Review on the contamination and remediation of polycyclic aromatic hydrocarbons (PAHs) in coastal soil and sediments

Mangrove guardians: Unearthing the enrichment patterns of PAHs in the Zhangjiang estuary ecosystem

Understanding the bioaccumulation of PAHs in mangrove plants is crucial as it reflects the ecosystem's ability to mitigate pollution and minimize its impacts on surrounding environments. The Zhangjiang Estuary mangrove ecosystem is a vital ecological asset in Fujian Province, however, the interactions between contaminants, such as polycyclic aromatic hydrocarbons (PAHs), and mangrove plant tissues remain underexplored. This study investigates the different bioaccumulation patterns and machanism of 26 PAHs in three mangrove species (Kandelia obovata, Aegiceras corniculatum, and Avicennia marina). PAHs concentrations in mangrove and estuarine sediments ranged from 55.68 to 247.76 ng/g and 119.16 to 346.03 ng/g, while Σ26PAHs in the mangrove plants ranged from 13.03 to 172.17 ng/g, which was dominated by two- and five-ring PAHs. The bioconcentration factors (BCFs) of plant tissues showed a wide range, from 0 to 330.17, stems exhibited the highest PAHs concentrations compared to roots and leaves, with BCFs in stems following average enrichment factors: two-ring PAHs (37.23 ± 13.33) > alkylated PAHs (9.40 ± 4.66) > three-ring PAHs (3.09 ± 2.20) > six-ring PAHs (2.29 ± 0.36) > five-ring PAHs (0.52 ± 0.06) > four-ring PAHs (0.03 ± 0.01). The BCFs in roots showed strong positive correlations with logKow and Koc values, while the trends in stems and leaves were reversed, suggesting that roots showed high affinity for hydrophobic compounds, while stems and leaves preferred more water-soluble PAHs. The bioaccumulation capacity was highest in Aegiceras corniculatum, followed by Kandelia obovata and Avicennia marina. Additionally, alkylated PAHs were more enriched than their parent compounds, indicating selective uptake potential in mangrove plants. These findings underscore the critical role of mangrove species in mitigating PAHs contamination through selective absorption and accumulation. The results provide valuable insights into the application of mangrove ecosystems in bioremediation and offer guidance for environmental management in coastal regions.

Bioaugmentation strategies for polycyclic aromatic hydrocarbons-contaminated intertidal zones: Effects and microbial community succession

The intertidal zone is one of the natural systems most vulnerable to threats from polycyclic aromatic hydrocarbons (PAHs). However, the natural attenuation rate of PAHs within intertidal zones is low, posing challenges for the short-term recovery of contaminated environments. This study developed a contaminated intertidal zone simulation system and used a composite bacterial consortium containing Cellulosimicrobium sp. RS and Brucella sp. BZ for bioaugmented remediation. The degradation rate of PAHs (initial concentration: 5000 μg/kg) in the sediments reached 85.37 % after 120 days of restoration, which was significantly higher than the 29.93 % observed in the control group. High-throughput sequencing was used to analyze the structure and function of sediment microbial communities. The exogenous bacteria Cellulosimicrobium became dominant after remediation, whereas Brucella did not dominate but contributed to synergistic degradation. Network analysis and PICRUSt predictions confirmed that the microbial community evolved toward stronger PAHs degradation capabilities and degraded PAHs through ring cleavage, side-chain metabolism, and central metabolism in bioaugmented sediments. This study provides theoretical guidance and data support for bioaugmented remediation of intertidal zone pollution.

Chemo-metric appraisal on the distribution of polycyclic aromatic hydrocarbons in marine environment of Alang Ship Breaking Yard, India

This study investigated the comparative assessment of 15 priority USEPA polycyclic aromatic hydrocarbons (PAHs) in marine sediments and seawater at the world's largest shipbreaking yard Alang, Gujarat. The ∑PAHs concentration was found in between 0.30 and 31.35 μg/g in marine sediment and 0.02 to 3.22 μg/L found in seawater among all sampling spots. Furthermore among all PAHs fluoranthene showed a higher concentration followed by pyrene, indeno [1,2,3-cd]pyrene, and benz[a]anthracene in marine sediment. Four-ring compounds present higher compared to 2-3 rings, 5 rings, and 6 rings of PAHs from selected study areas. Diagnostic ratios were also applied for the possible sources of identification and present study area contaminated by both pyrogenic and petrogenic sources. The analysed data were also used for correlation study with seawater physicochemical parameters to identify positive correlations for their occurrences. The Nap, Flu, Flt, Pyr and BaA having the strong positive correlation with the seawater quality. Dibenz[a,h]anthracene showing zero coefficient with measured sea water quality. Hierarchical cluster analysis indicates, the control sampling spot is significantly different from other spots and this pattern was found in both sediments and water.

Advancements in Biochar as a Sustainable Adsorbent for Water Pollution Mitigation

Biochar, a carbon-rich material produced from the partial combustion of biomass wastes is often termed "black gold" for its potential in water pollution mitigation and carbon sequestration. By customizing biomass feedstock and optimizing preparation strategies, biochar can be engineered with specific physicochemical properties to enhance its effectiveness in removing contaminants from wastewater. Recent studies demonstrate that biochar can achieve > 90% removal efficiency for heavy metals such as lead and cadmium, > 85% adsorption capacity for organic pollutants such as dyes and phenols, and > 80% reduction in microplastics and nanoplastics. This review explores recent advancements in biochar preparation technologies, such as pyrolysis, carbonization, gasification, torrefaction, and rectification, along with physical, chemical, and biological modifications that are crucial for efficient pollutant removal. The core of this review focuses on biochar's applications in removing a wide range of pollutants from wastewater, detailing mechanisms for organic pollutants, inorganic salts, pharmaceutical contaminants, microplastics, nanoplastics, and volatile organic compounds. In addition, the review introduces machine learning as a key technique for optimizing biochar production and functionality, showcasing its potential in advancing biochar technology. The conclusion provides a comprehensive outlook on biochar's future, emphasizing ongoing research and its role in sustainable environmental management.

Enhancing the efficiency of P-SMFCs in degrading phenanthrene by modifying the anode with carbon nanomaterials

In plant-sediment microbial fuel cells (P-SMFCs), the anode serves as the primary site for biochemical reactions. In this study, different carbon nanomaterials (graphenes (GNs), carbon nanotubes (CNT), hydroxylated-carbon nanotubes (CNT-OH), and carboxylated-carbon nanotubes (CNT-COOH)) were used to modify the anode of the P-SMFCs to explore the enhancement of phenanthrene (Phe) degradation. The devices were operated for 131 days, CNT-COOH-modified P-SMFCs (P-CNT-COOH) exhibited a shorter start-up period and higher voltage during the stable operation stage. The voltage of P-CNT-COOH during the stationary phase was approximately 250 mV higher than that of the control device. The voltage and Phe removal of P-CNT-COOH were higher than those of CNT-COOH (without plants in the SMFC), which achieved 67.5% Phe removal, which was 1.25 times higher than the P-CNT, whereas CNT (without plants in the SMFC) showed higher performance than P-CNT. The anode modified with P-CNT-COOH became enriched with small-molecule volatile fatty acids (VFAs) (e.g., acetic acid) and degrading bacteria (e.g., Thiobacillus and Desulfobulbus) attributed to the higher hydrophilicity. The removal of Phe was positively correlated with dehydrogenase activity (DHAA).

Assessment of persistent toxic substances in sediments of Gyeonggi Bay, Korea: Distributions, sources, and potential ecological risks

Persistent toxic substances (PTSs) from anthropogenic activities are a growing concern for marine ecosystems. In addition, the specific sources and ecological consequences of PTSs, particularly in coastal regions influenced by industrial and urban developments, remain insufficiently understood. This study evaluated the distribution, sources, and risks of 54 PTSs in Gyeonggi Bay. Polycyclic aromatic hydrocarbons (PAHs) ranged from 22.0 ng g-1 dw to 2710 ng g-1 dw, and alkylphenols (APs) peaked at 21,500 ng g-1 dw in source-dominated areas. Elevated levels were observed in Incheon Port and Lake Sihwa, from industrial and urban wastewater discharges. PMF modeling identified fossil fuel combustion as the main source of PAHs and natural and agriculture for metal(loid)s. Ecological risk assessments revealed significant contributions of metal(loid)s (49.1 %) and APs (39.3 %), with nonylphenols and arsenic posing the highest risks. These findings highlight the need for continuous monitoring and stricter regulations to mitigate the impacts of PTSs in marine ecosystems.

Metagenomic surveys show a widespread diffusion of antibiotic resistance genes in a transect from urbanized to marine protected area

Ports are hot spots of pollution; they receive pollution from land-based sources, marine traffic and port infrastructures. Marine ecosystems of nearby areas can be strongly affected by pollution from port-related activities. Here, we investigated the microbiomes present in sea floor sediments along a transect from the harbour of Livorno (Central Italy) to a nearby marine protected area. Results of 16S rRNA amplicon sequencing and metagenome assembled genomes (MAGs) analyses indicated the presence of different trends of specific bacterial groups (e.g. phyla NB1-j, Acidobacteriota and Desulfobulbales) along the transect, correlating with the measured pollution levels. Human pathogenic bacteria and antibiotic resistance genes (ARGs) were also found. These results demonstrate a pervasive impact of human port activities and highlight the importance of microbiological surveillance of marine sediments, which may constitute a reservoir of ARGs and pathogenic bacteria.

