Determining Soil Loss Using the Inventory Ratio of Excess Lead-210 to Cesium-137
Determining Soil Loss Using the Inventory Ratio of Excess Lead-210 to Cesium-137
复制标题
DOI：
10.2136/sssaj1996.03615995006000040035x
复制
发表时间：
1996-07
影响因子：
2.9
通讯作者：
P. Wallbrink;A. Murray
中科院分区：
文献类型：
--
作者：
P. Wallbrink;A. Murray
人为核素137cs被广泛用于测量土壤运动。然而，137cs面积浓度的变化可能不仅仅是土壤再分配的结果。由于雨影和在沉降时的小规模径流过程，137cs沉降物可能有相当大的变异性。放射性尘降物210的铅也受到这些过程的影响，因此两者的面浓度应该是相关的。在塔斯马尼亚州圣海伦斯未受干扰的对照森林中，沉降物210 Pb与137 Cs的比例将可变性降低了两倍。此外，这两种核素穿透深度不同，从而产生不同深度的活度比，这就产生了一种测定土壤流失量的新方法。测量了邻近控制区沉降物210 Pb / 137 Cs的平均盘存比；这些都经过了正常和最小影响的测井程序。对照地点的平均核心盘存比为2.24±0.14 (n = 18)，而正常和最小影响地点的平均值分别为0.74±0.09 （n = 10）和1.73±0.29 （n = 10）。然后通过将这些比率与各自对照点（正常点40±6 mm；最小点17±5 mm）的盘存活动比率曲线进行比较，计算从采伐点移走的土壤的平均深度。我们得出的结论是，与单独的面积浓度相比，放射性沉降核素的比率可能提供一种较少随机变量（因此更敏感）的方法，用于调查景观中的地表侵蚀，在垂直土壤混合还不够近的地方。
The anthropogenic nuclide 137 Cs is widely used to measure soil movement. However, changes in 137 Cs areal concentrations may not result from soil redistribution alone. There can be considerable variability in 137 Cs fallout due to rain shadowing and small-scale runonrunoff processes at the time of deposition. Fallout 210 Pb is also affected by these processes and thus areal concentrations of the two should be correlated. The ratio of fallout 210 Pb to 137 Cs reduces variability by up to a factor of two in undisturbed control forest sites at St. Helens, Tasmania. In addition, these two nuclides penetrate to different depths, thereby producing a varying activity ratio with depth, and this gives rise to a new method for determining soil loss. The average inventory ratios of fallout 210 Pb to 137 Cs from plots adjacent to the controls were measured; these had undergone normal and minimal impact logging procedures. The average core inventory ratio at the control locations was 2.24 ± 0.14 (n = 18), compared with means of 0.74 ± 0.09 (n = 10) and 1.73 ± 0.29 (n = 10) from the normal and minimal impact sites. The average depth of soil removed from the logged sites was then calculated by comparing these ratios with the inventory activity ratio curve from their respective control sites (40 ± 6 mm, normal site; 17 ± 5 mm, minimal site). We concluded that, compared with areal concentrations alone, ratios of fallout nuclides are likely to provide a less randomly variable (and thus more sensitive) method for investigating surface erosion in landscapes where vertical soil mixing is not sufficiently recent to be of concern.