Key Takeaways & Executive Findings
- •• • Cubic hematite (HNCs) achieved superior PSDOM degradation, reducing TOC from 18.4 to 12.3 mg·L−1 in 90 min, versus 13.3 mg·L−1 for flake-shaped HNPs, indicating morphology-specific catalytic efficiency for organic pollutant removal. • • HNCs amplified singlet oxygen (1O2) steady-state concentration to 2.80 times the PSDOM control, while HNPs elevated hydroxyl radical (·OH) levels to 1.98 times, demonstrating selective reactive oxygen species (ROS) generation pathways that can be tailored for targeted degradation. • • Both hematite morphologies suppressed carbon-centered radical (CH3C(=O)OO·) formation across all tested solvents, suggesting a potential mechanism to control radical-mediated side reactions and influence degradation pathways. • • The steady-state concentration of 1O2 was approximately 10^3 times higher than that of ·OH in all hematite-amended systems, underscoring the dominant role of singlet oxygen in PSDOM photodegradation and guiding oxidant selection for remediation strategies.
Abstract
The interaction between microplastic-derived dissolved organic matter (PSDOM) and iron oxides in soil environments can modulate its photosensitization effects, yet the underlying mechanisms remain elusive. This study investigated the influence of hematite with distinct morphologies—flake-shaped (HNPs) and cubic (HNCs)—on the photosensitization of polystyrene-derived dissolved organic matter (PSDOM). Under 500 W mercury lamp irradiation, both hematite morphologies promoted PSDOM degradation, with HNCs exhibiting superior performance: total organic carbon (TOC) decreased from 18.4 mg·L−1 to 12.3 mg·L−1 within 90 min, compared to 13.3 mg·L−1 for HNPs. Three-dimensional fluorescence spectroscopy indicated that hematite alters the humification process, thereby modifying photosensitization. Electron paramagnetic resonance (EPR) spectroscopy identified the generation of singlet oxygen (1O2), hydroxyl radicals (·OH), and carbon-centered radicals (CH3C(=O)OO·). HNCs significantly enhanced 1O2 production, while HNPs favored ·OH generation; both inhibited CH3C(=O)OO· formation. Quantitative analysis via high-performance liquid chromatography revealed that the steady-state concentration of 1O2 was highest with HNCs, reaching 2.80 times that of the PSDOM control, whereas ·OH concentration peaked with HNPs at 1.98 times the control. Notably, the steady-state concentration of 1O2 was approximately three orders of magnitude higher than that of ·OH. These findings elucidate the morphology-dependent role of hematite in PSDOM photosensitization, providing mechanistic insights into the environmental fate of microplastic-derived organic matter in complex soil systems.
1. Introduction
Microplastic pollution in soil has emerged as a critical environmental concern, with microplastic-derived dissolved organic matter (PSDOM) acting as a significant vector for contaminant transport and transformation. PSDOM exhibits photosensitization properties, generating reactive oxygen species (ROS) under solar irradiation, which can degrade organic pollutants. However, the presence of iron oxides, ubiquitous in soil, can modulate this photosensitization process, yet the specific influence of iron oxide morphology remains poorly understood. Conventional studies have focused on bulk iron oxides, often overlooking the distinct surface reactivities of different crystal facets, which can drastically alter ROS generation and subsequent degradation kinetics.
This research addresses this gap by systematically comparing the effects of two well-defined hematite morphologies—flake-shaped (HNPs) and cubic (HNCs)—on the photosensitization of PSDOM. By employing a combination of spectroscopic and chromatographic techniques, the study quantifies the production of key ROS (1O2, ·OH, and CH3C(=O)OO·) and correlates them with degradation efficiency. The findings reveal that HNCs preferentially enhance singlet oxygen generation, while HNPs favor hydroxyl radical production, leading to distinct degradation outcomes. This morphology-dependent behavior offers a strategic lever for optimizing photocatalytic systems in environmental remediation, enabling the design of iron oxide-based catalysts tailored to specific pollutant degradation pathways.
Loading authentic research manuscript (Pages 1–5)...
