Influence of biochar produced from negative pressure-induced carbonization on transformation of potentially toxic metal(loid)s concerning plant physiological characteristics in industrially contaminated soil.

Soil contamination and its subsequent impact on the food chain is a pressing challenge in the present day. The application of biochar has demonstrated a significant and positive effect on soil health, thereby enhancing plant growth and development. However, the application of biochar (BC) produced from negative pressure-induced carbonization to mitigate metal(loid) contamination is a new strategy that has been studied in current research. Results depicted that the application of biochar derived from the negative pressure carbonization (vacuum-assisted biochar (VBC) has a significant (p ≤ 0.05) positive impact on plant growth and physiological characteristics by influencing immobilization and speciation of metal(loid) in the soil system. Moreover, the interactive effect of VBC on physiological characteristics (photosynthesis, gas exchange, and chlorophyll contents) and antioxidant activities of maize (Zea mays L.) was significantly (p ≤ 0.05) positive by confining the translocation and movement of metal(loid)s to the aerial part of the maize plant. X-ray diffraction (XRD) provided information on the structural and chemical changes induced by the VBC-500 °C explaining metal(loid) adsorption onto mineral surfaces and complexation that can affect their mobility, availability, and toxicity in the contaminated soil. Fourier transform infrared spectroscopy (FTIR) further provided a more detailed understanding of the metal(loid)s and biochar complexation mechanisms influenced by VBC-based functional groups -OH, C-Hn, -COOH, CO, C-O-C, CC, C-O, C-H, OH, and C-C in the binding process. These results suggest that the application of biochar prepared at 500 °C under negative pressure-induced carbonization conditions to the soil is the most efficient way to reduce the uptake and transfer of metal(loid)s by influencing their mobility and availability in the soil-plant system.

Biochar-assisted transformation of engineered-cerium oxide nanoparticles: Effect on wheat growth, photosynthetic traits and cerium accumulation.

The extensive use of nano-fabricated products in daily life is releasing a large volume of engineered nanoparticles (ENPs) in the environment having unknown consequences. Meanwhile, little efforts have been paid to immobilize and prevent the entry of these emerging contaminants in the food chain through plant uptake. Herein, we investigated the biochar role in cerium oxide nanoparticles (CeO2NPs) bioaccumulation and subsequent translocation in wheat (Triticum aestivum L.) as well as impact on growth, photosynthesis and gas-exchange related physiological parameters. Results indicated that CeO2NPs up to 500 mg L-1 level promoted the plant growth by triggering photosynthesis, transpiration and stomatal conductance. Higher NPs concentration (2000 mg CeO2NPs L-1) has negatively affected the plant growth and photosynthesis related processes. Conversely, biochar amendment with CeO2NPs considerably reduced (~9 folds) the plants accumulated contents of Ce even at 2000 mg L-1 exposure level of CeO2NPs through surface complexation process and alleviated the phyto-toxic effects of NPs on plant growth. XPS and FTIR analysis confirmed the role of biochar-mediated carboxylate and hydroxyl groups bonding with CeO2NPs. These findings provides an inside mechanistic understanding about biochar interaction with nano-pollutants to inhibit their bioavailability to plant body.

Roles of exogenous plant growth regulators on phytoextraction of Cd/Pb/Zn by Sedum alfredii Hance in contaminated soils.

Plant growth regulators (PGRs) assisted phytoextraction was investigated as a viable phytoremediation technology to increase the phytoextraction efficiency in contaminated soils. This study aimed to evaluate the cadimum (Cd)/lead (Pb)/zinc (Zn) phytoextraction efficiency by a hyperaccumulator Sedum alfredii Hance (S. alfredii) treated with 9 PGRs, including indole-3-acetic acid (IAA), gibberellin (GA3), cytokinin (CKs), abscisic acid (ABA), ethylene (ETH), brassinosteroid (BR), salicylic acid (SA), strigolactones (SL) and jasmonic acid (JA), in slightly or heavily contaminated (SC and HC, respectively) soil. Results demonstrated that PGRs were able to improve S. alfredii biomass, the most significant increases were observed in GA3 and SL for HC soil, while for SC soil, IAA and BR exhibited positive effects. The levels of Cd, Pb and Zn in the shoots of S. alfredii treated with ABA and SL were noticeably greater than in the CK treatment in HC soil, while the uptake of metals were increased by IAA and CKs in SC soil. Combined with the results of biomass and metal contents in shoots, we found that ABA showed the highest Cd removal efficiency and the maximum Pb and Zn removal efficiency was observed with GA3, which was 62.99%, 269.23%, and 41.18%, respectively higher than the control in HC soil. Meanwhile, compared to control, the maximum removal efficiency of Cd by IAA treatment (52.80%), Pb by JA treatment (165.1%), and Zn by BR treatment (44.97%) in the SC soil. Overall, our results suggested that these PGRs, especially, ABA, SL, IAA, BR and GA3 had great potential in improving phytoremediation efficiency of S. alfredii grown in contaminated soils.

