Influence of Ecological Restoration on Mercury Mobility and Microbial Activities on Former Guyanese Mining Sites

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.

Positive Effect of Ecological Restoration with Fabaceous Species on Microbial Activities of Former Guyanese Mining Sites

“…However, the main point concerned the positive correlations between the microbial biomass (MBC) and the totality of the parameters related to the mineralization of organic matter and the parameters related to catabolic diversity. While MBC had already been shown to be a good indicator of enzymatic activities in soils [ 40 ], these results could also confirm the relevance of this indicator for estimating the catabolic diversity of microbial communities in sites undergoing ecological restoration.…”

The Impact of Ecological Restoration on Biogeochemical Cycling and Mercury Mobilization in Anoxic Conditions on Former Mining Sites in French Guiana

“…These soils could be considered anthroposols, and they have different structures and textures than natural tropical forest soils in the same topographic position. The five sites chosen to represent the different restoration modality adopted were already described in a previous research article [ 30 ] and are illustrated in Figure 1 .…”

“…Mercury concentrations (HgT) in soil samples and in the culture medium were determined directly by thermal decomposition atomic absorption spectrometry after gold amalgamation using an automatic mercury analyzer (AMA 254, Symalab) with a detection limit of 0.001 ng using the same method as described in a previous research article [ 30 ].…”

Mercury and Methylmercury Contamination of Terrestrial and Aquatic Ecosystems

“…The improvement of mining practices is thus key to regulating and mitigating these Hg emissions. Indeed, Couic et al [9] demonstrate that recent rehabilitation efforts in French Guyana's mining sites show promising results that depend on the type of ecological rehabilitation protocols. They demonstrate that specific plant species (e.g., fabaceous species) positively affect soil quality that can significantly reduce mercury mobility and toxicity.…”