PAH Concentrations Research Articles

Characterisation of flavourous sesame oil obtained from microwaved sesame seed by subcritical propane extraction

This study developed a novel and green method to produce fragrant sesame oil using microwaves and subcritical extraction (SBE). Sesame seeds were microwaved at 540 W for 0–9 min before subcritical propane extraction at 40 °C and 0.5 MPa. SBE caused less deformation to the cellular microstructure of sesame cotyledons while dramatically improving oil yield (96.7–97.1 %) compared to screw processing (SP) (53.1–58.6 %). SBE improved extraction rates for γ-tocopherol (381.1–454.9 μg/g) and sesame lignans (917.9–970.4 mg/100 g) in sesame oil compared to SP (360.1–443.8 μg/g and 872.8–916.8 mg/100 g, respectively). Microwaves generated aroma-active heterocyclics and phenolics faster than hot-air roasting in sesame oil with a better sensory profile. SBE had a higher extraction rate for aroma-active terpenes, alcohols, and esters while reducing the concentrations of carcinogenic PAHs and HCAs in sesame oil. The novel combination process of microwaves and subcritical extraction is promising in producing fragrant sesame oil with superior qualities.

Organic contaminants levels, distribution and risk assessment in Jeddah marine coastal zone sediments

Herein, various organic contaminants were determined in surface sediments collected from the Jeddah coastal zone, Saudi Arabia, to assess their levels, origin and probable toxic effects on marine organisms. High hydrocarbons concentrations, indicative of an enhanced pollutant burden, were recorded in the Jeddah Lagoon (mean value 4100 mg/kg for total aliphatic hydrocarbons (∑AHC) and 5800 μg/kg for total polycyclic aromatic hydrocarbons (∑PAH)), whereas mean values in Mena Jeddah were 258 mg/kg for ∑AHC and 615 μg/kg for ∑PAH. By using molecular diagnostic ratios/indices and applying Positive Matrix Factorization, petroleum related pollution seems to predominate in Jeddah lagoons, whereas carcinogenic contaminants of pyrolytic origin were dominant in Mena Jedda. Additionally, municipal wastewaters were identified as a major source of pollution in Jeddah lagoons. Comparison of the concentrations of individual PAHs and polychlorinated biphenyls with sediment quality guidelines indicates that, despite their high total values, adverse biological effects are unlikely to occur.

The occurrence and sources of PAHs, oxygenated PAHs (OPAHs), and nitrated PAHs (NPAHs) in soil and vegetation from the Antarctic, Arctic, and Tibetan Plateau

Although the fate of PAHs in the three polar regions (Antarctic, Arctic, and Tibetan Plateau) has been investigated, the occurrence and contamination profiles of PAH derivatives such as oxygenated PAHs (OPAHs) and nitrated PAHs (NPAHs) remain unclear. Some of them are more toxic and can be transformed from PAHs in environment. This study explored and compared the concentrations composition profiles and potential sources of PAHs, OPAHs, and NPAHs in soil and vegetation samples from the three polar regions. The total PAH, OPAH, and NPAH concentrations were 3.55–519, n.d.–101, and n.d.–1.10 ng/g dry weight (dw), respectively. The compounds were dominated by three-ring PAHs, and the most abundant individual PAH and OPAH were phenanthrene (PHE) and 9-fluorenone (9-FO), respectively. The sources of PAHs and their derivatives were qualitatively analyzed by the diagnostic ratios and quantified using the positive matrix factorization (PMF) model. The ratios of PAH derivatives to parent PAHs (9-FO/fluorene and 9,10-anthraquinone/anthracene) were significantly higher in the Antarctic samples than in the Arctic and TP samples, implying a higher occurrence of secondary OPAH and NPAH formation in the Antarctic region. To our knowledge, this is the first comparative study that simultaneously investigated the contamination profiles of PAHs and their derivatives in the three polar regions. The findings of this study provide a scientific basis for the development of risk assessment and pollution control strategies in these fragile regions.