Biochar-mediated transformation of titanium dioxide nanoparticles concerning TiO2NPs-biochar interactions, plant traits and tissue accumulation to cell translocation.

Titanium dioxide nanoparticles (TiO2NPs) application in variety of commercial products would likely release these NPs into the environment. The interaction of TiO2NPs with terrestrial plants upon uptake can disturb plants functional traits and can also transfer to the food chain members. In this study, we investigated the impact of TiO2NPs on wheat (Triticum aestivum L.) plants functional traits, primary macronutrients assimilation, and change in the profile of bio-macromolecule. Moreover, the mechanism of biochar-TiO2NPs interaction, immobilization, and tissue accumulation to cell translocation of NPs in plants was also explored. The results indicated that the contents of Ti in wheat tissues was reduced about 3-fold and the Ti transfer rate (per day) was reduced about 2 fold at the 1000 mg L-1 exposure level of TiO2NPs in biochar amended exposure medium. Transmission electron microscopy (TEM) with elemental mapping confirmed that Ti concentrated in plant tissues in nano-form. The interactive effect of TiO2NPs + biochar amendment on photosynthesis related and gas exchange traits was observed at relatively low TiO2NPs exposure level (200 mg L-1), which induced the positive impact on wheat plants proliferation. TiO2NPs alone exposure to wheat also modified the plant's bio-macromolecules profile with the reduction in the assimilation of primary macronutrients, which could affect the food crop nutritional value and quality. X-ray photoelectron spectroscopy (XPS) chemical analysis of biochar + TiO2NPs showed an additional peak, which indicated the binding interaction of NPs with biochar. Moreover, Fourier-transform infrared (FTIR) spectroscopy confirmed that the biochar carboxyl group is the main functionality involved in the bonding process with TiO2NPs. These findings will help for a mechanistic understanding of the role of biochar in the reduction of NPs bioavailability to primary producers of the terrestrial environment.

The effects of a combined amendment on growth, cadmium adsorption by five fruit vegetables, and soil fertility in contaminated greenhouse under rotation system.

Cadmium (Cd) exposure is related to a multitude of adverse health outcomes because food crops grown on Cd-polluted soil are widely consumed by the public. The present study investigates the different application techniques of a combined amendment (lime + zeolite + biochar + compost, LZBC) for soil Cd immobilization effect on growth performance, Cd uptake by the second season crops, and soil quality in greenhouse vegetable production (GVP) under a rotation system. Five fruit vegetables were cultivated as the second season crop in the same plots which have been used for pakchoi as the first season crop (with or without LZBC application). The results indicated that LZBC with the consecutive application (T3) promoted crops biomass and fruit yield the most, followed by LZBC with the second crop application (T2) and LZBC with the first crop application (T1). LZBC application showed increasing rhizosphere soil pH and improvement in soil fertility of all crops including available nitrogen, available phosphorus, available potassium, organic matter, and cation exchange capacity. LZBC had positive influences on soluble sugar, soluble protein, and vitamin C in edible parts of 5 vegetables. Cd contents in fruit, shoot, and root of eggplant, pimento, cowpea, and tomato except cucumber were reduced by adding LZBC. As for the economic performance, T3 had the highest output/input ratio in general. Overall, these results demonstrated that T3 was dramatically more effective for minimizing health risk, increasing production, and facilitating sustainable utilization of soil under the Cd-contaminated GVP system.

Succession Pattern in Soil Micro-Ecology Under Tobacco (Nicotiana tabacum L.) Continuous Cropping Circumstances in Yunnan Province of Southwest China.

Continuous cropping obstacle (CCO) is a common phenomenon in agricultural production and extremely threatens the sustainable development of agriculture. To clarify the potential keystone factors causing tobacco (Nicotiana tabacum L.) CCO, tobacco plants, topsoil, and rhizosphere soil were sampled from the fields with no, slight, and severe tobacco disease in Dali and Yuxi of Yunnan province in China. The physicochemical properties of topsoil and rhizosphere soil, the phenolic acids (PAs) contents in rhizosphere soil, and elemental contents in topsoil, rhizosphere soil, and tobacco plants were analyzed. Microbial diversity in rhizosphere soil was determined by the metagenomic sequencing method. The results showed that soil pH, texture, cation exchange capacity, organic matter, TC, TN, and available K contents showed a significant difference (p < 0.05) in soil physicochemical properties. There was a deficiency of B, K, Mg, and Mn contents in soil and/or tobacco plants. The contents of PAs, especially syringic acid in rhizosphere soil, varied significantly among the three sampling groups (p < 0.05). Meanwhile, microbial communities and functional genes changed from beneficial to harmful, showing an intimate correlation with soil pH and syringic acid content. It can be concluded that tobacco CCO could be allocated to the imbalance of soil micro-ecology, which possessed a regional feature at the two sampling sites.

