Mercury behaviour and C, N, and P biogeochemical cycles during ecological restoration processes of old mining sites in French Guiana

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.

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

Microorganisms ◽

10.3390/microorganisms9081702 ◽

2021 ◽

Vol 9 (8) ◽

pp. 1702

Author(s):

Ewan Couic ◽

Alicia Tribondeau ◽

Vanessa Alphonse ◽

Alexandre Livet ◽

Michel Grimaldi ◽

...

Keyword(s):

Ecological Restoration ◽

French Guiana ◽

Acacia Mangium ◽

Anaerobic Conditions ◽

Mining Sites ◽

Iron Reducing Bacteria ◽

Sulfate Reducing ◽

Sulphide Production ◽

Reducing Bacteria ◽

The Impact

Successive years of gold mining in French Guiana has resulted in soil degradation and deforestation leading to the pollution and erosion of mining plots. Due to erosion and topography, gold panning sites are submitted to hydromorphy during rainfall and groundwater increases. This original study focused on characterizing the impact of hydromorphic anaerobic periods on bio-geochemical cycles. We sampled soil from five rehabilitated sites in French Guiana, including sites with herbaceous vegetation and sites restored with fabaceous plants, Clitoria racemosa (Cli) mon-oculture, Acacia mangium (Aca) monoculture, Clitoria racemosa and Acacia mangium (Mix) bi-culture. We conducted mesocosm experiments where soil samples were incubated in anaerobic conditions for 35 days. To evaluate the effect of anaerobic conditions on biogeochemical cycles, we measured the following parameters related to iron-reducing bacteria and sulfate-reducing bacteria metabolism throughout the experiment: CO2 release, carbon dissolution, sulphide production and sulphate mobilization. We also monitored the solubilization of iron oxyhydroxides, manganese oxides, aluminum oxides and mercury in the culture medium. Iron-reducing bacteria (IRB) and sulfate-reducing bacteria (SRB) are described as the major players in the dynamics of iron, sulfur and metal elements including mercury in tropical environments. The results revealed two trends in these rehabilitated sites. In the Aca and Mix sites, bacterial iron-reducing activity coupled with manganese solubilization was detected with no mercury solubilization. In herbaceous sites, a low anaerobic activity coupled with sulphide production and mercury solubilization were detected. These results are the first that report the presence and activity of iron- and sulfate-reductive communities at rehabilitated mining sites and their interactions with the dynamics of metallic elements and mercury. These results report, however, the positive impact of ecological restoration of mining sites in French Guiana by reducing IRB and SRB activities, the potential mobility of mercury and its risk of transfer and methylation.

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Rock-Solubilizing Microbial Inoculums Have Enormous Potential as Ecological Remediation Agents to Promote Plant Growth

Forests ◽

10.3390/f12030357 ◽

2021 ◽

Vol 12 (3) ◽

pp. 357

Author(s):

Zhaohui Jia ◽

Miaojing Meng ◽

Chong Li ◽

Bo Zhang ◽

Lu Zhai ◽

...

Keyword(s):

Plant Growth ◽

Leaf Area ◽

Ecological Restoration ◽

Root Nodules ◽

Robinia Pseudoacacia ◽

Growth Index ◽

Nodule Formation ◽

Bare Rock ◽

Mining Sites ◽

Robinia Pseudoacacia L

Anthropogenic overexploitation poses significant threats to the ecosystems that surround mining sites, which also have tremendous negative impacts on human health and society safety. The technological capacity of the ecological restoration of mine sites is imminent, however, it remains a challenge to sustain the green restorative effects of ecological reconstruction. As a promising and environmentally friendly method, the use of microbial technologies to improve existing ecological restoration strategies have shown to be effective. Nonetheless, research into the mechanisms and influences of rock-solubilizing microbial inoculums on plant growth is negligible and the lack of this knowledge inhibits the broader application of this technology. We compared the effects of rock-solubilizing microbial inoculums on two plant species. The results revealed that rock-solubilizing microbial inoculums significantly increased the number of nodules and the total nodule volume of Robinia pseudoacacia L. but not of Lespedeza bicolor Turcz. The reason of the opposite reactions is possibly because the growth of R. pseudoacacia was significantly correlated with nodule formation, whereas L. bicolor’s growth index was more closely related to soil characteristics and if soil nitrogen content was sufficient to support its growth. Further, we found that soil sucrase activity contributed the most to the height of R. pseudoacacia, and the total volume of root nodules contributed most to its ground diameter and leaf area. Differently, we found a high contribution of total soil carbon to seedling height and ground diameter of L. bicolor, and the soil phosphatase activity contributed the most to the L. bicolor’ s leaf area. Our work suggests that the addition of rock-solubilizing microbial inoculums can enhance the supply capacity of soil nutrients and the ability of plants to take up nutrients for the promotion of plant growth. Altogether, our study provides technical support for the practical application of rock-solubilizing microbes on bare rock in the future.