Dietary Exposure to Polycyclic Aromatic Hydrocarbons and the Probabilistic Health Risk Assessment of Eating Roasted Yams (Dioscorea Species) by African Population

The roasting of food is one of the oldest food preparation and preservation technologies. Although roasted foods have been associated with potential health hazards, this processing method is still used in many foods. This study was carried out to ascertain the health risks of ingesting white (Dioscorea rotundata), and bitter yam (Dioscorea dumetorum) roasted with firewood, charcoal, and charcoal augmented with PET bottles. The PAH content in all the roasted yam samples was identified and analyzed using gas chromatography-mass spectroscopy (GC-MS). A total of 8 PAHs were identified in both yam species; however, bitter yam roasted with augmented charcoal contained 9 PAHs. The total EDI showed that bitter yam roasted with augmented charcoal (6.59E-1) had the highest PAH content while white yam roasted with only charcoal contained the lowest (1.27E-1). The hazard quotients and indexes revealed that bitter yam had the highest HQ in all the roasting methods except for napathalene, fluoranthene and benzo (a) pyrene in samples roasted with charcoal. The HI for both species in all the roasting methods was above 1 (>1), while firewood produced the highest HI. Benzo (a) anthracene was the most potent PAH identified across the yam species and the roasting techniques. The evaluated ILCR showed that dibenzo (a, h) anthracene identified in white yam smoked with charcoal had the highest tendency to cause cancer (6.38E-1) while the least PAH was acenaphthylene (3.35E-6) which was seen in bitter yam roasted with charcoal. Therefore, it is necessary to inform the consumers of the possible health implications associated with consuming roasted yams and especially yam roasted with augmented charcoal

Effect of gas additives on soot formation in flat laminar premixed ethylene/air flames under low pressure

This study reports on the effect of the additive gases, namely N2, CO2, and Ar, on the soot formation in laminar premixed C2H4/air flames at low pressure of 40 kPa. The flames blended with N2, CO2, or Ar were experimentally investigated, where the emission spectra of CH* and C2*, qualitative concentration of PAHs, and soot volume fraction (fv) were measured using laser and optical diagnostic methods. The flame temperature was measured using a thermocouple. The results reveal that additive gases significantly influence flame height above the burner and fuel combustion as well as reduce soot formation and flame temperature. With respect to N2 and CO2, Ar proves the most effective in reducing soot volume fraction, achieving a 100-fold reduction compared to the reference flame. Moreover, the additive gases were found to delay the ignition, leading to a 5 mm downstream shift in soot inception. Despite the difference in the properties of the three gas additives, it was found the first incepted soot particles were detected at a common temperature, Tinception, of 1515 ± 70 K. Three regimes related to the soot appearance rate were identified, which are the fast-increasing range from the soot inception location, the plateau region, and the decreasing range to the flame front of 20 mm. According to the Lagrangian time-derivative of soot volume fraction (dfv/dt) as a function of fv, the constant of surface growth (kSG) was determined to be 170 s−1 in the flame with additives of CO2 and Ar, measured at 40 kPa. The identified turning point between the plateau region and the negative soot increase regions can be used as an indicator of the transition from higher to lower soot formation rates in soot modeling.

Profile distribution of polycyclic aromatic hydrocarbons in coastal soils of the Lower Don and Taganrog Bay, Russia

The main regularities of pollutant distribution through the soil profile were established based on the analysis of the content of 15 priority PAHs in 29 soil sections of different soil types located in the coastal zone of the Lower Don and Taganrog Bay with different anthropogenic loads. It was shown that the total content of PAHs in the 0-20 cm layer of soils of coastal territories varies from 172 µg kg-1 to 16006 µg kg-1. In addition, according to the total pollution indicator, (Zc) determines the level of soil pollution, which varies from "not polluted" to "extremely polluted". The influence of pollution sources falls on the 0-20 cm layer of soils of different types and is especially pronounced for subordinate landscapes. With increasing sampling depth, the total PAH content decreases with the redistribution of individual compounds of the PAH group towards the dominance of low molecular weight and 4-ring compounds in the composition of the sum of 15 PAHs and depends largely on the content of organic matter and soil pH. Based on the cluster analysis results, the main factor determining the profile distribution of PAHs is the type of pollutant origin source and its intensity.

