Cadmium induced changes in rhizosphere microecology to enhance Cd intake by Ligusticum sinense cv. Chuanxiong.

As the most famous and widely used traditional Chinese medicine (TCM), Ligusticum sinense cv. Chuanxiong (L. Chuaniong) has been affected by cadmium (Cd) exceeding with high ability of Cd accumulation. There is relatively little research on Cd absorption and storage process in L. Chuanxiong, which is an important reason for the poor remediation efficiency. Hence, this study takes L. Chuanxiong as the point of penetration to explore how L. Chuanxiong affects rhizobacteria through root exudates to alter soil Cd intake, as well as to explore the migration and storage of Cd in its body with 0.10 (T0), 5.00 (T5), 10.00 (T10) mg/kg Cd contaminations. The results showed that the relative abundance of amino acids and phospholipids secreted from L. Chuanxiong root noticeably increased with increasing Cd levels, which directly activated soil Cd or extremely significantly (P < 0.01) recruited bacteria such as Bacillus, Arthrobacter to indirectly increase Cd availability. Under the interaction of root exudates and rhizobacteria, Cd bioavailability increased by 80.00% in rhizosphere soil and Cd accumulation in L. Chuanxiong increased 5.44-6.65 mg/kg. Cd subcellular distribution analysis demonstrated that Cd was mainly stored in the root (10-fold more than in the leaf), whose Cd content was cytoderm>cytoplasm>organelle in tissues. The sequential extraction results found that non-soluble phosphate and protein-chelated Cd dominated (85.00-90.00%) in the cell, while Cd cheated with alcohol soluble protein, amino acid salts, water-soluble organic acid in cell was minimal (5.50%). The phenomenon indicated that L. Chuanxiong fixed Cd in root (the medical part) with low translocation ability. This study can provide theoretical support for the high-quality production of L. Chuanxiong and other root medical plant in heavy metal influenced sites.

In situ mycoremediation of acid rain and heavy metals co-contaminated soil through microbial inoculation with Pleurotus ostreatus.

The combined pollution of acid rain and heavy metals in soil is a pressing environmental problem, especially in the regions with large-scale heavy industrial production activities. Low remediation efficiency and weak long-lasting stability are major challenges when disposing the heavy metals contaminated soil in acid rain polluted sites. Herein, a specific microbe, strain CT13 was isolated and domesticated to exhibit high tolerance to both acid rain and cadmium (Cd). Then, an in situ mycoremediation method by adopting a bioaugmentation technology of strain CT13 inoculation with Pleurotus ostreatus was developed. The remediation performance was investigated in acidic conditions with Cd concentrations in soil ranging from 0 to 15 mg/kg. While most of the bacteria strains (e.g. strain CT6/13) significantly improved the dry weight of mushroom and Cd accumulation in neutral environment, the performance of strain CT6 was remarkably deteriorated in acid rain environment. In contrast, strain CT13 maintained its behavior in acidic conditions, displaying ∼30 % and 150 % enhancements (vs the neutral environment) in the dry weight of mushroom and Cd accumulation, respectively. In addition, inoculation of strain CT13 led to significant reductions in the content of superoxide dismutase, peroxidase and lipid peroxidation in the fruiting body of P. ostreatus, indicating an improvement in the mushroom's tolerance to both acid rain and heavy metals. The synergistic effect of strain CT13 and P. ostreatus realized the significant improvement in soil remediation efficiency and long-lasting stability in acidic conditions, providing valuable insights into the remediation of heavy metal contaminated soil in the regions affected by acid rain.

Integrated biochemical and transcriptomic analysis reveals the effects of Burkholderia sp. SRB-1 on cadmium accumulating in Chrysopogon zizanioides L. under Cd stress.

Application of plant growth-promoting rhizobacteria plays a vital role in enhancing phytoremediation efficiency. In this study, multiple approaches were employed to investigate the underlying mechanisms of Burkholderia sp. SRB-1 (SRB-1) on elevating Cd uptake and accumulation. Inoculation experiment indicated that SRB-1 could facilitate plant growth and Cd tolerance, as evidenced by the enhanced plant biomass and antioxidative enzymes activities. Cd content in plant shoots and roots increased about 36.56%-39.66% and 25.97%-130.47% assisted with SRB-1 when compared with control. Transcriptomics analysis revealed that SRB-1 upregulated expression of amiE, AAO1-2 and GA2-ox related to auxin and gibberellin biosynthesis in roots. Auxin and gibberellin, as hormone signals, regulated plant Cd tolerance and growth through activating hormone signal transduction pathways, which might also contribute to 67.94% increase of dry weight. The higher expression levels of ATP-binding cassette transporter subfamilies (ABCB, ABCC, ABCD and ABCG) in Chrysopogon zizanioides roots contributed to higher Cd uptake in Cd15 B (323.83 mg kg-1) than Cd15 (136.28 mg kg-1). Further, SRB-1 facilitated Cd migration from roots to shoots via upregulating the expression of Nramp, ZIP and HMA families. Our integrative analysis provided a molecular-scale perspective on Burkholderia sp. SRB-1 contributing to C. zizanioides performance.

