Abstract
Abstract. Polymetallic mine tailings have great potential as carbon sequestration tools to stabilize atmospheric CO2 concentrations. However, previous studies focused on carbonate mineral precipitation, whereas the role of autotrophic bacteria in mine tailing carbon sequestration has been neglected. In this study, carbon sequestration in two samples of mine tailings treated with FeS2 was evaluated using 13C isotope, pyrosequencing and DNA-based stable isotope probing (SIP) analyses to identify carbon fixers. Mine tailings treated with FeS2 exhibited a higher percentage of 13C atoms (1.76±0.06 % for Yangshanchong and 1.36±0.01 % for Shuimuchong) than did controls over a 14-day incubation, which emphasized the role of autotrophs in carbon sequestration with pyrite addition. Pyrite treatment also led to changes in the composition of bacterial communities, and several autotrophic bacteria increased, including Acidithiobacillus and Sulfobacillus. Furthermore, pyrite addition increased the relative abundance of the dominant genus Sulfobacillus by 8.86 % and 5.99 % in Yangshanchong and Shuimuchong samples, respectively. Furthermore, DNA SIP results indicated a 8.20–16.50 times greater gene copy number for cbbL than cbbM in 13C-labeled heavy fractions, and a Sulfobacillus-like cbbL gene sequence (cbbL-OTU1) accounted for 30.11 %–34.74 % of all cbbL gene sequences in 13C-labeled heavy fractions of mine tailings treated with FeS2. These findings highlight the importance of the cbbL gene in bacterial carbon sequestration and demonstrate the ability of chemoautotrophs to sequester carbon during sulfide mineral oxidation in mine tailings. This study is the first to investigate carbon sequestration by autotrophic bacteria in mine tailings through the use of isotope tracers and DNA SIP.
Highlights
Soil ecosystems have great potential as carbon sinks to stabilize CO2 and regulate climate change (White et al, 2000)
No significant changes in chemical properties, pH values (3.25 ± 0.09 in YM_ck and 2.98 ± 0.04 in SM_ck), sulfate (SO24−) contents (13.15 ± 2.58 mg g−1 in YM_ck and 8.95 ± 2.19 mg g−1 in SM_ck), and total organic carbon (TOC) contents (16.75 ± 0.09 mg g−1 in YM_ck and 18.55 ± 0.12 mg g−1 in SM_ck) were found for the control groups compared to the original Yangshanchong and Shuimuchong acidic samples after 14 days of incubation (Fig. 1)
The bacterial composition in the different mine tailings varied greatly, with only Firmicutes increasing in both tested mine tailings under pyrite addition
Summary
Soil ecosystems have great potential as carbon sinks to stabilize CO2 and regulate climate change (White et al, 2000). Atmospheric CO2 can be fixed in plants via photosynthesis and assimilated into soils via decomposition and microbial activity (Deng et al, 2016; Antonelli et al, 2018), and autotrophic bacteria play a significant role in carbon sequestration in soil ecosystems (Berg, 2011; Alfreider et al, 2017). The CBB cycle is the most prevalent means of CO2 fixation by autotrophs including autotrophic bacteria (Tabita, 1999; Berg, 2011). The cbbL and cbbM genes encoding the large subunit of RuBisCO, with 25 % to 30 % amino acid sequence identity (Tabita et al, 2008), serve as autotroph markers (Berg, 2011; Alfreider et al, 2017)
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