Biochar with KMnO4-hematite modification promoted foxtail millet growth by alleviating soil Cd and Zn biotoxicity.

The excessive accumulation of Cd and Zn in soil poisons crops and threatens food safety. In this study, KMnO4-hematite modified biochar (MnFeB) was developed and applied to remediate weakly alkaline Cd-Zn contaminated soil, and the heavy metal immobilization effect, plant growth, and metal ion uptake of foxtail millet were studied. MnFeB application reduced the phytotoxicity of soil heavy metals; bioavailable acid-soluble Cd and Zn were reduced by 57.79% and 35.64%, respectively, whereas stable, non-bioavailable, residual Cd and Zn increased by 96.44% and 32.08%, respectively. The chlorophyll and total protein contents and the superoxide dismutase (SOD)activity were enhanced, whereas proline, malondialdehyde, the H2O2 content, glutathione reductase (GR), ascorbate peroxidase (APX) and catalase (CAT) activities were reduced. Accordingly, the expressions of GR, APX, and CAT were downregulated, whereas the expression of MnSOD was upregulated. In addition, MnFeB promoted the net photosynthetic rate and growth of foxtail millet plants. Furthermore, MnFeB reduced the levels of Cd and Zn in the stems, leaves, and grains, decreased the bioconcentration factor of Cd and Zn in shoots, and weakened the translocation of Cd and Zn from roots to shoots. Precipitation, complexation, oxidation-reduction, ion exchange, and π-π stacking interaction were the main Cd and Zn immobilization mechanisms, and MnFeB reduced the soil bacterial community diversity and the relative abundance of Proteobacteria and Planctomycetota. This study provides a feasible and effective remediation material for Cd- and Zn-contaminated soils.

A novel and recyclable silica gel-modified biochar to remove cadmium from wastewater: Model application and mechanism exploration.

Water pollution caused by heavy metals is a major environmental problem, threatening water production, food safety, and human health. Cadmium (Cd) pollution is particularly serious because of food-chain biomagnification at toxic concentrations. Modified biochar is promising for heavy metal removal; however, efficient adsorbents for Cd removal are lacking. In the present study, a novel adsorbent, silica gel-modified biochar (SGB), was prepared and applied to treat sewage polluted by Cd. Through the batch adsorption experiments, it is known that SGB possessed outstanding Cd removal ability and recycleability. Furthermore, the adsorption behavior and mechanisms were analyzed by the application of kinetic and isotherm models. The maximum Cd2+ adsorption capacity of SGB was 38.08 mg g-1, and after five recycling processes, the Cd2+ removal rate was still 86.89 %. When the pH of the solution was 7.0, SGB showed the strongest Cd2+ adsorption capacity (29.06 mg g-1). When competitive ions existed, biochar also had high Cd removal efficiency, although the effect of Pb2+ was greater than those of Cu2+ and Zn2+, indicating that SGB was applicable to complex polluted water. Additionally, the main Cd2+ adsorption mechanisms by SGB were electrostatic interactions, π-π interactions, complexation, and co-precipitation. These results showed that SGB can effectively treat Cd-contaminated wastewater as a new adsorbent.

Effects of a novel Cd passivation approach on soil Cd availability, plant uptake, and microbial activity in weakly alkaline soils.

Heavy metal pollution, including that caused by cadmium (Cd), is a matter of increasing concern. Although in situ passivation remediation has been widely used to treat heavy metal-polluted soils, most studies have focused on acidic soils, while studies on alkaline soil conditions are scarce. In this study, the effects of biochar (BC), phosphate rock powder (PRP), and humic acid (HA) on Cd2+ adsorption were examined alone and in combination to choose an appropriate Cd passivation approach for weakly alkaline soils. Additionally, the combined impact of passivation on Cd availability, plant Cd absorption, plant physiology indexes, and soil microbial community was elucidated. BC had a higher Cd adsorption capacity and removal rate than those of PRP and HA. Moreover, HA and PRP enhanced the adsorption capacity of BC. A combination of biochar and humic acid (BHA), and biochar and phosphate rock powder (BPRP) significantly affected soil Cd passivation. BHA and BPRP decreased the plant Cd content and soil Cd-DTPA (diethylenetriaminepentaacetic acid) by 31.36 %, 20.80 %, 38.19 %, and 41.26 %, respectively; however, they increased the fresh weight by 65.64-71.48 % respectively, and dry weight by 62.41-71.35 %, respectively. Notably, only BPRP increased the node and root tip number in wheat. Total protein (TP) content increased in BHA and BPRP, with BHA showing lower TP than BPRP. BHA and BPRP showed a reduction in glutathione (GSH), malondialdehyde (MDA), H2O2, and peroxidase (POD); BHA showed a significantly lower GSH than BPRP. Additionally, BHA and BPRP increased soil sucrase, alkaline phosphatase, and urease activities, with BPRP showing considerably higher enzyme activity than BHA. Both BHA and BPRP increased the number of soil bacteria, altered the community composition, and critical metabolic pathways. The results demonstrated that BPRP could be used as a highly effective, novel passivation technique for the remediation of Cd-contaminated soil.

