The ferromanganese nodules (FMNs) developing in soils of karst regions are naturally characterized by high heavy metal(loid)s contents due to several geological factors. Soil FMNs can considerably influence the geochemical behaviors of soil heavy metal(loid)s. However, the mechanisms of the FMN effects in soils of karst areas soils remain unclear, resulting in less understanding of the development process of karst soils. Therefore, the present study aims to investigate 21 individual FMNs collected in soils derived from carbonate rocks in Guangxi province, China, to reveal the mechanisms of heavy metal(loid)s enrichment in FMNs. The studied soil FMNs were mainly composed of Fe₂O₃, SiO₂, Al₂O₃, MnO₂, and TiO₂, with proportions of 25.95, 20.8, 19.07, 3.98, and 1.23%, respectively. Compared to the background soils of Guangxi, the soil FMNs exhibited great enrichment in heavy metal(loid)s. The enrichment factors followed the order of Cd (243.33), Cr (49.67), Cu (5.46), Ni (8.37), Pb (23.68), Zn (15.4), and As (20.11). The heavy metal(loid)s contents in the soil FMNs of the karst areas were much higher than those observed in non-karst areas worldwide. According to the principal component analysis (PCA) results, the first three principal components contributed to about 88.81% of the total variance of the FMN compositions. PC1 (50.90%) suggested the presence of quartz, feldspar, and clay minerals-related elements in the soil FMNs, whereas PC2 (27.10%) and PC3 (10.81%) indicated the presence of Mn(oxyhydr)oxides and Fe(oxyhydr)oxides-related elements in the soil FMNs, respectively. The obtained selective extraction results demonstrated that up to 93% of the total contents of heavy metal(loid)s, namely, Cd, Pb, Cu, Ni, and Zn, were bound to Mn(oxyhydr)oxides. In contrast, oxyanionic species (As and Cr) were predominantly sequestered in Fe(oxyhydr)oxides.

Mangroves play a pivotal role in carbon sequestration. To investigate the characteristics and driving factors of carbon sequestration in planted mangrove forests, we focused on planted mangrove forests in Wenzhou City, Zhejiang Province, China. Through a statistical analysis of soil physicochemical properties and plant morphological characteristics, we assessed carbon stock distribution patterns and identified key influencing factors, providing scientific support for the northward expansion of mangroves. The results demonstrated significant differences in soil properties and plant morphological characteristics among different stands (p < 0.05). The mean soil carbon stock of restored planted mangroves was 78.75 Mg C/ha (mature stands: 87.84 Mg C/ha; middle-aged stands: 74.09 Mg C/ha; young stands: 74.31 Mg C/ha), while the average plant carbon stock was 12.28 Mg C/ha, indicating that soil is the primary contributor to carbon sequestration in mangroves. Compared to natural mangroves, the restored planted mangroves still exhibited a lower carbon sequestration capacity. The variations in carbon sequestration levels among the planted mangrove forests were mainly attributed to differences in tree species and age composition, hydrothermal conditions, and biomass carbon quantification methods. Key drivers of soil carbon sequestration included total phosphorus content, bulk density, and clay content. Carbon storage in restored planted mangroves depends on short-term soil carbon accumulation and long-term biomass carbon accumulation. Ultimately, we recommend optimal species selection and planting design, improved soil carbon storage mechanisms, and integrated conservation monitoring systems to enhance carbon sequestration in mangrove plantations.

Red mud is a highly alkaline solid waste with an annual emission of over 200 million tons, which requires large-scale utilization methods. Soil Cd remediation is a global concern, due to its high toxicity and strong mobility. Given red mud’s potential for soil Cd remediation, this study reviews its basic characteristics, the mechanisms of soil Cd immobilization by red mud, and the use of red mud-based passivators for agricultural soil Cd remediation. In general, red mud regulates soil pH, thus increasing the soil’s Cd adsorption capacity; provides abundant surface active sites for adsorption and complexation with soil Cd; introduces cations to immobilize Cd via ion exchange; and enriches Cd-resistant microbe species to reduce soil Cd toxicity. Furthermore, the potential environmental risks and suggestions on red mud application are discussed. Further research should focus on improving the remediation effectiveness of red mud on cadmium-contaminated agricultural soil, demonstrating its long-term efficacy and economic costs, and proposing practical technical models and standards for application.