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Characterization of Enrichment Cultures Involved in the Carbon, Sulfur and Iron Biogeochemical Cycles in French Guiana Mobile Muds

Geomicrobiology Journal ◽

10.1080/01490451.2015.1137656 ◽

2016 ◽

Vol 34 (1) ◽

pp. 11-26 ◽

Cited By ~ 1

Author(s):

Tatiana Luzan ◽

Andrei Chistoserdov

Keyword(s):

French Guiana ◽

Biogeochemical Cycles ◽

Enrichment Cultures

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Prehospital Emergencies in Illegal Gold Mining Sites in French Guiana

Wilderness and Environmental Medicine ◽

10.1016/j.wem.2017.09.008 ◽

2018 ◽

Vol 29 (1) ◽

pp. 72-77 ◽

Cited By ~ 1

Author(s):

Gérald Egmann ◽

Pierre Tattevin ◽

Renaud Palancade ◽

Matthieu Nacher

Keyword(s):

Gold Mining ◽

French Guiana ◽

Mining Sites

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Impact of Old and Recent Gold Mining Sites on Mercury Fluxes in Suspended Particulate Matter, Water and Sediment in French Guiana

Applied Sciences ◽

10.3390/app10217829 ◽

2020 ◽

Vol 10 (21) ◽

pp. 7829

Author(s):

Jennifer Hellal ◽

Jörg Schäfer ◽

Régis Vigouroux ◽

Laurent Lanceleur ◽

Valérie Laperche

Keyword(s):

Particulate Matter ◽

Suspended Particulate Matter ◽

Rainy Season ◽

Gold Mining ◽

French Guiana ◽

Dry Season ◽

Mining Sites ◽

Suspended Particulate ◽

Current Impact ◽

Tailing Ponds

In 2006 the use of mercury (Hg) was banned for gold mining in French Guiana. However, mining of old placers could mobilize Hg accumulated in soils and sediment. This study aimed to measure the current impact of a mining concession (Boulanger site) on the Hg load in the watershed. Turbidity, Total Mercury (THg), and Monomethylmercury (MMHg) were measured in water, suspended particulate matter (SPM), river sediment and sediments from old tailing ponds along a river section of 30 km up and downstream from a mining concession in French Guiana during a dry and a rainy season. Total dissolved Hg (THgD) concentrations varied little from up- to down-stream but were all higher (fourfold on average) during the rainy season (3.2 to 4.4 ng L−1), than during the dry season and consistent with previous data known for the Amazonian area. Dissolved MMHg (MMHgD) represented up to 30% of THgD during the dry season, which is higher than previous results (typically around 2%). Mercury concentrations in sediments were highest in the vicinity of areas affected by old (before 2006) rather than new gold mining practices. Even though Hg was banned in 2006, present gold mining practices still release natural Hg and Hg inherited from older mining practices into the watershed.

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Ecological Restoration of Central European Mining Sites: A Summary of a Multi-site Analysis

Landscape Research ◽

10.1080/01426397.2010.547571 ◽

2011 ◽

Vol 36 (2) ◽

pp. 263-268 ◽

Cited By ~ 44

Author(s):

Karel Prach ◽

Klára Řehounková ◽

Jiří Řehounek ◽

Petra Konvalinková

Keyword(s):

Ecological Restoration ◽

Central European ◽

Mining Sites ◽

Site Analysis

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It Takes a Village: Microbial Communities Thrive through Interactions and Metabolic Handoffs

mSystems ◽

10.1128/msystems.00152-17 ◽

2018 ◽

Vol 3 (2) ◽

Cited By ~ 7

Author(s):

Laura A. Hug ◽

Rebecca Co

Keyword(s):

Sequence Data ◽

Anthropogenic Impacts ◽

Biogeochemical Cycles ◽

Microbial Consortia ◽

Data Sets ◽

Microbial Activities ◽

Community Members ◽

Exponential Increase ◽

Current Sequence

ABSTRACT An enduring theme in microbial ecology is the interdependence of microbial community members. Interactions between community members include provision of cofactors, establishment of redox gradients, and turnover of key nutrients to drive biogeochemical cycles. Pathways canonically conducted by isolated organisms in laboratory cultures are instead collective products of diverse and interchangeable microbes in the environment. Current sequence-based methods provide unprecedented access to uncultivated microorganisms, allowing prediction of previously cryptic roles in biogeochemical cycles and interactions within communities. A renewed focus on cultivation-based methods is required to test predictions derived from environmental sequence data sets and to address the exponential increase in genes lacking predicted functions. Characterization of enriched microbial consortia to annotate hypothetical proteins and identify previously unknown microbial functions can fundamentally change our understanding of biogeochemical cycles. As we gain understanding of microbial processes and interactions, our capacity to harness microbial activities to address anthropogenic impacts increases.

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