Mercury in soils impacted by alluvial gold mining in the Peruvian Amazon
Graphical abstract
Section snippets
Credit author statement
Manuel Gabriel Velásquez Ramírez: Conceptualization, Investigation, Resources, Writing – original draft, Claudia Maribel Vega Ruiz: Conceptualization, Investigation. resources, Ronald Corvera Gomringer: Conceptualization, Validation, Supervision, Martin Pillaca: Investigation, Visualization, Evert Thomas: Data curation, Formal analysis, Paul Michael Stewart: Writing – review & editing, Supervision, Luis Alfredo Gamarra Miranda: Data curation, formal análisis, Visualization, Francisco Roman
Study area
We carried out the present study in soils impacted by alluvial gold mining in the Madre de Dios Region (Fig. 1). The impacted areas were selected according to the two locally most used technologies to extract sediments: Highly Mechanized Mining (HMM) and Minimally Mechanized Mining (MMM) (Fig. 2). HMM uses heavy machinery such as excavators, front loaders, and dump trucks, whereas MMM uses suction pumps and high pressure water cannons to liquefy stream-side sediments, which are transported to
Results
The soil samples from gold mine spoils had significantly higher pH, but significantly lower SOM, CEC and clay content than soils of reference forests (non-impacted areas) adjacent to the mines, (Table 3).
The Hg levels of all soil samples were below permitted levels according to the Peruvian Environmental Quality Standards for Soil (6.6 mg kg−1; ECA), Canadian Environmental Quality Guidelines (6.6 mg kg−1; CCME) and Soil Guideline Value of the United Kingdom (10 mg kg −1); Table 4).
1 Soil characteristics and Hg levels in mined landscapes
The main characteristics of mine spoils are loss of top soil and extreme soil profile remodeling caused by sand and rock fragments moved from deeper soil layers to the top, with high permeability, excessive runoff, nearly level slope class (<2%), low erosion and more than 10% rock fragments at the surface (Román et al., 2015; Velásquez Ramírez et al., 2020). Our results reveal surface soils characterized as sandy soils with low CEC and SOM, where the texture of US and UCFM are sand and sandy
Conclusion
Hg levels in gold mine spoil soils were below the upper limits for agricultural and residential use as stipulated by Peruvian, Canadian and British environmental quality standards, and yielded similar values in areas under MMM and HMM mining operations. Vegetation cover, soil organic matter content, soil pH and clay particle content were the main factors explaining the variation of Hg concentrations in soils. The soil conditions of recently abandoned, uncovered mine spoils, characterized by low
Acknowledgements
This research owes special thanks to San Jacinto Native Community, Kotzimba Native Community and local miners who might use this research as a tool to manage land restoration. This study is made possible funding provided by the United States Agency for International Development (USAID) under the terms of USAID/WFU Cooperative Agreement No. AID-527-A-16-00001, Consejo Nacional de Ciencia y Tecnologìa (CONCYTEC) and Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT) (Proyecto
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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