air samplers at 15 locations during the second quarter of 2001.  Three of these samplers were located on the INEEL, seven were located off the INEEL near the boundary, and five were at locations distant to the INEEL.  One replicate sampler was located at Arco and one at Howe during the second quarter of 2001.  On June 13^th a new distant sampler was added in Jackson, Wyoming based on the concerns of local residents.  This additional sampler brought the total number to 18 samplers at 16 locations.  An average of 13,337 ft³ (578 m³) of air was sampled at each location, each week, at an average flow rate of 1.32 ft³/min (0.04 m³/min).  Particulates in air were collected on filters (1.2 µm pore size), while gases were pulled through activated charcoal cartridges.  Samplers are divided into INEEL, Boundary and Distant groups to determine if there is a gradient of radionuclide concentrations, increasing towards the INEEL.  (see sampling schedule)

Filters and charcoal cartridges were changed weekly at each station.  Each filter was screened for gross alpha and gross beta radioactivity using thin-window gas flow proportional counting systems after waiting about four days for naturally-occurring daughter products of radon and thorium to decay.  For more information concerning gross alpha and beta radioactivity, see the Gross versus Specific Analyses portion of the Helpful Information section of this report.   Charcoal cartridges were analyzed for gamma emitting radionuclides, specifically 131I.  Iodine-131 is of great interest because it is produced in relatively large quantities by nuclear fission and has a half-life of
	Jackson Sampler
only eight days.  This means any 131I that is detected would be from a recent release of fission products.  Finally, a composite of 13 filters, one for each week of the quarter, for each location was analyzed for gamma-emitting radionuclides with a subset analyzed for 90Sr, 238Pu, 239/240Pu, and 241Am.

If the INEEL was a significant source of offsite contamination, concentrations of contaminants would be higher at INEEL locations compared to Boundary locations which, in turn, would be higher than Distant locations.  An independent samples t-test (a= 0.05) was used to determine if there were statistically significant differences between the average gross alpha and gross beta concentrations at INEEL, Boundary, and Distant locations

INEEL, Boundary, and Distant location weekly average gross alpha concentrations in air are shown in Figure 8.  Weekly average gross beta concentrations are shown in Figure 9.  During two separate weeks (ending April 11, and May 23), the average gross beta concentration for INEEL locations was significantly higher than at Distant locations.  Also during two separate weeks (ending April 18 and May 23), the average gross beta concentration for INEEL locations was significantly higher than at Boundary locations.  During the week of April 11, the average gross beta concentration was higher at Boundary locations than at Distant locations.  

During two separate weeks, those ending April 4, and June 20, the average gross alpha concentration for INEEL locations was significantly higher than at Distant locations.  During those same weeks, the average gross alpha concentration at Boundary locations was significantly higher than Distant locations. 

There were no consistent trends over time of INEEL locations being higher than Boundary locations, being higher than Distant locations as one would expect if the INEEL was the source of radionuclide contamination.   Gross alpha and gross beta results for individual filters are listed in Table C-1 of Appendix C.  Monthly average gross alpha and beta concentrations in air at each sampling location are shown in Figures 10 – 15. 

• Figure 10.  Monthly average gross alpha concentrations in air at INEEL locations.

• Figure 11.  Monthly average gross alpha concentrations in air at Boundary locations.

• Figure 12.  Monthly average gross alpha concentrations in air at Distant locations.

• Figure 13.  Monthly average gross beta concentrations in air at INEEL locations.

• Figure 14.  Monthly average gross beta concentrations in air at Boundary locations.

• Figure 15.  Monthly average gross beta concentrations in air at Distant locations.

No 131I was detected in any of the weekly charcoal cartridges during the second quarter, 2001. Weekly 131I results for each location are listed in Table C-2 of Appendix C. Weekly filters for the second quarter of 2001 were composited by location.  All samples were analyzed for gamma emitting radionuclides, with a subset from several locations selected on a rotating basis and analyzed for 90Sr, 238Pu, 239/240Pu, and 241Am.    No 238Pu, or 137Cs were detected on any of the composite samples.

Filter head containing fiber particulate filter and charcoal cartridge

Of the nine samples submitted for analysis, ²⁴¹Am was detected in five of them.  Four of the five samples had levels greater than their respective two standard deviation (2s) and MDC (see Table 2).  One sample, from the Arco (QA-1) station, had an ²⁴¹Am result greater than 2s, but less than the MDC, indicating it is most likely a false positive.

^239/240Pu was detected in four of the samples submitted.  Three of the four samples had levels greater than their respective 2s and MDCs (see Table 2).  One sample, from the Main Gate location, had a result greater than 2s, but less than the MDC, indicating it is most likely a false positive.  

TABLE 2.        Specific radionuclides with results > 2s and results > MDC in composite air filters.

⁹⁰Sr was detected in two of the samples submitted at a level greater than their associated 2s values.  However, both were less than the MDCs, indicating they are most likely false positives.

Since ^239/240Pu and ²⁴¹Am were deposited around the world from atmospheric nuclear weapons testing the detected amounts do not necessarily indicate inputs from the INEEL, though this cannot be ruled out.  However, concentrations are within the range of values measured throughout the World (EPA, 2002).  In addition, detected values in composite samples for ²⁴¹Am ranged from 5,100 to over 10,500 times smaller than the DCG value of 2 x 10^-14 μCi/mL.  Values detected in composite samples for ^239/240Pu ranged from 5,800 to over 17,500 times smaller than the DCG value of 2 x 10^‑14 μCi/mL.  Results for composite filter samples from the second quarter, 2001, are shown in Table C-3 of Appendix C.