Effects of anthropogenic and environmental stressors on the current status of red mullet (Mullus barbatus L., 1758) populations inhabiting the Bulgarian Black Sea waters

The red mullet (Mullus barbatus Linnaeus, 1758) is a keynote species for the Bulgarian Black Sea ecosystem and fisheries; nevertheless, existing knowledge on population status is very scarce. The present study was intended to assess the health status and adaptive potential of M. barbatus populations inhabiting the Bulgarian waters of the Black Sea. Our findings revealed that populations of M. barbatus are exposed to a variety of anthropogenic and environmental stressors. The species’ status was assessed using representative genetic, morphological, biochemical and chemical biomarkers from specimens obtained in the research area’s northern and southern regions. Based on mtDNA markers, genetic analysis revealed low haplotype and nucleotide diversity, typically observed in overexploited or “threatened” populations. Examining the morphology of the specimens revealed no discernible pattern of differentiation. Except for aluminium and chrome, metal and PAH concentrations in fish were below the regulatory thresholds. The specimens from the southern region ingested more microplastics than those from the northern region. The majority of specimens collected from the southern region also exhibited elevated levels of oxidative stress and decreased antioxidant defence, which can be interpreted as an early indication that they had reached the limits of their adaptive potential. Further research on the composite effects of the stressogenic environment on the Black Sea biota are critically needed, as well as the introduction of new indicators and thresholds at molecular and cellular levels for adequate monitoring of both the ecological state of the marine environment and its biota.

Features of Seasonal Changes in PAH Concentration in the Bottom Sediments of Southern Baikal in the Town of Baikal’sk Area

Features of Seasonal Changes in PAH Concentration in the Bottom Sediments of Southern Baikal in the Town of Baikal’sk Area

Impact Assessment of Petrol Filling Stations on Groundwater Quality in Akure Metropolis, Ondo State

Abstract: The presence of PFSs in urban areas has increased significantly, leading to conflicts with existing land use planning and violations of the minimum environmental safety requirements set by the Department of Petroleum Resources (DPR) and have adverse social and environmental impacts despite their socioeconimic importance. This paper aim to investigate the spatial distribution of petrol filling stations and their impact on groundwater quality in Akure Metropolis of Ondo State. A total of 147 PFSs and 140 water wells were identified and recorded. Laboratory analysis was done purposefully on wells near PFSs that were both 26 years or older and still functional, as older underground storage tanks (USTs) pose a potential threat to groundwater safety. Findings revealed 119 functional filling stations, 28% located within residential area and 68% domiciled in commercial areas, 2% in outskirt of town and 1% in standalone environment. Findings showed all mapped filling stations were found to be within 50m from built up (residential) area, 104 mapped stations within residential and commercial areas violates the DPR standard. Using spatial analysis, it was also found that 116 of the 147 (78.9%) mapped filling stations were within 400m away from the next. 108 of the 147 (73.47%) mapped PFSs violated the standard of distance not less than 15meters from the edge of the road to the nearest pump. The findings also showed that groundwater system is contaminated by PAHs, which comprises; naphthalene.F, pyrene and acenaphthylene.F. Low mean concentrations of PAHs recorded in this study suggest that there is no major compromise in the quality of groundwater due to the operation of PFSs in Akure metropolise Hand-dug Wells in the study area. It is recommended that spatial compliance for siting PFSs should be strictly adhered to in order to avoid disaster that may occur due to the hazard they pose

The concentrations of polycyclic aromatic hydrocarbons in fish: A systematic review

