Soil Metaproteomics as a Tool for Environmental Monitoring of Minelands

Abstract

Opencast mining drastically alters the landscape due to complete vegetation suppression and removal of topsoil layers. Precise indicators able to address incremental changes in soil quality are necessary to monitor and evaluate mineland rehabilitation projects. For this purpose, metaproteomics may be a useful tool due to its capacity to shed light on both taxonomic and functional overviews of soil biodiversity, allowing the linkage between proteins found in soil and ecosystem functioning. We investigated bacterial proteins and peptide abundance of three different mineland rehabilitation stages and compared it with a non-rehabilitated site and a native area (evergreen dense forest) in the eastern Amazon. The total amount of identified soil proteins was significantly higher in the rehabilitating and native soils than in the non-rehabilitated site. Regarding soil bacterial composition, the intermediate and advanced sites were shown to be most similar to native soil. Cyanobacteria and Firmicutes phyla are abundant in the early stages of environmental rehabilitation, while Proteobacteria population dominates the later stages. Enzyme abundances and function in the three rehabilitation stages were more similar to those found in the native soil, and the higher accumulation of many hydrolases and oxidoreductases reflects the improvement of soil biological activity in the rehabilitating sites when compared to the non-rehabilitated areas. Moreover, critical ecological processes, such as carbon and nitrogen cycling, seem to return to the soil in short periods after the start of rehabilitation activities (i.e., 4 years). Metaproteomics revealed that the biochemical processes that occur belowground can be followed throughout rehabilitation stages, and the enzymes shown here can be used as targets for environmental monitoring of mineland rehabilitation projects.

Spectral and Soil Quality Index for Monitoring Environmental Rehabilitation and Soil Carbon Stock in an Amazonian Sandstone Mine

“…The SQI indicated differences between non-rehabilitated and rehabilitated areas, in agreement with previous studies [21,22]. Nevertheless, by only analyzing chemical attributes, the soil quality could be better or similar in the non-rehabilitated compared to the rehabilitated areas as it presents higher contents of the nutrients S, B, and Cu, for example.…”

“…In mining sites, it is suggested that SOM recovery may take decades to reach natural soils, or even not show complete recovery [46,47]. However, as observed in this study, Trindade et al [22] also found the maintenance of carbon cycling during the early stages in the progress of environmental rehabilitation by analyzing enzymes such as cellulase and beta-amylase. Based on the soil metaproteomic analysis, these authors found that, with rehabilitation, the reestablishment of important ecosystem processes can occur in short periods when topsoil is applied at the beginning of the process [22].…”

“…The enzymatic activity and microbial biomass in the areas undergoing rehabilitation presented values similar to those observed for the reference areas. In another study, Trindade et al [22] found in the same analyzed sites a recovery of the soil bacteria and other soil enzymes and these were attributed to the increase of soil organic matter and the stabilization of soil physical and chemical conditions.…”

“…After sand extraction, the total area of sandstone mine was filled with granite mining waste. For rehabilitation, the following techniques were applied: distribution of 30 cm of forest topsoil collected up to 50 cm layer in a nearby native reference area [20]; liming (1.5 Mg per ha of dolomitic lime); planting of native species (about 15 to 20 different species; density of 1700 seedlings ha −1 ); and applying in each planting pit 300 g ha −1 of NPK fertilizer (4-14-8) enriched with fritted glass material (FTE BR 12) containing S, B, Cu, Mn, and Zn and 1 kg of dried manure [21,22]. The estimated physical and chemical characteristics of the topsoil and the list of all 44 plant species planted or sowed for rehabilitation can be found in Gastauer et al [21].…”