Quantification of soil erosion using ⁷Be in a steep watershed used for natural grazing in Brazil

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.

KEYWORDS:

• cosmogenic nuclides
• actinium-228
• beryllium-7
• cesium-137
• fallout
• environmental tracers
• soil degradation
• wet deposition

Acknowledgements

The authors highly appreciate the substantial contribution of Dr João Herbert Moreira Viana from Embrapa Milho e Sorgo (Empresa Brasileira de Pesquisa Agropecuária) of Minas Gerais, Brazil.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability

The data supporting the conclusions of this article are included within the article. Any queries regarding these data may be directed to the corresponding author.

Additional information

Funding

This research project was supported by the following institutions: Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), Comissão Nacional de Energia Nuclear (CNEN), Instituto de Matemática Aplicada San Luis (IMASL), Universidad Nacional de San Luis (UNSL), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Sistema Nacional de Investigación (SNI) of SENACYT and the Universidad Tecnológica de Panamá (UTP).