Soil constitutes the fundamental basis for human survival, food security, and ecosystem stability. Nevertheless, accelerating industrialization, mining activities, agricultural intensification, and urban expansion have led to widespread soil pollution, among which heavy metal contamination represents one of the most persistent and hazardous environmental challenges. Heavy metals are characterized by high toxicity, environmental persistence, and strong bioaccumulation potential, enabling their migration through soil–water–plant systems and entry into the food chain, thereby posing serious risks to ecological integrity and human health.

A growing body of recent research shows that evaluating contaminated soils based solely on total metal concentrations is often insufficient for decision-making. Consequently, the field has increasingly adopted integrated assessment frameworks that combine contamination indices, spatial analysis, source apportionment, and exposure/risk models to identify priority elements, dominant pathways, and sensitive receptors (especially children) (Zhou et al., 2024; Birch et al., 2024).

At the same time, remediation science is undergoing a clear shift toward sustainable and field-deployable technologies that reduce metal mobility and bioavailability while preserving soil functions. In situ immobilization approaches, supported by amendment-assisted stabilization, biogeochemical processes, and integrated management, are increasingly emphasized because they can be less disruptive and more scalable than excavation-based options. For agricultural systems, this trend is closely linked to the need to reduce food-chain transfer of metals, particularly in staple crops grown on contaminated land. Recent papers highlight the rapid expansion of soil amendments, used alone, in combinations, or after modification, and summarize the mechanisms by which these materials can reduce metal bioavailability and plant uptake (Ye et al., 2025).

In parallel, biological processes are also receiving renewed attention; sulfate-reducing bacteria, for instance, have been investigated as a way to immobilize dissolved metals through sulfide formation and related sequestration pathways, with relevance to mine drainage and soil–water interface conditions (Si et al., 2023).

This Research Topic represents Volume II of the series Remediation and Health Risks of Heavy Metal Contaminated Soils, following the successful Volume I, reflecting the strong scientific and societal interest in this field. The contributions in Volume II collectively emphasize: (i) contaminant occurrence, spatial patterns, and source–risk characterization in soils and coastal sediments using integrated indices and geospatial approaches; (ii) ecological and human health risk assessment, including, where relevant, radiological indicators alongside metal pollution metrics; and (iii) practical, environmentally responsible remediation strategies, ranging from microbial immobilization to amendment-based in situ management, aimed at reducing metal mobility and limiting exposure through water–soil and soil–crop pathways. By linking mechanistic insights with field-relevant assessment and mitigation approaches, this volume supports more reliable risk management and the development of scalable solutions for contaminated environments.

This Volume II comprises of five original research articles, collectively illustrating the diversity of contamination scenarios, assessment methodologies, and remediation solutions across different environmental settings.

Two studies focus on coastal sediment systems along the Red Sea, Egypt, providing integrated assessments of heavy metal contamination (Ba, Co, Cr, Cu, Ni, Pb, Zn, V) and natural radioactivity (²³²Th, ⁴ K, and ²²⁶Ra) (Abdelaal et al.; Saleh et al.). These works demonstrate the importance of combining geochemical indices, ecological risk indicators, human health assessments, and radiological hazard evaluations to characterize multi-hazard environments. Their findings highlight that, although certain metals exceed background and guideline values, overall ecological and radiological risks remain within acceptable limits, emphasizing the need for continuous monitoring and site-specific management strategies.

Another contribution investigates metal contamination and human health risks in soils surrounding a Pb–Zn mining area in northeast China (Wang et al.). By applying enrichment factors, geoaccumulation indices, and USEPA health risk models, this study reveals significant anthropogenic inputs of toxic metals such as Cd, Hg, Pb, and Zn, whereas As, Ni, and Cr are primarily derived from natural sources. The results underscore children’s heightened vulnerability and confirm that ingestion is the dominant exposure pathway, providing critical insights for risk mitigation and soil restoration near abandoned or legacy mining sites.

From a remediation perspective, one study explores microbial biomineralization using sulfate-reducing bacteria (Desulfovibrio desulfuricans and Desulfobulbus propionicus) to immobilize Cd²⁺ and Pb²⁺ (Chen et al.). The results demonstrate high metal removal efficiencies, with D. propionicus achieving nearly complete Cd²⁺ immobilization under optimal conditions, while both strains showed effective Pb²⁺ removal at moderate initial concentrations. Detailed mechanisms of metal immobilization are discussed, including microbially induced sulfate reduction, sulfide precipitation, and the formation of stable metal-bearing mineral phases. The study further highlights the role of microbial metabolic activity and associated extracellular substances in enhancing metal sequestration and reducing metal mobility under contaminated conditions. Sulfate-reducing bacteria can be considered as a cost-effective and environmentally friendly solution for heavy metal remediation, particularly in mine drainage and contaminated water–soil interfaces.

Finally, an agricultural-focused study examines the combined application of soil amendments (red mud, silicon fertilizer, and phosphate fertilizer) to reduce cadmium availability and migration in contaminated paddy soils (Yang et al.). Among the tested materials, red mud contributed most strongly to Cd reduction in grain, followed by silicon and phosphate fertilizers, and the study proposes an optimized amendment combination for practical implementation. This work demonstrates how integrated amendment-based remediation can simultaneously improve soil conditions and mitigate food-chain transfer of Cd, supporting safe rice production in contaminated farmlands.

The studies collected in Volume II emphasize several important directions for future research. First, integrated assessment frameworks that simultaneously consider chemical toxicity, ecological effects, and human health risks, including radiological aspects, are essential for accurately evaluating contaminated sites. Second, environmentally friendly and in-situ remediation technologies, such as bioremediation and soil amendments, show strong potential for large-scale application but require long-term performance evaluation and life-cycle assessment. Third, addressing combined pollution scenarios and emerging contaminants remains a critical challenge that demands interdisciplinary collaboration and advanced modeling approaches.

The contributions in this Volume II provide valuable scientific evidence and practical insights into the behavior, risks, and remediation of heavy metals in soils and sediments. Volume II complements and extends the achievements of the first volume, reinforcing the necessity for sustainable remediation strategies and comprehensive risk assessments to protect ecosystems and human health. We hope that this Research Topic will stimulate further research, support policy development, and contribute to the sustainable management of contaminated soils worldwide.