Sustainable management of campus fallen leaves through low-temperature pyrolysis and application in Pb immobilization

Carbon quantum dots from fallen leaves of Lonicera caerulea L.: An innovative plant growth promoter and fruit quality enhancer

With increasing environmental pollution and resource wastage, utilizing waste for high-value applications has become crucial. This study explores the preparation of carbon dots (CDs) from blue honeysuckle leaves and their potential in enhancing plant photosynthesis. CDs derived from these leaves have a particle size of ∼2.6 nm and emit blue fluorescence under 365 nm UV light, making them suitable for foliar spraying. When applied, CDs enter leaf cells and impact chloroplasts, significantly improving photosystem II (PSII) performance and Rubisco enzyme activity. At an optimal concentration of 1000 mg/L, PSII electron transfer efficiency and Rubisco activity increased by 29.84% and 208.12%, respectively, boosting net photosynthetic rate by 60.4%. This treatment also enhanced blue honeysuckle yield and fruit quality, with higher levels of soluble solids, ascorbic acid, flavonoids, anthocyanins, and total phenolics. These improvements were linked to increased sucrose synthesis (up 25.99%) and leaf assimilative capacity (up 25%). Additionally, CDs enhanced post-harvest soil enzyme activity and microbial abundance, promoting nutrient cycling and soil utilization. This study demonstrates that preparing CDs from waste blue honeysuckle leaves not only mitigates environmental pollution but also offers a sustainable, high value use for plant resources. The findings highlight the potential of nanomaterials in improving agricultural productivity and provide a novel pathway for waste reuse.

Unveiling heavy metal removal mechanisms in mulberry and rice husk biochars via sacrificial mineral descriptors

Rice husk biochar (RBC) and mulberry biochar (MBC) have gained significant attention in the removal of heavy metals in aquatic environments. Their easy affordability and eco-friendly nature make these biochar's a powerful adsorbent for sustainable water remediation applications. Although their heavy metal adsorption characteristics of individual biochar's have been widely studied, a clear understanding of how the inherited mineral composition in RBC and MBC influences Pb2+, Cd2+, and Zn2+ removal in both deionized water (DIW) and Organization for Economic Co-operation and Development (OECD) water is currently lacking. In this study, heavy metal removal mechanisms of RBC and MBC in these water systems were investigated using various kinetic models and correlated them with their mineral composition. With the highest correlation coefficient of modified two-compartment first-order kinetic model (MTCFOKM), the measured qe values highlight MBC as a promising candidate for heavy metal removal in both acidic and alkaline conditions. pH edge experiments revealed significant differences in metal removal efficiency between these biochars, despite their similar specific surface areas and surface charges (pHpzc). XRD and FTIR characterization provided a strong support in explaining the high heavy metal removal ability of MBC stem from calcite mineral that inherited from biomass. Furthermore, the pH edge experiment combined with MINEQL+ speciation profiles revealed that heavy metal removal by MBC at low pH is linked to calcite leaching, shift in system pH, and heavy metal precipitation.

Lead toxicity regulation via protein degradation and tetrapyrrole biosynthesis pathways in Brassica species: A comparative quantitative analysis of proteomic study

Understanding the heavy metals (HMs) tolerance mechanism is crucial for improving plant growth in metal-contaminated soil. In order to evaluate the lead (Pb) tolerance mechanism in Brassica species, a comparative proteomic study was used. Thirteen-day-old seedlings of B. juncea and B. napus were treated with different Pb(NO3)2 concentrations at 0, 3, 30, and 300 mg/L. Under 300 mg/L Pb(NO3)2 concentration, B. napus growth was significantly decreased, while B. juncea maintained normal growth similar to the control. The Pb accumulation was also higher in B. napus root and shoot compared to B. juncea. Gel-free proteomic analysis of roots revealed a total of 68 and 37 differentially abundant proteins (DAPs) in B. juncea and B. napus-specifically, after 300 mg/L Pb exposure. The majority of these proteins are associated with protein degradation, cellular respiration, and enzyme classification. The upregulated RPT2 and tetrapyrrole biosynthesis pathway-associated proteins maintain the cellular homeostasis and photosynthetic rate in B. juncea. Among the 55 common DAPs, S-adenosyl methionine and TCA cycle proteins were upregulated in B. juncea and down-regulated in B. napus after Pb exposure. Furthermore, higher oxidative stress also reduced the antioxidant enzyme activity in B. napus. The current finding suggests that B. juncea is more Pb tolerant than B. napus, possibly due to the upregulation of proteins involved in protein recycling, degradation, and tetrapyrrole biosynthesis pathway.

Enhancing efficient reclaim of phosphorus from simulated urine by magnesium-functionalized biochar: Adsorption behaviors, molecular-level mechanistic explanations and its potential application

Magnesium-functionalized Magnolia grandiflora Linn leaf-derived biochar (MBC) capable of efficiently reclaiming phosphorus from urine was synthesized by slow co-pyrolysis. Four adsorption kinetic and seven adsorption isotherm models were fitted to the batch adsorption and desorption experimental data, and it was found that pseudo-first-order kinetic model and multilayer model with saturation best described the phosphate-phosphorus (PO43--P) adsorption process by MBC. MBC and phosphorus-saturated MBC (P-MBC) were found to offer outstanding phosphorus adsorption and slow release properties, respectively. Based on material characterization, statistical physics, adsorption energy distribution and statistical thermodynamics, a multi-ionic, inclined orientation, entropy-driven spontaneous endothermic process of MBC on PO43--P was proposed, involving physicochemical interactions (porous filling, electrostatic attraction, ligand exchange and surface precipitation). Further, seed germination and early seedling growth experiments proved that P-MBC can be used as a slow-release fertilizer. Overall, MBC offers prospective applications as an efficient phosphorus adsorbent and then as a slow-release fertilizer.