24-Epibrassinolide combined with heavy metal resistant bacteria enhancing phytoextraction of Amaranthus hypochondriacus L. in Cd-contaminated soil.

The remediation efficiency of phytoextraction on heavy metal could be influenced by metal bioavailability and plant growth. Hence, we applied a synergistic intensification system with plant hormone (24-Epibrassinolide, EBR) and metal-resistant bacterium (Serratia sp. CTZ4) to enhance Cd extraction of Amaranthus hypochondriacus L. in contaminated soil. Results demonstrated that the combination of CTZ4 and EBR promoted soil microecology through decreasing soil pH, improving soil enzymatic activity (dehydrogenase, invertase, acid phosphate, urease). Besides, microbial community structure was evaluated to understand the diversity and relative abundance of microbe in soil after remediation. Moreover, the maximum extraction of Cd was 5.91 mg kg-1 and increased about 60.16 % to CK. Meanwhile, the antioxidant system (SOD, CAT activities) of plant was improved significantly as well as plants biomass increasing by 46.02 % with the combination of EBR and CTZ4. Thus, our results proved that the utilization of EBR and CTZ4 is an alternated method to enhance phytoextraction efficiency of A. hypochondriacus in Cd-contaminated soil.

High-effectively degrade the di-(2-ethylhexyl) phthalate via biochemical system: Resistant bacterial flora and persulfate oxidation activated by BC@Fe3O4.

Di-(2-ethylhexyl) phthalate (DEHP) has been classified as a priority pollutant which increased the healthy risk to human and animals dramatically. Hence, a novel biochemical system combined by DEHP-resistant bacterial flora (B) and a green oxidant of persulfate (PS) activated by Nano-Fe3O4 was applied to degrade DEHP in contaminated soil. In this study, the resistant bacterial flora was screened from activated sludge and immobilized by sodium alginate (SAB). Nano-Fe3O4 was coated on biochar (BC@Fe3O4) to prevent agglomerating in soil. X-ray diffraction (XRD) and scanning electron microscope (SEM) were utilized to characterize BC@Fe3O4. Results demonstrated that the treatment of biochemical system (SAB + BC@Fe3O4 + PS) presented the maximum degradation rate about 92.56% within 24 days of incubation and improved soil microecology. The 16S rDNA sequences analysis of soil microorganisms showed a significantly different abundance and a similar diversity among different treatments. Kyoto Encyclopedia of Genes and Genomes (KEGG) functional genes difference analysis showed that some metabolic pathways, such as metabolism of cofactors and vitamins, energy metabolism, cell growth and death, replication and repair, were associated with the biodegradation of DEHP. Besides, DEHP was converted to MEHP and PA by biodegradation, while DEHP was converted to DBP and PA by persulfate and BC@Fe3O4, and then ultimately degraded to CO2 and H2O.

Ecological responses of soil microbial abundance and diversity to cadmium and soil properties in farmland around an enterprise-intensive region.

Microorganisms play a vital role in soil biochemical process in contaminated managed ecosystems. In the present study, a field investigation was conducted in farmland around an industrial intensive region contaminated with cadmium, and the changes of microbial assemblages in contaminated soils were assessed by 16S rRNA sequencing and the further statistical analysis. The results revealed obvious variations in microbial richness between referenced and contaminated soils, with Proteobacteri, Chloroflexi, Actinobacteria, Acidobacteria and Nitrospirae dominating the studied communities around the industrial intensive region. Redundancy analysis and Spearman correlation heatmap revealed that about 68.95 % of overall variation in microbial community composition was explained by soil physiochemical properties and Cd existence, among which pH, soil total phosphorus, total nitrogen, organic carbon (OC) and available Cd were identified as dominant factors. No significant difference was found in the similarities and Beta-diversity analysis among different groups. In conclusion, this study revealed the ecological effects of physiochemical parameters and Cd stress on the diversity and abundance of microbial communities, and these findings provided the detailed and integrated correlation between the main factors and microbial indexes in Cd contaminated farmland around the industrial intensive region.

Mechanism study of Chromium influenced soil remediated by an uptake-detoxification system using hyperaccumulator, resistant microbe consortium, and nano iron complex.

