Aromatic Hydrocarbon Contamination Research Articles

Influence of Thermal Desorption Technology on Removal Effects and Properties of PAH-Contaminated Soil Based on Engineering Experiments

Polycyclic aromatic hydrocarbon (PAH) contamination in soil poses a serious threat to ecological safety, human life, and health. Thermal desorption is commonly used to remediate PAH-contaminated soil. Current thermal desorption research primarily focuses on parameters for engineering designs through in-house simulations. In this study, based on a PAH-contaminated site thermal desorption remediation project, the removal efficiency of PAHs in soil (S1, S2) after disposal at different heating temperatures (400, 450, 500, 550 °C) and different residence times (20, 25 min) was investigated, and changes in soil properties before and after disposal were analyzed. The removal rate of 16 PAHs from soil at two concentrations reached 100% after 20 min at 500 °C and 550 °C, respectively. The three-phase structural distances of S1 and S2 soils, respectively, increased by 1.65 and 2.99 times after disposal, sand content increased by 3.20% and 8.27%, water-stable macroaggregates decreased by 8.14% and 2.06%, organic carbon content decreased by 7.27% and 27.05%, heavy fraction organic carbon increased by 33.68% and 5.12%, pH decreased from 10.00 and 10.35 to 8.81 and 8.69, and cation exchange decreased by 13.79% and 26.65%. Soil nutrient content such as TP, AP, TK, and AK increased after thermal desorption, and TN content decreased; approximately 1.0 mg/kg of NO3−-N remained. Our results are expected to support the design of programs for soil reuse after disposal.

Transformation and Degradation of PAH Mixture in Contaminated Sites: Clarifying Their Interactions with Native Soil Organisms.

Soil contamination of polycyclic aromatic hydrocarbons (PAHs), especially caused by the mixture of two or more PAHs, raised great environmental concerns. However, research on the migration and transformation processes of PAHs in soils and their interactions with native communities is limited. In this work, soil samples from uncontaminated sites around the industrial parks in Handan, Hengshui, and Shanghai were artificially supplemented with three concentrations of anthracene (Ant), 9-chloroanthracene (9-ClAnt), benzopyrene (BaP), and chrysene (Chr). Ryegrass was planted to investigate the degradation of PAHs and its interaction with native soil organisms in the constructed ryegrass-microbe-soil microcosmic system. The bacterial and fungal communities in soil were affected by PAHs; their species diversity and relative abundance changed after exposure to different concentrations of PAHs, among which Lysobacter, Bacillus, Pseudomonas, and Massilia bacteria were correlated to the degradation of PAHs. On the 56th day, the contents of BaP, Chr, and Ant decreased with the degradation process, while the degradation of 9-ClAnt was limited. Nineteen intermediates, including hydroxylation and carboxylated compounds, were identified. The present research would help clarify the potential interactions between PAHs and native organisms in contaminated sites, providing fundamental information for evaluating the transformation risks of PAHs in the natural environment.

Polycyclic Aromatic Hydrocarbons Contamination and Quality of Locally Produced Crude Palm Oil in South-South Zone, Nigeria

Background: Oil palm, Elaeis guineensis Jacq is a perennial crop mainly cultivated for its vegetable oil. The fatty acid composition of crude palm oil (CPO) is mostly composed of palmitic, stearic oleic, and linoleic acids. Objectives: This study evaluated the quality of locally produced CPO from six states of South-South zone, Nigeria. Methods: The parameters of CPOs were characterized by specific gravity (SG), acid value (AV), percentage of free fatty acid (%FFA), and saponification value (SV) and peroxide value (PV). Polycyclic aromatic hydrocarbons (PAHs) in CPO were quantified using standard procedures, the related risk due to daily consumption of 25 g was characterized by lifetime cancer risk (LCR) and margin of exposure (MOE). Results: The study observed that the mean values of the parameters were 0.931 SG; 5.01 mgKOH g-1 AV; 2.28% FFA; 177.27 mgKOH g-1 SV and 29.65 meqO2 kg-1 PV. Apart from %FFA, the others did not meet the requirements recommended by the Codex Alimentarius Commission of the joint WHO/FAO. Diagnostic ratios of PAHs suggested a mixture of petrogenic and pyrogenic origins. The MOEs showed low health concern while 16PAH-LCR values which ranged from 2.48E-04 - 4.48E-04 were unacceptable. The screening value 0.003 was significantly (p> 0.05) lower than the computed total BaP equivalent (BaPeq) values indicating potential human health concerns. It is recommended that CPO processing and storage methods should be properly monitored to prevent quality reduction and contamination, which might have adverse effect on consumers.

