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The combined wet and dry depositions of 137Cs and 7Be was measured at 1 and 3 m heights were using 10 m2 rain collectors. The amount of airborne radioactive material was determined with high-volume air samplers. The average resuspension factor for 137Cs during the three and a half years of measurements was 3.6×10-10 m-1. 137Cs had high dry deposition velocities, and showed little or no correlation with precipitation. The high deposition velocities, about 0.02 m s-1, correspond to the sedimentation velocity of rather large particles, about 26 μm. For 7Be, dry deposition velocities were found to be much smaller, around 5.6×10-4 m s-1, and a strong dependence on precipitation was observed. 7Be showed a deposition pattern similar to that of long-range transported particles. The dry deposition velocities found in one month without precipitation were used to estimate the influence of dry deposition in other months. It was estimated that the amount deposited by dry deposition constituted about 10% for 7Be and 90% for 137Cs. |
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