Soil contamination with heavy metals has caused serious environmental problems and increased the risks to humans and biota. Herein, we developed an effective bottom up metals removal system based on the synergy between the activation of immobilization metal-resistant bacteria and the extraction of bioaccumulator material (Stropharia rugosoannulata). In this system, the advantages of biochar produced at 400 °C and sodium alginate were integrated to immobilize bacteria. Optimized by response surface methodology, the biochar and bacterial suspension were mixed at a ratio of 1:20 (w:v) for 12 h when 2.5% sodium alginate was added to the mixture. Results demonstrated that the system significantly increased the proportion of acid soluble Cd and Cu and improved the soil microecology (microbial counts, soil respiration, and enzyme activities). The maximum extractions of Cd and Cu were 8.79 and 77.92 mg kg, respectively. Moreover, details of the possible mechanistic insight into the metal removal are discussed, which indicate positive correlation with the acetic acid extractable metals and soil microecology. Meanwhile, the "dilution effect" in S. rugosoannulata probably plays an important role in the metal removal process. Furthermore, the metal-resistant bacteria in this system were successfully colonized, and the soil bacteria community were evaluated to understand the microbial diversity in metal-contaminated soil after remediation.

To investigate the impact of intensive mining on pollution of heavy metals in aqueous environment, water samples and seven sediment profiles adjacent to REE mine, iron mine, and V-Ti magnetite mine at Anning River, southwest China were collected and analyzed. Our study reveals that: (1) no significant pollution in water near mining regions of Maoniuping REE and Lugu iron mines were observed; (2) most outliers of As, Cd, Ni, Pb, Zn, and Cu in water are distributed at sites near towns not mining regions, except Cr that has been detected only in downstream waters near the V-Ti magnetite mine, because Cr was enriched in V-Ti magnetite mine and existed as oxyanions in water so that CrO 4 2− can be preserved longer than heavy metals existing as cations in alkaline water; (3) although these trace elements in sediment profiles indicated significantly decreased recently, most heavy metals in sediment of Anning River were considerably higher than local background values; (4) source identification of heavy metals in sediment near mining regions is complicated, because the natural contribution from undeveloped ore can also increase content of heavy metals in sediment which cannot be directly assigned as anthropogenic activities.