Answer to Question #985 Submitted to "Ask the Experts"

1. The state of New Mexico WIPP Emergency Response Coordinator (B. Lopez) provided a summary of surface soil samples (published in the WIPP Operations Manual) for the state of New Mexico. Samples were collected at various highway route locations. The four Albuquerque locations reported ²³⁸Pu concentrations from 0.02-0.03 pCi g^-1 and ^239/240Pu concentrations at 0.01 pCi g^-1.
    
2. The Los Alamos Environmental Monitoring Report for 1999 reports Pu concentrations at background locations which are about 40 miles from Albuquerque (Cochiti and Jemez). The reported values for ²³⁸Pu are 0.00 - 0.004 pCi g-1 and for ^239/240Pu are 0.008 to 0.010 pCi g-1.
    
3. Inhalation Toxicology Research Institute (south boundary of Albuquerque), supplied by Steve Rohrer, RSO for Lovelace Respiratory Research Institute: Site Environmental Report, 1995 (ITRI) Samples collected at the south perimeter of Albuquerque ²³⁸Pu values of 0.009 pCi g^-1 (range of 0.00 to 0.013) ^239/240Pu range of 0.0034 to 0.026 pCi g^-1 ITRI Ponds Site Closure Report (September 16, 1997): background sampling ²³⁸Pu: 0.01 pCi g^{-1 239/240}Pu: 0.01 pCi g^-1

We also recommend as a reference NCRP Report No. 131 "Scientific Basis for Evaluating the Risks to Populations from Space Applications of Plutonium," which has a good discussion of ²³⁸Pu concentrations, behavior in the environment and populations, and associated risks.

With regard to fallout, the proceedings of the Second International Symposium on Plutonium in the Environment, 9-12 November 1999, states that the concentration of ^239/240Pu in the first 30 cm of the earth's crust in the northern hemisphere is 7.1±3.1 Bq kg^-1 (0.19 ± 0.08 pCi g^-1) and of ²³⁸Pu is 0.17±0.09 Bq kg^-1 (0.0046 ± 0.0024 pCi g^-1).

Gloria E. Chavez