Xiaomeng Chen, Marcin Musiałowski, Klaudia Dębiec-Andrzejewska, Robert Stasiuk, Luisella Celi, Michela Schiavon, Maria Martin, Silvia Celletti
Iron (Fe) oxy(hydr)oxides regulate soil Fe and phosphorus (P) cycling, but how bacterial siderophores and co-produced metabolites mobilize these nutrients across pH remains unclear. We hypothesized that siderophore-mediated Fe complexation and P mobilization depend on pH and mineral crystallinity and that siderophore-associated metabolites (SAM) are more effective than purified siderophores. A purified pyoverdine-like siderophore fraction from Antarctic Pseudomonas strain ANT_H12B was chemically and spectroscopically characterized and evaluated for Fe³ + complexation from FeCl 3 between pH 5 and 9. Iron mobilization from ferrihydrite (Fh), goethite (Gt), and hematite (Hm) was examined at pH 5.5 and 8.5 across mineral concentrations of 0.5–2 g L⁻¹; purified siderophores and SAM were compared in four P-deficient soils of contrasting pH. Iron³ + complexation increased from 6% at pH 5 to 10% at pH 9, reflecting ligand deprotonation. Ferrihydrite showed the greatest dissolution, although Fe release at pH 8.5 was 30% and 37% lower than at pH 5.5 at 1 and 1.5 g L⁻¹, respectively. Conversely, Gt dissolution at 2 g L⁻¹ was 40% higher at pH 8.5, whereas Hm showed the lowest dissolution, reaching 3 and 1.9 μM at pH 5.5 and 8.5, respectively. Purified siderophores moderately increased Olsen-P in neutral and high-Fe alkaline soils, whereas SAM increased Olsen-P approximately 1- to 26-fold across all soils, with the greatest effect in high-Fe alkaline soil. SAM also increased soluble P 11- to 40-fold and NaOH-EDTA-extractable P by 25–104% relative to controls. The results support our hypothesis, showing that siderophores contribute to Fe and P mobilization but act more effectively within SAM, where organic acids provide complementary dissolution and sorption-competition mechanisms. This finding agrees with previous ANT_H12B studies reporting improved nutrient availability and plant performance and supports using unpurified metabolite mixtures for sustainable P management. Indeed, retaining the co-produced mixture could reduce purification requirements and preserve complementary functions relevant to sustainable P management.
Soil-contaminant risk is commonly screened using total concentrations, yet the total fraction alone does not establish biological exposure, ecological impairment, or recovery of soil functions. This Perspective proposes a function-centered extension of established risk assessment, linking sources and legacy stores to soil-controlled speciation, receptor-specific exposure, biological responses, and changes in ecosystem processes. Soil pH, redox conditions, dissolved organic matter, moisture, mineralogy, and particle properties modify the fate of metals and metalloids, organic chemicals, and particulate contaminants. We distinguish potentially accessible contaminant pools from bioaccessibility measured by a specified mobilization assay and from bioavailability to a defined receptor. Geochemical indices and exposure-based hazard quotients retain their screening roles; they are complemented by matched exposure measurements, biological tests, direct process measurements, and uncertainty analysis. An eight-step workflow connects problem formulation, baseline characterization, screening, exposure refinement, functional assessment, risk characterization, intervention selection, and verification. The framework supports contamination monitoring, risk assessment, and remediation evaluation across diverse soil settings. Its proposed decision rule requires acceptable residual exposure, recovery of the specified soil functions, and control of contaminant transfer, with repeated observations to establish durability. The added predictive value of this integration remains a testable proposition rather than an established universal result.
Caterina Agrimonti, Sara Graziano, Giuseppe Lamanna, Vittorio Scanferla, Marina Caldara, Federica Marra, Annamaria Bevivino, Michele Donati, Chuauxin Ma, Chunyang Li, Nelson Marmiroli
Utilizing agri-food by-products and residues to create soil improvers reduces waste and promotes environmentally friendly agriculture within a sustainability framework. This study evaluates the agronomic, biological, and economic impacts of biochars produced from three agri-food residues: vinasses, olive pomace, and tomato peels. Biochars were applied to tomato (Solanum lycopersicum cv Heinz 1301) and wheat (Triticum durum cv Svevo) in a greenhouse experiment at concentrations of 0.1-0.25-0.5% w/w, to assess their effects on plant biomass, physiology and gene expression, total countable microorganisms, enzymes involved in nitrogen mineralization (arylamidase), cellulose degradation (β-glucosidase) and phosphorus release (phosphatases). Economic and environmental assessments were also carried out. Vinasse biochar contained the highest levels of nitrogen (12000 mg/kg), potassium (11700 mg/kg), and phosphorus (4200 mg/kg), performing comparably to vinasse-based compost. A concentration of 0.5% biochar derived from vinasses increased canopy cover in tomato (+125%), and stem length (+13%), fresh and dry root weight (+97% and 57%, respectively), and stem weight (+41% and 44%, respectively) in wheat. The same biochar modulated genes involved in plant growth and development, cell wall biogenesis, nutrient transport, hormone signaling, and stress response in both plants. All biochars, particularly those derived from vinasses, enhanced arylamidase activity in tomato plants compared with the control. The same biochar enhanced activity of β-glucosidase when added at 0.5% in wheat (+ 29%) and tomato (+20%) over the control. Biochar derived from tomato peels at 0.5% enhanced the phosphatase activity (+27%) in tomato plants, while biochar derived from olive at 0.5% enhanced the same activity (+45%) in wheat. Economic and environmental evaluations revealed that these biochars were better than composts derived from the same residues, in terms of sustainability and economic value.