Effects of compound immobilized bacteria on remediation and bacterial community of PAHs-contaminated soil

Immobilized microorganism technology is expected to enhance microbial activity and stability and is considered an effective technique for removing soil polycyclic aromatic hydrocarbons (PAHs). However, there are limited high-efficiency and stable bacterial preparations available. In this study, alkali-modified biochar (Na@CBC700) was used as the adsorption carrier, sodium alginate (SA) and polyvinyl alcohol (PVA) as embedding agents, and CaCl2 as the cross-linking agent to prepare immobilized Acinetobacter (CoIMB) through a composite immobilization method. The CoIMB preparation was optimized using response surface methodology and applied to PAH-contaminated soil remediation. Results indicated that CoIMB exhibited improved mechanical strength and microbial activity, achieving degradation rates of 2-5 rings PAHs up to 82.41 %, averaging 1.5 times higher than CK. High dose CoIMB treatment enhanced soil microbial community diversity, enriching Acinetobacter, and increased the abundance of functional genes related to fatty acid metabolism and energy metabolism (K00249, K01897, K00059). This composite immobilized bacterial particle provides a novel, broad-spectrum, and cost-effective solution for remediating organic pollutants in soil environments.

Degradation of naphthalene in aqueous solution using a microbial symbiotic system founded by degrading and ureolytic bacteria

Although single bacteria have been applied to the Polycyclic Aromatic Hydrocarbons (PAHs) remediation, its efficacy is severely restricted by long degradation periods and low efficacy. A microbial symbiotic system founded by two or more bacterial strains may be an alternative to traditional remediation approaches. Its construction is, however, hampered by antagonistic interactions and remains challenging. The present work proposed a microbial symbiotic system consisting of the naphthalene degrading bacteria and the non-PAHs degrading bacteria and improved their interspecies interactions by using sequential inoculation. The non-PAHs degrading bacteria were inoculated after the inoculation of the naphthalene degrading bacteria. The sequential inoculation not only promoted the non-PAHs degrading bacteria to use the metabolites of the naphthalene degrading bacteria as an energy source but developed a resistance of the two bacterial strains to naphthalene. Vaterite and aragonite were identified following urea hydrolysis by the non-PAHs degrading bacteria. The faster precipitation rate in naphthalene degradation by the symbiotic system elevated the proportion of vaterite, allowing more naphthalene and its metabolites to be wrapped in or attached to minerals with the bacteria through the physisorption (van der Waals force) and chemisorption (Ca-π interaction with aromatic rings) and promoting the formation of aggregates. The formation of aggregates further reduced the mobility of naphthalene. Results indicate that 40% of naphthalene in the non-inoculated sterile control group was quickly released into the atmosphere, causing serious public concerns regarding health safety. According to the thermogravimetry-gas chromatography mass spectrometry (TG-GC/MS) analysis, no trace of naphthalene was found in the samples, indicating that the degrading bacteria fully degraded naphthalene after its adsorption. As a result, the degradation efficiency of 100% was attained using the symbiotic system even at 200 mg/L naphthalene. The findings underscore the relative merits of the symbiotic system applied to the remediation of naphthalene in an aqueous solution.

In vitro chrysene degradation by purified cell free laccase (P-CFL) from Cochliobolus lunatus strain CHR4D in the presence of various redox mediator systems (RMSs) and computational evaluation of their laccase-ligand interactions

An immense progression in global industrialization in recent years has astonishingly elevated the contamination of marine, coastal, aquatic and terrestrial habitats with pervasive pollutants such as polycyclic aromatic hydrocarbons. Despite being discovered early and exploited for the years, laccases - a copper oxidase has a wide spectrum of applications in the fields of toxicological studies, bioremediation and restoration of impacted ecological matrices. The present study focuses on purification of mid-redox potential laccase from marine-derived fungus C. lunatus strain CHR4D, which has very high capacity to degrade chrysene - a four ringed hydrocarbon. The purified laccase (66 kDa) was further used for the in vitro chrysene degradation in non-growth conditions, in the presence of various redox mediator systems (RMSs) containing ABTS, HBT and VA. RMS including ABTS was found the most effective, resulting in 53.30% chrysene degradation in 24 h, followed by HBT (30.99%) and VA (28.98%), when compared to control conditions (27.78%). Laccase-ligand interactions were further explained by computational simulations and docking protocols. It revealed that laccase exhibited the highest binding energy towards chrysene. It also showed hydrophobic interactions with HBT and VA. The study would be helpful to further establish role of laccase in in vitro degradation of HMW PAHs.

Pesticide and hydrocarbon toxicity in fish: effects on Chelon labrosus (Risso, 1827) along the northeastern Sicilian coast (Italy) evaluated by enzymatic biomarkers

Pesticides intoxication affects aquatic organisms as well as a group of contaminants that are represented by crude oil, petroleum hydrocarbons (PHs), polycyclic aromatic hydrocarbons (PAHs) and their derivatives. Useful tools for ecotoxicological studies of marine ecosystems are based on biomarker application on bioindicator key fish species. The aim of the present study was to highlight the presence of pesticides and hydrocarbons in a coastal marine environment, the harbour of Capo d'Orlando town (northeastern Sicily, Italy), by using the ecotoxicological biomarker Acetylcholinesterase (AChE) and Butyrylcholinesterase (BChE) enzymatic activities in the key fish species Chelon labrosus. A reference site was selected. Chemical analysis of water samples was also carried out to analyze and eventually confirm the presence of pesticides in the study area. Results showed significant inhibition in AChE (80%) and BChE (77%) activities in fish from the harbour of Capo d'Orlando compared to the reference site. The esterase inhibition is primarily due to the presence of organophosphorus insecticides and carbamates, that resulted in higher concentrations of contaminants in the water of the harbour of Capo d'Orlando compared to the reference quality standard decree (Ministerial Decree 260, 2010). This study highlighted the contamination by insecticides and most probably by hydrocarbons in fish from the harbour of Capo d'Orlando, which also represents a threat to the human population consuming affected fish.

Unveiling the impact of anthropogenic wastes on greenhouse gas emissions from the enigmatic mangroves of Indian Sundarban

The greenhouse gas (GHG) emissions from the mangrove ecosystem due to climate change have been an emerging environmental issue in the present scenario. However, the GHGs, emitted through anthropogenic causes in these vulnerable regions are often neglected. The level of soil pollution has increased due to the uncontrolled disposal of wastes from ports, ferry services, plastics, and metals, emitting huge amounts of GHGs. Here, a novel dynamic model on GHG emission was proposed for the simulation of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emissions using R programming language, where, anthropogenic and environmental drivers were considered. The CO2 emission was sensitive to HMeff2 (impact rate of heavy metals on microbial respiration process) and MPeff3 (impact rate of microplastics on microbial respiration process). The CH4 dynamics was sensitive to HMeff1 (impact rate of heavy metal on methanogenesis process) and MPeff1 (impact rate of microplastics on methanogenesis process) and the N2O pool was sensitive to N2O dif rt. (N2O diffusion rate). Fish waste, heavy metals, and microplastics are the prime emitters of GHG in the Sundarbans. Control and monitoring of plastics, fish wastes, and heavy metals, and strategic implementation of no-plastic or no-waste zones in line with the Sustainable Development Goals (SDGs) would ensure solutions to the present problem.

Thin film microextraction of PAHs from wastewater samples using an oxine modified iron mesh followed by dispersive liquid-liquid microextraction prior to gas chromatography analysis

In the present research, an attempt has been made to develop a new thin film microextraction method for the extraction of several polycyclic aromatic hydrocarbons from aqueous samples collected from different industrial units prior to their analysis by gas chromatography combined with a flame ionization detector. In this approach, a thin iron mesh was modified by the formation of iron(II) oxinate on its surface and used for the extraction of analytes without an additional sorbent. For this purpose, first, the mesh was immersed in a sulfuric acid solution and then transferred into an 8-hydroxy quinoline (oxine) solution dissolved in ammonia solution. By doing so, iron(II) oxinate was formed on the surface of the mesh and enhanced its adsorption efficiency towards the analytes. It is worth noting that the unique structure of the prepared mesh provided a large contact area and high affinity for adsorption of the analytes. After desorption of the analytes from the sorbent surface with an elution solvent, the analytes were more concentrated by performing dispersive liquid-liquid microextraction. Under optimum conditions, the method demonstrated limits of detection and quantification within the ranges of 0.27-54 and 0.89-1.7 ng mL-1, respectively. The relative standard deviation values for intra- and inter-day precisions ranged from 5.2-8.1% and 8.2-11.6%, respectively. Furthermore, the enrichment factors for the target analytes varied between 200 and 255, while the extraction recoveries fell within the range of 40-51%. These findings illustrate the sensitivity, precision, and effectiveness of the method for quantifying the desired analytes.

