Soil chemical washing has the disadvantages of long reaction time, slow reaction rate and unstable effect. Thus, there is an urgent need to find a cost-effective and widely applicable alternative power to facilitate the migration of washing solutions in the soil, so as to achieve efficient removal of heavy metals, reduce the risk of soil compaction, and mitigate the damage of soil structure. Therefore, the study used a combination of freeze-thaw cycle (FTC) and chemical washing to obtain three-dimensional images of soil pore structure using micro-X-ray microtomography, and applied image analysis techniques to study the effects of freeze-thaw washing on the characteristics of different pore structures of the soil, and then revealed the effects of pore structure on the removal of heavy metals. The results showed that the soil pore structure of the freeze-thaw washing treatment (FT) became more porous and complex, which increased the soil imaged porosity (TIP), pore number (TNP), porosity of macropores and irregular pores, permeability, and heavy metal removal rate. Macroporosity, fractal dimension, and TNP were the main factors contributing to the increase in TIP between treatments. The porous structure resulted in larger effective pore diameters, which contain a greater number of branching pathways and pore networks, allowing the chemical washing solutions to fully contact the soil, increasing the roughness of the soil particle surface, mitigating the risk of soil compaction, and decreasing the contamination of heavy metals. The results of this study contribute to provide new insights into the management of heavy metal pollution in agricultural soils.

Nitrogen is an essential element for life but its excessive release into the environment in the form of reactive nitrogen causes severe damage, including acidification and eutrophication. One of the main sources of nitrogen pollution is the use of fertilizers in agricultural soils. Feammox is a recently described pathway that couples ammonium (NH4+) oxidation with iron (Fe) reduction. In this study, the enrichment and bioaugmentation of anaerobic sludge under conditions that promote Feammox activity were investigated. The first enrichment stage (E1) achieved 28% of ammonium removal after 28 days of incubation, with a production of 30 mg/L of Fe2+. E1 was then used as inoculum for two enrichments at 35 degrees C with different carbon sources: sodium acetate (E2) and sodium bicarbonate (E3). Neither E2 nor E3 showed significant NH4+ removal, but E2 was highly effective in iron reduction, reaching Fe2+ concentrations of 110 mg/L. Additionally, an increase in nitrate (NO3-) concentration was observed, which may indicate the occurrence of this pathway in the Feammox process. The Monod kinetic model, analyzed using AQUASIM software, showed a good fit to the experimental data for NH4+, NO3-, and Fe2+. Sequencing analysis revealed the presence of phyla associated with Feammox activity. Although there was only a slight difference in NH4+ removal between the bioaugmented and non-augmented control sludge, the bioaugmented sludge was statistically superior in nitrate production and iron reduction. This study provides valuable insights into the enrichment and bioaugmentation of the Feammox process potential large-scale wastewater treatment applications.

The environmental threat, pollution and damage posed by heavy metals to air, water, and soil emphasize the critical need for effective remediation strategies. This review mainly focuses on microbial electrochemical technologies (MET) for treating heavy metal pollutants, specifically includes Chromium (Cr), Copper (Cu), Zinc (Zn), Cadmium (Cd), Lead (Pb), Nickel (Ni), and Cobalt (Co). First, it explores the mechanisms and current applications of MET in heavy metal treatments in detail. Second, it systematically summarizes the key microbial communities involved, analyzing their extracellular electron transfer (EET) processes and summarizing strategies to enhance the EET efficiencies. Next, the review also highlights the synergistic microbial interactions in bioelectrochemical systems (BES) during the recovery and removal (remediation) processes of heavy metals, underscoring the crucial role of microorganisms in the transfer of the electrons. Then, this paper discussed how factors including pH values, applied voltages, types and concentrations of electron donors, electrode materials, biofilm thickness and other factors affect the treatment efficiencies of some specific metals in BES. BES has shown its great superiority in treating heavy metals. For example, for the treatments of Cr6+, under low pH conditions, the recovery and removal rate of Cr-6(+) by double chambers microbial fuel cell (DCMFC) can generally reach 98-99%, with some cases even achieving 100% (Gangadharan & Nambi, 2015). For the treatments of heavy metal ions such as Cu2+, Zn2+ and Cd2+, BES can also achieve the rates of treatments of more than 90% under the corresponding conditions of appropriate pH values and applied voltages(Choi, Hu, & Lim, 2014; W. Teng, G. Liu, H. Luo, R. Zhang, & Y. Xiang, 2016; Y. N. Wu et al., 2019; Y. N. Wu et al., 2018). After that, the review outlines the future challenges and the research opportunities for understanding the mechanisms of BES and microbial EET in heavy metal treatments. Finally, the prospect of future BES researches are pointed out, including the combinations with existing wastewater treatment systems, the integrations with the wind energy and the solar energy, and the application of machine learning (ML) in future BES. This article has certain significance and value for readers to better understand the working principles of BES and better operate and control BES to deal with heavy metal pollutants.

