Ring Polycyclic Aromatic Hydrocarbons Research Articles

On the protonated forms of alkyl-bonded polycyclic aromatic heterocycles: Structure prediction and characterization using density functional theory

When alkyl chains with electron-donating properties are bonded to heterocyclic rings in polycyclic aromatic hydrocarbons, a certain class of molecules is formed. These molecules become protonated in some industries as a result of their intimate contact with the acidic aqueous phase. However, little attention has been paid to the protonation of these molecules. The purpose of this article was to use computational methods to predict and characterize the final protonated states of these molecules. This study considered three distinct types of these molecules. DFT method was used to determine the most likely proton-accepting sites for the molecules, followed by optimization of their protonated states. The final stable forms were collected and compared based on their energy values, chemical hardness and dipole moments. Additionally, the geometrical properties and FTIR spectra of the most stable form of each type were determined. We found that π-bonding orbitals account for a significant portion of the proton-accepting region in all molecules, potentially allowing carbon atoms and heteroatoms to bond with proton. Not all of them, however, exhibited stable protonated states. This study has revealed the critical role of intramolecular non-bonding interactions in determining the proton-accepting ability of a probable site as well as the relative stability of protonated forms. Additionally, significant energy drop were demonstrated during protonation, as well as corresponding stability improvements. The final protonated molecular structures are critical for those studying the phenomena associated with these molecules specially designing agents for preventing protonation.

Influence of temperature and precipitation on the fate of polycyclic aromatic hydrocarbons: simulation experiments on peat cores from a typical alpine peatland in Central China.

The corresponding relationships between temperature, precipitation, and polycyclic aromatic hydrocarbon (PAH) concentration in a typical ombrotrophic peatland in Dajiuhu, Shennongjia, were quantitatively characterized by field sampling tests validated with simulation experiments. The PAH concentrations of peat cores in Dajiuhu peatland ranged from 262 to 977ng·g-1, with a mean value of 536 ± 284ng·g-1. PAHs were mainly composed of 2-3 ring PAHs, accounting for 31.7% ± 2.00% and 31.7% ± 5.00%, respectively. The concentration of PAHs in peat cores showed a significant decrease with increasing temperature, while the low molecular weight PAHs (LMW-PAHs) were more sensitive to temperature changes compared to the high molecular weight PAHs (HMW-PAHs). Besides, with the increase of quantity and velocity of leaching liquid, PAHs in peat were first transferred in the form of attached large-size particles and then gradually entered the aqueous phase. According to the IPCC projections of global warming, Dajiuhu peatland will release 956 ± 26.3kg·°C-1 PAHs into gas phase during 2030-2052, and a conservative projection based on local temperature trends showed that 459 ± 12.6kg·°C-1 PAHs will be released into gas phase by 2047 in Dajiuhu peatland. The projected release fluxes of PAHs in Dajiuhu peatland with precipitation volume and precipitation velocity are 381 ± 201kg·100mm-1 and 1052 ± 167kg·min·mL-1, respectively, which are primarily from peat into particulate and aqueous phase.

Physicochemical characteristics of polycyclic aromatic hydrocarbons in condensable particulate matter from coal-fired power plants: A laboratory simulation

The objective of this study was to examine the physicochemical characteristics of polycyclic aromatic hydrocarbons (PAHs) in condensable particulate matter (CPM) during fast condensation (within several seconds). The concentration of PAHs increased as the condensation temperature decreased, indicating that the conversion of gaseous PAHs to CPM would be enhanced at low temperatures. PAH concentrations increased in relation to the number of rings in the fragment, with the high-ring (4-,5- and 6-ring) PAHs accounting for 89.70–92.30% and 99.78–99.80% of the total concentration and total toxic equivalent of PAHs. In addition, particulate-phase PAHs (0.1–1.0 μm), developed through the synergistic effect of PAHs and fine particles, were difficult to collect by fast condensation. Inorganic fine particles could be formed when ammonia-rich conditions prevail, reducing PAH condensation further. Furthermore, CPM was morphologically and chemically characterized. During the experiment, fine and well-aggregated CPMs were detected on the membrane, and the diameter of CPMs was further enhanced by the addition of 16 PAHs. Most of the C element was collected in the rinse fluid, thus indicating that PAHs in CPM were collected through condensation. Based on these findings, basic guidelines can be provided for the control of PAHs in flue gas from coal-fired power plants.

