Alleviating the toxicity of heavy metals by combined amendments in cultivated bag of Pleurotus cornucopiae

Combined passivators regulate the heavy metal accumulation and antioxidant response of Brassica chinensis grown in multi-metal contaminated soils

Passivation of heavy metals is one of the most efficient techniques to remediate soil pollution. However, passivators with single component are usually unsatisfactory in the case of multi-metal contaminated soils. To resolve this problem, a series of combined passivators containing different ratios of Fe-Mn ore, Fe powder, zeolite, bentonite, etc. were designed and used to study their effects on the growth, heavy metal accumulation, and the antioxidant response of Chinese cabbage (Brassica chinensis L.) as well as the soil available forms of heavy metals in a copper refinery's multi-metal (As, Cd, Pb, Cu) contaminated yellow-brown soil and an artificially contaminated (As, Cd, Pb, Cu) calcareous alluvial soil. The results showed that compared with the control, the addition of combined passivators significantly promoted cabbage growth, with the biomass increase up to 1.77 and 3.54 times in yellow-brown soil and calcareous alluvial soil, respectively. The activity of antioxidant enzymes (SOD, CAT, POD) and the content of malondialdehyde (MDA) and glutathione (GSH) decreased, while the chlorophyll content increased significantly, as compared with no passivators. In addition, passivator application decreased As, Cd, Pb, and Cu contents in shoots and roots by 34.8%, 45.6%, 34.9%, and 11.1% and 49.2%, 63.8%, 38.6%, and 46.4% in yellow-brown soil and by 29.8%, 27.3%, 26.8%, and 25.5% and 45.8%, 55.2%, 61.8%, and 5.7% in calcareous alluvial soil, respectively. Besides, the content of soil available heavy metals was reduced by 8.0-17.1% in yellow-brown soil and 3.3-19.1% in calcareous alluvial soil after the application of passivators. The results indicated that the combined passivators formulated in this experiment could efficiently reduce the content of the multi-metals in cabbage and relieve the oxidant stress and could be used as a way to remediate multi-metal polluted soils.

Comparative Study on Lead and Copper Biosorption Using Three Bioproducts from Edible Mushrooms Residues

Agricultural waste products can be used as biosorbents for bioremediation once they are low-cost and high-efficient in pollutants removal. Thus, waste products from mushroom farming such as cutting and substrate of Lentinula edodes (popularly known as shiitake) and Agaricus bisporus (also known as champignon) were evaluated as biosorbents for metallic contaminants copper (Cu) and lead (Pb). Shiitake and champignon stalks, and shiitake substrate (medium in which shiitake was cultivated) were dried, grounded, characterized and experimented to remove Cu and Pb from contaminated water. The Sips model was used to establish the adsorption isotherms. Regarding Cu, champignon stalks have the best removal efficiency (43%), followed by substrate and stalks of shiitake (37 and 30%, respectively). Pb removals were similar among three residues (from 72 to 83%), with the champignon stalks standing out. The maximum adsorption capacities (q_max) for Cu in shiitake and champignon stalks were 22.7 and 31.4 mg/g⁻¹, respectively. For Pb, q_max for shiitake and champignon stalks, and shiitake substrate were 130.0, 87.0 and 84.0 mg/g⁻¹, respectively. The surface morphology of the champignon stalks revealed an organized and continuous structure. After an interaction with metals, the stalk of champignon accumulated the metal ions into interstices. Mushroom residues showed a relevant adsorption efficiency, especially for Pb. Mushroom farming waste are a very low-cost and promising alternative for removing toxic heavy metals from aquatic environment.

Responsiveness change of biochemistry and micro-ecology in alkaline soil under PAHs contamination with or without heavy metal interaction

