Clark M J, Smith F B
National Radiological Protection Board, Chilton, Didcot, Oxon, UK.
Nature. 1988 Mar 17;332(6161):245-9. doi: 10.1038/332245a0.
The passage of the Chernobyl plume over the United Kingdom in May 1986 led to the deposition of radionuclides on the ground by wet and dry deposition processes. Here we analyse rainfall during the passage of the plume and the published monitoring data obtained afterwards, and show that levels of deposited 137Cs can be closely related to rainfall intercepting the plume. 137Cs was present in the atmosphere mostly as particulate species with wet deposition mechanisms dominating. In contrast, 131I was present as particulate and vapour phase material, and reported levels on grass and in cow's milk show that both wet and dry deposition mechanisms were important. 131I on grass and in cow's milk therefore shows a different geographic pattern to 137Cs, and is not so closely related to rainfall. We have calculated washout factors for locations where there are data on deposition, rainfall and air concentrations during the passage of the Chernobyl plume. From these factors and interpolated concentrations in the atmosphere, the total deposition of 137Cs has been estimated at each of 4,000 rain gauge stations in the United Kingdom. The results are presented as deposition contours and have been compared with measurements in parts of the country. Estimates of the total deposition of 131I and 137Cs show that less than or equal to 1% of the estimated total releases from Chernobyl were deposited on the United Kingdom.
1986年5月，切尔诺贝利核事故产生的放射性烟羽飘过英国，通过干湿沉降过程使放射性核素沉积在地面。在此，我们分析了烟羽飘过期间的降雨情况以及之后公布的监测数据，结果表明，沉积的137Cs水平与拦截烟羽的降雨密切相关。137Cs在大气中主要以颗粒形式存在，湿沉降机制占主导。相比之下，131I以颗粒和气相物质形式存在，草和牛奶中的报告水平表明，干湿沉降机制都很重要。因此，草和牛奶中的131I呈现出与137Cs不同的地理分布模式，且与降雨的相关性不那么紧密。我们计算了切尔诺贝利烟羽飘过期间有沉积、降雨和空气浓度数据的地点的冲刷因子。根据这些因子和大气中的插值浓度，估算了英国4000个雨量站每个站点的137Cs总沉积量。结果以沉积等值线呈现，并与该国部分地区的测量值进行了比较。131I和137Cs总沉积量的估算结果表明，切尔诺贝利估计总释放量中不到或等于1%沉积在了英国。
