Schuller P, Handl J, Ellies A
Universidad Austral de Chile, Valdivia.
Health Phys. 1998 Jul;75(1):86-8. doi: 10.1097/00004032-199807000-00014.
The time dependency of nuclear test 137Cs in soil, prairie plants, and milk was observed on pastures of seven dairy farms in the 10th Region, Chile, from 1982 to 1997, without any appreciable deposition of radioactive fallout after 1983. Whereas the 137Cs concentration in the soil decreased at a rate close to that of the radionuclide's physical decay during the whole observation period, the rate of decrease of the 137Cs concentration in the prairie plants and in the milk, having been very rapid between 1982-1990, became slower between 1991-1997. The effective half-lives of the concentration in plants were found to be 5.6 y and 12 y during the first and second observation periods, respectively. Similar half-lives of 5.5 y and 13 y were found for the concentration decline in milk during each period. These data clearly demonstrate a reduction in the long-term decrease of the 137Cs plant uptake, and consequently in the decrease of the 137Cs concentration in milk, resulting from a decline of 137Cs availability for prairie plants in the Hapludand soils over the whole 15-y observation period.
1982年至1997年期间，在智利第10大区的7个奶牛场的牧场上观察了土壤、草原植物和牛奶中核试验137Cs的时间依赖性，1983年之后没有明显的放射性沉降物沉积。在整个观察期内，土壤中137Cs的浓度以接近该放射性核素物理衰变的速率下降，而草原植物和牛奶中137Cs浓度的下降速率在1982 - 1990年间非常快，在1991 - 1997年间变得较慢。在第一个和第二个观察期内，植物中137Cs浓度的有效半衰期分别为5.6年和12年。在每个时期，牛奶中137Cs浓度下降的半衰期分别为5.5年和13年。这些数据清楚地表明，在整个15年的观察期内，由于Hapludand土壤中草原植物可利用的137Cs减少，137Cs在植物中的吸收以及牛奶中137Cs浓度的长期下降速度有所降低。
