The fallout of Chernobyl radioactivity in central Ontario, Canada

The levels of Chernobyl-derived 103Ru, 106Ru, 134Cs and 137Cs were measured in Algoma, Ontario rain samples collected as weekly composites until September 30, 1986. The radionuclides were consistently measurable until about mid-June. The data, when analyzed in conjunction with 7Be measurements, yield a mean tropospheric residence time of about 14 days for the four radionuclides. This value is significantly lower than the previous estimates based on nuclear explosion-derived radionuclides but is within the range of values reported using radon daughters. (author)