Co-presence of organic pollutants and heavy metals in soil is causing increasing concerns, but the lack of knowledge of relation between soil ecology and pollutant fate is limiting the developing of specific control strategy. This study investigated soil change under pyrene stress and its interaction with cadmium (Cd). Soil physicochemical properties were not seriously influenced. However, pollutants' presence easily varied soil microbial activity, quantity, and diversity. Under high-level pyrene, Cd presence contributed to soil indigenous microorganisms' adaption and soil microbial community structure stability. Soils with both pyrene and Cd presented 7.11-12.0% higher pyrene degradation compared with single pyrene treatment. High-throughput sequencing analysis indicated the proportion of Mycobacterium sp., a commonly known PAHs degrader, increased to 25.2-48.5% in treatments from 0.52% in control. This phenomenon was consistent with the increase of PAHs probable degraders (the ratio increased to 2.86-6.57% from 0.24% in control). Higher Cd bioavailability was also observed in soils with both pollutants than that with Cd alone. And Cd existence caused the elevation of Cd resistant bacterium Limnobacter sp. (increased to 12.2% in CdCK from 2.06% in control). Functional gene prediction also indicated that abundance of genes related to nutrient metabolism decreased dramatically with pollutants, while the abundances of energy metabolism, lipid metabolism, secondary metabolites biosynthesis-related genes increased (especially for aromatic compound degradation related genes). These results indicated the mutual effect and internal-interaction existed between pollutants and soils resulted in pollutants' fate and soil microbial changes, providing further information regarding pollutants dissipation and transformation under soil microbial response.

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.

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.

Transcriptome analysis reveals the role of nitric oxide in Pleurotus eryngii responses to Cd2+ stress

Pleurotus eryngii is widely cultivated in China. However, our understanding of its transcriptional response to heavy metal stress and the underlying mechanism of nitric oxide (NO) in enhancing its tolerance to heavy metals is limited. In the present study, RNA-seq was used to generate large transcript sequences from P. eryngii exposed to cadmium chloride (CdCl₂) and exogenous NO. A total of 45,833 unigenes were assembled from the P. eryngii transcriptome, of which 32,333 (70.54%) unigenes matched known proteins in the nr database. Transcriptional analysis revealed that putative genes encoding heat shock proteins (HSPs) and genes participating in glycerolipid metabolism and steroid biosynthesis were significantly up-regulated in P. eryngii exposed to 50 μM Cd (P < 0.05). P. eryngii mycelia exposed to extremely high levels of heavy metals showed an increase in biomass when exogenous NO was added to the culture. The collaboration of putative oxidoreductase, dehydrogenase, reductase, transferase genes and transcription factors such as "GTPase activator activity", "transcription factor complex", "ATP binding", "GTP binding", and "enzyme activator activity", which were significantly up-regulated in samples induced by exogenous NO, contributed to the enhancement of P. eryngii tolerance to extremely high levels of heavy metals. The study provides a new insight into the transcriptional response of P. eryngii to extremely high levels of heavy metals and the mechanism of NO in enhancing heavy metal tolerance.

Remediation Performance and Mechanism of Heavy Metals by a Bottom Up Activation and Extraction System Using Multiple Biochemical Materials

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^-1, 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.

Determination of Glutathione, Selenium, and Malondialdehyde in Different Edible Mushroom Species

In this study, the amount of reduced glutathione (GSH), oxidized glutathione (GSSG), and malondialdehyde (MDA) were determined by high performance liquid chromatography (HPLC), and selenium was determined by using the fluorescence spectrophotometer in eight different species of edible mushrooms. Brittlegill mushroom (Russula delica), meadow mushroom (Agaricus campestris), dryad's saddle mushroom (Polyporus squamosus), white button mushroom (Agaricus bisporus), Pleurotus spp., ink mushroom (Coprinus atramentarius), ebekari mushroom (slimy) (Elazığ local) and çaşır mushroom (Pleurotus eryngii) (Tunceli local) were used for analysis. The amounts of GSH, GSSG, Se, and MDA with GSH/GSSG ratio in the eight different species of edible mushrooms were observed in between 269.10 ± 16.94-1554.83 ± 58.12 μg/g; 23.55 ± 1.89-841.90 ± 20.03 μg/g; 15.06 ± 1.56-82.10 ± 3.84 μg/g; 5.46 ± 0.50-27.45 ± 2.58 μg/g wet weight and 0.32-41.35, respectively. There is a weak correlation (R ² = 0.389) between MDA and Se, on the other hand, the correlation (R ² = 0.831) between GSH/GSSG ratio and selenium in mushrooms are reasonable well. In a similar manner, there is a weak correlation (R ² = 0551) between GSH/GSSG and MDA ratios in mushrooms. It was found that these edible mushroom species are good source of glutathione (GSH, GSSG), and selenium (Se) in terms of quantities obtained; therefore, it can be said that mushrooms are a rich source of antioxidants.