Multimedia contaminant environmental exposure assessment methodology as applied to Los Alamos, New Mexico

The MCEA (Multimedia Contaminant Environmental Exposure Assessment) methodology assesses exposures to air, water, soil, and plants from contaminants released into the environment by simulating dominant mechanisms of contaminant migration and fate. The methodology encompasses five different pathways (i.e., atmospheric, terrestrial, overland, subsurface, and surface water) and combines them into a highly flexible tool. The flexibility of the MCEA methodology is demonstrated by encompassing two of the pathways (i.e., overland and surface water) into an effective tool for simulating the migration and fate of radionuclides released into the Los Alamos, New Mexico region. The study revealed that: (a) the 239Pu inventory in lower Los Alamos Canyon increased by approximately 1.1 times for the 50-y flood event; (b) the average contaminant 239Pu concentrations (i.e., weighted according to the depth of the respective bed layer) in lower Los Alamos Canyon for the 50-y flood event decreased by 5.4%; (c) approx. 27% of the total 239Pu contamination resuspended from the entire bed (based on the assumed cross sections) for the 50-y flood event originated from lower Pueblo Canyon; (d) an increase in the 239Pu contamination of the bed followed the general deposition patterns experienced by the sediment in Pueblo-lower Los Alamos Canyon; likewise, a decrease in the 239Pu contamination of the bed followed general sediment resuspension patterns in the canyon; (e) 55% of the 239Pu reaching the San Ildefonso Pueblo in lower Los Alamos Canyon originated from lower Los Alamos Canyon; and (f) 56% of the 239Pu contamination reaching the San Ildefonso Pueblo in lower Los Alamos Canyon was carried through towards the Rio Grande. 47 references, 41 figures, 29 tables