This study was conducted on the concentrations of PAHs, including benzo[a]pyrene and the sum of four PAHs (benz[a]anthracene, chryseno, benzo[b]fluoranthene, and benzo[a]pyrene), in unsmoked fish tissues. The values were related to the time period, locality (country and region), living habits, eating habits, and types of environments of the fish species. The data obtained has been also compared with the limits established by the United States Environmental Protection Agency (U.S. EPA) and European Union (E.U.) legislation. The data were collected through a PRISMA systematic review (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) from 1982 to 2020. Only documents that presented the PAHs concentration values were selected. China, Nigeria, and Iran had the highest number of studies. The species Coptodon zillii, Siganus punctatus, and Liza abu were the most commonly used bioindicators. Fish inhabiting demersal and pelagic environments showed the highest concentrations of PAHs. The majority of PAH concentrations of the analyzed documents fell within permissible limits for human consumption, representing a total percentage of 79.49 % for benzo[a]pyrene and 82.86 % for the sum of the 4 PAHs. Although some studies identified concentrations of benzo[a]pyrene alone and benzo[a]pyrene, benz[a]anthracene, chryseno, benzo[b]fluoranthene above the legislation limits, in most of them, the concentrations reported in fish tissue were below the limits defined by European Legislation for human consumption.

Characterization and Source Apportionment of Polycyclic Aromatic Hydrocarbons in PM2.5 in Lanzhou

To study the pollution characteristics and sources of 16 PAHs in PM2.5 in Lanzhou, PM2.5 samples were collected in four seasons. GC-MS was employed to analyze the concentration of PAHs. Positive matrix factorization(PMF), trajectory cluster, and potential source contribution function(PSCF) were used to identify the sources of PAHs. The results indicated that the average concentration of PAHs in PM2.5 in Lanzhou decreased in the order of winter[(118±16.2) ng·m-3]>autumn[(50.8±21.6) ng·m-3]>spring[(22.2±8.87) ng·m-3]>summer[(4.65±1.32) ng·m-3]. The results of correlation analysis showed that PM2.5 and TPAHs in Lanzhou had an extremely significant negative correlation with temperature; an extremely significant positive correlation with atmospheric pressure; and a poor correlation with wind direction, wind speed, and relative humidity. The proportion of PAHs with 4-5 rings was much higher than that of those with 6 rings and 2-3 rings, with similar results across the four seasons. Source apportionment results illustrated that the contribution of industrial emissions and biomass and natural gas combustion were dominant in spring and summer seasons. Industrial emissions and coal combustion were dominant in autumn and winter, respectively. The vehicle emissions had no significant change across the four seasons. Trajectory cluster and PSCF analyses showed that the airflow coming from Mongolia, northeast Xinjiang, and Qinghai had important effects on the ambient air quality in Lanzhou.

Study the Concentration of PAHS in Al-Rumayth River Water-Iraq

This study’s goals were to look into PAH concentrations and compositions as well as chemical and physical water characteristics. In Al –Rumaytha river. This study was conducted out during from November 2021 to October 2022. According to the results, sixteen PAHs compounds were found in the water, including According to the results, water contained sixteen different PAHs components including Acenaphthene and Acenaphthylene ranged between (47.1-91.5, 24.9-55.7) ppm, The values Anthracene, Naphthalene, phenanthene and fluorine results ranged (14.9-48.9 ppm,18.9 -68.7ppm,8.9-41.7 ppm,8.5-41 ppm) respectively, the minimum and maximum concentrations of Benzo[A]anthracen, Benzo[B]fluoranthene, Benzo [K] fluorantyene, Benz [G,H] perylen, Benz [A] Pryene, Chrysene, Dibenzo [A,H] Anthracene, Anthracene, Fluoranthene, Indeno and Pryene was 4.1-20.6 ppm, 20.1-69.7ppm, 30.1-97.4 ppm,4.1-36.9 ppm,0.29-1.6ppm 10.5-40.8 ppm, 8.9-36.9 ppm, 6.5-33.4 ppm,2.5-10.2 ppm,1.3-10.4 ppm. The results show that the Al-Rumaytha River is PAH-polluted, with human activities having the greatest negative effects on the river’s water quality and health.

