Investigating the effects of biochar colloids and nanoparticles on cucumber early seedlings

Ball milling nano-sized biochar: bibliometrics, preparation, and environmental application

Nano-sized biochar, which is a small structure prepared from biochar by grinding, has surpassed traditional biochar in performance, showing enhanced effects and potential for a wide range of environmental applications. Firstly, this paper visualizes and analyzes the literature in this field by CiteSpace to clarify the development trend of nano-sized biochar. The review intuitively shows the most influential countries, the most productive institutions, and the most concerned hot spots in the field of nano-sized biochar. Secondly, these hotspots in environment management are summarized by keywords and clustering: (1) The application of ball milling is a modification scheme that researchers have paid attention to, and it is also a key method for preparing biochar nanomaterials. It has a more dispersed structure and can support more modified materials. (2) Nano-sized biochar in the comprehensive utilization of water, soil, and plants was discussed and is a small range of application modification methods. (3) The bidirectional effects of nano-sized biochar on plants were analyzed, and the challenges in its application were listed. Finally, the economic management of nano-sized biochar and the relationship between microorganisms are the focus of the next research.

Putting Biochar in Action: A Black Gold for Efficient Mitigation of Salinity Stress in Plants. Review and Future Directions

Soil salinization is a serious concern across the globe that is negatively affecting crop productivity. Recently, biochar received attention for mitigating the adverse impacts of salinity. Salinity stress induces osmotic, ionic, and oxidative damages that disturb physiological and biochemical functioning and nutrient and water uptake, leading to a reduction in plant growth and development. Biochar maintains the plant function by increasing nutrient and water uptake and reducing electrolyte leakage and lipid peroxidation. Biochar also protects the photosynthetic apparatus and improves antioxidant activity, gene expression, and synthesis of protein osmolytes and hormones that counter the toxic effect of salinity. Additionally, biochar also improves soil organic matter, microbial and enzymatic activities, and nutrient and water uptake and reduces the accumulation of toxic ions (Na+ and Cl), mitigating the toxic effects of salinity on plants. Thus, it is interesting to understand the role of biochar against salinity, and in the present Review we have discussed the various mechanisms through which biochar can mitigate the adverse impacts of salinity. We have also identified the various research gaps that must be addressed in future study programs. Thus, we believe that this work will provide new suggestions on the use of biochar to mitigate salinity stress.

A systematic review of biochar aging and the potential eco-environmental risk in heavy metal contaminated soil

Biochar is widely accepted as a green and effective amendment for remediating heavy metals (HMs) contaminated soil, but its long-term efficiency and safety changes with biochar aging in fields. Currently, some reviews have qualitatively summarized biochar aging methods and mechanisms, aging-induced changes in biochar properties, and often ignored the potential eco-environmental risk during biochar aging process. Therefore, this review systematically summarizes the study methods of biochar aging, quantitatively compares the effects of different biochar aging process on its properties, and discusses the potential eco-environmental risk due to biochar aging in HMs contaminated soil. At present, various artificial aging methods (physical aging, chemical aging and biological aging) rather than natural field aging have been applied to study the changes of biochar's properties. Generally, biochar aging increases specific surface area (SSA), pore volume (PV), surface oxygen-containing functional group (OFGs) and O content, while decreases pH, ash, H, C and N content. Chemical aging method has a greater effect on the properties of biochar than other aging methods. In addition, biochar aging may lead to HMs remobilization and produce new types of pollutants, such as polycyclic aromatic hydrocarbons (PAHs), environmentally persistent free radicals (EPFRs) and colloidal/nano biochar particles, which consequently bring secondary eco-environmental risk. Finally, future research directions are suggested to establish a more accurate assessment method and model on biochar aging behavior and evaluate the environmental safety of aged biochar, in order to promote its wider application for remediating HMs contaminated soil.

Migration of phosphorus in pig manure during pyrolysis process and slow-release mechanism of biochar in hydroponic application

Pyrolysis is an effective method for treating of livestock and poultry manure developed in recent years. It can completely decompose pathogens and antibiotics, stabilize heavy metals, and enrich phosphorus (P) in biochar. To elucidate the P migration mechanism under different pig manure pyrolysis temperatures, sequential fractionation, solution 31P nuclear magnetic resonance, X-ray photoelectron spectroscopy, X-ray diffraction, and K-edge X-ray absorption near-edge structure techniques were used to analyze the P species in pig manure biochar (PMB). The results indicated that most of the organic P in the pig manure was converted to inorganic P during pyrolysis. Moreover, the transformation to different P groups pathways was clarified. The phase transition from amorphous to crystalline calcium phosphate was promoted when the temperature was above 600 °C. The content of P extracted by hydrochloric acid, which was the long-term available P for plant uptake, increased significantly. PMB pyrolyzed at 600 °C can be used as a highly effective substitute for P source. It provides the necessary P species (e.g. water-soluble P.) and metal elements for the growth of water spinach plants, and which are slow-release comparing with the Hogland nutrient solution.