A current perspective on polycyclic aromatic hydrocarbons contamination and their bioremediation aspects

A current perspective on polycyclic aromatic hydrocarbons contamination and their bioremediation aspects

Genetic redundancy in the naphthalene-degradation pathway of Cycloclasticus pugetii strain PS-1 enables response to varying substrate concentrations.

Polycyclic aromatic hydrocarbon (PAH) contamination in marine environments range from low-diffusive inputs to high loads. The influence of PAH concentration on the expression of functional genes (e.g., those encoding ring-hydroxylating dioxygenases; RHDs), has been overlooked in PAH biodegradation studies. However, understanding marker-gene expression under different PAH loads can help monitor and predict bioremediation efficiency. Here, we followed the expression (via RNA sequencing) of Cycloclasticus pugetii strain PS-1 in cell suspension experiments under different naphthalene (100 and 30 mg L-1) concentrations. We identified genes encoding previously uncharacterized RHD subunits, termed rhdPS1α and rhdPS1β, that were highly transcribed in response to naphthalene-degradation activity. Additionally, we identified six RHD subunit-encoding genes that responded to naphthalene exposure. In contrast, four RHD subunit genes were PAH-independently expressed and three other RHD subunit genes responded to naphthalene starvation. Cycloclasticus spp. could, therefore, use genetic redundancy in key PAH-degradation genes to react to varying PAH loads. This genetic redundancy may restrict the monitoring of environmental hydrocarbon-degradation activity using single-gene expression. For Cycloclasticus pugetii strain PS-1, however, the newly identified rhdPS1α and rhdPS1β genes might be potential target genes to monitor its environmental naphthalene-degradation activity.

Is Fucus a suitable biomonitoring organism for polycyclic aromatic hydrocarbon contamination? A study from the Faroe Islands

To evaluate seaweed as a biomonitoring organism, Fucus was sampled in the Faroe Islands. Nineteen PAHs, including the EPA 16, and four groups of alkylated PAHs were quantified using GC–MS analysis of extracts obtained using a modified QuEchERS method with ultrasonication in acetonitrile, back-extraction into hexane, and Florisil® cleanup. Samples from the harbor of Tórshavn collected at high tide were the most polluted with PAH concentrations between 1.3 × 102 and 1.7 × 102 ng/g wet weight. All samples contained a factor 10 higher concentrations of alkylated PAHs compared to their parent compounds. These results suggest that Fucus might be suitable as a biomonitoring organism for PAH pollution. Differences between samples collected in close proximity and on different days were observed (same range of RSD 14–120% and 60–102%, respectively), suggesting that water exchange, tide levels, and direct exposure to surface diesel pollution have a strong influence on pollutant uptake in Fucus. The findings stress the need for further evaluation of the sampling strategy.

Examining diverse remediation mechanisms of biochar in soil contaminated with polycyclic aromatic hydrocarbon (PAH) of various ring structures: A global meta-analysis

Biochar is a widely recognized solution for addressing polycyclic aromatic hydrocarbon (PAH) contamination. However, it is unclear how the different physicochemical properties of PAHs affect remediation mechanisms, thereby affecting the remediation efficiency of biochar. In this study, a meta-analysis of 56 studies with 2236 observations was conducted to quantify the contributions of the preparation parameters and physicochemical properties of biochar, soil properties, and application measures to remediation efficiency. The research results revealed that PAH contents in the contaminated soil were significantly reduced by an average of 24.99 % after the application of biochar. Random Forest analysis identified feedstock, biochar SSA, soil pH, and rate of biochar application to be the most critical factors among the four categories. The reduction of PAH contents in the contaminated soil first decreased from 37.61 % to 17.44 % and then increased to 40.29 % with an increase in the number of aromatic rings from 2 to 6. Our study results suggest that biochar prepared from bio-waste at low temperatures could be favorable for reducing the content of NAP in soil. Wood-derived biochar pyrolyzed at a relatively high temperature is recommended for remediation of soil contaminated with PAHs with 5 or 6 aromatic rings. Our study provides a new perspective and an optimized strategy for the remediation of PAH-contaminated soils with biochar.