The Effect of Hydrocarbon Pollution on Niger Delta Root Crops: A Case Study of Cocoyam [Colocasia Esculenta

This paper investigates effects of re-occurring oil spillages on cocoyam, Colocasia esculenta (L.). It studies changes in petiole lengths, leaf blades, chlorophyll concentrations in leaves, and PAH and BTEX concentrations in tubers for three generations under diverse conditions. 8 10-gallon grow bags were used: Grow bags 5–8 were treated with a controlled quantity (4 L/cubic metre) of liquid crude hydrocarbon in the months of June 2019–2021; with 2 replications, after a 2-3-day interval within a week. In grow bags 3, 4, 7, and 8, poultry manure were applied once in 2 months after small seedlings emerged from soil surfaces. Grow bags 1 and 2, 3, and 4 served as “controls” for non-contaminated growth. Grow bags 7 and 8 were treated with hydrocarbons and poultry manure. In the first generation, coco yams planted in grow bags 7-8 showed growth responses (average values of 1.04 m, 51 cm, 4.45 mg/g for petiole length, leaf blade length, and chlorophyll concentration, respectively) very similar to coco yams planted in pristine soil with poultry manure with average values of 1.00 m, 50 cm, 3.45 mg/g. The cocoyams planted in pristine organic rich soils showed similar response with or without fertilizers (average values of 0.98 m, 48 cm 1.83mg/g and 1.00m, 50 cm, 3.45mg/g) with progressively smaller leaves as generation increases. The cocoyams in hydrocarbon impacted soils generally perform poorer than uncontaminated soil with or without poultry manure by the second and third generation. Poultry manure on soils with re-occurring hydrocarbon contamination exacerbates soil weakening. Mean PAH and mean BTEX concentrations in tubers were 0.001-0.0035 mg/kg and <0.001mg/kg respectively. Cocoyams are not strong BTEX bioactive scavenger but gradually became more concentrated in PAH.

Analysis of PAHs content, source and risk assessment in surface sediments from Laizhou Bay and Bohai Bay

To understand the levels of PAHs and ecological risks to the marine environment in Laizhou Bay and Bohai Bay, 33 sediment samples were collected in the region for analysis. PAH concentrations ranged from 98.22 ng·g−1 (dw) to 239.01 ng·g−1 (dw). PAHs in the region are at low to medium pollution levels compared to studies worldwide. Diagnostic ratios and PCA indicate that PAHs are primarily sourced from fuel combustion. PAHs carried into the Bohai Sea by means of river water and sediment are more likely to settle to the seafloor as opposed to diffuse. This results in a slightly higher proportion of low-ring PAHs than high-ring PAHs. Low-ring PAHs accounted for 56 % of the total. Low-ring PAHs are key contributors to ecosystem risk. The SQGs and RQ∑PAHs show that PAHs do not pose a considerable ecological danger within the region.

Polycyclic Aromatic Hydrocarbons (PAHs) in paddy soil around Nam Son landfill area, Ha Noi, Viet Nam

The paddy soils were collected in the rice growing fields and the uncultivated lands around the Nam Son domestic waste landfill in Hanoi. The average concentration of 16 US EPA priority PAHs in dry soil was 61.61 ng/g, with a range of 22.15-115.1 ng/g. The higher levels of PAHs in soil samples were observed in cultivated paddy fields near the landfill in comparison with the fields far from the landfill. On the other hand, there was no difference in PAHs levels in cultivated paddy fields near the landfill and along the irrigation water canal. Concentrations of 16 PAHs in paddy soils decreased in the order: 5 rings > 3 rings > 4 rings > 2 rings > 6 rings in this area. The PAH isomeric diagnostic ratios including Fluth/(Fluth+Pyr) ratio (Ave 0.43, a range of 0.17-0.61), BaA/(BaA+Chr) ratio (Ave 0.51, a range of 0.26-0.63), IcdP/(IcdP+BghiP) ratio (Ave 0.71, a range of 0.51-0.90) indicated that the potential main sources emitted PAHs in paddy soils from pyrogenic biomass combustion and coal burning. Compared with the risk threshold causing adverse impacts on the ecological environment from different countries in the world, concentrations of PAHs in the soil surrounding the Nam Son landfill area were still below the affected limit. However, environmental quality around the landfill area still needs to be regularly monitored to take timely measures to protect the environment in this area.

