No abstract

Many researchers have paid attention to solving the problem of multiple heavy metals pollution in the tailings area. However, the studies only stay at the laboratory level, which cannot completely demonstrate an efficient approach to remediate polluted environment due to iron tailings. This study aimed at investigating the effects and mechanisms of compound bacterial flora combined with peganum harmala to remediate the tailings area of Linze County, Zhangye City, Gansu Province due to the accumulation of numerous heavy metals such as Pb, Cd and Mn. The preliminary experiment was conducted in the laboratory to obtain data that should be compared with the tailings data. Compared with the control, after 84 days of restoration, parameters of the tailings soil inoculated with the compound bacterial flora were improved, pH was decreased from 7.74 to 7.18, the electrical conductivity was decreased by 21.15% ~70.49%, and activities of alkaline phosphatase, sucrase and urease were increased by 95.94%~99.64%、88.42%~98.43%、83.28%~86.95% respectively. The improvement of soil parameters was more evident in the treatment groups inoculated with compound bacterial flora and Peganum harmala. The results of high-throughput sequencing at different remediation stages showed that the structure of the soil microbial community changed after inoculation with compound bacterial flora, but the dominant species remained unchanged, only their relative abundance changed. At the phylum level, the dominant species in T (total tailings soil treatment groups) were Proteobacteria, Bacteroidota and Actinobacteriota, while the dominant species in 3:1 (H: add yellow cinnamon soil treatment groups) were more than Chloroflexi and Acidobacteriota. According to the analysis of Heatmap, the environmental factors such as pH, WHC, EC, Pb, Cd and Mn have evinced a significant impact on the bacterial community structure. This study provides a reference basis for the remediation approach to the soil polluted by different heavy metals.

Many researchers have paid attention to solving the problem of multiple heavy metals pollution in the tailings area. However, the studies only stay at the laboratory level, which cannot completely demonstrate an efficient approach to remediate polluted environment due to tailings. This study aimed at investigating the effects of compound bacterial flora we constructed to remediate the tailings area of Linze County, Zhangye City, Gansu Province due to the accumulation of numerous heavy metals such as Pb, Cd and Mn. The remediation effects of different treatment groups were evaluated by monitoring the physical and chemical properties of soil and studying the bacterial community structure during the remediation process. Compared with the control (TCK), after 84 days of restoration, parameters of the tailings soil inoculated with the compound bacterial flora were improved, pH was decreased from 7.74 to 7.02, EC (electrical conductivity) was decreased by 21.15% ~70.49%, and activities of alkaline phosphatase, sucrase and urease were increased by 95.94%~99.64%、88.42%~98.43%、83.28%~86.95% respectively. Among the 43 identified core optional taxonomic units (OTUs), Proteobacteria (44.9%), Actinobacteriota (21.7%), Bacteroidota (17.9%) were the dominant bacterial phyla, and Sphingobacterium (20.2%), Arthrobacter (8.5%), Sphingomonas (6.1%) were the dominant bacterial genus. The results of alpha diversity showed that the bacterial diversity and richness of the treatment groups inoculated with compound bacterial flora were significantly higher than controls (TCK and HCK). The correlation analysis of RDA, VPA and Spearman showed that soil pH, WHC, EC, POR, TEMP and heavy metals had significant effects on the composition and distribution of bacterial communities. Our study monitored the changes of soil physical and chemical properties and bacterial community structure during the whole remediation process, which will provide a reference basis for the remediation approach to the soil polluted by multiple heavy metals.