Fluoranthene biotreatment using prominent freshwater microalgae: physiological responses of microalgae and artificial neural network modeling of the bioremoval process

Due to the intensified industrial activities and other anthropogenic actions, contamination of polycyclic aromatic hydrocarbons (PAHs) has been growing at an alarming rate, turning in to a serious environmental concern. Bioremediation, as an eco-friendly and sustainable removal technology, can be used by organisms to reduce the resulting contaminations. In the present study, the ability of Tetradesmus obliquus to remove of fluoranthene (FLA) was evaluated. It was confirmed that FLA removal efficiency was managed by various environmental parameters and pH was found to be one of the most important influencial factors. The reusability of the algae in long-term repetitive operations confirmed the occurrence of biodegradation along with other natural attenuation and 10 intermediate compounds were identified in the FLA biodegradation pathway by GC-MS. As a result of physiological assays, induced antioxidant enzymes activities and augmentation of phenol and flavonoids contents, after the treatment of the microalgae by a high concentration of FLA, confirmed the ability of the microalgae to upregulate its antioxidant defense system in response to the toxic effects of FLA. An artificial neural network (ANN) model was then developed to predict FLA biodegradation efficiency and the appropriate predictive performance of ANN was confirmed by comparing the experimental FLA removal efficiency with its predicted amounts (R2 = 0.99).

Low levels of flavonoids in Arabidopsis thaliana during phenanthrene exposure suggest new roles for a flavanone 3-hydroxylase

Polycyclic aromatic hydrocarbons (PAHs) contamination impacts the well-being of fauna, flora, and the environment. PAHs are a group of compounds consisting of two or more benzene rings. Due to their structure, PAHs are very stable, generally non-reactive and resistant to biodegradation; yet these compounds are cytotoxic in biological systems. In plants, PAHs induce oxidative stress and cell death, and inhibit growth. Previous PAH exposure studies from our laboratory showed an up-regulation of the Arabidopsis thaliana gene At3g51240. At3g51240 encodes a flavanone 3-hydroxylase (F3H), an enzyme catalyzing the hydroxylation of flavanones, key intermediates in the flavonoid biosynthesis pathway. Considering that flavonoids may act as antioxidants and protect cells against oxidative stress, we hypothesized that F3H was important in alleviating PAH-induced stress symptoms. Analysis of flavonoid content by high performance liquid chromatography showed low levels of flavonoids in phenanthrene-treated plants. Analysis of At3g51240 loss-of-function mutant plant lines growing on phenanthrene-containing growth media showed reduced phenotypic stress responses. Interestingly, low levels of H2O2 were observed in the mutant plants, suggesting that this putative flavanone 3-hydroxylase may be involved in PAH oxidation, with the consequent H2O2 generation. Furthermore, in vitro assays with purified recombinant 6xHis tagged AT3G51240 showed enzyme activity on the PAH when phenanthrene was used as a substrate. Together, these data suggest that F3H is involved in PAH detoxification in planta with the subsequent accumulation of toxic metabolites. This research also indicates the potentiality of using specialized metabolism enzymes such as oxidoreductase in the genetic engineering of plants to remediate PAH-contaminated soils.

Methods of Minimizing Polycyclic Aromatic Hydrocarbon Content in Homogenized Smoked Meat Sausages Using Different Casings and Variants of Meat-Fat Raw Material.