Source characteristics of polycyclic aromatic hydrocarbons and polychlorinated biphenyls in surface soils of Shenyang, China: A comparison of two receptor models combined with Monte Carlo simulation

The surface soil concentrations of 16 PAHs and 15 PCBs were simultaneously determined by gas chromatography-tandem mass spectrometry in 21 locations of urban areas of Shenyang. The average concentrations of PAHs and PCBs were 26.40 ± 34.68 mg/kg and 48.03 ± 27.47 μg/kg, respectively. Factor analysis with nonnegative constraints (FA-NNC) and absolute principal component score with multiple linear regression (APCS-MLR) model were used to explore and evaluate the sources of PAHs and PCBs in the study area. The results of FA-NNC showed that PAHs in soils were mainly from traffic emissions (49.64%), coal combustion (46.88%) and petrogenic source (3.49%). The PCBs in soils were mainly from commercial and high temperature combustion mixed sources (20.3%), combustion and industry emission mixed sources (21.1%), electrical equipment sources (22.2%) and traffic emission sources (36.4%). The results of APCS-MLR were consistent with those of FA-NNC. The uncertainty of FA-NNC and APCS-MLR model was analyzed by Monte Carlo simulation method. The results revealed the reliability of the two receptor models on source apportionment. The estimated carcinogenic risks indicated that the risks of PAHs in soils exceed the acceptable range (10−6-10−4), while the risks of PCBs were below the acceptable risk level of 10−6.

Polycyclic aromatic hydrocarbon concentrations in soil of three communities in Rivers State

The study was conducted in three communities in Rivers State. These communities include Okochiri community in Okrika, Mgbuodohia in Obio-Akpor and Chokocho in Etche. Soil at two different depths were sampled on a composite basis using EGASPIN 2018 procedures, extracted and analyzed for sixteen priority PAHs using US EPA 8270 (2014) procedures. Studies show the total concentration of PAHs in soil sample taken from Okochiri community in Okrika at depths of 0 - 15 cm and 15 - 30 cm was found to be 145.32 mg/kg and 101.6 mg/kg during the dry season respectively but in the wet season the total concentration was found to be 607.08 mg/kg and 242.46 mg/kg at the two depths. In Mgbuodohia, the dry season result for the two depths, showed a total concentration of 14.68 mg/kg and 27.33 mg/kg and, 16.12 mg/kg and 14.94 mg/kg in the wet season. In Chokocho, the result showed a total concentration of 4.33 mg/kg and 252 mg/kg in the dry season and 23.87 mg/kg and 10.23 mg/kg in the wet season. Result showed a higher concentration of PAHs in the tops soil (0- 15 cm) compared to the subsoil at the depth (15 - 30 cm). The total PAHs concentration was consistently higher in the wet season than in the dry season. The concentration of PAHs was found to be majorly higher in the topsoil than the subsoil both in the dry and wet season. Diagnostic ratios reveal major source to be petrogenic. The concern for the environment and humans should prompt important stakeholders to take measures that will lead to mitigate the impact of these toxic chemical.

Microbial Community Response to Various Types of Exogenous Organic Matter Applied to Soil.

Recycling of solid biowaste and manure would reduce the dependence of agriculture on synthetic products. Most of the available studies on the effects of exogenous organic matter (EOM) application to soil were focused on nutrients and crop yield, with much less attention to microbiological processes in soil, especially using modern molecular methods. The aim of this study was to evaluate the effects of various types of manure, sewage sludge and bottom sediment on the biochemical activity and biodiversity of soil and plant yield in a pot experiment. The soil was treated with a range of EOM types: six types of manure (cattle, pig, goat, poultry, rabbit and horse manure; two bottom sediments (from urban and rural systems); and two types of municipal sewage sludge. All EOMs stimulated dehydrogenases activity at a rate of 20 t ha-1. Alkaline phosphatase was mostly stimulated by poultry manure and one of the sludges. In general, the two-fold greater rate of EOMs did not further accelerate the soil enzymes. The functional diversity of the soil microbiome was stimulated the most by cattle and goat manure. EOMs produce a shift in distribution of the most abundant bacterial phyla and additionally introduce exogenous bacterial genera to soil. Poultry and horse manure introduced the greatest number of new genera that were able to survive the strong competition in soil. EOMs differentiated plant growth in our study, which was correlated to the rate of nitrate release to soil. The detailed impacts of particular amendments were EOM-specific, but in general, no harm for microbial parameters was observed for manure and sludge application, regardless of their type. There was also no proof that the PAH and pesticide contents measured in manure or sludge had any effect on microbial activity and diversity.