Features of particle-phase PAHs from traffic emissions using tunnel measurement and urban roadside observation in China

Vehicle emissions are recognized as a primary source of particle-phase polycyclic aromatic hydrocarbons (PAHs), significant contributors to the hazardous properties of PM2.5. This study investigates the profiles of PAHs through measurements conducted in a tunnel and an urban roadside environment in 2020. We quantified real-world vehicle emission factors for mixed fleets in the Zhongshu tunnel in Guizhou, southwest China, and found that the total PAHs had an emission factor of 8.15 μg veh-1km-1, with higher factors observed for high-ring PAHs. Additionally, we analyzed concentrations of 15 PAHs at a roadside environment in Hefei, southern China, with an average concentration of 23.81 ng/m3. PAHs with 4, 5, and 6 rings comprised 80% of total PAHs at the roadside and 87% in the tunnel. Gasoline emissions were the predominant source in both the tunnel and roadside environments, supplemented by non-tailpipe emissions, catering, domestic cooking, and asphalt from road surfaces. Notably, while the total toxicity equivalent concentration of Benzo[a]pyrene (BaP) significantly exceeded the World Health Organization (WHO) guidelines of 1 ng/m3, the presence of additional compounds such as Dibenzo[a,h]anthracene (DahA) markedly increased the toxicological impact of PM2.5 from vehicle emissions. Therefore, it is essential to implement targeted pollution control strategies in central urban areas that address not only the overall concentration of PAHs but also their specific toxic contributions Continuous monitoring and assessment of PAHs in the urban environment are indispensable for effectively reducing their health impacts.

Laccase-loaded CaCO3 sustained-release microspheres modified SBES anode for enhance performance in the remediation of soil contaminated with phenanthrene and pyrene

This study aimed to enhance the efficiency of SBES in remediating polycyclic aromatic hydrocarbon (PAH)-contaminated soils by modifying the anode with laccase. The experiment involved four SBES anodes: a carbon nanotube-modified anode (CNT), a free laccase-modified anode (Lac), a gelatin-encapsulated laccase-modified anode (Lac-Gel), and a CaCO3 sustained-release microsphere-loaded laccase-modified (CaCO3-SMs@Laccase) anode (Lac-SMs). The CaCO3-SMs@Laccase notably extended the active period of laccase, with laccase activity in the Lac-SMs measured at 1.646 U/g after 16 days, which was significantly higher than the 0.813 U/g observed in the Lac-Gel group and the 0.206 U/g in the Lac group. The superior electricity generation and degradation efficiency observed in the Lac-SMs group were due to the sustained enzymatic activity provided by the CaCO3-SMs@Laccase. The prevention of anode acidification through CaCO3 decomposition, and promote the forward progress of electrochemical reactions. The phenanthrene (Phe) and pyrene (Pyr) removal efficiency in the soil of the Lac-SMs reached 90.78 % and 84.72 %, surpassing those of the Lac-Gel (80.36 % and 79.14 %), Lac (79.38 % and 69.31 %), and CNT (63.22 % and 56.98 %). The degradation pathway from Pyr to Phe was possible started with hydroxylation. In addition, the laccase also transformed the predominant microbial communities and metabolism pathways.

Lignin-derived compounds assisted with Kocuria marina H-2 and Pseudomonas putida B6-2 co-culture enhanced naphthalene biodegradation

The implementation of environmentally friendly and sustainable remediation strategies positively impacts solid waste management. In this study, the Kocuria marina H-2 and Pseudomonas putida B6-2 co-culture system demonstrated enhanced naphthalene biodegradation efficiency compared to single-strain cultures. Under optimal conditions of 35 °C, 200 rpm/min, and a 1:1 ratio of the co-culture system, the naphthalene biodegradation potential was further increased. Notably, the addition of both ethylenediamine-pretreated lignin and p-hydroxybenzoic acid significantly elevated naphthalene degradation rates to 68.5 %. In addition, the oil-liquid surface tension decreased, while cell surface hydrophobicity and colony-forming units increased with the addition of lignin-derived compounds. The modification of naphthalene bioavailability by ethylenediamine-pretreated lignin would accelerate the uptake and transport of hydrocarbons via ABC transporters and flagellar assembly. Importantly, genes related to bacterial chemotaxis and fatty acid biosynthesis were upregulated during the co-metabolism of naphthalene and p-hydroxybenzoic acid, further enhancing naphthalene bioconversion.

Apportioning sources of natural and anthropogenic organic matter in sediment from Lake Shihwa: An integrated approach using molecular ratios and compound-specific stable-isotope analysis

We tested an integrated multi-isotopic analysis framework to quantitatively estimate anthropogenic organic matter (OM) loads in different land-use types of a watershed (Lake Shihwa, South Korea). The isotopic signatures of increased bulk-element abundances in urban areas and industrial complexes may reflect the mixed contributions of natural and anthropogenic sources. Together with the predominant abundance of n-alkanes and polycyclic aromatic hydrocarbons at both boundaries, specific indices derived from their abundance may be indicative of mixed contributions from terrestrial plants, petroleum, and combustion deposited through various pathways (e.g., atmospheric deposition, outfall pipes, and surface runoff). Based on these properties, compound isotopic signatures (δ13CC27+C29+C31, δ13CFl, δ13CPyr, δ13CBaA+Chry, δ13CIcdP, δ13CBghiP,) for both land-use types may provide significant evidence of an increase in anthropogenic derived-OM loads (> 90 %) in Lake Shihwa. This approach suggests that total organic carbon-weighted source apportionments can provide useful quantitative estimates of OM loads within complex river systems.

Bioaccumulation of organic and inorganic contaminants in biota: A long-term evaluation in the Belgian part of the North Sea

Determining the extent of pollution in the marine environment remains challenging. Polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and metals can, during dredging operations, be transported from a port or harbour into the open sea, where they may exert a harmful effect on the marine ecosystem. To fully understand the impact of these chemicals, monitoring programs should not only focus on sediment concentrations, but should also take into account the bioaccumulated concentration in the tissue of multiple target organisms. In this study, the concentration of primary contaminants is determined in common starfish (Asterias rubens), flying crab (Liocarcinus holsatus), and brown shrimp (Crangon crangon) and the difference in the concentration of contamination between different dredge disposal sites at open sea is investigated. Different factors such as lipid weight, dry weight, grain size, and total organic carbon were measured and used to understand the difference between the observed bioaccumulation and the measured sediment concentrations. KEY MESSAGE: Different contaminants are detected in biota such as common starfish, flying crab and brown shrimp. These contaminants can be linked to dredging activities, with disposal sites associated with industrial ports showing higher contamination.

Effects of simulated low-temperature thermal remediation on the microbial community of a tropical creosote contaminated soil

In the search for more sustainable remediation strategies for PAH-contaminated soils, an integrated application of thermal remediation and bioremediation (TEB) may allow the use of less impacting temperatures by associating heating to biological degradation. However, the influence of heating on soil microbiota remains poorly understood, especially in soils from tropical regions. This work investigated the effects of low-temperature heating on creosote-contaminated soil bacteria. We used culture-dependent and 16 S rRNA sequencing methods to compare the microbial community of soil samples heated to 60 and 100 oC for 1 h in microcosms. Heating to 60 °C reduced the density of cultivable heterotrophic bacteria compared to control soil (p < 0.05), and exposure to 100 °C inactivated the viable heterotrophic community. Burkholderia-Caballeronia-Paraburkholderia (BCP) group and Sphingobium were the predominant genera. Temperature and incubation time affected the Bray-Curtis dissimilarity index (p < 0.05). At 60 °C and 30 days incubation, the relative abundance of Sphingobium decreased and BCP increased dominance. The network of heated soil after 30 days of incubation showed fewer nodes and edges but maintained its density and complexity. Both main genera are associated with PAH degradation, suggesting functional redundancy and a likely potential of soil microbiota to maintain biodegradation ability after exposure to higher temperatures. We concluded that TEB can be considered as a potential strategy to bioremediate creosote-contaminated soils, allowing biodegradation in temperature ranges where thermal remediation does not completely remove contaminants. However, we recommend further research to determine degradation rates with this technology.

Resting for viability: Gordonia polyisoprenivorans ZM27, a robust generalist for petroleum bioremediation under hypersaline stress

The intrinsic issue associated with the application of microbes for practical pollution remediation involves maintaining the expected activity of engaged strains or consortiums as effectively as that noted under laboratory conditions. Faced with various stress factors, degraders with dormancy ability are more likely to survive and exhibit degradation activity. In this study, a hydrocarbonoclastic and halotolerant strain, Gordonia polyisoprenivorans ZM27, was isolated via stimulation with resuscitation-promoting factor (Rpf). Long-term exposure to dual stresses of 10% NaCl and starvation induced ZM27 to enter a viable but nonculturable (VBNC)-like state, and ZM27 cells could be resuscitated upon Rpf stimulation. Notable changes in both morphological and physiological characteristics between VBNC-like ZM27 cells and resuscitated cells confirmed the response to Rpf and their robust resistance against harsh environments. Whole-genome sequencing and analysis indicated ZM27 could be a generalist degrader with dormancy ability. Subsequently, VBNC-like ZM27 was applied in a soil microcosm experiment to investigate the practical application potential under harsh conditions. VBNC-like ZM27 combined with Rpf stimulation exhibited the most effective biodegradation performance, and the initial n-hexadecane content (1000 mg kg-1) decreased by 63.29% after 14-day incubation. Based on 16S rRNA amplicon sequencing and analysis, Gordonia exhibited a positive response to Rpf stimulation. The relative abundance of genus Gordonia was negatively correlated with that of Alcanivorax, a genus of obligate hydrocarbon degrader with the greatest abundance during soil incubation. Based on the degradation profile and community analysis, generalist Gordonia may be more efficient in hydrocarbon degradation than specialist Alcanivorax under harsh conditions. The characteristics of ZM27, including its sustainable culturability under long-term stress, response to Rpf and robust performance in soil microcosms, are valuable for the remediation of petroleum pollution under stressful conditions. Our work validated the importance of dormancy and highlighted the underestimated role of low-activity degraders in petroleum remediation.

