Sutherland R A, de Jong E
Saskatchewan Institute of Pedology, University of Saskatchewan, Saskatoon, Canada.
Health Phys. 1990 Apr;58(4):417-28. doi: 10.1097/00004032-199004000-00004.
During 1988, the spatial variability of the natural gamma-emitting radionuclides (238U, 232Th, and 40K) and the artificial radionuclide 137Cs were studied in three near-level unfertilized fields in Saskatchewan, Canada. One field was used as a native (uneroded) control site; the other two sites have been cultivated, one since 1979 and the other since at least the 1940s. The two cultivated sites have been eroded by aeolian processes and tillage practices. Autocorrelation analysis indicated that most of the radionuclides were not serially correlated for the two depth increments sampled (0-15 cm and 15-30 cm). Autocorrelation is a necessary procedure when equally spaced transect sampling is employed, since sample independence cannot be assumed. Robust and nonrobust statistical summaries are presented for the selected gamma-emitting radionuclide concentrations. Robust statistical estimates of location and dispersion are favored when distributions are not normal or when the distribution is skewed. Median concentrations for the three fields indicated that 238U, 232Th, 40K, and 137Cs were similar to areas in the U.S. and to other areas in southern Saskatchewan. Median 238U activity concentrations were between 31.4 and 34.1 Bq kg-1; 232Th concentrations were between 29.6 and 31.2 Bq kg-1; 40K concentrations were between 471 and 502 Bq kg-1; and 137Cs concentrations were between 10.0 and 12.6 Bq kg-1. The variability of natural radionuclides in a given field for a specific depth increment was generally low, with coefficients of variation less than or equal to 10%. The variability of 137Cs concentrations was greater, ranging from 18% to 23%. Nonparametric tests indicated a significant decrease in 214Bi concentration (238U indicator corrected for 222Rn) with depth of the 1979 field, and an increase in 228 Ac (232Th) with depth in the 1940s field. Significant differences in concentration between fields were indicated for all radionuclides except for 228 Ac. The possible reasons for differences in depth and between fields are briefly discussed.
1988年期间，对加拿大萨斯喀彻温省三块近水平未施肥农田中天然伽马发射放射性核素（238U、232Th和40K）以及人工放射性核素137Cs的空间变异性进行了研究。一块农田用作原生（未侵蚀）对照点；另外两块农田已用于耕种，一块自1979年起，另一块至少自20世纪40年代起。这两块耕种过的农田受到了风蚀过程和耕作方式的侵蚀。自相关分析表明，对于所采集的两个深度增量（0 - 15厘米和15 - 30厘米），大多数放射性核素不存在序列相关性。当采用等间距样带采样时，自相关是一个必要步骤，因为不能假定样本具有独立性。针对选定的伽马发射放射性核素浓度给出了稳健和非稳健的统计汇总。当分布不正常或分布呈偏态时，倾向于采用位置和离散度的稳健统计估计。三块农田的中位数浓度表明，238U、232Th、40K和137Cs与美国的地区以及萨斯喀彻温省南部的其他地区相似。238U活度中位数浓度在31.4至34.1贝克勒尔/千克之间；232Th浓度在29.6至31.2贝克勒尔/千克之间；40K浓度在471至502贝克勒尔/千克之间；137Cs浓度在10.0至12.6贝克勒尔/千克之间。特定深度增量下给定农田中天然放射性核素的变异性通常较低，变异系数小于或等于10%。137Cs浓度的变异性更大，范围在18%至23%之间。非参数检验表明，1979年农田中214Bi浓度（经222Rn校正的238U指示物）随深度显著降低，而20世纪40年代农田中228Ac（232Th）随深度增加。除228Ac外，所有放射性核素在不同农田之间的浓度均存在显著差异。简要讨论了深度和农田之间差异的可能原因。