Hydrocarbon markers for assessing the influence of human activities in the tropical semi-arid region (Acaraú River, state of Ceará, Brazil)

Coastal ecosystems are facing increasing anthropogenic stressors, including rapid urbanization rates and extensive fossil fuel usage. Nevertheless, the distribution of hydrocarbons in the Brazilian semi-arid region remains relatively uncharacterized. In this study, we analyzed ten surface sediment samples (0–2 cm) along the banks of the Acaraú River to assess the chronic contributions of aliphatic and aromatic hydrocarbons. The Acaraú River is a crucial riverine-estuarine area in the semi-arid region of Northeast Brazil. Ultrasound-assisted extraction and gas chromatograph coupled to a mass spectrometer were used to identify target compounds: 45 PAHs, 27 n-alkanes (C10–C38), and two isoprenoids. At most stations, the predominant grain size was sand, and the organic carbon content was less than 1%. The total n-alkanes concentration ranged from 14.1 to 170.0 μg g−1, while individual pristane and phytane concentrations ranged from not detected (nd) to 0.4 μg g−1 and nd to 0.7 μg g−1, respectively. These concentrations resemble those found in unpolluted sediments and are lower compared to samples from urbanized coastal areas. The total USEPA PAHs concentration varied from 157.8 to 1364 ng g−1, leading to the characterization of sediment samples as moderately polluted. Based on diagnostic ratios calculated from both alkane and PAH concentrations, the sediment samples were predominantly deriving from pyrolytic sources, with some contribution from petrogenic sources. The most abundant group was 5-ring PAHs (mean: 47.3 ± 36.7%), followed by 3-ring PAHs (mean: 17.9 ± 13.7%). This predominance indicates a pyrolytic origin of hydrocarbons in the Acaraú River. The concentrations reported here were representative of the level of background hydrocarbons in the region. Regarding the sediment quality assessment, BaP TPE calculated for the Acaraú River ranged from 13.2 to 1258.4 ng g−1 (mean: 409.3 ± 409.4 ng g−1). When considering site-specific sediment quality values for the coast of the state of Ceará, half of the stations are classified as strongly contaminated, and toxic effects are expected to occur (SQGq >0.25) for the ∑16 PAHs measured in the samples, especially due to dibenz [a,h]anthracene concentrations.

Linking PAHs concentration, risk to PAHs source shift in soil and water in epikarst spring systems, Southwest China

A systematic assessment of the variations in the ecological risk of PAHs and the key emission sources controlling the variations is of great importance to human health and aquatic organisms. PAH concentrations, composition, source, and ecological risk in soils and water in two different periods (2010–2011 and 2019) of three typical epikarst springs in Southwest China were investigated. Results showed that PAH concentrations in soil and water have an overall downward trend (a reduction of 57 % and 93 %, respectively) in the past 10 years, which is consistent with the downward trend in the relative contribution rate of raw coal production (a 66 % reduction). In terms of composition, the proportion of low-ring PAHs decreased, medium-ring and high-ring PAHs increased in the soil profile. The proportion of low-ring PAHs did not change obviously, the proportion of medium-ring PAHs increased, and the proportion of high-ring PAHs decreased in epikarst springs. The source of PAHs changed remarkably over time, the relative contribution of coal combustion to PAHs decreased from 38 % to 20 %, and the vehicle contribution of PAHs increased from 31 % to 44 % in soils. The relative contribution rate of unburned oil and coke oven and biomass combustion change is less. Furthermore, the ecological risk of PAHs in the soils was reduced from moderate risk 2 to moderate risk 1, the risk in epikarst spring was reduced from high risk to moderate risk 2 after 10 years. This study demonstrates that substituting petroleum and coal with green energies can reduce PAH concentrations and risk.