Agricultural soils worldwide carry a growing imbalance of heavy metal(loid)s—arsenic (As), cadmium (Cd), lead (Pb), mercury (Hg), and chromium (Cr)—driven by mining, industry, and intensive farming inputs. Crop uptake is governed by the bioavailable fraction rather than by total content alone, but the two are not independent: the total pool sets the ceiling from which the available fraction is drawn, so the relationship is real yet neither direct nor linear. This critical review appraises green management strategies that control metal(loid) accumulation in the edible tissues of staple crops, and it does so comparatively rather than by catalog. We first define the evidence base—search strategy, screening and quality criteria, and the geographic and crop distribution of the literature—and then evaluate four strategy families against seven explicit criteria (efficacy, evidence level, durability, co-metal trade-off, cost, life-cycle footprint, applicability domain): water, redox and agronomic management; immobilization amendments, including lime, biochar, iron/manganese oxides, and nano-enabled sorbents; plant-based strategies, from low-accumulation cultivars to silicon/selenium supplementation; and microbial-assisted remediation. Four patterns recur across independent field studies. First, redox- and pH-based interventions are the most reproducible where Cd dominates, but their reported efficacy spans an order of magnitude because performance depends on baseline pH, contaminant load and control definition. Second, every Cd-effective measure is neutral or adverse for As, so As-dominated and co-contaminated sites require opposing prescriptions; this is the single most consequential contradiction in the literature. Third, durability rather than initial efficacy is the binding constraint, because most field trials report three seasons or fewer. Fourth, microbial and nano-enabled approaches are the least transferable, with most quantitative claims resting on pot or mesocosm data. We conclude that no currently available measure, and no validated combination, guarantees compliance in edible tissues at every site; safe use is conditional on diagnosis of the bioavailable fraction, a site-specific package, and grain-level verification before marketing, and diversion to non-food or industrial cropping is the defensible fallback where that assurance cannot be given.

Agricultural soils worldwide face a growing imbalance of heavy metal(loid)s—arsenic (As), cadmium (Cd), lead (Pb), mercury (Hg), and chromium (Cr)—driven by mining, industry, and intensive farming inputs. Because bioavailability rather than total content governs crop uptake, metal(loid)s accumulate in edible tissues and threaten food safety, particularly in rice-based diets. This review critically evaluates green management strategies that control metal(loid) accumulation along the soil–crop–food continuum while preserving soil functions and minimizing energy inputs. We first synthesize sources, soil biogeochemical controls on bioavailability, and plant uptake and translocation pathways, then appraise four strategy families: water, redox, and agronomic management; immobilization amendments, including lime, biochar, iron/manganese oxides, and nano-enabled sorbents; plant-based strategies, from low-accumulation cultivars to silicon/selenium supplementation and phytoextraction; and microbial-assisted remediation. We then link these strategies to food-safety outcomes, comparing international regulatory limits for staple foods, and identify field validation, amendment longevity, co-metal trade-offs, and life-cycle sustainability as the key remaining challenges. An integrated, site-specific green management framework—coupling cultivar selection, water control, and low-cost amendments—emerges as the most practical route to safe production on contaminated land.

Organic contaminants such as dyes, phenols, pesticides, antibiotics, pharmaceuticals and personal care products (PPCPs), and endocrine-disrupting chemicals (EDCs) are widespread in water and wastewater, and are highly harmful to human health and the environment. Biochar, a solid carbon material derived from waste biomass under limited oxygen conditions, is a promising low-cost sustainable adsorbent for their removal. This review critically integrates recent advances in biochar preparation—feedstock selection, thermochemical conversion routes, activation, and modification—with the physicochemical properties that govern performance. Removal mechanisms are systematically analyzed, spanning adsorption (pore filling, hydrophobic partitioning, π–π electron donor–acceptor interactions, hydrogen bonding, electrostatic attraction, cation bridging) and catalytic degradation mediated by persistent free radicals, persulfate/peroxymonosulfate activation, and photocatalysis. Key influencing factors (solution pH, temperature, coexisting ions, natural organic matter, dosage, particle size), regeneration, and engineering application are evaluated. Current challenges—heterogeneity and standardization, safety of biochar-borne hazardous constituents, performance in real matrices, and spent material management—and future directions, including machine-learning-assisted design and integrated treatment trains, are identified. This review aims to guide the rational design of biochar-based materials toward practical water and wastewater treatment.