LIAN Yongxuan, XU Runxin, ZHOU Yuan, HUANG Yan, SONG Jia, XU Xiang, LI Shangze, YU Qizheng, YANG Jingwen, WANG Jingzhen (2026). Effect of Hematite Morphology on the Photosensitive Response of Microplastic-Derived Dissolved Organic Matter. Environmental Chemistry. https://doi.org/10.7524/j.issn.0254-6108.2025120801
Research & Educational Purpose Only: The translations, structured abstracts, analytical annotations, and data reports provided by SinoGreenTechare intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoGreenTech claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What is the underlying mechanism for the morphology-dependent enhancement of singlet oxygen (1O2) generation by cubic hematite (HNCs) compared to flake-shaped hematite (HNPs)?
The enhanced 1O2 generation by HNCs is attributed to the higher surface energy and specific crystal facets of cubic hematite, which facilitate more efficient energy transfer from excited PSDOM to molecular oxygen. EPR and quantitative HPLC analyses confirmed that HNCs increased the steady-state concentration of 1O2 to 2.80 times that of the PSDOM control, whereas HNPs only achieved a 1.98-fold increase in ·OH. This facet-dependent activity likely arises from differences in surface defects and electronic structure, which modulate the generation of triplet-state PSDOM and subsequent energy transfer to oxygen.
How does the presence of hematite affect the degradation pathway of PSDOM, and what are the implications for the formation of toxic byproducts?
Hematite alters the degradation pathway by shifting the ROS profile: HNCs promote 1O2-mediated oxidation, while HNPs enhance ·OH-driven reactions. Both pathways lead to PSDOM mineralization, as evidenced by TOC reduction. However, the suppression of CH3C(=O)OO· radicals by both hematite types suggests a reduction in peroxy radical-mediated side reactions, potentially lowering the formation of persistent toxic intermediates. The humification degree, assessed by fluorescence spectroscopy, was lower in the HNCs system, indicating a more complete degradation to smaller molecules.
What are the scalability and practical implications of using hematite nanoparticles for microplastic remediation in real soil environments?
The study demonstrates that hematite nanoparticles can significantly enhance PSDOM photodegradation under UV irradiation, with HNCs achieving a 33% TOC reduction in 90 minutes. However, scalability requires consideration of factors such as nanoparticle aggregation, light penetration in soil, and potential toxicity. The use of 500 W mercury lamps in the lab may not directly translate to solar-driven applications, but the findings provide a basis for developing photocatalytic coatings or amendments that could be applied to contaminated soils. Further research is needed to assess long-term stability and environmental safety.
Can the morphology-dependent ROS generation be exploited to selectively degrade specific types of microplastic-derived organic matter?
Yes, the selective enhancement of 1O2 by HNCs and ·OH by HNPs suggests that hematite morphology can be tailored to target different pollutant classes. For instance, 1O2 is effective for oxidizing electron-rich compounds, while ·OH is non-selective and attacks most organics. By choosing the appropriate hematite morphology, one could optimize the degradation of specific PSDOM components or co-contaminants. However, the actual selectivity in complex environmental matrices would require validation with mixed contaminants and natural organic matter.
What are the limitations of the experimental setup, and how do they affect the interpretation of the results?
The study used a high-intensity 500 W mercury lamp, which provides a broader spectrum and higher photon flux than natural sunlight, potentially accelerating degradation rates. Additionally, the experiments were conducted in aqueous suspensions, which may not fully represent soil conditions where adsorption and aggregation can alter reactivity. The TOC measurements reflect overall mineralization but do not identify intermediate products. Future studies should employ solar simulators and soil column experiments to better mimic environmental conditions and assess the formation of transformation products.
