a x 22 mw 00 oO ~ ™N th fH n a 3° a oO oO wn Tt ca an ve] ° wt o 2 o fo] an * 2 . o : ™~ . mt . S o oo .© F se a oO Oo Oo oO a a2 a4 y a vs) a om a ~ a wn t eS |io os 6 6a oOo CHEMICAL ASSOCIATIONS Once plutonium comes in contact with soil and sediment particles, it becomes firmly attached to the host particle. This strong attraction is exemplified by the high adsorption coefficients exhibited by soils and sediments in laboratory studies with soils (Rhodes, 1957a and b; Prout, 1958), in sediments from fallout (Wahlgren et al., 1976), in sediments from accidental release of soluble plutonium (Rogers, 1975), and in soils from bomb testing activities (Noshkin et al., 1976). The distribution coefficient, Kd, which is defined as the ratio of the adsorbed plutonium per unit weight to that in solution per unit volume, ranged from about 1,000 in laboratory studfes to about 100,000 in field situations. The high Kd naturally leads to the question of mechanism(s) of the attraction. One attempt to define the Pu associations in a naturd] system was that by ‘Edgington et al. (1976). Sediments from Lake Michigan contaminated at fallout levels were sequentially treated to remove plutonium. Selected results from their study are included in Table Ll. The MgCl» treatment was used to remove easily exchangeable forms. The citrate-dithionite treatment was used to remove the reductant-soluble forms (those which might be associated with tron and manganese oxides), and the NaOH treatment was used to extract the organically associated forms. Not included in the table is the crystalline phase determined by fusion analysis. From the result obtained, Edgington et a2. (1976) concluded that most of che plutonium is associated with iron and manganese oxides. They also changed the sequence of extractions in order to evaluate the effect of preceding treatments on the succeeding treatment. The major effect reported by them was that the organic associated plutonium increased slightly (Table 1), One of the modifications in treatment was extraction with heated sodium citrate without the sodium dithionite. This treatment extracted 35% of the plutonium. Tamura (1976b) also treated several contaminated soils and sediments with unheated sodium citrate; the amount extracted ranged from 7 to 14%. These same samples, when extracted with unheated citric acid, released ?3 to 59%. One might suspect that if citric acid had been used to extract the plutonium from the Lake Michigan samples, a higher percentage of the plutonium would 98 Sediments OD istribution 239,240), in Selected Lake Michigan Modified After D. N. Edgington et al., 1976, nium index" is derived for each site. 0 nee * . . . ‘ ~ 3 z ne col ° o wm v ww Ice ve uo - . nr wow . OA x o Ww OO Oo © a u Me ° eB 3 Table 1. These sites, which present no immediate hazard to man, provide opportunities for understanding plutonium behavior under natural environmental situations. Major emphasis in the paper is placed on the association of plutonium on sail particle sizes and the size relationship to potential deposition in the lung. As an initial approach to relate the relative importance of plutonium in soils when the pathway to man is through resuspension and inhalation, a "soil pluto- * a E Ww Q &og Qo oO un Qo §oo 4 pe 2 a oO DH No sed a= a mo : a + a u [1] = aad uw ~ = v 7 Ae 4 a4 ct a ~~ v ua 9° a Ww ut Se Oo B A o 7: aw 5 a > 3 a bu ° = wo Ned re) ° wn oo — + 0 — x << wn ) wy a uy “a un n e Ee c OH cw af uo ona a ‘Al a A et a) a Oo dl uw 9 + wn a v 0 uw wn 4 u oy a wi -_~ — ~~ — oo“ — ~— — — — — Set dt on “ 2 u h v wn E e oO 6S a a «i a Oo 99 a ® o m a. a ° o SG m *#eNaQH treatment before Citrate-Dithionite. ak all other samples showed on plutonium. *Including 1.5% recovery from fusion analysis; This paper reviews the association of plutonium in contaminated soils and sediments. The above-background contamination which exists at several nuclear facilities is the result of defense-related activities.