DISTRIBUTION OF PLUTONIUM IN ECOSYSTEMS 373 



Plutonium in liquid effluents released from Oak Ridge National Laboratory (ORNL) 

 during the Manhattan Project contaminated environments in the White Oak Drainage 

 Basin. The Oak Ridge site, approximately 0.5 km downstream from ORNL, received 

 effluents containing plutonium when it served, for 6 months in 1944, as a temporary 

 settling basin for radioactive wastes. The impoundment drained in late 1944, and since 

 then a forest has developed on the floodplain. 



Mortandad Canyon has received liquid waste since 1963, and from 1972 to 1973 the 

 release rate was approximately 9 mCi ^^^?\\jyi. Soil has become contaminated with both 

 ^^^Pu and ^•^^Pu; concentrations range from 250 pCi/g at the waste outfall to 9 pCi/g 

 about 2 km down the canyon. Surface water from the outfall completely infiltrates into 

 the alluvium within 1.2 km of the eftluent outfall. Downstream transport of plutonium 

 into dry portions of the streambed occurs only during storm runoff events (Hakonson, 

 Nyhan, and Purtymun, 1976). 



Chemical and isotopic characteristics of plutonium released from Oak Ridge and Los 

 Alamos are also different. The Oak Ridge method of treating radioactive liquid waste in 

 1944 involved coprecipitation with carbonate to remove radionuclides, primarily ^°Sr. At 

 Los Alamos plutonium may be associated with laundry and laboratory chelating agents 

 [e.g., nitrilotri (methylene phosphoric) acid-ATMP; 1 -hydroxyethyhdene 1,1 di- 

 phosphoric acid-HEDP] . The environmental stability of these complexes is unknown, 

 but plutonium is presently associated with the soil-sediment component of the canyon. 



Soil and Biotic Characteristics of the Oak Ridge Floodplain 



The floodplain is representative of bottomlands of the East Tennessee valley. The soil 

 profile is azonal because of periodic erosion and deposition of sediments related to 

 flooding. An accumulation of humus is evident from the dark-brown appearance of soil in 

 the 0- to 3-cm zone. Soil texture is a loamy clay (72% silt and 24% clay). The soil 

 reaction is neutral to slightly alkaline (pH = 7.1 to 7.6), which is atypical of regional 

 forest soils. The sliglitly alkaline condition is attributed to the alkaline coprecipitation of 

 wastes during the Manliattan Project. 



The forest ecosystem of the floodplain occupies a 3-ha area. The present successional 

 stage of the forest is dominated by sycamore (Platanus occidentalis L.) and white ash 

 {Fraximis americana L.). Ground vegetation is chiefly wild rye grass (Elvmus virginicus 

 L.), Microstegium vimineum [(Trinus) A. Canus] , jewelweed (Impatiens capensis Meerb.j, 

 and Japanese honeysuckle {Lonicera japonica Thunberg). The resident small-mammal 

 population includes the white-footed mouse (Peromyscus leucopus), the rice rat 

 (Oryzomys palustris), and the short-tailed shrew (Blarina brevicaiida). Earthworms 

 ( Lumbricus rubellus) and crayfish {Cambams sp.) are important soil invertebrates. 



Biomass [grams (dry weight)] of the major compartments of the floodplain 

 ecosystem is given in Table 2. Biomass for arborescent species was estimated from 

 mensuration data (Van Voris and Dalilman, 1976) and from regression equations (Harris, 

 Goldstein, and Henderson, 1973). The arborescent component (leaf, root, and wood) 

 contains 95% of the total forest biomass, whereas animals comprise only 0.02%. These 

 estimated biomass standing crops compare favorably witli average values compiled for 

 different forest stands of the eastern deciduous forest biome (EDFB) (Burgess and 

 O'Neill, 1975) with the exception of litter (550 g/m), which was considerably less than 

 the average for EDFB (~2000 g/m^). The low estimate for Utter was probably due to (1) 

 the young age of the floodplain forest (approximately 30 yr); (2) the effect of periodic 