Spatial interaction and risk zoning of compound pollutants in farmland soils: Insights from heavy metals and polycyclic aromatic hydrocarbons in Hezhang County, China

The accurate identification and assessment of comprehensive risks associated with compound pollution in agricultural ecosystems remain significant challenges due to the complexity of pollution sources, soil heterogeneity, and spatial variability. In this study, bivariate local indicators of spatial association (LISA) were applied to analyze the spatial interaction between heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) in farmland soils in Hezhang County. The results revealed distinct clusters with elevated concentrations of both HMs and PAHs, predominantly in areas affected by long-standing lead-zinc mining and smelting activities. Positive matrix factorization (PMF) was utilized to identify mining and smelting activities, and associated coal consumption as common sources of both pollutants, contributing 53 % and 28 %, respectively. Ecological health risk assessment results indicated that the combined pollution in this area has led to particularly severe ecological and cancer risks, with the pollution coefficient (Pc) exceeding 3.0, and risk values for both adults and children surpassing the threshold of 10-4. Through the integration of advanced bivariate LISA mapping and thorough risk assessment, this study precisely delineated ecological risk zones (33.1 %) and more refined health risk zones (40.1 %) associated with combined pollution. The southwest of Hezhang was identified as a critical hotspot for combined pollution risks, primarily due to intensive mining and smelting activities in the region. Overall, this study underscores the utility of bivariate LISA as a robust approach for delineating spatial clustering patterns caused by combined pollutants. It provides crucial insights for identifying regions with heightened human health and ecological risks in rural settings.

Environmental applications and risks of engineered nanomaterials in removing petroleum oil in soil

Oil-contaminated soil posed serious threats to the ecosystems and human health. The unique and tunable properties of engineered nanomaterials (ENMs) enable new technologies for removing and repairing oil-contaminated soil. However, few studies systematically examined the linkage between the change of physicochemical properties and the removal efficiency and environmental functions (e.g., potential risk) of ENMs, which is vital for understanding the ENMs environmental sustainability and utilization as a safety product. Thus, this review briefly summarized the environmental applications of ENMs to removing petroleum oil from complex soil systems: Theoretical and practical fundamentals (e.g., excellent physicochemical properties, environmental stability, controlled release, and recycling technologies), and various ENMs (e.g., iron-based, carbon-based, and metal oxides nanomaterials) remediation case studies. Afterward, this review highlights the removing mechanism (e.g., adsorption, photocatalysis, oxidation/reduction, biodegradation) and the impact factor (e.g., nanomaterials species, natural organic matter, and soil matrix) of ENMs during the remediation process in soil ecosystems. Both positive and negative effects of ENMs on terrestrial organisms have been identified, which are mainly derived from their diverse physicochemical properties. In linking nanotechnology applications for repairing oil-contaminated soil back to the physical and chemical properties of ENMs, this critical review aims to raise the research attention on using ENMs as a fundamental guide or even tool to advance soil treatment technologies.

Identification of key anthropogenic and land use factors and ecological risk assessment of dissolved polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) in an urbanized estuary in China

This study investigated dissolved PAHs and OCPs in Quanzhou Bay estuaries, assessed their ecological risk, and examined anthropogenic impacts on contaminant distribution. Results showed that dissolved ∑24PAH concentrations ranged from 117 to 709 ng/L (mean: 358 ng/L), with dominance of 2-ring PAHs (Naphthalene, 1-Methylnaphthalene, and 2-Methylnaphthalene). Dissolved DDT levels ranged from 0.06 to 0.49 ng/L (mean: 0.28 ng/L), while HCBz concentrations varied from 0.02 to 0.44 ng/L (mean: 0.20 ng/L). PAHs were higher in the north due to urbanization and transport, while OCPs showed higher levels in the south due to historical agricultural use. Rural areas, water bodies, and wetlands significantly influenced the behavior of PAHs according to Spearman correlation and lasso regression analyses. Quanzhou Bay was categorized as a low to medium risk area based on dispersion simulation and ecological risk assessment, highlighting implications for future sustainable development and policy planning. CAPSULE: The coupled relationship between human activities and the distribution of dissolved PAHs and OCPs in urbanized estuaries was explored using statistical methods and GIS technology, providing valuable insights into environmental processes and pollutant control policies.

Evaluation of Differentially Expressed Candidate Genes in Benzo[a]pyrene Degradation by Burkholderia vietnamiensis G4

Bacteria-mediated bioremediation is widely employed for its environmental benefits. The genus Burkholderia can degrade persistent organic compounds, however, little is known about its mechanisms. To increase this knowledge, Burkholderia vietnamiensis G4 bacteria were exposed to benzo[a]pyrene, a recalcitrant compound, and the expression of twelve genes of interest was analyzed at 1, 12 and 24 h. In addition, benzo[a]pyrene degradation, evaluation of cell viability and fluorescence emission of assimilated benzo[a]pyrene was performed over 28 days. The up-regulated genes were xre, paaE, livG and pckA at the three times, ACAD, atoB, bmoA and proV at 1 h and AstB at 12 h. These genes are important for bacterial survival in stress situations, breakdown and metabolization of organic compounds, and nutrient transport and uptake. Furthermore, a 52% reduction of the pollutant was observed, there was no significant variation in the viability rate of the cells, and fluorescence indicated an accumulation of benzo[a]pyrene after 24 h. Our study demonstrates the bacteria adaptability and ability to modulate the expression of genes at different times and as needed. This increases our understanding of biodegradation processes and opens new possibilities for using this bacterial strain as a tool for the bioremediation of contaminated areas.

Plant Defense Mechanisms against Polycyclic Aromatic Hydrocarbon Contamination: Insights into the Role of Extracellular Vesicles

Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants that pose significant environmental and health risks. These compounds originate from both natural phenomena, such as volcanic activity and wildfires, and anthropogenic sources, including vehicular emissions, industrial processes, and fossil fuel combustion. Their classification as carcinogenic, mutagenic, and teratogenic substances link them to various cancers and health disorders. PAHs are categorized into low-molecular-weight (LMW) and high-molecular-weight (HMW) groups, with HMW PAHs exhibiting greater resistance to degradation and a tendency to accumulate in sediments and biological tissues. Soil serves as a primary reservoir for PAHs, particularly in areas of high emissions, creating substantial risks through ingestion, dermal contact, and inhalation. Coastal and aquatic ecosystems are especially vulnerable due to concentrated human activities, with PAH persistence disrupting microbial communities, inhibiting plant growth, and altering ecosystem functions, potentially leading to biodiversity loss. In plants, PAH contamination manifests as a form of abiotic stress, inducing oxidative stress, cellular damage, and growth inhibition. Plants respond by activating antioxidant defenses and stress-related pathways. A notable aspect of plant defense mechanisms involves plant-derived extracellular vesicles (PDEVs), which are membrane-bound nanoparticles released by plant cells. These PDEVs play a crucial role in enhancing plant resistance to PAHs by facilitating intercellular communication and coordinating defense responses. The interaction between PAHs and PDEVs, while not fully elucidated, suggests a complex interplay of cellular defense mechanisms. PDEVs may contribute to PAH detoxification through pollutant sequestration or by delivering enzymes capable of PAH degradation. Studying PDEVs provides valuable insights into plant stress resilience mechanisms and offers potential new strategies for mitigating PAH-induced stress in plants and ecosystems.

Nationwide monitoring of legacy and emerging persistent organic pollutants and polycyclic aromatic hydrocarbons along the Korean coast

Comprehensive studies simultaneously investigating the occurrence of chemicals of concern are limited. In this study, sediments and bivalves were collected from 24 locations along the Korean coast to evaluate the relative distribution, contamination characteristics, and ecological risks of legacy/emerging persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs). Our findings reveal that the concentrations of these contaminants were comparable to or lower than historical levels in the same Korean coast and other Asian countries. Notably, PAHs exhibited the highest distribution in sediments (84 %), whereas short-chain chlorinated paraffins (SCCPs) were dominant in bivalves (91 %). This study highlighted significant correlations in the sediment levels of each legacy pollutants, suggesting similar sources and geochemical behaviors. However, SCCPs displayed unique contamination patterns. Ecologically, PAHs and SCCPs presented low risks in sediments compared to Canadian Sediment Quality Guidelines, however 100 % and 33 % of bivalves, respectively, exceeded US EPA/Canadian Fish Tissue Guidelines.

