Resuspension And Transport Of Plutonium In The Palomares Area

J. Environ. Radioacrivify, Vol. 37, No. 1, pp. 101-l 14, 1997 0 1997 Elsevier Science Ltd

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Resuspension and Transport of Plutonium in the Palomares Area

Antonio Garcia-Olivares
LITEC-Consejo Superior de Investigaciones Cientificas, C/Maria de Luna, 3, 50015 Zaragoza, Spain

&C. Enma Iranzo
Centro de Investigaciones Energtticas Medioambientales y TecnolbgicasInstituto de Medio Ambiente, Avda. Complutense 22, 28040 Madrid, Spain (Received 12 February 1992; accepted 19 August 1996)

ABSTRACT A model of resuspension and air transport of particles has been used in a scenario of natural contamination in Palomares, Spain, to improve the understanding of the availabledata on soil and air concentrations. Meteorological conditions in 1988 and air concentrations measured over several years and at four points have been used to calibrate the model. The model predicts the order of magnitude of the air concentration within a factor of 3 at the points with the measurements available. This has made it possible to estimate the order of magnitude of the resuspension rateand deposition velocity in the area. The resuspension factor shows abnormally low values in relation to the large mass loading observed. This seems to be related to the association of a large fraction of plutonium with large particles. The limitations of the model used and the data available have been studied and some further approaches are suggested to improve the understanding of the processes ofregional transport. cc) 1997 Elsevier Science Ltd. 101

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A, Garcia-Olivares,

C. E. Iranzo

INTRODUCTION This article presents a compartmental model of resuspension and transport of particles by wind action that has been applied to the area of Palomares in Southern Spain. The scenario of Palomares, a roughly rectangular area of 226 ha, contaminated with plutonium and americium (Fig.l), has been documented in Iranzo & Richmond, 1987; Iranzo et al., 1987). The cause of the contamination was the collision of two planes of the US Army during a mid-air refuelling operation. The two planes were destroyed, and four thermonuclear bombs fell in the area, three of them on to soil and one into the Mediterranean sea. Two bombs failed to deploy their parachutes, and they exploded onimpact. The explosion was chemical and resulted in the oxidation and release of part of the fissile material. This produced aerosols that were transported downwind, causing the contamination of 226 ha of cultivated and uncultivated lands and urban areas. The scenario of Palomares offers the possibility of experimental studies oriented to obtain information on the resuspension and transport ofcontaminated soil particles in a semi-arid natural environment.

DISTRIBUTION OF ACTIVITY IN THE SOIL AND METEOROLOGICAL DATA After the decontamination work, the remaining contamination was distributed as shown in Fig. 1. The areas with the maximum level of activity surrounded the points of impact. The plumes of high activity drawn on the soil from these two points show the local wind direction at themoment of the impact. Currently, all the contamination detectable is in a rectangle of 2320 m x 4040 m. Most of the area (120 ha) shows an activity lower than 12 kBq rne2, 87 ha show an activity between 12 and 120 kBq/m*, 17 ha show an activity between 120 and 1200 kBq mu2 and 2.2 ha show an activity larger than 1200 kBq rnp2. The data in Fig. 1 and more detailed measurements available in differentexperimental stations in the rectangle (Iranzo & Richmond, 1987; Iranzo et al., 1987), were used to construct a matrix of equally spaced 24 x 42 points of activity concentration representing the spatial variation of the total activity concentration in the soil. This matrix is shown in Table 1. The spatial variation of the soil roughness has not been quantified

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