To ensure food safety and protect human health, the levels of polycyclic aromatic hydrocarbon (PAH) contamination in model smoked-pork meat products were examined to select which type of casing and variant of raw material contributes to minimizing the content of PAHs in the final products. The sausages were smoked in a steam smoke chamber with an external smoke generator. The determination of PAHs was performed using the QuEChERS-HPLC-FLD/DAD method. The analyzed products met the requirements of Commission Regulation (EU) No. 835/2011 on the maximum permissible levels of PAHs. Statistically higher sums of 19 PAHs, including 15 heavy and 4 marker PAHs, were stated in smoked sausages in natural and cellulose casings. Synthetic casings like collagen and polyamide exhibited better barriers against PAH contamination than cellulose and natural casings. For each type of casing, significantly higher concentrations of PAHs were found in the external parts of the products. An increase in the fat content of the raw material increased the levels of PAH contamination in the products, regardless of the casing. Therefore, in industrial practice, the selection of an appropriate type of casing and raw material with the lowest possible fat content can be an effective method for reducing PAH levels in the interior of smoked meat products.

Contamination of Polycyclic Aromatic Hydrocarbons (PAHs) on Processed Food: A Review

Polycyclic Aromatic Hydrocarbons (PAHs) are wide range of environmental pollutants that commonly contaminate processed food as combustion by-products and constitute a wide range of toxic, carcinogenic, mutagenic adverse health risk. PAHs as an endocrine disruptor can also interfere with the production, release, metabolism, and elimination of unwanted substance in the body or can mimic the occurrence of natural hormones. PAHs formed during food processing largely depends on a number of factors such as type of the food, heating and processing methods. The major sources of PAHs in the environment includes petrogenic, pyrogenic and biological sources. PAHs contamination on processed food via processes such as smoking, roasting, frying or grilling (barbecued) is a function of both the fat content in the food substance and its proximity to the heat source. Studies revealed that eating contaminated food substances can cause reduced pregnancy, foetal reabsorption, gastric neoplasms, increased liver weight, fibrosis, having neurological and carcinogenic risk. PAHs can be removed from the environment via the following processes of either Biodegradation, Photolysis degradation, Dry deposition and/or Wet deposition.

Contamination and persistence of polycyclic aromatic hydrocarbons (PAHs) in rice grains after drying in direct-fired dryer.

The objective of this work was to study PAHs contamination in rice grains subjected to different milling types, after drying at different air temperatures in a direct-fired dryer and using firewood with different moisture contents as a heating source. In addition to verifying the persistence of these compounds after storage. Drying of rice grains was performed in a cross-flow dryer at air temperatures of 55 and 65ºC. As heating source firewood containing different moisture contents was used. The presence of nine PAHs was detected. The drying air temperature, as well as the storage time, did not significantly influence the PAHs contamination of grains. The highest PAHs contamination was observed in grains from the brown subgroup. Grain polishing promoted a reduction in the PAH concentration. The grains subjected to parboilization showed a higher PAHs concentration. The use of firewood with higher moisture content promoted greater PAHs contamination in the grains.

Contamination and source-specific health risk assessment of polycyclic aromatic hydrocarbons in soil from a mega iron and steel site in China

The iron and steel industry has always been a key and difficult point of environmental pollution control. In the present study, 493, 175, 153, 72, and 42 soil samples were collected from the soil depths of 0–0.5, 0.5–2, 2–3, 3–4, and 4–5 m (herein called the layers) of the Shougang Steel site, respectively. Compared with the evaluation criteria, the Shougang Steel surface soil was severely polluted by polycyclic aromatic hydrocarbons (PAHs). Inverse distance-weighted interpolation and the Kruskal-Wallis H test revealed that the soil PAH pollution in the iron-making area, especially the coking area, was severer than those in other areas. The PAH concentrations first decreased, and then, increased with the increase of depth. With the increase in depth, the contributions of 2- and 3-ring PAHs increased, while those of 4-, 5-, and 6-ring PAHs decreased. The bivariate local indicators of spatial association (LISA) analysis was used to identify the areas prone to soil PAH pollution due to atmospheric deposition of industrial waste gas and traffic emissions. The method could be used to analyze the impact of anthropogenic activities on soil's PAH pollution for other contaminated sites. Three main pollution sources of soil PAHs, the backfill source, the combustion of coal, and the traffic emissions, were identified based upon three diagnostic ratios, positive matrix factorization and the bivariate LISA analysis, and accounted for 53.8%, 23.5%, and 22.7%, respectively. The combination of bivariate LISA analysis and other source analysis methods could improve the accuracy of source analysis. Benzo[a]pyrene contributed the most to the total health risk among sixteen PAHs. The health risks related to the three pollution sources decreased in the order of backfill sources > coal combustion > traffic emissions. The incremental life-time carcinogenic risks were all below 10−4, indicating negligible or acceptable risks.