Biochar-derived dissolved and particulate matter effects on the phytotoxicity of polyvinyl chloride nanoplastics

Nanoplastics in environments are potentially detrimental to plant growth. Appropriate doses of biochar can alleviate the phytotoxicity of nanoplastics under hydroponic conditions. However, the specific mechanisms remain unknown. In this study, the effects of biochar-derived dissolved matter (BCDM) and biochar-derived particulate matter (BCPM) on the phytotoxicity of polyvinyl chloride (PVC) nanoplastics were investigated and the underlying influencing mechanisms were elucidated. The results showed that PVC nanoplastics can be adsorbed and taken up by lettuce roots, inducing oxidative damage to lettuce shoots and roots and reducing their fresh weight. BCDM can promote the aggregation and sedimentation of PVC nanoplastics, and BCPM can adsorb PVC nanoplastics and cause barrier effect, which will reduce the exposure dose of PVC nanoplastics. Furthermore, nutrients in BCDM can promote lettuce growth. As a result, the presence of both BCDM and BCPM significantly mitigated the oxidative stress of lettuce shoots and roots as demonstrated by the decrease in hydrogen peroxide and malondialdehyde levels (p < 0.05). Meanwhile, lettuce biomass was significantly increased after addition of BCDM and BCPM compared to the single PVC treatment group (p < 0.05). This study provides a theoretical basis for finding solutions to alleviate the phytotoxicity of nanoplastics.

Waste-derived nanobiochar: A new avenue towards sustainable agriculture, environment, and circular bioeconomy

The greatest challenge for the agriculture sector in the twenty-first century is to increase agricultural production to feed the burgeoning global population while maintaining soil health and the integrity of the agroecosystem. Currently, the application of biochar is widely implemented as an effective means for boosting sustainable agriculture while having a negligible influence on ecosystems and the environment. In comparison to traditional biochar, nano-biochar (nano-BC) boasts enhanced specific surface area, adsorption capacity, and mobility properties within soil, allowing it to promote soil properties, crop growth, and environmental remediation. Additionally, carbon sequestration and reduction of methane and nitrous oxide emissions from agriculture can be achieved with nano-BC applications, contributing to climate change mitigation. Nonetheless, due to cost-effectiveness, sustainability, and environmental friendliness, waste-derived nano-BC may emerge as the most viable alternative to conventional waste management strategies, contributing to the circular bioeconomy and the broader goal of achieving the Sustainable Development Goals (SDGs). However, it's important to note that research on nano-BC is still in its nascent stages. Potential risks, including toxicity in aquatic and terrestrial environments, necessitate extensive field investigations. This review delineates the potential of waste-derived nano-BC for sustainable agriculture and environmental applications, outlining current advancements, challenges, and possibilities in the realms from a sustainability and circular bioeconomy standpoint.

Nano-biochar uptake and translocation by plants: Assessing environmental fate and food chain risk

Nano-biochar (N-BC) is an emerging nanomaterial with potential applications in various fields. Understanding its behavior in the environment and its interaction with plants is crucial for assessing its ecological implications and potential risks to the food chain. In this study, we investigated the absorption and transportation of N-BC by wheat and Chinese cabbage plants using microscopy techniques and stable isotope analysis. Our results revealed that N-BC particles were readily absorbed by the plants through their root systems and transported to the aboveground tissues. Scanning electron microscopy and transmission electron microscopy provided visual evidence of N-BC particles inside the plants, predominantly located in the xylem and cell walls of the cortical tissue. Stable isotope analysis confirmed the uptake and transportation of N-BC, with elevated isotopic values observed in the plant tissues exposed to 13C-N-BC. Our results demonstrated that around 50.2 %-52.4 % of the absorbed N-BC by plants was accumulated in the roots of wheat and Chinese cabbage, and the remaining fraction was transferred to the shoots including steam (31.0 %-32.1 %) and leaf (16.5 %-17.6 %). Importantly, we observed significant accumulation of N-BC in the edible parts of Chinese cabbage, raising concerns about its potential entry into the food chain and associated health risks. These findings highlight the need for further research to explore the specific pathways and modes of N-BC uptake and transport in plants. Monitoring the presence of N-BC in the environment and its potential impact on the food chain is crucial for ensuring food security and safeguarding human health.

