Abstract
As rehabilitation efforts in Guyana are recent, there is little information on the effect of different ecological rehabilitation protocols for Guyana’s mining sites on biogeochemical cycles and mercury mobility. This study was conducted to assess the impact of different ecological restoration protocols on soil quality with the use of soil microbial indicators and by estimating the mercury mobility. We sampled soil from six rehabilitated mining sites in French Guyana with different ecological restoration procedures. We carried out measurements of enzymatic activities and an analysis of mercury environmental speciation to assess its potential toxicity according to a mobility gradient. The results obtained in this study show that the rehabilitation of mining sites has been carried out in a heterogeneous manner and soil quality is very variable, even in nearby sites. Sites that have been rehabilitated with fabaceous species have positive soil quality indicators. In addition, the results highlight a change in mercury mobility that is 82.1% correlated after co-inertia analysis with soil texture properties, which also confirms a direct effect of rehabilitation on mercury mobility. The non-restored sites had a much higher potential of mercury mobility and toxicity than the sites where ecological restoration was successful. These results highlight the positive effect of controlled rehabilitation and ecological restoration on microbiological activities and the potential toxicity of mercury.
Highlights
Deforestation is currently one of the sectors that emit the most greenhouse gases [1,2]and forest areas are increasing globally, tropical forests are affected by this crisis [3]
We evaluated the effect of the rehabilitation of Guyana’s mining sites in order to link soil texture with the quality of ecological restoration to the biochemical quality of the soil and the potential toxicity of mercury
The results indicated very variable and heterogeneous soil textures, even on nearby sites
Summary
Deforestation is currently one of the sectors that emit the most greenhouse gases [1,2]and forest areas are increasing globally, tropical forests are affected by this crisis [3]. Among the causes of deforestation in the Amazon, agriculture, silviculture, cattle ranching, selective logging, coca farming, and artisanal scale gold mining (ASGM). In Guyana, gold mining impacts land use and the functioning of the forest system, including the soil [4,5]. In addition to the direct damage caused by deforestation, these practices lead to heavy soil losses through erosion, which will lead to increased turbidity in aquatic systems and the remobilization of toxic metallic trace elements such as mercury [7]. Due to amalgamating chemical properties for gold mining, mercury was widely and legally used until 2006 and the problem of mercury in Guiana has already been described in many scientific studies [8,9]. It was shown that mercury of anthropogenic origin in Guyana was the most reactive, highly disorganized and often had suboxic physico-chemical conditions of the mining sites, which are favored its mobility and methylation [10,11]
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