Effective utilization of weak alkaline soils with Cd-contamination by wheat and rape intercropping.

Recently, there has been increasing concern about the health hazards of heavy metal-polluted farmlands. Recent findings suggest that intercropping could be effective remediation strategy for agricultural soils without affecting crop biomass yield. However, there are concerns on the heavy metal accumulation in plant organs in phytoremediation, emphasizing the need to develop an effective intercropping remediation model. In this study, we evaluated the effects of intercropping rape and wheat with different accumulation characteristics of cadmium (Cd), and crop growth and physiological characteristics. Intercropping significantly reduced the Cd content of rape shoot and root, with the rape-low Cd-accumulating wheat intercropping system yielding the best results. However, intercropping had no significant effect on Cd accumulation in wheat. Additionally, intercropping affected the root system configuration and structure, photosynthetic indicators, chlorophyll content, crop enzyme content, and rhizosphere enzyme activity of both species, but did not significantly affect the biomass of wheat and rape. Overall, our findings showed that intercropping rape with a low Cd-accumulating wheat variety could be an effective model for safe production of wheat and rape in weak alkaline soils without compromising biomass yield. The study demonstrates that similar innovative, effective, and judicious intercropping strategy can enrich the theory of contaminated soil remediation.

Treatment of cadmium and zinc-contaminated water systems using modified biochar: Contaminant uptake, adsorption ability, and mechanism.

Cd and Zn contamination in water occurs frequently that threatens water supply, human health, and food production. MnFeB, a novel absorbent biochar modified using KMnO4 and hematite, was prepared and used for the treatment of Cd2+ and Zn2+solutions. MnFeB exhibits a rough surface structure, large specific surface area, higher total pore volume, massive functional groups, and abundant iron oxide, all of which contribute to higher Cd2+ and Zn2+ adsorption capacity. In single metal systems, maximum Cd2+ and Zn2+ adsorption capacities of MnFeB were 1.88 and 1.79 times higher than those of unmodified biochar (CSB). The maximum Cd2+ and Zn2+ adsorption capacities of MnFeB were 2.73 and 2.65 times higher than CSB in the binary metal system. Key adsorption mechanisms of Cd2+ and Zn2+ by MnFeB included electrostatic interaction, co-precipitation, π-π interaction, complexation, and ion exchange. Thus, MnFeB can be used as a novel absorbent to treat Cd and Zn-polluted water.

Biochar Alleviates Phytotoxicity by Minimizing Bioavailability and Oxidative Stress in Foxtail Millet (Setaria italica L.) Cultivated in Cd- and Zn-Contaminated Soil.

Soil contamination with multiple heavy metals is a global environmental issue that poses a serious threat to public health and ecological safety. Biochar passivation is an efficient and economical technology to prevent heavy metal contamination of Cd; however, its effects on compound-contaminated and weakly alkaline soil remain unclear. Further, the mechanisms mediating the immobilization effects of biochar have not been evaluated. In this study, three biochar treated at different pyrolytic temperatures [300°C (BC300), 400°C (BC400), and 500°C (BC500)] were applied to Cd-/Zn-contaminated soils, and their effects on plant growth, photosynthetic characteristics, Cd/Zn accumulation and distribution in foxtail millet were evaluated. Further, the effect of biochar application on the soil physicochemical characteristics, as well as the diversity and composition of the soil microbiota were investigated. Biochar significantly alleviated the phytotoxicity of Cd and Zn. DTPA (diethylenetriamine pentaacetic acid)-Cd and DTPA-Zn content was significantly reduced following biochar treatment via the transformation of exchangeable components to stable forms. BC500 had a lower DTPA-Cd content than BC300 and BC400 by 42.87% and 39.29%, respectively. The BC500 passivation ratio of Cd was significantly higher than that of Zn. Biochar application also promoted the growth of foxtail millet, alleviated oxidative stress, and reduced heavy metal bioaccumulation in shoots, and transport of Cd from the roots to the shoots in the foxtail millet. The plant height, stem diameter, biomass, and photosynthetic rates of the foxtail millet were the highest in BC500, whereas the Cd and Zn content in each organ and malondialdehyde and hydrogen peroxide content in the leaves were the lowest. Moreover, biochar application significantly increased the abundance of soil bacteria and fungi, as well as increasing the fungal species richness compared to no-biochar treatment. Overall, biochar was an effective agent for the remediation of heavy metal-contaminated soil. The passivation effect of biochar exerted on heavy metals in soil was affected by the biochar pyrolysis temperature, with BC500 showing the best passivation effect.

Biochar mitigation of soil acidification and carbon sequestration is influenced by materials and temperature.