Kinetic analysis of slow pyrolysis of oily sludge at medium temperature (350 ℃-650 ℃) and the effects of heating rate on pyrolysis

ABSTRACTPyrolysis is an effective way for the harmless treatment of oily sludge. The composition, physicochemical properties, and pyrolysis of oily sludge were experimentally studied in the present study. The Starink and Coats-Redfern methods were used to analyze the pyrolysis kinetics of oily sludge. Pyrolysis of oily sludge is divided into four stages: water evaporation stage, light component evaporation stage, heavy component pyrolysis stage, and final pyrolysis stage. The light component evaporation and heavy component pyrolysis stages are the main stages of medium-temperature pyrolysis. The pyrolysis characteristic parameters under heating rates of 10, 20, 30, and 40 K/min were obtained, and the effects of heating rates on the pyrolysis characteristics of oily sludge were discussed. The results show that with the increase in heating rate, the temperature range of each stage expands, and the temperature of the pyrolysis peaks also increases, with an average increase of 14.88%. The activation energies of the main pyrolysis stages obtained by the Starink method and Coats-Redfern method are consistent. In the light component evaporation stage, the activation energies obtained by the two methods are 61.93kJ/mol and 68.6kJ/mol, while the activation energies are 294.88kJ/mol and 367kJ/mol in the heavy component pyrolysis stage. The pyrolysis mechanism functions are obtained, and the pyrolysis kinetic equations under 10, 20, 30, and 40 K/min were constructed and validated by comparison with the results of the calculated properties and experimental measurement. This study can provide a better insight into the heat and mass transfer processes of oily sludge in pyrolysis reactors for further development and optimization.

Environmental contamination with polycyclic aromatic hydrocarbons and contribution from biomonitoring studies to the surveillance of global health

This work presents an integrated overview of polycyclic aromatic hydrocarbons' (PAHs) ubiquity comprising environmental contamination in the air, aquatic ecosystems, and soils; characterizes the contamination in biota; and identifies main biomonitors and human exposure to PAHs and associated health risks. Urban centers and industrial areas present increased concentrations in the air (1344.4-12,300 versus 0.03-0.60 ng/m3 in industrial/urban and rural zones) and soils (0.14-1.77 × 106 versus 2.00-9.04 × 103 versus 1.59-5.87 × 103 ng/g in urban, forest, and rural soils), respectively. Increased concentrations were found in coastal zones and superficial waters as well as in sediments (7.00 × 104-1.00 × 109 ng/g). Benzo(a)pyrene, a carcinogenic PAH, was found in all environmental media. Mosses, lichens, tree leaves, bivalves, cephalopods, terrestrials' snails, and honeybees are good biomonitors of biota contamination. More studies are needed to improve characterization of PAHs' levels, distribution, and bioaccumulation in the environmental media and assess the associated risks for biota and human health. Actions and strategies to mitigate and prevent the bioaccumulation of PAHs in the environment and trophic chains toward the WHO's One-Health Perspective to promote the health of all ecosystems and human life are urgently needed.

Removal of environmental pollutants using biochar: current status and emerging opportunities

In recent times, biochar has emerged as a novel approach for environmental remediation due to its exceptional adsorption capacity, attributed to its porous structure formed by the pyrolysis of biomass at elevated temperatures in oxygen-restricted conditions. This characteristic has driven its widespread use in environmental remediation to remove pollutants. When biochar is introduced into ecosystems, it usually changes the makeup of microbial communities by offering a favorable habitat. Its porous structure creates a protective environment that shields them from external pressures. Consequently, microorganisms adhering to biochar surfaces exhibit increased resilience to environmental conditions, thereby enhancing their capacity to degrade pollutants. During this process, pollutants are broken down into smaller molecules through the collaborative efforts of biochar surface groups and microorganisms. Biochar is also often used in conjunction with composting techniques to enhance compost quality by improving aeration and serving as a carrier for slow-release fertilizers. The utilization of biochar to support sustainable agricultural practices and combat environmental contamination is a prominent area of current research. This study aims to examine the beneficial impacts of biochar application on the absorption and breakdown of contaminants in environmental and agricultural settings, offering insights into its optimization for enhanced efficacy.

PAHs contamination in ports: Status, sources and risks

Polycyclic aromatic hydrocarbons (PAHs) constitute important organic contaminants that have been degrading coastal ecosystems over the years. Evaluating PAH status in port ecosystems aligns with societal goals of maintaining clean habitats and sustainability. This comprehensive review systematically analyzed 123 articles, exploring the global distribution, sources, and ecological risks linked to PAH contamination in ports, focusing on water, sediment, and biota. The mean concentrations of 16 PAHs in water, sediment, and biota across worldwide ports were 175.63 ± 178.37 ng/L, 1592.65 ± 1836.5 μg/kg, and 268.47 ± 235.84 μg/kg, respectively. In line with PAH emissions and use in Asia, Asian ports had the highest PAH concentrations for water and biota, while African ports had the highest PAH concentrations for sediment. The temporal trend in PAH accumulation in sediments globally suggests stability. However, PAH concentrations in water and biota of global ports exhibit increasing trends, signaling aggravating PAH contamination within port aquatic ecosystems. Some ports exhibited elevated PAH levels, particularly in sediments with 4.5 %, 9.5 %, and 21 % of the ports categorized as very poor, poor, and moderate quality. Some PAH isomers exceeded guidelines, including the carcinogenic Benzo(a)pyrene (BaP). Coal, biomass, and petroleum combustion were major sources for PAHs. The structure of ports significantly influences the concentrations of PAHs. PAH concentrations in sediments of semi-enclosed ports were 3.5 times higher than those in open ports, while PAH concentrations in water and biota of semi-enclosed ports were lower than those in open ports. Finally, risk analyses conducted through Monte Carlo simulation indicated moderate to high risks to aquatic species, with probabilities of 74.8 % in water and 34.4 % in sediments of ports worldwide. This review underscores the imperative to delve deeper into the accumulation of PAHs and similar pollutants in ports for effective management and environmental protection.

A study on source identification of contaminated soil with total petroleum hydrocarbons (aromatic and aliphatic) in the Ahvaz oil field

The oil industry in Khuzestan province (Southwest Iran) is one of the main reasons contributing to the pollution of the environment in this area. TPH, including both aromatic and aliphatic compounds, are important parameters in creating pollution. The present study aimed to investigate the source of soil contamination by TPH in the Ahvaz oil field in 2022. The soil samples were collected from four oil centers (an oil exploitation unit, an oil desalination unit, an oil rig, and a pump oil center). An area outside the oil field was determined as a control area. Ten samples with three replicates were taken from each area according to the standard methods. Aromatic and aliphatic compounds were measured by HPLC and GC methods. The positive matrix factorization (PMF) model and isomeric ratios were used to determine the source apportionment of aromatic compounds in soil samples. The effects range low and effects range median indices were also used to assess the level of ecological risk of petroleum compounds in the soil samples. The results showed that Benzo.b.fluoranthene had the highest concentration with an average of 5667.7 ug/kg in soil samples in the Ahvaz oil field. The highest average was found in samples from the pump oil center area at 7329.48 ug/kg, while the lowest was found in control samples at 1919.4 ug/kg-1. The highest level of aliphatic components was also found in the pump oil center, with a total of 3649 (mg. Kg-1). The results of source apportionment of petroleum compounds in soil samples showed that oil activities accounted for 51.5% of the measured PAHs in soil. 38.3% of other measured compounds had anthropogenic origins, and only 10.1% of these compounds were of biotic origin. The results of the isomeric ratios also indicated the local petroleum and pyrogenic origin of PAH compounds, which is consistent with the PMF results. The analysis of ecological risk indices resulting from the release of PAHs in the environment showed that, except for fluoranthene, other PAHs in the oil exploitation unit area were above the effects range median level (ERM) and at high risk. The results of the study showed that soil pollution by total petroleum hydrocarbons (TPH), both aromatic and aliphatic, is at a high level, and is mainly caused by human activities, particularly oil activities.

Genotoxic effects of marine pollutants on coastal meso-zooplankton populations - A mini-review

Meso-zooplankton plays a vital role in maintaining healthy marine ecosystems, and some of the taxa provide biological indications for the monitoring of environmental and climate change. Recently, several newly emerging stressors were shown to impact marine and coastal meso-zooplankton in some ways. Marine organisms' genomic core, tightly packed with high-level integrity, can be damaged by anthropogenic activities in coastal zones worldwide and impact their integrity. Genomic integrity loss leads to a cascade of effects on the destruction of the food chain sequences, from primary producers to higher invertebrates. Therefore, monitoring genomic integrity loss using ecotoxicological approaches that focus on genetic changes appears to be a suitable approach. A literature review shows that different stressors severely impact genomic integrity through DNA damage at different concentrations and exposure times. Contaminated sediments also strongly impact the genomic integrity of estuaries and adjacent coastal meso-zooplankton communities.

