Abstract
Microbial community succession in tailings materials is poorly understood at present, and likely to be substantially different from similar processes in natural primary successional environments due to the unusual geochemical properties of tailings and the isolated design of tailings storage facilities. This is the first study to evaluate processes of primary succession in microbial communities colonizing unamended tailings, and compare the relative importance of stochastic (predominantly dust-borne dispersal) and deterministic (strong selection pressures from extreme geochemical properties) processes in governing community assembly rates and trajectories to those observed in natural environments. Dispersal-based recruitment required > 6 months to shift microbial community composition in unamended, field-weathered gold tailings; and in the absence of targeted inoculants, recruitment was dominated by salt- and alkali-tolerant species. In addition, cell numbers were less than 106 cells/g tailings until > 6 months after deposition. Laboratory experiments simulating microbial cell addition via dust revealed that high (>6 months’ equivalent) dust addition rates were required to effect stabilization of microbial cell counts in tailings. In field-weathered tailings, topsoil addition during rehabilitation works exerted a double effect, acting as a microbial inoculant and correcting geochemical properties of tailings. However, microbial communities in rehabilitated tailings remained compositionally distinct from those of reference soils in surrounding environments. pH, water extractable Mg, and water extractable Fe emerged as major controls on microbial community composition in the field-weathered gold tailings. Overall, this study highlights the need for application of targeted microbial inoculants to accelerate rates of microbial community succession in tailings, which are limited primarily by slow dispersal due to physical and spatial isolation of tailings facilities from inoculant sources; and for geochemical properties of tailings to be amended to moderate values to encourage microbial community diversification and succession.
Highlights
7 Gt of tailings are produced globally each year as wastes and by products of mineral extraction and beneficiation processes, with gold tailings accounting for onefifth (1.27 Gt) of this total (Mudd and Boger, 2013)
Microbial community composition in the gold tailings overall was similar to that observed in other alkaline tailings, dominated by Proteobacteria, Actinobacteria, and Firmicutes (Santini and Banning, 2016)
Beta diversity analyses based on Bray–Curtis dissimilarity matrices revealed that microbial community composition in unamended tailings was invariant over the first 6 months after deposition (Figure 1; PERMANOVA: p > 0.05, Supplementary Table 1; all pairwise comparisons between sites p > 0.05, Supplementary Table 2); and that these communities were distinctly different to those found in unamended tailings 1 year after deposition, rehabilitated tailings, and reference soils (PERMANOVA: p < 0.05, Supplementary Table 1; all pairwise comparisons between unamended tailings ≤ 6 months old and other sites < 0.05, Supplementary Table 2 and Figure 1)
Summary
7 Gt of tailings are produced globally each year as wastes and by products of mineral extraction and beneficiation processes, with gold tailings accounting for onefifth (1.27 Gt) of this total (Mudd and Boger, 2013). In the absence of targeted rehabilitation or amendment strategies, in situ natural weathering of the tailings, including combined physical, chemical and microbial processes, can take 50 years or more to decrease and stabilize the pH and decrease salinity to plant-tolerable values (pH 5.5– 8; EC < 1 mS cm−1; Londry and Sherriff, 2007; Young et al, 2012). Physical, and biological conditions abate during natural weathering, spontaneous colonization of the tailings by pioneer vegetation species (typically grasses) may occur, followed by shrubs and trees, which in turn supports in situ accumulation of organic carbon and nitrogen and development of stable soil aggregates (Londry and Sherriff, 2007; Young et al, 2012)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