Bamboo-biochar and hydrothermally treated-coal mediated geochemical speciation, transformation and uptake of Cd, Cr, and Pb in a polymetal(iod)s-contaminated mine soil.

In this study, polymetal(iod)s-contaminated mining soil from the Huainan coalfield, Anhui, China, was used to investigate the synergistic effects of biochar (BC), raw coal (RC), and hydrothermally treated coal (HTC) on the immobilization, speciation, transformation, and accumulation of Cd, Cr, and Pb in a soil-plant system via geochemical speciation and advanced spectroscopic approaches. The results revealed that the BC-2% and BC-HTC amendments were more effective than the individual RC, and/or HTC amendments to reduce ethylene-diamine-tetraacetic acid (EDTA)-extractable Cd, Cr, and Pb concentrations by elevating soil pH and soil organic carbon content. Soil pH increased by 1.5 and 2.5 units after BC-2% and BC-HTC amendments, respectively, which reduced EDTA-extractable Cd, Cr, and Pb to more stabilized forms. Metal speciation and X-ray photoelectron spectroscopy analyses suggested that the BC-HTC amendment stimulated the transformation of reactive Cd, Cr, and Pb (exchangeable and carbonate-bound) states to less reachable (oxide and residual) states to decrease the toxicity of these heavy metals. Fourier transform infrared spectroscopy and X-ray diffraction analyses suggested that reduction and adsorption by soil colloids may be involved in the mechanism of Cd(II), Cr(VI), and Pb(II) immobilization via hydroxyl, carbonyl, carboxyl, and amide groups in the BC and HTC. Additionally, the BC-2% and BC-HTC amendments reduced Cd and Pb accumulation in maize shoots, which could mainly be ascribed to the reduction of EDTA-extractable heavy metals in the soil and more functional groups in the roots, thus inhibiting metal ion translocation by providing the electrons necessary for immobilization, compared to those in roots grown in the unamended soil. Therefore, the combined application of BC and HTC was more effective than the individual application of these amendments to minimize the leaching, availability, and exchangeable states of Cd, Cr, and Pb in polymetal(iod)s-contaminated mining soil and accumulation in maize.

Synergistic effects of biochar and processed fly ash on bioavailability, transformation and accumulation of heavy metals by maize (Zea mays L.) in coal-mining contaminated soil.

In the paper, hydrothermally (HT) treated, sulfuric acid (H2SO4), and hydrochloric acid (HCl) washed fly ashes (FA) were used to examine the applied effects with and without biochar (BC) on the bioavailability of heavy metals (HMs) and growth of maize (Zea mays L.) plants in coal-mining contaminated soil. Addition of BC in combination with these processed fly ashes (PFA) significantly increased the soil pH, EC, and soil organic carbon (SOC). Individual application of BC and PFA increased the available contents of Mg, Mn, and Fe, while the combination of BC and PFA significantly decreased the bioavailability of HMs in soil compared to control. The BC + HT-FA and BC + H2SO4-FA were most efficient treatments followed by BC + HCl-FA in promoting plant growth parameters (i.e., fresh and dry biomass, root and shoot lengths), reduction in the uptake of HMs and increase in the uptake of macronutrients. The results established that the combined application of BC and PFA synergistically increased HMs immobilization and maize biomass yields. The lowest transfer rate (TR), bioconcentration factor (BCF), and translocation factor (TF) for Cr, Co, Ni, Cu, Zn, Cd, and Pb were detected in BC + HT-FA, followed by BC + H2SO4-FA and BC + HCl-FA treatments after 60 days of maize crop harvesting. It could be suggested that using BC along with PFA as a soil stabilizer may be a promising source to immobilize HMs in a coal-mining contaminated soil.

Simultaneous functionalization and magnetization of biochar via NH3 ambiance pyrolysis for efficient removal of Cr (VI).

Enhancing biochar adsorption capabilities and recollection ability is essential for efficient biochar application. In this study, Nitrogen-doped magnetic biochar was prepared via one-step heating of FeCl3-laden agar biomass under NH3 environment. Synthesized magnetic biochar ABF-N800 shows a maximum Cr (VI) adsorption capacity up to 142.86 mg g-1, outperforming that of magnetic biochar and many other previously reported materials. Moreover, a significant increase of magnetic properties obtained by NH3 ambiance pyrolysis enables easy separation of the adsorbent from the solution after treated with Cr (VI). The physiochemical properties of composites characterized by SEM, EDS, XRD, XPS, VSM, BET surface and pore, Elemental content, and FTIR analysis. The NH3 ambiance pyrolysis confirmed as an efficient process for surface modification, increased magnetic properties and activated N-functional groups. The Langmuir isotherm model and pseudo-second-order model are applicable for describing adsorption behavior. The thermodynamic study shows that the adsorption was spontaneous and endothermic. The present results warrant the application of simultaneous functionalized and magnetized biochar for Cr (VI) contaminated wastewater treatment.