Related Chinese Research & Cross-Citations
Exploring the Potential Molecular Mechanisms of Eight Environmental Pollutants in Lung Adenocarcinoma through Network Toxicology, Machine Learning, and Multi-Omics Analysis
Epidemiological studies have established a significant association between exposure to environmental pollutants (EP) and the risk of lung adenocarcinoma (LUAD). This study integrates network toxicology and multi-omics analysis to elucidate the EP-LUAD molecular regulatory network and identify key regulatory genes, thereby revealing novel mechanisms of environmental carcinogenesis. Transcriptomic data from GEO and TCGA databases yielded 4,971 and 4,488 disease-related targets, respectively. Integration of toxicology databases (TargetNet, Swiss Target Prediction, CTD, SEA) identified 24,860 potential targets for eight common pollutants (SO2, NO, CO, NO2, O3, benzene, toluene, and polycyclic aromatic hydrocarbons). Intersection of these datasets produced 1,536 EP-LUAD common target genes. Protein-protein interaction network analysis identified 247 core targets. Machine learning selected five key genes: AGER, CAV1, CD44, CEP55, and GNB3, which demonstrated robust diagnostic and prognostic efficacy. Their expression correlated with immune cell infiltration, including CD4+ memory T cells and macrophages. Single-cell RNA sequencing revealed epithelial cell-specific expression patterns. Molecular docking confirmed stable pollutant-target binding, with PAH showing highest affinity for CD44 (binding energy −9.32 kcal·mol−1) and GNB3 (−8.32 kcal·mol−1). These findings establish AGER, CAV1, CD44, CEP55, and GNB3 as core molecular mediators of pollution-related LUAD. The high-affinity binding of PAH to CD44 and GNB3 underscores its carcinogenic potential. This study constructs a multi-level regulatory network for EP-LUAD, revealing underlying molecular mechanisms and providing novel potential targets and theoretical basis for early warning and intervention.
Effects of Different Functionalized Nanoplastics on the Transformation of Extracellular Antibiotic Resistance Genes in Aquatic Environments
The rapid dissemination of antibiotic resistance genes (ARGs) in aquatic environments poses serious threats to public health and environmental safety under the 'One Health' framework. Nanoplastics (NPs), as co-occurring pollutants, can exacerbate ARG risks by promoting horizontal gene transfer (HGT), yet the influence of different functional groups on extracellular ARG (eARG) transformation remains unclear. This study investigated the effects of carboxy-modified polystyrene NPs (PS-COOH) and amino-functionalized polystyrene NPs (PS-NH2) compared to unmodified polystyrene NPs (PS) on the transformation of the extracellular resistance plasmid IE-V1955 (carrying an ampicillin resistance gene) into Escherichia coli DH5α. Results showed that PS-COOH exposure promoted plasmid transformation similarly to PS, with effects increasing over 0.1–20 mg·L−1. Low concentrations (0.1–0.5 mg·L−1) of PS-NH2 also enhanced transformation, with stronger effects than PS-COOH at equal doses, whereas high concentrations (1–20 mg·L−1) inhibited it. Mechanistically, PS-COOH (0.1–20 mg·L−1) and low PS-NH2 induced intracellular reactive oxygen species (ROS), increased cell membrane permeability, elevated the protein-to-polysaccharide ratio in extracellular polymeric substances (EPS), and promoted biofilm formation, thereby facilitating transformation. High PS-NH2 concentrations caused excessive ROS leading to cell lysis and formed aggregates with plasmids larger than membrane pores, blocking uptake. These findings provide a theoretical basis for assessing the combined environmental health risks of NPs and ARGs.
Cardiovascular Toxicity Induced by Micro/Nano-Plastics and Its Mechanisms
Micro/nano-plastics (MNPs) are emerging contaminants widely detected in human circulatory systems, including blood, heart, and vascular endothelium, raising concerns about cardiovascular health risks. This systematic review analyzed 61 peer-reviewed studies (2008–2024) to elucidate the cardiotoxic effects and molecular mechanisms of MNPs. Evidence indicates that MNPs exposure elevates risks of atherosclerosis, thrombosis, and arrhythmias through oxidative stress, inflammatory cascades, endothelial dysfunction, and metabolic dysregulation. Notably, co-exposure with persistent organic pollutants (POPs) or heavy metals may produce synergistic or antagonistic effects. Current research relies predominantly on animal and cell models, with critical gaps in low-dose, long-term exposure data and epidemiological evidence. Future studies should optimize experimental designs, integrate metabolomics and epigenetics, and explore transgenerational effects and combined toxicity mechanisms to inform pollution control policies and mitigate cardiovascular risks.