A novel eco-friendly strategy for removing phenanthrene from groundwater: Synergism of nanobubbles and rhamnolipid

Nanobubbles (NBs), given their unique properties, could theoretically be paired with rhamnolipids (RL) to tackle polycyclic aromatic hydrocarbon contamination in groundwater. This approach may overcome the limitations of traditional surfactants, such as high toxicity and low efficiency. In this study, the remediation efficiency of RL, with or without NBs, was assessed through soil column experiments (soil contaminated with phenanthrene). Through the analysis of the two-site non-equilibrium diffusion model, there was a synergistic effect between NBs and RL. The introduction of NBs led to a reduction of up to 24.3 % in the total removal time of phenanthrene. The direct reason for this was that with NBs, the retardation factor of RL was reduced by 1.9 % to 15.4 %, which accelerated the solute replacement of RL. The reasons for this synergy were multifaceted. Detailed analysis reveals that NBs improve RL's colloidal stability, increase its absolute zeta potential, and reduce its soil adsorption capacity by 13.3 %–19.9 %. Furthermore, NBs and their interaction with RL substantially diminish the surface tension, contact angle, and dynamic viscosity of the leaching solution. These changes in surface thermodynamic and rheological properties significantly enhance the migration efficiency of the eluent. The research outcomes facilitate a thorough comprehension of NBs' attributes and their relevant applications, and propose an eco-friendly method to improve the efficiency of surfactant remediation.

Assessment of High-temperature Refined Charcoal to Improve the Safety of Grilled Meat Through the Reduction of Carcinogenic PAHs

This study presents mitigation strategies for reducing carcinogenic polycyclic aromatic hydrocarbon (PAH) contamination levels in grilled meat using high-temperature refined charcoal (HTC) prepared by Iwate kiln, also known as high-quality charcoal. Four different types of HTC were investigated for their properties in conjunction with their potential to reduce PAHs in grilled meat, including high-temperature Eucalyptus charcoal (HTEC), Leucaena charcoal (HTLC), Acacia charcoal (HTAC), and bamboo charcoal (HTBC). The results showed that all HTCs had higher fixed carbon, higher heating value, and lower volatile compounds (83.07–87.81%, 7,306–7,765 Kcal/g, and 6.98–11.97%, respectively) than commercial low-temperature refined charcoal (LTC) (65.33%, 6,728 Kcal/g, and 22.22%, respectively). The current high fixed carbon content and heating value responded to the rising maximum temperature of charcoal up to 500–600°C, providing heat source stabilization to control the radiant energy exposure of charcoal during grilling, thereby shortening grilling time. The PAH16 value of the LTC-grilled sample (144.41 μg/kg) was significantly higher than that of the HTEC, HTLC, and HTAC-grilled samples (98.21, 80.75, and 79.56 μg/kg, respectively). However, PAH16 levels in the sample grilled with HTBC were unexpectedly high (265.75 μg/kg), and cooking loss was not significantly different between samples grilled with all charcoals. Overall, the findings indicated that using HTC prepared from Eucalyptus, Leucaena, and Acacia woods could reduce PAH contamination in grilled pork by up to 45%. However, more research is needed to determine the best preparation method for high-quality charcoal made from bamboo.

Nanosized core-shell (NiFe2O4/TiO2) heterostructure for enhanced photodegradation against polycyclic aromatic hydrocarbons

The global level of attention has been raised for photocatalytic pollutant removal technologies for degrading organic pollutants because of rising concerns about their toxicity. In this study, NiFe2O4/TiO2 core shells and pure samples of NiFe2O4 and TiO2 were synthesized using the sol-gel process and used to degrade naphthalene which is one among the polycyclic aromatic hydrocarbons (PAHs) pollutant. The synthesized materials were evaluated using a variety of analytical techniques, and the typical NiFe2O4/TiO2 core-shell results showed good purity and a lack of other impurity structures. Through morphological characterization, the core-shell structure of NiFe2O4/TiO2 has been established. However, the activity of visible light degradation was boosted by the generation of hydroxyl radicals after the electron-hole pair was delayed. Additionally, a lower band gap in NiFe2O4/TiO2 than in pure materials promotes photocatalytic activity. Similarly, photocatalytic naphthalene elimination by the core-shell achieved 67% efficiency after 150 min of visible light exposure. Furthermore, the produced core-shell has a high magnetic property, making separation from the photo-irradiated solutions easier; as a result, recycling was likely successful up to three cycles. The photocatalytic mechanism of the NiFe2O4/TiO2 composite was proposed. This research could also be applied to the degradation of other polycyclic aromatic hydrocarbon contaminants.