Mohamed El Mderssa, Meysara ELMALKI, Fouad Malki, Taha Abdelhakim, Younes Abbas, Jamal Ibijbijen
Soil organic carbon (SOC) stored in forest ecosystems represents one of the largest terrestrial carbon reservoirs and plays a crucial role in climate change mitigation and ecosystem functioning. In Mediterranean mountain regions, SOC storage is characterized by pronounced spatial variability resulting from the combined influence of vegetation, climate, topography, parent material and soil-forming processes. Although numerous studies have examined the influence of dominant tree species on SOC accumulation, comparatively few have investigated how the diversity of forest ecosystems interacts with geological substrate to regulate soil carbon storage across heterogeneous protected landscapes. This study evaluates the combined effects of forest ecosystem diversity and geological substrate on SOC storage by comparing two major Moroccan Mediterranean protected areas: Ifrane National Park, located in the Middle Atlas Mountains, and Talassemtane National Park, located in the Rif Mountains. A harmonized dataset comprising 67 observations was assembled from independent field inventories. In Ifrane, the sampled ecosystems were distributed over basaltic and dolomitic substrates, whereas all Talassemtane sites developed on calcareous formations. SOC stocks differed markedly between the two national parks. Mean SOC stock reached 173.99 t C ha - ¹ in Ifrane compared with 69.44 t C ha - ¹ in Talassemtane. Ecosystem type significantly affected SOC storage in both parks. In Ifrane, the highest SOC stocks were recorded in Zeen oak and Holm oak forests, whereas matorral, cork oak, and fir ecosystems showed the highest values in Talassemtane. Furthermore, basalt-derived soils in Ifrane were associated with markedly greater SOC stocks (200.84 t C ha - ¹) than dolomitic soils (147.14 t C ha - ¹) in this pooled, ecosystem-confounded comparison; however, the two available ecosystem-matched tests holding vegetation constant (Cedar forest and Holm oak forest, basalt vs dolomite) were both non-significant (P = 0.680 and P = 0.143), so this pooled association should not yet be read as confirmed, independent evidence that geological substrate drives SOC accumulation. Although both parks exhibited similar ecosystem richness, Ifrane showed considerably greater spatial variability in SOC storage than Talassemtane, reflecting stronger ecological differentiation among ecosystem types. These findings demonstrate that forest ecosystem diversity should be interpreted as landscape heterogeneity rather than simply species richness, and that the influence of vegetation on soil carbon cannot be separated from the pedological constraints imposed by geological substrate. These results have important implications for ecosystem-based forest management, carbon accounting and climate-change mitigation strategies in protected areas.
Hao Xu, Xueqin Liu, Shujuan Chen, Lingzhi Luo, Wang Wenfan, Lihui Ma, Mohamed A. E. AbdelRahman, D. M. Sabra
Potentially hazardous element (PHE) contamination threatens agroecosystem sustainability and food security, particularly in irrigated regions. The Yellow River Basin in Northwest China is a critical agricultural zone where intensive irrigation and fertilizer use may accelerate soil contamination. A total of 487 topsoil samples were collected under a stratified random design. Concentrations of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) were analyzed with strict quality assurance protocols. Spatial heterogeneity was quantified using the Optimal Parameters-based Geographical Detector (OPGD) model, while source apportionment was performed through Positive Matrix Factorization (PMF). Marked spatial variability was observed, with coefficients of variation exceeding 50% for As, Pb, and Cd. Hotspots were concentrated in northern and central irrigation zones. Total nitrogen showed the strongest statistical association with PHE distribution (Q = 0.796), followed by soil texture. PMF analysis identified agriculture-related inputs (Cd), industrial emissions (Zn, Cu), geogenic background (Cr, Ni), and traffic residues (Pb) as major contributors. Although most concentrations remained below national screening thresholds (GB 15618-2018), cadmium slightly exceeded the threshold (mean = 0.32 mg·kg⁻¹ vs. 0.30 mg·kg⁻¹), with localized enrichment hotspots for Cd, Pb, and Zn. Hazard mapping delineated high-risk zones in the eastern and southern districts, underscoring the importance of targeted management. These findings highlight nutrient status and agricultural practices as key drivers of PHE accumulation, providing insights for cadmium control and sustainable fertilization strategies in irrigated agroecosystems.
