Distribution and Variability of 7Be in Soils Under Different Surface Cover Conditions and its Potential for Describing Soil Redistribution Processes
Distribution and Variability of 7Be in Soils Under Different Surface Cover Conditions and its Potential for Describing Soil Redistribution Processes
复制标题
DOI：
10.1029/95wr02973
复制
发表时间：
1996-02
影响因子：
5.4
通讯作者：
P. Wallbrink;A. Murray
中科院分区：
文献类型：
--
作者：
P. Wallbrink;A. Murray
土壤中7Be的测量可以用来指示表层土壤的移动，本研究旨在通过检测土壤中的7Be在一系列条件下对这项技术做出贡献。测定了7Be在裸土、草地和桉树林中的穿透浓度和面浓度，并与总的测量结果进行了比较。在采样期内，裸土中的库存量从开始逐渐下降到总降雨量的46%，这可能是由于入渗能力的下降。这可能会对类似条件下137Cs库存的解读产生影响。对于草地土壤，平均库存量占总沉降物的96%-142%；对于桉树凋落物和土壤，库存量为73%-95%。核素面积浓度的自然变异性被计算为约20%(相对标准偏差)，与土壤类型和/或表面覆盖无关。然而，采伐作业后的土壤干扰使7Be的变异性增加到约50%，即使7Be已经过了7个以上的半衰期。裸土和无凋落物桉树林地土壤的平均入渗量可用指数函数近似，平均入渗半深度Ph分别为0.7 mm和3.4 mm。结果表明，随着颗粒尺寸的减小，铍7的浓度增加。在任何土壤或地表覆盖条件下，在20毫米以下的深度都没有发现核素，从而证实了它在定性模型中的用途，这些模型通过将核素用作表层土壤的示踪剂来推断侵蚀过程。
Measurements of 7Be in soils can be used to indicate movement of topsoil, and this study aims to contribute to this technique by examining 7Be in soils under a range of conditions. The penetration and areal concentration of 7Be have been measured in bare soil, grassland, and eucalypt forest and compared with total measured fallout. Inventories in the bare soil decreased progressively from 64 to 46% of total fallout over the sampling period, probably owing to a decrease in infiltration capacity. This may have an effect on the interpretation of 137Cs inventories under similar conditions. For grassed soil, average inventories were 96–142% of total fallout; for eucalypt litter plus soil, inventories were 73–95%. Natural variability of areal concentration of the nuclide was calculated to be about 20% (relative standard deviation), irrespective of soil type and/or surface cover. However, soil disturbance following logging operations increased variability to about 50%, even after more than 7 half-lives of 7Be had elapsed. Penetration could be approximated by an exponential in bare soil and in eucalypt forest soil without litter, and average penetration half depths (Ph) in these soils were calculated to be 0.7 and 3.4 mm, respectively. Beryllium 7 concentration was found to increase as particle size decreased. The nuclide was not found below 20 mm depth in any soil or surface cover condition, thus confirming its utility in qualitative models that infer erosion processes by its use as a tracer of surface soil.