Silica nanoparticle accumulation in plants: current state and future perspectives

With their excellent biocompatibility, adjustable size, and high specific surface area, silica nanoparticles (SiO2 NPs) offer an alternative to traditional bulk fertilizers as a means to promote sustainable agriculture. SiO2 NPs have been shown to promote the growth of plants and to reduce the negative effects of biotic and abiotic stresses, but their bioaccumulation is a crucial factor that has been overlooked in studies of their biological effects. In this review, the techniques to quantify and visualize SiO2 NPs in plants were examined first. We then provide a summary of the current state of knowledge on the accumulation, translocation, and transformation of SiO2 NPs in plants and of the factors (e.g., the physicochemical properties of SiO2 NPs, plant species, application mode, and environmental conditions) that influence SiO2 NP bioaccumulation. The challenges in analyzing NP-plant interactions are considered as well. We conclude by identifying areas for further research that will advance our understanding of NP-plant interactions and thus contribute to more sustainable, eco-friendly, nano-enabled approaches to improving crop nutrient supplies. The information presented herein is important to improve the delivery efficiency of SiO2 NPs for precision and sustainable agriculture and to assess the safety of SiO2 NPs during their application in agriculture.

Aggregation kinetics of biochar nanoparticles in aqueous environment: Interplays of anion type and bovine serum albumin

The colloidal particles, especially those at the nanoscale, are the most active part of the pyrogenic carbon (biochar). Increasingly applied biochar has resulted in a large number of biochar nanoparticles (NPs) being released into the environment. The aggregation of biochar NPs affects their environmental behavior and fate. The complex effects of anion type (Cl^-, SO₄^2-) and protein (bovine serum albumin, BSA) on the aggregation of wheat straw biochar (WB) and pinewood biochar (PB) NPs in solutions were investigated by the time-resolved dynamic light scattering method. The critical coagulation concentration (CCC) of WB and PB NPs in Na₂SO₄ solution was higher than their CCCs in NaCl solution, which was consistent with the Hofmeister series that SO₄^2-, a kosmotrope anion, increased the interaction between water molecules, thus enhancing the hydrophobic interactions between biochar NPs in solution and promoting their aggregation, while Cl^-, a chaotropic agent, exhibited the opposite effect. When BSA was added into the solution, BSA was adsorbed on the surface of biochar NPs and BSA corona was formed, which inhibited the aggregation of biochar NPs by inducing steric force. The enhanced stability of biochar NPs by BSA was more significant in NaCl than in Na₂SO₄ solution because BSA corona had a more negatively charged surface and a more steric structure in NaCl solution, thus generating stronger electrical repulsion and steric hindrance. The classical DLVO theory and the XDLVO theory incorporating the steric repulsion (in the presence of BSA) were used to interpret the aggregation and dispersion of biochar NPs. Through this study, we found that anion type indirectly affected the aggregation of biochar NPs by influencing the interaction between water molecules, while the aggregation of BSA-biochar NPs conjugates is mainly influenced by the surface charge and structure of BSA corona.

Effects of the increases in soil pH and pH buffering capacity induced by crop residue biochars on available Cd contents in acidic paddy soils

To explore the effects of the increases in pH and pH buffering capacity (pHBC) induced by crop residue biochars on the changes in soil available Cd content, six acidic paddy soils developed from different parents were amended with seeded sunflower plate biochar (SSPBC), peanut straw biochar (PSBC) and corn straw biochar (CSBC). The pH, pHBC, and available Cd of the soils were measured after laboratory incubation. The results showed that the incorporation of crop residue biochars led to the increases in soil pH and pHBC, but a decrease in soil available Cd content. The decreasing order of available Cd content was SSPBC > PSBC > CSBC and was consistent with the changes in soil pH induced by the biochars. During submerging and draining, soil pH increased first and then declined, however the content of available Cd decreased first and then increased significantly. Soil pH in the treatments with biochars showed little change during draining, which was different from the control without the biochars added. This was attributed to the enhancing effect of the biochars on soil pHBC. Also, there was a significant negative correlation between the change in available Cd content and soil pHBC during submerging/draining alternation and suggested that higher pHBC corresponded to smaller soil available Cd content. Consequently, the amount of Cd absorbed by rice was reduced, thereby reducing the potential risk of soil Cd to humans. These results can provide useful references for the remediation of Cd-contaminated paddy soils.