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Results for “Co-contaminated soil”

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PubMed2026

Birnessite-mediated simultaneous remediation of lead and benzo[a]pyrene co-contaminated soils.

It is currently challenging to remediate soils co-contaminated by heavy metals and polycyclic aromatic hydrocarbons. Birnessite is a naturally ubiquitous manganese oxide mineral with strong oxidation and adsorption capacities, but its specific roles in pollutant transformation and interfacial interaction within co-contaminated systems remain elusive. This study investigated the simultaneous remediation of lead (Pb) and benzo[a]pyrene (BaP) in soils by birnessite through incubation experiments and density functional theory calculation. Birnessite treatment decreased CaCl2- and toxicity characteristic leaching procedure-extractable Pb content by 64.3% and 86.6% and reduced the BaP content by 33.8%. Mechanistically, Pb immobilization was primarily driven by spontaneous adsorption, including ion exchange and surface complexation, which facilitated Pb transformation into Fe-Mn oxide-bound fractions. Concurrently, BaP removal occurred via a synergistic pathway involving reactive species and electron transfer processes. Increasing dosage of birnessite promoted Pb immobilization, but had little effect on BaP oxidation. Moreover, the co-existing Pb affected birnessite-mediated BaP adsorption and oxidation by promoting the formation of [BaP-Pb]2+ and [BaP-Pb(H2O)]2+ complexes via cation-π interactions. These complexes were more preferentially adsorbed on birnessite compared with BaP molecules, but exhibited higher electron transfer barriers. The findings provide critical insights into the remediation of co-contaminated soils and the fate of co-existing contaminants.

Birnessite↗
PubMed2026

Long-term PFOA and cadmium Co-contamination alters soil carbon, nitrogen, and phosphorus cycling: Insights from metagenomics and metabolomics.

The co-existence of perfluorooctanoic acid (PFOA) and cadmium (Cd) in soil poses a combined threat to microbial communities. However, the ecological effects and underlying mechanisms of their long-term combined exposure remain poorly understood. This study conducted a 90-day soil microcosm experiment to systematically investigate the effects of individual and combined effects of PFOA and Cd on microbial communities. Our results demonstrated that combined pollution of PFOA and Cd significantly affected four soil enzyme activities associated with carbon, nitrogen, and phosphorus cycling. It also influenced microbial thermal activity with an IC50 of PFOA at 0.94 mg/kg. The toxic interaction between PFOA and Cd varied with both toxicity indicators and exposure time. At the community level, PFOA and Cd synergistically reduced bacterial diversity and richness, while exerting more complex interactive effects on fungal communities. Metagenomic analysis revealed that PFOA and Cd significantly affected carbon, nitrogen, and phosphorus cycling by inhibiting inorganic phosphorus solubilization genes (gcd, pqqC) and altering key genes in carbon fixation and nitrogen transformation. Metabolomic profiling further demonstrated that PFOA disrupted membrane lipid homeostasis and amino acid metabolism. Meanwhile, the co-existence of Cd exacerbated disturbances in sugar and carbon metabolism. Our findings provide genetic-level insights into microbial responses to long-term PFOA and Cd co-contamination. These results are essential for risk assessment at such co-contamination sites.

Cadmium↗
PubMed2025

Synergic impact mechanisms of cover crop residue on Cd and As availability and native organic carbon mineralization in Cd and As co-contaminated paddy soil.

The synergic impacts of cover crop residue on heavy metal and metalloid availability and soil organic carbon (SOC) mineralization in contaminated paddy soil and the underlying microbial mechanism remain unclear. This study investigated the availability of cadmium (Cd) and arsenic (As) and mineralization of native SOC in paddy soil treated with 0, 0.4 %, 0.8 % and 1.2 % of δ13C-labeled cover crop residue (Astragalus sinicus L.) via 90-day incubation experiments, the related functional genes and functional microbial communities were analyzed using metagenomic binning assembly. Cover crop residue with addition rate from 0.4 % to 1.2 % significantly decreased available Cd by 56 %-85 % but increased available As by 39 %-66 % compared to the control treatment. Cover crop residue resulted in a positive priming effect on native SOC mineralization but benefited SOC sequestration. Cover crop residue increased the abundance of genes encoding iron reductase (mtrABC, pilA, omcB), sulfate reductase (sir, fpr), As(V) reductase (ArsC), organic carbon hydrolases, methanogenesis, and methylotrophy. Genomes associated with Chloroflexota and Bacteroidota encoded all these key pathways, and their abundance increased with cover crop residue application. Cover crop residue decreased soil Eh, dissolved crystalline iron oxides, enriched specific microorganisms, including Chloroflexota and Bacteroidota, and then synergistically promoted the decrease in Cd availability and the increase in As availability and native SOC mineralization in the examined paddy soil. These findings provided practical and feasible guidance for achieving both safe production and carbon sequestration in contaminated paddy fields, highlighting the requirement to cautious utilization of cover crop residue in As-contaminated paddy fileds.

Soil Pollutants↗