Environmental microbial diversity and water pollution characteristics resulted from 150 km coastline in Quanzhou Bay offshore area

As a typical transitional area between the land and sea, the offshore area is subjected to the triple synergistic pressure from the ocean, land, and atmosphere at the same time, and has obvious characteristics such as complex and diverse chemical, physical, and biological processes, coupled and changeable environmental factors, and sensitive and fragile ecological environment. With the deepening of the urbanization process, the offshore area has gradually become the final receptions of pollutants produced by industry, agriculture, and service industries, and plays a key role in the global environmental geochemical cycle of pollutants. In this study, the Quanzhou Bay offshore area was selected as the research object. Sediment and water samples were collected from 8 sampling points within about 150 km of coastline in the Quanzhou Bay offshore area. 16s rDNA high-throughput sequencing method was used to investigate the variation rule of microbial diversity in the offshore area, and multi-parameter water quality analysis was carried out at the same time. The results showed that the distribution characteristics of microbial communities and water quality in the Quanzhou Bay offshore area showed significant differences in different latitudes and longitudes. This difference is closely related to the complexity of offshore area. This study can provide scientific support for protecting and improving the ecological environment of offshore areas.

Predicting the bioavailability of polycyclic aromatic hydrocarbons in rhizosphere soil using a new novel in situ solid-phase microextraction technique

In situ measurement of the bioavailability of organic pollutants in soil is crucial for understanding their environmental behavior and assessing health risks. Due to the high heterogeneity of soil, microscale determination is crucial for achieving high accuracy, but few methods are available. In this study, microsized probes coated with polydimethylsiloxane (PDMS) were used to measure the bioavailability of polycyclic aromatic hydrocarbons (PAHs) in soil in situ. The concentrations of PAHs enriched by the PDMS-coated probes correlated well with the results of bioassays using earthworms (R2 = 0.92-0.99) and ryegrass roots (R2 = 0.92-0.99). Compared with other chemical extraction methods, such as n-butanol extraction, the proposed method has advantages such as in situ operation, microvolume analysis, and negligible interference to the soil environment. In the soil rhizosphere zone, PAHs bioavailability decreased in the following order: rhizosphere > near-rhizosphere > far-rhizosphere. The bioavailability of PAHs in soil amended with biochar was also successfully characterized by the proposed method. Thus, this study developed an in situ and microscale method to predict the bioavailability of organic pollutants in contaminated soils and provides new insight into migration and transformation processes in rhizosphere soil.

Microplastics and PAHs mixed contamination: An in-depth review on the sources, co-occurrence, and fate in marine ecosystems

Microplastics (MPs) and polycyclic aromatic hydrocarbons (PAHs) are toxic contaminants that have been found in marine ecosystems. This review aims to explore the sources and mechanisms of PAHs and MPs mixed contamination in marine environments. Understanding the released sources of PAHs and MPs is crucial for proposing appropriate regulations on the release of these contaminants. Additionally, the mechanisms of co-occurrence and the role of MPs in distributing PAHs in marine ecosystems were investigated in detail. Moreover, the chemical affinity between PAHs and MPs was proposed, highlighting the potential mechanisms that lead to their persistence in marine ecosystems. Moreover, we delve into the various factors influencing the co-occurrence, chemical affinity, and distribution of mixed contaminants in marine ecosystems. These factors, including environmental characteristics, MPs properties, PAHs molecular weight and hydrophobicity, and microbial interactions, were critically examined. The co-contamination raises concerns about the potential synergistic effects on their degradation and toxicity. Interesting, few studies have reported the enhanced photodegradation and biodegradation of contaminants under mixed contamination compared to their individual remediation. However, currently, the remediation strategies reported for PAHs and MPs mixed contamination are scarce and limited. While there have been some initiatives to remove PAHs and MPs individually, there is a lack of research specifically targeting the removal of mixed contaminants. This deficiency highlights the need for further investigation and the development of effective remediation approaches for the efficient remediation of PAHs and MPs from marine ecosystems.

Enhancing biodegradation of vegetable oil-contaminated soil with soybean texturized waste, spent mushroom substrate, and stabilized poultry litter in microcosm systems

Industrial activities contribute to environmental pollution, particularly through unregulated effluent discharges, causing adverse effects on ecosystems. Vegetable oils, as insoluble substances, exacerbate this pollution, forming impermeable films and affecting the oxygen transfer, leading to serious habitat disruption. Organic wastes, such as soybean texturized waste, spent mushroom substrate, and stabilized poultry litter, were assessed for their efficacy in enhancing the degradation of vegetable oil in contaminated soil. For this purpose, contaminated soil was amended with each of the wastes (10% w/w) using microcosm systems, which were monitored physico-chemically, microbiologically and toxicologically. Results indicate that the wastes promoted significant oil degradation, achieving 83.1, 90.7, and 86.2% removal for soybean texturized waste, spent mushroom substrate, and stabilized poultry litter, respectively, within a 90-day period. Additionally, they positively influenced soil microbial activity, as evidenced by increased levels of culturable microorganisms and hydrolytic microbial activity. While bioassays indicated no phytotoxicity in most cases, soybean texturized waste exhibited inhibitory effects on seed germination and root elongation of Lactuca sativa. This study significantly enhances our comprehension of remediation techniques for sites tainted with vegetable oils, highlighting the critical role of organic waste as eco-friendly agents in soil restoration. Emphasizing the practical implications of these findings is imperative to underscore the relevance and urgency of addressing vegetable oil contamination in soil. Moving forward, tailored strategies considering both contaminant characteristics and soil ecosystem traits are vital for ensuring effective and sustainable soil remediation.

Simultaneously removal of PAHs from contaminated soil and effluent by integrating soil washing and advanced oxidation processes in a continuous system: Water saving, optimization and scale up modeling

Every year a large amount of clean water turns into contaminated effluent by soil washing (SW) process. The release of this effluent has become a growing environmental threat. In this study, a sustainable approach was developed for effective removal of PAHs from contaminated soil and the effluent by integrating SW and advanced oxidation processes (AOPs) in a continuous system. In the constructed continuous system, first small amount of clean water passed through the contaminated soil to remove PAHs. Then, the polluted effluent was treated by a quick AOPs and recycled for SW processes again and again until a complete removal of PHE be achieved. The performance of the continuous system was optimized and compared with batch system (no circulation) at lab scale. In addition, a scale up modeling was developed to predict the performance of continuous system at large scale. According to the results, under the optimum conditions: Tween 80 (TW80) = 6 g/L, ultrasonic = 160 kW, UV = 30 W, O3 = 5 g/h and TiO2 = 2 g/m2, the final PHE degradation efficiency of 98 % and 94 % were achieved by the continuous and batch systems after 130 and 185 min, respectively. The continuous system used 5 times less water volume than the batch system but resulted in better PAHs degradation. The scale up modeling revealed at large scale (100 kg soil), the continuous system could decrease the energy consumption and the required washing solution (water + TW80) up to 50 % and 80 %, respectively in comparison to the batch system. This work suggests a promising and practical approach for contaminated soil remediation without producing polluted water.

Advanced oxidation of polycyclic aromatic hydrocarbons in tropical soil: Self-catalytic utilization of natural iron contents in an oxygenation reactor supported with persulfate

The catalysts derived from natural iron minerals in the advanced oxidation process offer several advantages. However, their utilization in soil remediation is restricted due to the presence of soil impurities, which can inhibit the catalytic activity of these minerals. The soils in tropical regions exhibit lower organic matter content, limited cation exchange capacity, and are non-saline, this enhances the efficiency of utilizing natural iron minerals from tropical soil as a catalyst. In this regard, the catalytic potential of naturally iron-bearing tropical soil was investigated to eliminate phenanthrene (PHE), pyrene (PYR), and benzo[α]pyrene (B[α]P) using an oxygenated reactor supported with persulfate (PS). The system showed an efficient performance, and the removal efficiencies under the optimum conditions were 81 %, 73 %, and 86 % for PHE, PYR, and B[α]P, respectively. This indicated that the catalytic activity of iron was working efficiently. However, there were changes in the soil characteristics after the remediation process such as a significant reduction in iron and aluminum contents. The scavenging experiments demonstrated that HO• had a minor role in the oxidation process, SO4•- and O2•- emerged as the primary reactive species responsible for the effective degradation of the PAHs. Moreover, the by-products were monitored after soil remediation to evaluate their toxicity and to propose degradation pathways. The Mutagenicity test showed that two by-products from each PHE and B[α]P had positive results, while only one by-product of PYR showed positive. The toxicity tests of oral rat LD50 and developmental toxicity tests revealed that certain PAHs by-products could be more toxic from the parent pollutant itself. This study represents a notable progression in soil remediation by providing a step forward in the application of the advanced oxidation process (AOP) without requiring additional catalysts to activate oxidants and degrade pollutant PAHs from the soil.

