Abstract
Salix integra Thunb., a fast-growing woody plant species, has been used for phytoremediation in recent years. However, little knowledge is available regarding indigenous soil microbial communities associated with the S. integra phytoextraction process. In this study, we used an Illumina MiSeq platform to explore the indigenous microbial composition after planting S. integra at different lead (Pb) contamination levels: no Pb, low Pb treatment (Pb 500 mg kg–1), and high Pb treatment (Pb 1500 mg kg–1). At the same time, the soil properties and their relationship with the bacterial communities were analyzed. The results showed that Pb concentration was highest in the root reaching at 3159.92 ± 138.98 mg kg–1 under the high Pb treatment. Planting S. integra decreased the total Pb concentration by 84.61 and 29.24 mg kg–1, and increased the acid-soluble Pb proportion by 1.0 and 0.75% in the rhizosphere and bulk soil under the low Pb treatment compared with unplanted soil, respectively. However, it occurred only in the rhizosphere soil under the high Pb treatment. The bacterial community structure and microbial metabolism were related to Pb contamination levels and planting of S. integra, while the bacterial diversity was only affected by Pb contamination levels. The dominant microbial species were similar, but their relative abundance shifted in different treatments. Most of the specific bacterial assemblages whose relative abundances were promoted by root activity and/or Pb contamination were suitable for use in plant-microbial combination remediation, especially many genera coming from Proteobacteria. Redundancy analysis (RDA) showed available nitrogen and pH having a significant effect on the bacteria relating to phytoremediation. The results indicated that indigenous bacteria have great potential in the application of combined S. integra-microbe remediation of lead-contaminated soil by adjusting soil properties.
Highlights
Lead (Pb) is a widely distributed toxic element in soil with no biological function (Kushwaha et al, 2018)
The total amount of Pb uptake by S. integra was highest in the high Pb treatment, followed by the low Pb treatment
Pb concentration was highest in the root, reaching 1221.36 ± 111.36 mg kg−1 in the low Pb treatment and 3159.92 ± 138.98 mg kg−1 in the high Pb treatment, followed by the trunk and leaf, and lowest in the branch whether in CK, low Pb treatment, or high Pb treatment
Summary
Lead (Pb) is a widely distributed toxic element in soil with no biological function (Kushwaha et al, 2018). It is produced by mining and smelting activities, burning of leaded gasoline, as well as disposal of sewage sludge, batteries, and other leadcontaining products (Huang et al, 2006). Many techniques to reduce its effects on ecosystems and humans have been tried, including physical, chemical, and biological processes, while most of them are high cost and lead to secondary pollution (Ma et al, 2016). Combined microbial and plant remediation has become an popular way for its low cost, no secondary contamination, and being superior to single phytoremediation and microbiological methods (Khalid et al, 2017).
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