Lead Tolerance and Remediation Potential of Four Indocalamus Species in Lead-Contaminated Soil.

Indocalamus plants are low-growing shrubby bamboos with growth advantages, such as high biomass and strong resistance, and they are rich in germplasm resources in southern China. This study conducted soil lead (Pb) stress experiments on Indocalamus latifolius (Keng) McClure (LA), Indocalamus hunanensis B.M. Yang (HU), Indocalamus chishuiensis Y.L. Yang and Hsueh (CH) and Indocalamus lacunosus Wen (LC). Five Pb treatments (0, 500, 1000, 1500 mg·kg-1 Pb, and 1000 mg·kg-1 Pb + 1000 mg·kg-1 ethylenediamine tetraacetic acid (EDTA)) were established. EDTA was applied to explore the tolerance mechanism of different Indocalamus species after absorbing large amounts of heavy metals. The results were as follows: (1) under Pb treatment, the total relative biomass of LA, HU and LC was <100%, whereas the total relative biomass of CH was >100%; (2) after applying EDTA, the bioconcentration coefficient, translocation factor, and free proline content of the four Indocalamus species increased; and (3) the Pb mobility and distribution rates of the underground parts of the four Indocalamus species were consistently greater than those of the aboveground parts. The Pb mobility and distribution rates in the stems increased after applying EDTA, while those in the leaves decreased, as the plants tended to transfer Pb to their stems, which have lower physiological activity than their leaves.

Sasa argenteostriata - A potential plant for phytostabilization remediation of lead-zinc tailing-contaminated soil.

Phytoremediation is an effective way to remediate metal-contaminated soils. During phytoremediation, plants immobilize heavy metals through the roots to reduce the mobility, toxicity and dispersal of the metals, and the changes in the activity of the roots are often accompanied by changes in the rhizosphere ecosystems, in which rhizobacteria are essential components and interact with roots to maintain the stability of the rhizosphere ecosystem and improve soil health. In this study, the phytoremediation potential of Sasa argenteostriata (Regel) E.G. Camu and the response of rhizobacteria were revealed with different levels of lead-zinc tailing contamination (Pb, Zn, and Cd concentrations of 1197.53, 3243.40, and 185.44 mg/kg for M1 and 2301.71, 6087.95, and 364.00 mg/kg for M2, respectively). The BCF of Sasa argenteostriata increased with increasing soil pollution, and the BCFPb, BCFZn, and BCFCd were 0.19, 0.27, and 0.08, respectively, under the M2 treatment; in contrast, the TF decreased with increasing soil pollution, and the TFPb, TFZn, and TFCd were 0.39, 0.85, and 0.07, respectively, under the M1 treatment. The mobility of Pb in the rhizosphere was higher than that of Zn and Cd, and the percentage of residual (Res) Zn and Cd in the rhizosphere increased, while the acid-soluble (Aci) Pb was significantly higher, leading to obvious uptake of Pb by the roots. Correlation analysis showed that Sasa argenteostriata affected the rhizobacterial community by changing the rhizosphere soil pH, the contents of organic matter and NRFM, and bacteria such as Proteobacteria and MND1, which are highly resistant to heavy metals (HMs), became the dominant species in the community. Further PICRUSt2 analysis showed that reducing metal transport across the membranes and increasing the efficiency of cellular reproduction were the main metabolic mechanisms of bacterial tolerance to HMs. Overall, the roots of Sasa argenteostriata were able to immobilize more heavy metals in PbZn tailing-contaminated soil, reducing the toxicity of HMs in the soil, and then influencing the rhizobacteria to change the community structure and metabolism mechanism to adapt to the HM-contaminated environment, and the soil fertility was increased, which together promoted the health and stability of the soil. This study is the first to illustrate the phytoremediation potential and response of the rhizobacterial community of Sasa argenteostriata under multimetal contamination of PbZn tailings. The results of the study provide some guidance for the practice of lead-zinc tailing-phytoremediation and soil health.

Effects of Simultaneous Application of Double Chelating Agents to Pb-Contaminated Soil on the Phytoremediation Efficiency of Indocalamus decorus Q. H. Dai and the Soil Environment.

Recent studies have shown that the combined application of ethylenediaminetetraacetic acid (EDTA) and degradable chelating agents can enhance EDTA's affinity for heavy metals and reduce its toxicity, but the effect of this combination on the phytoremediation remains largely unknown. This study evaluated and compared the effects of EDTA, nitrilotriacetic acid (NTA), and glutamic acid-N,N-diacetic acid (GLDA) alone (E, N, G treatment), and in combination (EN and EG treatment), on the growth of dwarf bamboo (Indocalamus decorus Q. H. Dai), their phytoremediation efficiency, and the soil environment in Pb-contaminated soil. The results showed that treatment E significantly reduced the biomass, while treatments N and EN were more conducive to the distribution of aerial plant biomass. Except for treatment E, the total Pb accumulation in all treatments increased significantly, with the highest increase in treatment EN. For double chelating agents, the acid-soluble Pb concentrations in rhizosphere and non-rhizosphere soils of treatments EN and EG were lower than those of treatment E, and the soil water-soluble Pb content after 20 days of treatment EN was significantly lower than that of treatment EG. Furthermore, chelating agents generally increased soil-enzyme activity in rhizosphere soil, indicating that chelating agents may promote plant heavy-metal uptake by changing the rhizosphere environment. In conclusion, treatment EN had the highest phytoremediation efficiency and significantly lower environmental risk than treatments E and EG, highlighting its massive potential for application in phytoremediation of Pb-contaminated soil when combined with I. decorus.