Body Burden of Polybrominated Diphenyl Ethers and Joint Effects on Thyroid Function in a Physical Examination Population in Shenzhen
This study characterized the body burden of polybrominated diphenyl ethers (PBDEs) in a physical examination population in Shenzhen and evaluated its impact on thyroid function. Serum samples from 368 residents were analyzed for eight PBDE congeners using atmospheric pressure gas chromatography-tandem mass spectrometry (APGC-MS/MS). The median concentration of ∑8PBDEs was 10.2 ng·g⁻¹ lipid weight (lw), ranging from 0.13 to 2089.4 ng·g⁻¹ lw, with BDE-209 predominating (59.7% of total). Multiple linear regression revealed that a 1.7-fold increase in serum BDE-153 was associated with a 0.4% increase in free triiodothyronine (FT3) (P<0.05), while a 1.7-fold increase in BDE-183 was associated with a 0.9% decrease in total triiodothyronine (T3) and a 0.7% decrease in FT3 (P<0.05). Bayesian kernel machine regression (BKMR) indicated a negative correlation between mixed PBDE exposure and thyroid-stimulating hormone (TSH) at high exposure levels. Weighted quantile sum (WQS) regression showed that mixed exposure was associated with decreased T3 levels and T3/FT3 ratio, with BDE-153 and BDE-183 as the primary contributors. These findings suggest that PBDE exposure may adversely affect thyroid function and disrupt thyroid hormone homeostasis, with BDE-183 and BDE-153 playing key roles. This study provides a scientific basis for PBDE health risk assessment and thyroid protection.
Mechanisms of Natural Organic Matter in Regulating Microplastic Aggregation and Transport in Soil-Groundwater Systems: A Review
Microplastics (MPs) are persistent emerging contaminants ubiquitously distributed in soil-groundwater environments, where their aggregation and transport critically govern pollutant fate and ecological risks. Natural organic matter (NOM), a complex assemblage of organic compounds, interacts with MPs and porous media via hydrogen bonding, π-π interactions, hydrophobic effects, and electrostatic binding, thereby modulating MP surface properties and environmental behavior. This review systematically synthesizes the mechanisms by which NOM influences MP aggregation and transport, with emphasis on the distinct roles of humic substances, proteins, and extracellular polymeric substances (EPS), and their synergistic modulation with solution chemistry (pH, ionic strength, ion type). Additionally, NOM accelerates MP aging and alters surface characteristics, consequently impacting transport capacity. Current research limitations are identified, and future directions are proposed to inform MP pollution risk assessment and management strategies. Key findings indicate that NOM generally enhances MP stability and mobility at low ionic strengths, while high ionic strengths may induce aggregation depending on NOM type and ion valence. Humic substances predominantly increase electrostatic repulsion, whereas proteins and EPS can bridge particles, promoting aggregation. Aging processes, accelerated by NOM photochemical activity, increase surface oxygen functionality and hydrophilicity, further altering transport. The review underscores the need for systematic studies under environmentally relevant conditions to predict MP fate accurately.
Neurotoxicity of Carboxyl-Modified Polystyrene Microplastics on Zebrafish at Early Developmental Stage
Carboxyl-modified polystyrene microplastics (PS-COOH) are negatively charged particles formed by surface oxidation and functional group modification of polystyrene microplastics (PS), widely used in biomedical and analytical chemistry. However, studies on their neurotoxic effects on aquatic organisms are scarce. This study employed zebrafish (Danio rerio) as a model organism, exposing embryos to environmentally relevant concentrations (0.1, 1, 10, 100 μg·L−1) of PS and PS-COOH. Neurotoxic effects were assessed by measuring tail coiling frequency at 24 hpf and swimming velocity under alternating light/dark cycles at 120 hpf. Results demonstrated that both PS and PS-COOH induced neurotoxicity, with PS-COOH significantly reducing tail coiling frequency and average swimming speed compared to PS (P<0.05). Exposure to 10 μg·L−1 PS-COOH disrupted neurotransmitter homeostasis, altering levels of acetylcholine (ACh), serotonin (5-HT), and γ-aminobutyric acid (GABA). Transgenic zebrafish Tg(huc:EGFP) fluorescence assays revealed that PS-COOH (0.1–100 μg·L−1) caused damage to central neurons. These findings indicate that PS-COOH exposure impairs cholinergic, serotonergic, and GABAergic neurotransmission, induces neuronal damage, and exerts neurotoxic effects on zebrafish larvae. This study provides a theoretical basis for assessing the ecological and health risks of modified microplastics.