Spatial distribution of polycyclic aromatic hydrocarbons in dust and soils from informal trade sites in southern Nigeria: Implications for risk and source analysis

Polycyclic aromatic hydrocarbons (PAHs) are a group of semi-volatile and persistent organic compounds considered priority pollutants because of their pervasive nature and high toxicity to the ecosystem and humans. Therefore, this study aimed to evaluate the PAH concentrations in dust and soils around informal trade sites (ITS) in Nigeria to determine the level of risk, sources, and significance of these activities to the PAH load of the environment. The 16 US EPA PAHs in dust and soils from ITS were determined by gas chromatography-mass spectrometry (GC-MS). The PAH concentrations in dust from these informal trade sites varied from 120 to 8790, 56 to 4780, and 102–1090 μg kg−1 for automobile mechanic workshops (AMW), car dismantling (CDS), and material recovery sites (MRS), respectively, whereas those of soils ranged from 3000 to 95,500, 554 to 14,700, and 966–25,200 μg kg−1 for AMW, CDS, and MRS respectively. The PAH profiles indicated that 3- to 5-ring PAHs were prominent in dust and soils around the ITS. The concentrations of the US EPA 16 PAHs in dust and soils from these ITS showed no correlation with organic matter, while the concentrations of PAH homologues in soils of these ITS showed no correlation with those of dust. Incremental lifetime cancer risk (ILCR) values in the magnitude of 10−4 to 101 were obtained for adult and childhood exposure to PAHs in dust and soils from these ITS. Exposure to PAHs in dust from these ITS gives rise to less risk than for soils. The results indicated that automobile mechanic workshops contribute more PAHs to the environment than car dismantling and material recovery activities. The source analysis showed that the PAH contamination of these sites arises from burning of biomass, plastic materials, and oils, and emissions from vehicles.

Comparative Toxicity of 3-5 Ringed Polycyclic Aromatic Hydrocarbons to Skeletal Development in Zebrafish Embryos and the Possible Reason.

Polycyclic aromatic hydrocarbons (PAHs) are pervasive pollutants in the environment. To compare the developmental toxicity of PAHs with different ring numbers to fish embryos, benzo(a)pyrene (BaP), pyrene (Pyr) and phenanthrene (Phe) were selected as the representatives of 3, 4 and 5-ringed PAHs, and fertilized embryos of zebrafish (Danio rerio) were exposed to 5 nM PAHs for 72h. The PAH-treated embryos showed defects in craniofacial cartilage. The order of toxicity to the development of craniofacial cartilage was Phe > Pyr > BaP. The transcription of genes related to the development of craniofacial cartilage was downregulated. The GC-MS/MS detection showed that bioaccumulation of BaP in the exposed embryos was two orders of magnitude lower than that of Phe and Pyr. It is suggested that the more uptake and accumulation of Phe and Pyr could be one of the reasons for their greater toxicity to development in early stage embryos.

Enhancement of soil high-molecular-weight polycyclic aromatic hydrocarbon degradation by Fusarium sp. ZH-H2 using different carbon sources

High-molecular-weight PAHs (HMW-PAHs) in soil cannot be easily degraded. However, nutrient supplementation could stimulate the growth of exogenously added strains to enhance the degradation of HMW-PAHs in polluted soil. This study evaluated the applicability of Fusarium sp. ZH-H2, a polycyclic aromatic hydrocarbon (PAH)-degrading strain isolated by our research group, for the bioremediation of contaminated soil from the Hebei coal mining area in China. A soil incubation experiment was conducted to investigate the effect of two carbon sources and different carbon, nitrogen, and phosphorus (C:N:P) ratios on the remediation of high-molecular-weight PAHs (HMW-PAHs) in soil by Fusarium sp. ZH-H2, as well as the induction of lignin peroxidase activity. Our findings indicated that the HDF2 treatment (equal parts of humic acid and starch as carbon sources at a 50:1:0.5 C:N:P ratio) enhanced the removal rate of total HMW-PAHs from soil, reaching a maximum removal rate of 37.15 %. The removal rates of Pyr (a 4-ring PAH), BaP (a 5-ring PAH), and BghiP (a 6-ring PAH) were the highest in HDF2 treatment, and the removal rates were 39.51 %, 54.63 %, and 38.60 %, respectively. Compared with the ZH-H2 treatment, different carbon sources and C:N:P ratios significantly induced soil lignin peroxidase activity and the HDF2 treatment also resulted in the highest enzyme activity (up to 34.68 U/L). Furthermore, there was a significant or highly significant linear positive correlation between the removal rate of HMW-PAHs and enzyme activity in all cases. Our findings suggest that the optimal HMW-PAH degradation performance and enhancement of lignin peroxidase activity by ZH-H2 were achieved when both starch and humic acid were used as carbon sources at a C:N:P ratio of 50:1:0.5.

