Characteristic study of biological CaCO3-supported nanoscale zero-valent iron: stability and migration performance.

nZVI has attracted much attention in the remediation of contaminated soil and groundwater, but the application is limited due to its aggregation, poor stability, and weak migration performance. The biological CaCO3 was used as the carrier material to support nZVI and solved the nZVI agglomeration, which had the advantages of biological carbon fixation and green environmental protection. Meanwhile, the distribution of nZVI was characterised by SEM-EDS and TEM carefully. Subsequently, the dispersion stability of bare nZVI and CaCO3@nZVI composite was studied by the settlement experiment and Zeta potential. Sand column and elution experiments were conducted to study the migration performance of different materials in porous media, and the adhesion coefficient and maximum migration distances of different materials in sand columns were explored. SEM-EDS and TEM results showed that nZVI could be uniformly distributed on the surface of biological CaCO3. Compared with bare nZVI, CaCO3@nZVI composite suspension had better stability and higher absolute value of Zeta potential. The migration performance of nZVI was poor, while CaCO3@nZVI composite could penetrate the sand column and have good migration performance. What's more, the elution rates of bare nZVI and CaCO3@nZVI composite in quartz sand columns were 5.8% and 51.6%, and the maximum migration distances were 0.193 and 0.885 m, respectively. In summary, this paper studies the stability and migration performance of bare nZVI and CaCO3@nZVI composite, providing the experimental and theoretical support for the application of CaCO3@nZVI composite, which is conducive to promoting the development of green remediation functional materials.

Effects of remediation agents on rice and soil in toxic metal(loid)s contaminated paddy fields: A global meta-analysis.

Toxic metal(loid)s contamination of paddy soil is a nonnegligible issue and threatens food safety considering that it is transmitted via the soil-plant system. Applying remediation agents could effectively inhibit the soil available toxic metal(loid)s and reduce their accumulation in rice. To comprehensively quantify how remediation agents impact the accumulation of Cd/Pb/As in rice, rice growth and yield, the accumulation of available Cd/Pb/As in paddy soil, and soil characteristics, 50 peer-reviewed publications were selected for meta-analysis. Overall, the application of remediation agents exhibited significant positive effects on rice plant length (ES = 0.05, CI = 0.01-0.08), yield (ES = 0.20, CI = 0.13-0.27), peroxidase (ES = 0.56, CI = 0.18-0.31), photosynthetic rate (ES = 0.47, CI = 0.34-0.61), and respiration rate (ES = 0.68, CI = 0.47-0.88). Among the different types of remediation agents, biochar was the most effective in controlling the accumulation of Cd/Pb/As in all portions of rice, and was also superior in inhibiting the accumulation of Pb in rice grains (ES = -0.59, 95 % CI = -1.04-0.13). This study offers an essential contribution for the remediation strategies of toxic metal(loid)s contaminated paddy fields.

The effects of iron-based nanomaterials (Fe NMs) on plants under stressful environments: Machine learning-assisted meta-analysis.

Mitigating the adverse effects of stressful environments on crops and promoting plant recovery in contaminated sites are critical to agricultural development and environmental remediation. Iron-based nanomaterials (Fe NMs) can be used as environmentally friendly nano-fertilizer and as a means of ecological remediation. A meta-analysis was conducted on 58 independent studies from around the world to evaluate the effects of Fe NMs on plant development and antioxidant defense systems in stressful environments. The application of Fe NMs significantly enhanced plant biomass (mean = 25%, CI = 20%-30%), while promoting antioxidant enzyme activity (mean = 14%, CI = 10%-18%) and increasing antioxidant metabolite content (mean = 10%, CI = 6%-14%), reducing plant oxidative stress (mean = -15%, CI = -20%∼-10%), and alleviating the toxic effects of stressful environments. The observed response was dependent on a number of factors, which were ranked in terms of a Random Forest Importance Analysis. Plant species was the most significant factor, followed by Fe NM particle size, duration of application, dose level, and Fe NM type. The meta-analysis has demonstrated the potential of Fe NMs in achieving sustainable agriculture and the future development of phytoremediation.