Enhanced surfactant remediation of diesel-contaminated soil using O3 nanobubbles

Currently, nanobubbles are widely discussed in environmental research due to their unique properties, including significant specific surface area, transfer efficiency, and free radical generation. In this study, O2 and O3 nanobubbles (diameters ranging from 0 to 500 nm) were combined with conventional surfactant technology to investigate their enhanced efficacy in removing diesel contaminants from soil. The impact of various factors such as surfactant concentration, temperature, and soil aging duration on pollutant removal rates was examined across different experimental approaches (stirring/flushing). Soil samples subjected to different treatments were characterized using TG-DTG and FTIR analysis, while GC/MS was employed to assess the degradation products of diesel constituents in the soil. The results indicated that the elution efficiencies of the three surfactants (SDS, SDBS, and TX-100) for diesel in soil correlated positively with concentration (0.3-1.4 CMC) and temperature (18-60 °C), and inversely with aging time (10-300 days), with the elution capacity was SDS > SDBS > TX-100. Mechanical stirring (500 rpm) and temperature variations (18-60 °C) did not affect the stability of the nanobubbles. Upon the introduction of O3 nanobubbles to the surfactant solution, there was a consistent increase in both the removal (degraded and removed) efficiency and rate of diesel under varying experimental conditions, resulting in an enhancement of removal rates by approximately 8-15%. FTIR spectroscopy showed that surfactants containing O3 nanobubbles mitigated the impact on the primary functional groups of soil organic matter. GC/MS analyses indicated that residual pollutants were predominantly alkanes, with degradation difficulty ranking as: alkanes < alkenes < cycloalkanes < aromatic compounds. TG-DTG coupled with GC/MS analysis demonstrated that O3 nanobubbles contributed to a reduction in surfactant residues. This study significantly advances our understanding of how nanobubbles facilitate and optimize surfactant-assisted remediation of contaminated soil, thereby advancing the precise application of nanobubble technology in soil remediation.

AI-assisted systematic review on remediation of contaminated soils with PAHs and heavy metals

This systematic review addresses soil contamination by crude oil, a pressing global environmental issue, by exploring effective treatment strategies for sites co-contaminated with heavy metals and polycyclic aromatic hydrocarbons (PAHs). Our study aims to answer pivotal research questions: (1) What are the interaction mechanisms between heavy metals and PAHs in contaminated soils, and how do these affect the efficacy of different remediation methods? (2) What are the challenges and limitations of combined remediation techniques for co-contaminated soils compared to single-treatment methods in terms of efficiency, stability, and specificity? (3) How do various factors influence the effectiveness of biological, chemical, and physical remediation methods, both individually and combined, in co-contaminated soils, and what role do specific agents play in the degradation, immobilization, or removal of heavy metals and PAHs under diverse environmental conditions? (4) Do AI-powered search tools offer a superior alternative to conventional search methodologies for executing an exhaustive systematic review? Utilizing big-data analytics and AI tools such as Litmaps.co, ResearchRabbit, and MAXQDA, this study conducts a thorough analysis of remediation techniques for soils co-contaminated with heavy metals and PAHs. It emphasizes the significance of cation-π interactions and soil composition in dictating the solubility and behavior of these pollutants. The study pays particular attention to the interplay between heavy metals and PAH solubility, as well as the impact of soil properties like clay type and organic matter on heavy metal adsorption, which results in nonlinear sorption patterns. The research identifies a growing trend towards employing combined remediation techniques, especially biological strategies like biostimulation-bioaugmentation, noting their effectiveness in laboratory settings, albeit with potentially higher costs in field applications. Plants such as Medicago sativa L. and Solanum nigrum L. are highlighted for their effectiveness in phytoremediation, working synergistically with beneficial microbes to decompose contaminants. Furthermore, the study illustrates that the incorporation of biochar and surfactants, along with chelating agents like EDTA, can significantly enhance treatment efficiency. However, the research acknowledges that varying environmental conditions necessitate site-specific adaptations in remediation strategies. Life Cycle Assessment (LCA) findings indicate that while high-energy methods like Steam Enhanced Extraction and Thermal Resistivity - ERH are effective, they also entail substantial environmental and financial costs. Conversely, Natural Attenuation, despite being a low-impact and cost-effective option, may require prolonged monitoring. The study advocates for an integrative approach to soil remediation, one that harmoniously balances environmental sustainability, cost-effectiveness, and the specific requirements of contaminated sites. It underscores the necessity of a holistic strategy that combines various remediation methods, tailored to meet both regulatory compliance and the long-term sustainability of decontamination efforts.

Effect of polycyclic aromatic compounds (PAH & Polar-PAC) availability on their ecotoxicity towards terrestrial organisms

The exposure of terrestrial organisms to soils freshly contaminated by polycyclic aromatic compounds (PACs, including PAHs and polar-PACs) is known to cause significant toxicity effects. However, historically contaminated soils, such as former coking plant soils, usually induce a limited toxic impact, due to the "aging" phenomenon which is the result of several processes causing a reduction of PAC availability over time. For a better understanding of these behaviors, this study aimed to compare the toxic responses of terrestrial organisms exposed to aged contaminated soils and their counterparts submitted to a moderate heating process applied to increase PAC availability. Two aged "raw" soils (limited PAC availability) were selected for their representativeness of former industrial soils in terms of PAC contamination. These soils were submitted either to moderate heating (expected PAC availability increase) or solvent-extraction (expected PAC removal). Physico-chemical parameters, contamination levels and availability were determined for these three soil modalities. Additionally, standardized limit bioassays on plants and earthworms were performed to assess soil ecotoxicity. The findings demonstrated that historically contaminated soils exposed to moderate heating induced the highest ecotoxic responses from terrestrial organisms. Heating increased PAC (bio)availability, without modifying any other soil physico-chemical properties. These results pointed out the importance of considering the contamination availability parameter in risk evaluation and also provide a possible tool for protective long-term risk assessment.

PAH levels in sediments from a coastal area heavily subjected to anthropogenic pressure (Asturias, north of Spain)

Ninety-two sediment samples collected along the Asturias coastline (north of Spain), were studied based on their concentrations of 16PAHs. Concentrations of Σ16PAH showed an average of 12.650 mg kg-1 d.w., which is higher than most other studies conducted around the world. The origins of PAHs present in the sediments are mainly from fuel combustion in industrial processes. The main source of PAH to the coastal system seems to be the Nalón River, which played a significant past role related to different industrial activities, highlighting thermal power stations located in the basin. On the other hand, the Avilés Estuary, hotspot of the regional heavy metallurgical industry was the area with the highest concentrations of Σ16PAH, with an average of 5 to 6 times higher than the rest studied. The risk assessment of Σ16PAH concentrations in the study area showed a high potential risk of contamination transfer to other environmental compartments.

Distribution and source identification of polycyclic aromatic hydrocarbons (PAHs) with PCA-MLR and PMF methods in the topsoil of Chengdu at SW, China

In spite of extensive studies on the features of polycyclic aromatic hydrocarbons (PAHs) as typical persistent organic pollutants (POPs) in cities, lack of understanding on the distribution and source characteristics of PAHs in big city with basin climate that can easily accelerate the pollution. Therefore, we sampled and analyzed PAHs from forty-five topsoil samples evenly distributed in Chengdu and the data shows that: (1) concentrations of ∑16PAHs in the study area ranged from 88.56 to 4448.34 ng/g, with a mean value of 739.07 ng/g, which is a lower level compared to similar cities, the distribution and proportion of LMW-PAHs show that the migration of pollution is blocked by the topography of the basin; (2) principal component analysis-multiple linear regression (PCA-MLR) and positive matrix factorization (PMF) indicated that combustion of fossil fuels and biomass is the most important source of PAHs in Chengdu; (3) the toxic equivalency factors of benzo[a]pyrene indicated a low risk of ∑16PAHs in all areas in Chengdu; (4) the inherited lifetime carcinogenic risk (ILCR) showed a relatively low level of potential risk in the region, while female inhabitants in several regions seem to suffer from higher health risks. Overall, our case study of PAHs in the topsoil at Chengdu city at SW China indicates that the PCA-MLR analysis is useful to identify the source of PAHs in the urban region with complicated pollution source.

The remediation of marine sediments containing polycyclic aromatic hydrocarbons by peroxymonosulfate activated with Sphagnum moss-derived biochar and its benthic microbial ecology

This research was to study the efficiency of Sphagnum moss-derived biochar (SMBC) in removing polycyclic aromatic hydrocarbons (PAHs) from marine sediment using a peroxymonosulfate (PMS)-based carbon-advanced oxidation process (PMS-CAOPs). Sphagnum moss-derived biochar (SMBC) was generated via a simple thermochemical process for PMS activation toward enhancing decontamination of sediments. At pH 6, the SMBC/PMS system achieved a PAH removal efficiency exceeding 78% in 12 h reaction time. Moreover, PAHs of 6-, 5-, 4-, 3-, and 2-ring structures exhibited 98%, 74%, 68%, 85%, and 91%, of removal, respectively. The SMBC activation of PMS generated both radicals (SO4•- and HO•) and nonradical (1O2), species responsible for PAHs degradation, attributed primarily to inherent iron and carbon moieties. The significant PAHs degradation efficiency showcased by the SMBC/PMS process holds promise for augmenting the performance of indigenous benthic microbial activity in sediment treatment contexts. The response of sediment microbial communities to PAH-induced stress was particularly associated with the Proteobacteria phylum, specifically the Sulfurovum genus. The findings of the present study highlight the efficacy of environmentally benign reactive radical/nonradical-based PMS-CAOP using pristine carbon materials, offering a sustainable strategy for sediment treatment.