A soil heavy metal decontamination system was developed based on the immobilization of bioavailable metal fraction by iron-biochar nano-complex (BC@Fe3O4) and the uptake by Chromium (Cr) hyperaccumulator Leersia hexandra (L. hexandra) under the assistance of metal resistant microbe consortium (MC). In this system, L. hexandra was able to accumulate 485.1-785.0 mg kg-1 in root and 147.5-297.2 mg kg-1 of Cr in its aerial part. With MC assistance, more Cr could be translocated to the aerial part of L. hexandra, which dramatically improved its remediation potential. Meanwhile, BC@Fe3O4 application decreased bioavailable Cr in soil and reduced soil toxicity, which contributed to soil microbial community adaption and L. hexandra performance under high level of Cr concentration (elevated microbial activity, decreased plant stress response, enhanced L. hexandra growth and accumulation) without negative influence on accumulation efficiency. Moreover, details of the possible mechanistic insight into metal removal were discussed, which indicated a negative correlation of the extractable Cr with soil microecology and hyperaccumulator performance. Furthermore, the resistant bacteria successfully altered soil microbial community, enhanced its diversity, which was in favor of the soil quality improvement.

Effect of Serratia sp. K3 combined with organic materials on cadmium migration in soil-vetiveria zizanioides L. system and bacterial community in contaminated soil.

Phytoremediation is an economical strategy to harvest cadmium (Cd) from contaminated soil, but the efficiency of phytoremediation was affected by many factors. This study investigated the potential of Serratia sp. K3 (K3) assisted with straw biogas residue (SBR) or leavening fertilizer (LF) on improving the Cd migration efficiency and micro-environment in soil-vetiveria zizanioides L. system. The results showed that the acid soluble Cd in soil was increased by 2.83-29.79% in treatments compared with control (CK). In addition, Cd accumulation in the roots and shoots of vetiveria zizanioides were significantly enhanced by the combination of K3 and SBR/LF. Especially, the translocation factor of Cd increased by 21.53-62.37% in groups with K3 compared with the groups without K3, correspondingly. Furthermore, SBR/LF effectively changed bacterial community structure, and improved bacterial abundance. Relative abundance of functional genes related with carbohydrate/energy/amino acid metabolism were increased in groups of SBRB/LFB rhizosphere compared with CK. These results provide insight into the change of phytoremediation efficiency and soil bacterial communities in the vetiveria zizanioides rhizosphere after inoculation. This study may provide a promising method for improving phytoremediation in Cd contaminated soil.

Effects of amendments on heavy metal immobilization and uptake by Rhizoma chuanxiong on copper and cadmium contaminated soil.

An improved method was applied for remediating cadmium and copper co-contaminated soil and reducing the metal concentration in Rhizoma chuanxiong. Pot experiments were conducted with six amendments (composed with bentonite, phosphate, humic acid, biochar, sepiolite powder, etc.). The results showed that soil pH, biological activities (soil enzymatic activities and microbial counts) and R. chuanxiong biomass were greatly improved with the addition of amendments in all treatments, especially in T3 and T6. Also, amendments effectively decreased the concentration of malondialdehyde and H2O2 in R. chuanxiong. In the T3 treatment, the bio-available Cd and Cu in soil were significantly decreased by 0.53 and 0.41 mg kg-1, respectively. Meanwhile, the amendment in T3 reduced Cd and Cu accumulation in R. chuanxiong about 45.83 and 39.37%, respectively, compared to T0. Moreover, the Fourier transform infrared spectroscopy spectra showed the surface functional groups of every amendment. To conclude, this study offers an effective and environmental method to reduce metal accumulation in R. chuanxiong on heavy metal co-contaminated soil.

Effect of modified coconut shell biochar on availability of heavy metals and biochemical characteristics of soil in multiple heavy metals contaminated soil.

On account of the potential in immobilizing metals and improving soil environment, various biochar materials have been extensively applied in environmental remediation. The purpose of this experiment was to evaluate the effect of modified coconut shell biochar (MCSB) on the availability of metals and soil biological activity in multi-metals (cadmium (Cd), nickel (Ni) and zinc (Zn)) contaminated soil. MCSB was obtained from coconut shell biochar (CSB) by hydrochloric acid pickling and ultrasonication, which has significantly improved its surface functional groups and microcosmic pore structure. Sandy soil samples were incubated at 25 °C amended with MCSB or CSB by 0%, 2.5% and 5% addition for 63 days, respectively. The results showed that the acid soluble Cd, Ni and Zn decreased by 30.1%, 57.2% and 12.7%, respectively, in groups with 5% MCSB addition, which indicated MCSB had a better effect on immobilizing metals compared with CSB. In addition, higher soil biological activities were detected in different treatments compared with control (CK). Especially, the maximum bacterial number was found in 5% MCSB treatment, which increased by 149.43% compared with CK. Accordingly, our results suggested that MCSB could be used as an ameliorant to immobilize heavy metals in contaminated soils and improve soil physicochemical and biological properties.