Internal Electric Field-Modulated Charge Migration Behavior in MoS2 /MIL-53(Fe) S-Scheme Heterojunction for Boosting Visible-Light-Driven Photocatalytic Chlorinated Antibiotics Degradation.

Inadequate photo-generated charge separation, migration, and utilization efficiency limit the photocatalytic efficiency. Herein, a MoS2 /MIL-53(Fe) photocatalyst/activator with the S-scheme heterojunction structure is designed and the charge migration behavior is modulated by the internal electric field (IEF). The IEF intensity is enhanced to 40 mV by modulating band bending potential and the depletion layer length of MoS2 . The photo-generated electron migration process is boosted by constructing the electron migration bridge (Fe-O-S) and modulating the IEF as the driving force, confirmed by the density functional theory calculation. Compared with the pristine materials, the photocurrent density of MoS2 /MIL-53(Fe) is significantly enhanced 27.5 times. Contributed by the visible-light-driven cooperative catalytic degradation and the high-efficiency direct photo-generated electron reduction dichlorination process, satisfactory chlorinated antibiotics removal and detoxification performances are achieved. This study opens up new insights into the application of heterojunctions in photocatalytic activation of PDS in environmental remediation.

Effects of the application of nanoscale zero-valent iron on plants: Meta analysis, mechanism, and prospects.

In order to determine the ideal conditions for the application of nanoscale zero-valent iron (nZVI) in agricultural production, this review studies the effects of nZVI application on plant physiological parameters, presents its mechanism and prospective outcomes. In this research, it was observed that the application of nZVI had both favorable and unfavorable effects on plant growth, photosynthesis, oxidative stress, and nutrient absorption levels. Specifically, the application of nZVI significantly increased the biomass and length of plants, and greatly reduced the germination rate of seeds. In terms of photosynthesis, there was no significant effect for the application of nZVI on the synthesis of photosynthetic pigments (chlorophyll and carotenoids). In terms of oxidative stress, plants respond by increasing the activity of antioxidant enzyme under mild nZVI stress and trigger oxidative burst under severe stress. In addition, the application of nZVI significantly increased the absorption of nutrients (B, K, P, S, Mg, Zn, and Fe). In summary, the application of nZVI can affect the plant physiological parameters, and the degree of influence varies depending on the concentration, preparation method, application method, particle size, and action time of nZVI. These findings are important for evaluating nZVI-related risks and enhancing nZVI safety in agricultural production.

Mitigating soil salinity stress with titanium gypsum and biochar composite materials: Improvement effects and mechanism.

Titanium gypsum and biochar are considered effective amendments for mitigating soil salinity stress. However, the knowledge is inadequate regarding their efficiency and application as an improvement. In this study, TG-B composite was prepared by using industrial by-products titanium gypsum and biochar as raw materials and then modified by ball milling method, to characterize its microscopic characteristics and explore the improvement effect on saline-alkali soil and plant growth. Besides, we explored the mechanism of TG-B in improving saline-alkali soil and the dynamic balance of the solution reaction process. Our results showed that the CaSO4·2H2O particles in TG-B were finer, dispersed evenly, and contacted fully with soil gelatinous particles, which was more conducive to the improvement of saline-alkali soil. The results of TG-B with different ball milling ratios and different materials dosages indicated that the application rate of TG-B was 5%, and the optimum ratio of TG-B was TG: B (mass ratio) = 10:1, with the best soil improvement effect. The pot experiment proved that the indicators of indicating soil salinity such as pH, EC, SAR, and soluble Na+ decreased by 20.74%, 77.24%, 68.77%, and 44.70%, respectively, thus playing a good role in improving saline-alkali soil. In addition, pot experiments demonstrated that compared with the control group, the soil porosity and soil moisture content in the TG-B group increased by 15.95% and 38.71%, respectively, and further improve the structure and diversity of soil bacterial community when compared with titanium gypsum and biochar alone. Finally, the application of TG-B promoted the germination and growth of rice significantly through the synergistic effects of composite material components. These results all suggested that the application of TG-B was an effective strategy to improve soil salinity and promote plant growth. Therefore, it might provide new insights into the utilization of solid waste resources to improve saline-alkali lands.