New insights into thermal desorption remediation of pyrene-contaminated soil based on an optimized numerical model

Thermal desorption (TD) is known as an effective technique to remediate PAHs-contaminated sites. However, effectively removing PAHs using TD while saving time, and energy, and minimizing soil damage remains a challenge. In this study, we examined the combined effects of various factors on the removal efficiency of pyrene (PYR) by TD and developed an optimal numerical model based on conducting a series of soil experiments. The results showed that temperature (T) and time (t) promoted the desorption of PYR, while water (Sw) and organic matter (fom) were just the opposite. Besides, water and organic matter had a synergistic effect proportionally. It was found that adjusting the soil-water ratio (which can be controlled by organic matter) maximized the desorption rate of PYR. An ideal Sw/fom 1.56 and a minimized recommended temperature (173 °C) were proposed based on the model. Finally, the efficacy of the optimized scheme was validated in real-world site soil. These findings not only mechanistically revealed the desorption behavior of PYR under the influence of various factors, but also provided an optimized scheme for efficiently removing PAHs using TD, thereby accelerating the remediation process and reducing energy consumption. The modeling ideas and conclusions obtained may be applicable to other PAHs, guiding the effective remediation of PAHs-polluted sites.

Degradation of Benzo[a]pyrene and 2,2',4,4'-Tebrabrominated Diphenyl Ether in Cultures Originated from an Agricultural Soil

Benzo[a]pyrene (BaP) and 2,2',4,4'-tetrabrominated diphenyl ether (BDE-47) are common contaminants in the environment, posing a threat to the ecosystems and human health. Currently, information on the microbial metabolism of BaP and BDE-47 as well as the correlated bacteria is still limited. This research aimed to study the degradation of BaP and BDE-47 by enriched cultures originated from an agricultural soil in Tianjin (North China) and characterize the bacteria involved in the degradation. Two sets of experiments were set up with BaP and BDE-47 (2 mg/L) as the sole carbon source, respectively. The degradation of BaP and BDE-47 occurred at rate constants of 0.030 /d and 0.026 /d, respectively. For BaP, the degradation products included benzo[a]pyrene-9,10-dihydrodiol or its isomers, ben-zo(a)pyrene-7,8-dihydrodiol-9,10-epoxide, and cis-4 (8-hydroxypyrenyl-7)-2-oxo-3-butenoic acid. For BDE-47, the degradation products included 2,2',4-tribrominated diphenyl ether (BDE-17), 2,4-dibrominated diphenyl ether (BDE-7), and hydroxylated dibromodiphenyl ether. The bacterial community structures in the original soil, the BaP culture, and the BDE-47 culture were quite different. The richness and diversity of bacteria in the two cultures were much lower than that in the original soil, and the BaP culture had higher richness and diversity than the BDE-47 culture. In the BaP culture, multiple species such as Niabella (23.4%), Burkholderia-Caballeronia-Paraburkholderia (13.7%), Cupriavidus (8.3%), and Allorhizobi-um-Neorhizobium-Pararhizobium-Rhizobium (8.0%) were dominant. In the BDE-47 culture, an unassigned species in the Rhizobiaceae was dominant (82.3%). The results from this study provide a scientific basis for the risk assessment and bioremediation of BaP and/or BDE-47 in a contaminated environment.

G-C3N4-Ag composite mediated photocatalytic degradation of phenanthrene - A remedy for environmental pollution

In recent years, g-C3N4-Ag nanocomposite synthesis has gained considerable attention for its potential to treat polycyclic aromatic hydrocarbons (PAHs) and to act against bacteria and fungi. In this study, we present a novel approach to the synthesis of g-C3N4-Ag nanocomposite and evaluate its efficiency in both PAH removal and antimicrobial activity. The synthesis process involved the preparation of g-C3N4 by thermal polycondensation of melamine. The factors that affect the adsorption process of PAHs, like time, pH, irradiation type, and adsorbent dosage, were also evaluated. Isotherm models like Langmuir and Freundlich determined the adsorption capability of g-C3N4-Ag. In simulated models, phenanthrene was degraded to a maximum of 85% at lower concentrations of catalyst. The adsorption profile of phenanthrene obeys the pseudo-second-order and Freundlich isotherms pattern. The g-C3N4-Ag nanocomposite also exhibited antimicrobial activity against bacteria (Escherichia coli, Bacillus subtilis, Staphylococcus aureus, Klebsiella pneumoniae) and fungi (Candida albicans). The present study is the first report stating the dual application of g-C3N4-Ag nanocomposite in reducing the concentration of PAH and killing bacterial and fungal pathogens. The higher adsorption capability proclaimed by g-C3N4-Ag nanocomposite shows the fabricated nanomaterial with great potential to remediate organic pollutants from the ecosystem.

Microbiological status of natural and anthropogenic soils of the Taganrog Bay coast at different levels of combined pollution with heavy metals and PAHs

The effect of heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) pollution on the microbiological status of soils on the coast of the Taganrog Bay and adjacent areas was studied. The content of total and exchangeable forms of HMs, the content of 16 priority PAHs and the abundance of several groups of culturable microorganisms was determined, namely copiotrophic, prototrophic, aerobic spore-forming bacteria, actinomycetes, molds and yeasts. The content of total and exchangeable forms of HMs in urban coastal soils in industrial zone significantly exceeded that in non-urban soils. The maximum concentrations of total forms of Mn, Cr, Ni, Cu, Zn, Pb and Cd are 1821, 871, 143, 89, 1390, 317 and 10 mg/kg, respectively. The median value of the total content of 16 PAHs in urban soils is 3 times higher than in the soils of natural areas and reached 4309 ng/g. The lowest numbers of copiotrophic bacteria, prototrophic bacteria and aerobic spore-forming bacteria were found in the soils of industrial zone: 6.8, 13.8 and 0.63 million CFU g-1 dry soil, respectively. The largest numbers of copiotrophic bacteria, prototrophic bacteria and aerobic spore-forming bacteria were recorded in the soils of natural areas-72.5, 136 and 5.73 million CFU g-1 dry soil, respectively. It was found that the abundance of copiotrophs, prototrophs, and aerobic spore-forming bacteria is more affected by the urbanization of coastal soils including the pollution of HMs and PAHs. Other groups of microorganisms (actinomycetes, molds and yeasts) turned out to be more resistant to anthropogenic factors.

Targeted degradation of naphthalene by peroxymonosulfate activation using molecularly imprinted biochar

Polycyclic aromatic hydrocarbons (PAHs) in aquatic environments are threatening ecosystems and human health. In this work, an effective and environmentally friendly catalyst based on biochar and molecular imprinting technology (MIT) was developed for the targeted degradation of PAHs by activating peroxymonosulfate. The results show that the adsorption amount of naphthalene (NAP) by molecularly imprinted biochar (MIP@BC) can reach 82% of the equilibrium adsorption capacity within 5 min, and it had well targeted adsorption for NAP in the solution mixture of NAP, QL and SMX. According to the comparison between the removal rates of NAP and QL by MIP@BC/PMS or BC/PMS system in respective pure solutions or mixed solutions, the MIP@BC/PMS system can better resist the interference of competing pollutants (i.e., QL) compared to the BC/PMS system; that is, MIP@BC had a good ability to selectively degrade NAP. Besides, the removal rate of NAP by MIP@BC/PMS gradually decreased as pH increased. The addition of Cl- greatly promoted the targeted removal of NAP in the MIP@BC/PMS system, while HCO3- and CO32- both had an inhibitory effect. Furthermore, SO4•-, O2•- and 1O2 produced by BC activating PMS dominated the NAP degradation, and it was inferred that the vacated imprinted cavities after NAP degradation can continue to selectively adsorb NAP and this could facilitate the reusability of the material. This study can promote the research on the targeted degradation of PAHs through the synergism of biochar/PMS advanced oxidation processes and MIT.

Surfactant-enhanced anoxic degradation of polycyclic aromatic hydrocarbons (PAHs) in aged subsurface soil at high temperature (60 °C)

Thermally enhanced anoxic biodegradation is emerging as a promising method for removing PAHs from subsurface soil. However, some PAHs still remain in soil following remediation with thermally enhanced anoxic degradation due to low bioavailability of these residual PAHs. The effects of five surfactants (Tween 80, TX 100, Brij 30, SDS, and SDBS) on the desorption of PAHs, anoxic degradation of PAHs, and native bacteria in soil at high temperature (60 °C) were evaluated in this study. The desorption of PAHs in soil increased as surfactant concentration increased. Low doses of surfactants (0.08%, w/w) enhanced the growth of potential PAHs degrading bacteria and promoted the anoxic degradation of PAHs, whereas high doses of surfactants (0.3%-0.8%, w/w) displayed the opposite effect, and the degree of inhibition increased with increasing surfactant concentration. The results also indicated that the inhibitory effect of anionic surfactants (SDS and SDBS) on microbial growth and PAHs degradation is stronger than that of nonionic surfactants (Tween 80, TX 100 and Brij 30) at the same concentration. These results suggest a feasible way of enhancing the anoxic degradation of PAHs in soil where heat cannot be effectively utilized when in situ thermal desorption (ISTD) technology is used.