Pollution Characteristics, Source Apportionment, and Health Risk of Polycyclic Aromatic Hydrocarbons (PAHs) of Fine Street Dust during and after COVID-19 Lockdown in Bangladesh

The COVID-19 period has had a significant impact on both the global environment and daily living. The COVID-19 lockdown may provide an opportunity to enhance environmental quality. This study has evaluated the effect of the COVID-19 lockdown on the distribution of polycyclic aromatic hydrocarbons (PAHs) in the street dust (diameter < 20 µm) of different land use areas in Dhaka city, Bangladesh, using gas chromatography–mass spectrometry (GC–MS). The maximum (2114 ng g−1) concentration of ∑16 PAHs was found in the industrial area during without lockdown conditions and the minimum (932 ng g−1) concentration was found in the public facilities area during the complete lockdown. Meanwhile, due to the partial lockdown, a maximum of 30% of the ∑16 PAH concentration decreased from the situation of without lockdown in the industrial area. The highest result of 53% of the ∑16 PAH concentration decreased from the situation without lockdown to the complete lockdown in the commercial area. The 4-ring PAHs had the highest contribution, both during and after the lockdown conditions. PAH ratios, correlation, principal component analysis (PCA), and hierarchical clustering analysis (HCA) were applied in order to evaluate the possible sources. Two major origins of PAHs in the street dust were identified as petroleum and petrogenic sources, as well as biomass and coal combustion. Ingestion and dermal pathways were identified as the major exposure routes to PAHs in the dust. The total incremental lifetime cancer risk (ILCR) due to exposure for adults and children ranged from 8.38 × 10−8 to 1.16 × 10−7 and from 5.11 × 10−8 to 1.70 × 10−7, respectively. These values were lower than the baseline value of acceptable risk (10–6), indicating no potential carcinogenic risk. This study found that the COVID-19 lockdown reduced the distribution of PAHs in the different sites of Dhaka city, thus providing a unique opportunity for the remarkable improvement of degraded environmental resources.

Polycyclic aromatic hydrocarbons in commercial tea from China and implications for human exposure

Tea consumption may increase the level of human exposure to polycyclic aromatic hydrocarbons (PAHs), while relevant health risks are unclear. This study collected 218 samples of five categories of tea (dark, green, black, oolong, and white) from seven major tea sources in China. High performance liquid chromatography was used to determine the concentrations of 16 common PAHs. The concentration of all 16 PAHs (ΣPAHs) varied from 11.4 to 1251 ng/g, with a median value of 86.4 ng/g. Of the five tea categories from the seven source provinces, the median ΣPAHs concentration values were ordered as 189 ng/g (dark tea) > 110 ng/g (oolong tea) > 83.3 ng/g (green tea) > 49.7 ng/g (black tea) > 33.7 ng/g (white tea). Dark tea from Hunan had the highest level of PAHs, and white tea was the least contaminated with PAHs. The 3-ring PAHs and 4-ring PAHs were dominant in tea. The sources of PAHs in tea were mainly attributed to grass, wood, and coal combustion. The median margin of exposure (MOE) and incremental lifetime cancer risk (ILCR) values of benzo(a)pyrene (BaP) were 4.22E+ 04 and 6.86E-06 (dark tea), 8.14E+ 04 and 3.55E-06 (green tea), 1.71E+ 05 and 1.69E-06 (black tea), 4.97E+ 04 and 5.88E-06 (oolong tea), 7.42E+ 05 and 3.89E-07 (white tea), respectively. The results showed that chronic exposure to PAHs via the consumption of dark, oolong, black, and green tea, can result in a carcinogenic risk to humans, which should be a public health concern.