The alleviation effects on soil acidification by different raw materials and pyrolysis temperatures can broaden the utilization of biochar. In this study, nine types of biochar produced from three raw materials, namely fruit tree branch, peanut shell, and cow dung, at three pyrolysis temperatures (300, 450, and 600 °C) were used to amend acidified brown soil; the rape growth, physiology character, soil chemical and microbial, along with soil organic carbon mineralization were also investigated. The results showed that application of biochar increased soil pH by 8.48-79.25% and reduced exchangeable acidity, exchangeable Al, and exchangeable H by 56.94-94.95%, 34.38-95.66%, and 58.72-93.27%, respectively. Biochar alleviated oxidative stress in plants, reduced malondialdehyde and glutathione content in leaves, promoted rape growth, and increased microbial community diversity and the relative abundances of Acidobacteria and Olpidiomycota in the acidic soil. Moreover, biochar reduced the mineralization rate of organic carbon and the proportion of mineral-bonded organic carbon. Overall, biochar application is an effective strategy to ameliorate soil acidification and enhance rape production and carbon sequestration. The mitigation effect of branch biochar and cow dung biochar on soil acidification was superior to that of peanut shell biochar. The effects of biochar depended on the pyrolysis temperature; the positive effects of biochar samples pyrolyzed at 450 and 600 â„ƒ were stronger than those pyrolyzed at 300 â„ƒ. In this study, the optimum biochar materials and carbonization temperature for acidified soil improvement, as well as the effects of biochar application on soil microbial and carbon mineralization were clarified, which provides a new potential strategy for acidified soil improvement and expand the application range of biochar.

Genotypic diversity of quality traits in Chinese foxtail millet (Setaria italica L.) and the establishment of a quality evaluation system.

Foxtail millet (Setaria italica L.) is an important reserve cereal crop, and its nutritional and medicinal properties have seen its demand increase in recent years. Therefore, it is important to establish an evaluation system for the comprehensive assessment of its quality. We assessed 90 accessions of foxtail millet from China for 23 quality traits. The results showed that the 23 quality traits had diverse coefficients of variation, with the greatest variation in a*, phosphorus content, and potassium contents, at 37.71, 28.81, and 20.18%, respectively. Cluster analysis defined five categories that were consistent with the geographical origins of the accessions. Seven principal components were also extracted from the 23 traits using principal component analysis. A comprehensive quality evaluation system was established, and 8 high-quality accessions were identified. The findings of the present study could facilitate the breeding of high-quality foxtail millet and enhance quality evaluation activities.

Application of principal component analysis method for micro-resonator weak resonant signal detection.

The characteristic of weak resonant signal output by an electrothermally excited microresonator is analyzed, and the principal component analysis (PCA) method is proposed and applied in the resonant frequency detection of the output weak signal by separating the noises. Simulation on weak resonant signals under different levels of noises and different quality factors of the resonator was conducted after the influence of the data selection window width and the principal component number on detection results was analyzed. Finally, the experiment platform was built, and the output signal of the sensor sample was used to verify the detection effect of the proposed PCA method. Simulation and experiment results show that the proposed PCA method could accurately obtain the resonant frequency compared with the resonant frequency obtained by the smoothing filter and Lorentzian fitting method.

Quantitative identification of nitrate sources in the surface runoff of three dominant forest types in subtropical China based on Bayesian model.

Nitrate pollution is a global environmental issue. Forests play an important role in altering hydrological processes and purifying water pollutants in rainfall and runoff. The quantitative identification of nitrate concentration and sources in surface runoff is of great significance for watershed management and water environment improvement. In this study, water quality of surface runoff was monitored in three typical forest types in subtropical eastern China: Phyllostachys pubescens, Cunninghamia lanceolate, and Cyclobalanopsis glauca. Combined with hydrochemical analysis, we adopted the dual isotope approach (δ15N-NO3- and δ18O-NO3-) and Bayesian model (SIAR) to identify nitrate sources in forests that are subject to low anthropogenic disturbance. Results showed that the temporal variability of NO3-N concentrations was similar for all forest types, with higher values in periods of low rainfall and lower values in heavy rainfall periods. The NO3--N concentration in runoff was much higher in C. glauca forests relative to P. pubescens and C. lanceolata. Both the Cl- concentrations and NO3-/Cl- molar ratio suggested the fertilizer inputs was the dominant source of nitrate in surface runoff. In agreement, δ15N-NO3- and δ18O-NO3- values inferred atmospheric deposition and chemical fertilizers to be the main sources of nitrate in all forest types. The Bayesian model outputs demonstrated that atmospheric deposition was the main source in the runoff in P. pubescens and C. lanceolate forests, contributing 28.83% and 35.08% to the total nitrate, respectively. In contrast, chemical fertilizers were identified as the main source in C. glauca forests, with NH4+ fertilizers and NO3- fertilizers accounting for 27.07% and 24.83%, respectively. Both chemical and isotopic analysis indicated that nitrification had little contribution to nitrate concentrations in runoff. Our results suggest that, even in forests with low anthropogenic disturbance, the application of fertilizer in surrounding agricultural regions should be effectively managed to minimize watershed nitrogen contamination.