ABSTRACT

Cosmogenic ⁷Be was used to evaluate soil loss in a mountainous micro-watershed near Belo Horizonte, Southwest Brazil. Two nearby sites were selected, a reference site in a flat area and an eroded site in a hill slope. At the reference site, soil samples were collected monthly throughout the year in order to evaluate seasonal variations of ⁷Be inventory in soil and its relation with the precipitation regime. Additionally, rainwater was collected and the expected ⁷Be soil content was predicted. At the reference site, the ⁷Be inventory shows seasonal variations, in accordance with the rainy season, and its distribution in the soil profile shows an exponential decrease in depth (h₀ = 6.9 ± 0.6 kg m^–2; r² = 0.97). At the eroded site, two soil sampling campaigns were performed in order to measure soil erosion in the watershed. The estimated net erosion was 42.2 ± 3.7 t ha^–1, indicating the loss of upper 5mm of soil per year. This corresponds to soil losses in the area in the range from moderate to severe erosion.

摘要

在巴西西南部贝洛奥里藏特附近的一个山区微型流域中，使用了宇宙成因⁷ Be来评估土壤流失。选择了附近的两个站点，一个是平坦区域的参考站点，另一个是山坡上的侵蚀站点。在参考站点，全年每月收集一次土壤样本，以评估土壤中⁷ Be的季节性变化及其与降水状况的关系。另外，收集雨水并预测了预期的⁷ Be土壤含量。在参考地点，⁷ Be清单显示了根据雨季的季节变化，并且其在土壤剖面中的分布显示深度呈指数下降（h ₀  = 6.9±0.6 kg m^–2 ; r ²  = 0.97）。在被侵蚀的地点，进行了两次土壤采样活动，以测量流域内的土壤侵蚀。估计的净侵蚀量为42.2±3.7 t ha ^–1，表明每年上层5mm的土壤流失。这相当于从中度到严重侵蚀范围内的土壤流失。