UMBRELLA: Using MicroBes for the REgulation of heavy metaL mobiLity at ecosystem and landscape scAle

Abstract

This special issue focuses on metal-contaminated areas resulting from mining activities. These sites are characterized by low nutrient availability, poor soil quality, and low pH, in addition to high metal loads. The contamination at former mining sites most often is associated with acid mine drainage leading to the dispersal of metals. The resulting areas are compromised with respect to both use of land for, e.g., agronomy and forestry, and groundwater, the main source of drinking water, restricting future use. In addition, the contamination can spread, if not attended to, contaminating additional, previously non-contaminated ecosystems. Government regulations for effective management of contaminated sites exist worldover, and reclamation of acid mine drainage-influenced areas attracts growing interest. Remediation actions are necessary, which, in addition to geo-engineering strategies, increasingly include monitored natural attenuation and bioremediation. This needs to be based on a detailed understanding of processes in bio-geo interactions at metal-contaminated sites, which is addressed here to provide an integrated approach summarized in a scheme for useful application of each of these remediation actions shown in this special issue at a generalized former mining site. The proposed applications help to minimize the risk to human health and environmental impact and are cost-efficient.Soil is the basis of terrestrial life and has a major impact on human life through its use for agriculture, forestry, or general land use. In addition, it remains the largest terrestrial ecosystem that is shaped by high numbers of microorganisms and plant roots. The metabolic activities of both microorganisms and plants sustain pedogenesis which, however, differs with respect not only to base rock material and climatic conditions, but also to, e.g., pollution. Root exudates as well as microbiological acidification and release of chelating agents take part in heavy metal mobilization and immobilization processes, which are of high impact at metal-rich sites. The ecotoxicologically relevant heavy metal concentrations are dependent on interaction with soil particles and microbial surfaces; hence, inoculation strategies may improve future land use.Mobilization and distribution pathways for metals from source, where geo-engineering techniques may be deployed, to sink need to be re-evaluated. Nature has evolved ecosystems able to cope with high metal loads, and by learning from the evolutionary and biological processes, it may be feasible to adopt additional strategies for bioremediation. During natural attenuation, new minerals can be formed. This might lead to supergenic ore formation and hence provides means to even use these metals without disturbing new, natural sites. In this special issue, we will discuss all mentioned mobilization and immobilization mechanisms to contribute to a general understanding of bioremediation potentials. Thus, we may draw on the potential of natural attenuation instead of premature application of high...

Transfer of heavy metals through terrestrial food webs: a review

“…In metal-accumulating Indian mustard (Brassica juncea; Brassicaceae), heavy metal-tolerant microbes in the rhizosphere stimulate root elongation and could potentially be used to improve the growth of metalaccumulating plants for phytoremediation and phytostabilization (Belimov et al 2005). Thus, microbes have an intimate relationship with plants, and plantmicrobe pairs should be considered when bioremediating metal-polluted sites (Idris et al 2004;Brandl and Faramarzi 2006;Wenzel 2009;Kothe and Büchel 2014).…”

Biomineralization by Extremely Halophilic and Metal-Tolerant Community Members from a Sulfate-Dominated Metal-Rich Environment

“…They play a key role in biogeochemical cycles such as metal and mineral transformations and bioweathering [42][43][44]. They can be applied to bioremediation approaches reducing the impact of high contamination caused by salt or heavy metals including radionuclides [12]. We expected to find highly different, specialized microbiomes in a gradient of contamination with high salt and metal concentrations [1][2][3][4].…”

“…An example of such a site where acid mine drainage with high metal and sulfate loads at circum-neutral pH is the former uranium mining and milling site near Seelingstädt, Germany, where remediation activities started in 1990 including dry in situ stabilization of the tailings, re-vegetation, and the treatment of seepage waters [12,13]. A total of about 110,000 t U were processed from 1960 to 1990 [14].…”

Pollution Intensity of Hazardous Metals, Microbiome and Potential Bacterial-Based Toxic Metal Sequestration of Coal Mine Drainage

“…AMD impact on receiving environments has been the focus of extensive restoration efforts with the goals of reducing metal loads, as well as enhancing biotic structure (diversity and abundance) [9]. Remediation of AMD via application of chemical neutralization, ion exchange and construction of wetland has been suggested with some limitations opposing outright removal of AMD effect on water sources [10][11][12].…”

“…Remediation of AMD via application of chemical neutralization, ion exchange and construction of wetland has been suggested with some limitations opposing outright removal of AMD effect on water sources [10][11][12]. Therefore, bioremediation approach through the activities of autochthonous microorganisms has been suggested as the best eco-friendly option to decommissioning AMD stressors [9,[12][13]. In conjunction with oligotrophic heterotrophs (such as Acidocella and Thermoplasma), the early microbial colonizers indirectly ameliorate HMs toxicity via syntrophic commensal associations with iron-and sulphuroxidizers [3].…”