The removal of straw from the seed bed to the inter-row prior to sowing maize is a critical agricultural practice. However, this process is inherently uncertain due to the variability in straw displacement. To investigate this interaction, this study developed a flexible straw model utilizing a discrete element approach, employing hollow cylinders to linearly connect the particles. Experiments were conducted to ascertain the mechanical properties of the flexible straw, with a focus on its biological and mechanical parameters. Subsequently, a full-coverage soil bin model of wheat straw was established to simulate the straw removal process, enabling the analysis of the interaction between the removal device and the straw during operation. The results indicate that varying operating speeds significantly enhance the influence of the straw removal device on the straw, thereby improving the straw removal rate. The maximum relative error of the traction force required for both simulation and experimental testing was found to be 21.27%. Additionally, a combined device was employed to simulate the straw removal process, with straw disturbance analyzed in both paired and single-direction scenarios. Finally, by comparing simulation results with bench test outcomes, the established model demonstrated a high degree of accuracy in simulating the straw displacement process. This research provides a valuable reference for the development of discrete element models for other crops and for enhancing the efficiency of straw removal devices.

This study investigated the effectiveness of enzyme-induced carbonate precipitation (EICP) technology in remediating Pb- and Zn-contaminated sand. The research focused on the immobilization of heavy metals and the enhancement of sand strength. Experimental results demonstrated that urease activity increased linearly with enzyme concentration, stabilizing at 100 g/L with an activity of 18 mmol/min, and reached a peak at a pH of 8. Temperature variations also positively impacted urease activity, and effective remediation levels were achieved at standard room temperature. The EICP method effectively transformed heavy metal ions from a mobile exchangeable state to a stable carbonate-bound state, and removal rates exceeded 80% for Zn2+ and 90% for Pb2+ after three treatment cycles. Furthermore, the technology significantly improved the unconfined compressive strength of contaminated sand, increasing Pb-contaminated sand strength to 0.57 MPa and Zn-contaminated sand strength to 0.439 MPa. These findings highlight the potential of EICP technology as a viable solution for the remediation of heavy metal-contaminated sand, offering both immobilization of contaminants and enhancement of sand mechanical properties.

This paper puts forward a vibrable prefabricated vertical drain (V-PVD) that combines vibrators on PVD to alleviate the clogging on PVD and enhances the reinforcement effect of vacuum preloading method. To validate the reinforcement effect of V-PVD, a full-scale on-site test was conducted including four zones with different V-PVD installations. The ground surface settlement and pore water pressure in each zone were monitored. In addition, a comparative analysis was conducted on vane shear strength and water content before and after soil reinforcement. The test results indicates that the vibrable prefabricated vertical drain in vacuum preloading method can effectively improve the soil reinforcement effect. The ground surface settlement increased by 20.9% to 43.8% compared to conventional vacuum preloading method, and the dissipation value of pore water pressure increased by 17.1% to 58.6%, and vane shear strength increases by 5.9% to 24.5%. The activation of the vibrator helps to remove clogging around PVD, and the more vibrators installed on PVD surface, the better the soil reinforcement effect is achieved. However more vibrators installed on PVD, the drainage area on the PVD surface was influenced and drainage efficiency reduced initially, which implies that a reasonable installation of vibrator should be considered in practice.

Soil salinization severely restricts the growth and development of crops globally, especially in the northwest Loess Plateau, where apples constitute a pillar industry. Nanomaterials, leveraging their unique properties, can facilitate the transport of nutrients to crops, thereby enhancing plant growth and development under stress conditions. To investigate the effects of nano zinc oxide (ZnO NP) on the growth and physiological characteristics of apple self-rooted rootstock M9-T337 seedlings under saline alkali stress, one-year-old M9-T337 seedlings were used as experimental materials and ZnO NPs were used as donors for pot experiment. Six treatments were set up: CK (normal growth), SA (saline alkali stress,100 mmol/L NaCl + NaHCO3), T1 (saline alkali stress + 50 mg/L ZnO NPs), T2 (saline alkali stress + 100 mg/L ZnO NPs), T3 (saline alkali stress + 150 mg/L ZnO NPs) and T4 (saline alkali stress + 200 mg/L ZnO NPs). The results were found to show that saline alkali stress could significantly inhibit the growth and development of M9-T337 seedlings, reduce photosynthetic characteristics, and cause ion accumulation to trigger osmotic regulation system, endogenous hormone and antioxidant system imbalances. However, the biomass, plant height, stem diameter, total leaf area and leaf perimeter of M9-T337 seedlings were significantly increased after ZnO NP treatment. Specifically speaking, ZnO NPs can improve the photosynthetic capacity of M9-T337 by increasing the content of photosynthetic pigment, regulating photosynthetic intensity and chlorophyll fluorescence parameters. ZnO NPs can balance the osmotic adjustment system by increasing the contents of soluble protein (SP), soluble sugar (SS), proline (Pro) and starch, and can also enhance the activities of enzymatic (SOD, POD, and CAT) and non-enzymatic antioxidant enzymes (APX, AAO, GR, and MDHAR) to enhance the scavenging ability of reactive oxygen species (H2O2, O2 center dot-), ultimately reducing oxidative damage; ZnO NPs promoted the growth of M9-T337 seedlings under saline alkali stress by synergistically responding to auxin (IAA), gibberellin (GA3), zeatin (ZT) and abscisic acid (ABA). Additionally, the Na+/K+ ratio was reduced by upregulating the expression of Na+ transporter genes (MdCAX5, MdCHX15, MdSOS1, and MdALT1) and downregulating the expression of K+ transporter genes (MdSKOR and MdNHX4). After comprehensive analysis of principal components and correlation, T3 (150 mg/L ZnO NPs) treatment possessed the best mitigation effect. In summary, 150 mg/L ZnO NPs(T3) can effectively maintain the hormone balance, osmotic balance and ion balance of plant cells by promoting the photosynthetic capacity of M9-T337 seedlings, and enhance the antioxidant defense mechanism, thereby improving the saline alkaline tolerance of M9-T337 seedlings.