Exploring the bioremediation capability of petroleum-contaminated soils for enhanced environmental sustainability and minimization of ecotoxicological concerns.

The bioremediation of soils contaminated with petroleum hydrocarbons (PHCs) has emerged as a promising approach, with its effectiveness contingent upon various types of PHCs, i.e., crude oil, diesel, gasoline, and other petroleum products. Strategies like genetically modified microorganisms, nanotechnology, and bioaugmentation hold potential for enhancing remediation of polycyclic aromatic hydrocarbon (PAH) contamination. The effectiveness of bioremediation relies on factors such as metabolite toxicity, microbial competition, and environmental conditions. Aerobic degradation involves enzymatic oxidative reactions, while bacterial anaerobic degradation employs reductive reactions with alternative electron acceptors. Algae employ monooxygenase and dioxygenase enzymes, breaking down PAHs through biodegradation and bioaccumulation, yielding hydroxylated and dihydroxylated intermediates. Fungi contribute via mycoremediation, using co-metabolism and monooxygenase enzymes to produce CO2 and oxidized products. Ligninolytic fungi transform PAHs into water-soluble compounds, while non-ligninolytic fungi oxidize PAHs into arene oxides and phenols. Certain fungi produce biosurfactants enhancing degradation of less soluble, high molecular-weight PAHs. Successful bioremediation offers sustainable solutions to mitigate petroleum spills and environmental impacts. Monitoring and assessing strategy effectiveness are vital for optimizing biodegradation in petroleum-contaminated soils. This review presents insights and challenges in bioremediation, focusing on arable land safety and ecotoxicological concerns.

Contamination and Possible Health Risks of Polycyclic Aromatic Hydrocarbons in Soil and Crops from Cultivated Floodplains of Some Rivers in Ekiti State, Southwest Nigeria

Contamination and Possible Health Risks of Polycyclic Aromatic Hydrocarbons in Soil and Crops from Cultivated Floodplains of Some Rivers in Ekiti State, Southwest Nigeria

PAHs and PAEs in the surface sediments from Nenjiang River and the Second Songhua River, China: Distribution, composition and risk assessment

The contamination of polycyclic aromatic hydrocarbons (PAHs) and phthalic acid esters (PAEs) in river sediments have attracted wide attention. However, the distribution characteristics of PAHs and PAEs in sediments of some rivers in China stay unclear, notably in some tributaries. To elucidate the distribution, sources, and risk of 16 priority PAHs and 6 priority PAEs in sediments of the Nenjiang River (NR) and the Second Songhua River (DR) in Northeast China, that were all the tributary of the Songhua River, a total of 42 surface sediment samples from 14 sampling locations were collected. The sediment samples included 76.5–9447 ng/g (mean=2069 ng/g) and 832–17,817 ng/g (mean=6392 ng/g) of the 16 PAHs and 6 PAEs, respectively, in total concentration. Of the 16 PAHs, BaA contributed the most, and DEHP and DBP were the most prevalent PAE compounds. According to the positive matrix factorization (PMF) model, three sources were identified: biomass combustion and vehicle emission, coal and coking combustion and petrogenic source, and contributed 66.81%, 16.96% and 16.23% of Σ16PAHs, respectively. The ecological risks posed by PAHs in the study are negligible, especially for BaA, which might cause frequent ecological risks to exposed organisms. The order of the PAEs' possible environmental risks was DEHP > DBP > DEP > DMP, and none of them are harmful to sensitive algae, crustaceans, or fish.

Polycyclic aromatic hydrocarbons contamination levels of dried herbal teas and their infusions

Polycyclic aromatic hydrocarbons contamination levels of dried herbal teas and their infusions