To address prominent issues in the spring soil removal process for wine grapes in northern China, such as incomplete soil clearing, vine damage, and low operational efficiency, a dual-sided soil removal machine combining scraping, rotary, and vibration functions was designed and developed. The machine primarily consists of a gantry frame, rotary soil components, scraping components, and vibrating components. Using EDEM 2020 discrete element software analysis and Design-Expert 13 orthogonal experiments, a three-factor, three-level orthogonal simulation experiment was conducted, with rotary soil component speed, scraping component angle, and vibrating component frequency as test factors and soil removal rate as the evaluation index. The optimal operating parameters were determined: rotary soil component speed at 720.6 r/min, scraping component angle at 42.4 degrees, and vibrating component frequency at 179.1 Hz, yielding a soil removal efficiency (K value) of 83.48% and the best simulation results. A physical prototype was manufactured, and field experiments were conducted, resulting in an actual soil removal rate of 76.81%, with a deviation of 7.09% from the simulation results. The field test results were consistent with the simulation data, and the exposed vines in the field after soil removal met the operational requirements for actual production. The research outcomes of this machine provide a reference for the further development of dual-sided soil removal equipment for wine grape vines.

Terrestrial enhanced rock weathering (ERW) is a promising carbon dioxide removal technology that consists in applying ground silicate rock such as basalt on agricultural soils. On top of carbon sequestration, ERW has the potential to raise the soil pH and release nutrients, thereby improving soil fertility. Despite these possible co-benefits, concerns such as heavy metal pollution or soil structure damage have also been raised. To our knowledge, these contrasted potential effects of ERW on soil fertility have not yet been simultaneously investigated. This field trial aimed at assessing the impact of ERW on biological, physical, and chemical soil properties in a temperate agricultural context. To do so, three vineyard fields in Switzerland were selected for their distinct geochemical properties and were amended with basaltic rock powder at a dose of 20 tons per hectare (2 kg.m(-2)). On each field, basaltic rock powder was either applied one year before the sampling campaign, one month before the sampling campaign, or not applied (control) for a total of 27 plots with 9 repetitions of each level. Overall, basaltic rock powder addition had a predominantly positive to neutral effect on soil fertility. Most soil properties showed no significant change either 1 month or 1 year post application. Nevertheless, our study highlighted a significant increase in earthworm abundance (+71 % on average), soil respiration (+50 %) and extractable sodium concentration (+23 %) as early as 1 month post application. The higher soil respiration raises the question of CO2 losses from organic matter mineralization that could limit ERW's efficiency. The increase in sodium raises concerns about a sodification risk potentially damaging soil fertility. These elements now require further investigation before enhanced rock weathering can be considered a viable and secure carbon dioxide removal technology.

The accumulation of heavy metal in circulating TCMs has attracted widespread attention because the security and therapeutic efficacy are inevitably imperiled by the survival ecological environment and human production activities. How to reduce the pollution level and improve the toxicity damage becomes an urgent issue. This article provides a comprehensive overview of the current status of heavy metal contamination over a thousand types of single herbal (botanical, animal and mineral medicines) and TCM preparations published over nearly two decades. The survey revealed that growth ecosystems (soil, water sources), anthropogenic factors (harvesting, processing, storage), specific varieties and medicinal parts utilized as well as the inherent resistance capacity are the key factors that affect the accumulation of heavy metals in TCMs. And Pb, Cu and Cr are the major cumulative elements for botanicals, while mineral and animal medicines are dominated by As and Cu elements, respectively. Ongoing efforts aimed at mitigating the level and translocation rate of heavy metals by optimized cultivation processes, appropriate processing methodologies and advanced adsorption techniques are effective removal strategies. And the prospects of TCMs as a detoxifying agent for heavy metal toxicity damage posed development potential. Besides, the correlation between the speciation of arsenic (As) and chromium (Cr) and their toxicity should also be elaborated in order to provide effective references for standardizing drug dosage and cycle. And the imperative from the perspective of improving limitations standards of HMs for animal medicines, external preparations and folk medicines as well as exploring the interaction mechanisms between heavy metals and active ingredients of TCMs provides the direction for the follow-up study.