Upgrading and PAHs formation during used lubricant oil pyrolysis at different heating modes

Recycling used lubricant oil (ULO) to produce valuable products through pyrolysis is a flexible and efficient method. Presently, the mechanisms of oil conversion and polycyclic aromatic hydrocarbons (PAHs) formation during ULO pyrolysis at different thermal conditions were poorly explored. In this study, ULO pyrolysis at different heating modes (slow: 10 °C min−1, medium: ∼10,00 °C min−1, fast: >10000 °C min−1) were conducted at the temperature range of 400–700 °C. Extensive analyses on the chemical compositions and carbon number distributions of pyrolytic products were conducted to illustrate the mechanisms of ULO evolution and the formation of PAHs. Increasing temperature or heating rate can lead to more gas but less liquid production. The high temperature at fast heating mode can greatly promote the aromatization of pyrolytic oil. Various types of valuable products, such as base oil, fuel, and chemical feedstock, can be obtained at different heating rate conditions. More than 98% of PAHs produced from ULO pyrolysis were gathered in the liquid phase. Naphthalene, phenanthrene, and pyrene were the primary PAH species in both the liquid and gaseous products. Elevating the heating rate can lead to more PAH production and the enrichment of more toxic (5-/6-ring) PAHs in pyrolytic oil. Comparatively, distillation dominated in the slow pyrolysis, and chemical reactions of cracking and recombination occurred markedly at the medium and fast heating modes for both the ULO evolution and PAHs formation.

Emission characteristics and influencing mechanisms of PAHs and EC from the combustion of three components (cellulose, hemicellulose, lignin) of biomasses

Biomass burning is an important source of polycyclic aromatic hydrocarbons (PAHs) and elemental carbon (EC), but the formation mechanisms are still unclear. Cellulose, hemicellulose, and lignin are the three major components of biomass. In this study, the three-components extracted from three typical biomass raw materials were used for laboratory combustion experiments, to investigate the differences in the emission factors and chemical compositions of PAHs and EC. The average emission factors of the 16 kinds of PAHs were showing as lignin (135 ± 180 mg/kg) > cellulose (97.8 ± 124 mg/kg) > hemicellulose (48.9 ± 65.2 mg/kg), and the average emission factors of EC presented in the descending order of cellulose (1.65 ± 3.02 g/kg), lignin (1.30 ± 1.04 g/kg), and hemicellulose (0.450 ± 0.480 g/kg), respectively. The proportion of naphthalene emitted from cellulose and hemicellulose combustion is higher, while fluoranthene and pyrene accounted significantly higher proportion for lignin. Moreover, the influence of ignition temperature and oxygen content on the emission characteristics of PAHs and EC were also discussed. The influence of ignition temperature on the emission of EC and PAHs is more significant compared to oxygen content, because it obviously promoted the PAHs and EC formations through resonance-stabilized hydrocarbon-radical chain reaction (RSR) pathway. However, correlation analysis combined with cluster analysis showed that the RSR-pathway probably had different effects on PAH growth for the three-components, as the indene-involved RSR-pathway were mainly related to 4–6 ring PAHs for cellulose and lignin (except fluoranthene and pyrene), but 2–4 ring PAHs for hemicellulose. We also found that the fitted results according to the proportion of three-components were significantly higher than the measured values of raw materials for indene, medium-molecular-weight PAHs, and soot-EC. These results presented the different formation pathways for medium-molecular-weight PAHs and the two EC components emitted by biomass combustion, which are worthy of further studies in exploring the generation mechanisms of PAHs and EC.

The effect of temperature on hydrocarbon profiles and the microbial community composition in North Saskatchewan River water during mesoscale tank tests of diluted bitumen spills

Despite many studies of diluted bitumen (DB) behavior during spills in saltwater, limited information is available on DB behavior in fresh water. This study examined the collective weathering processes on changes of fresh DB spilled in the North Saskatchewan River water and sediment mixture in a mesoscale spill tank under average air/water temperatures of 14 °C/15 °C and 6 °C/2 °C. Temporal changes of the hydrocarbon and microbial community compositions in the water column were assessed during the two 35-day tests under intermittent wave action. The contents of total organic carbon (TOC), benzene/toluene/ethylbenzene/xylenes (BTEX) and polycyclic aromatic hydrocarbons (PAHs) in water decreased with time during both tests. The final contents remained at higher values in warm water (15 °C) than in cold water (2 °C) after the collective weathering processes. A quick response of the main phyla, Proteobacteria and Actinobacteria, was observed, where the members of Proteobacteria enriched during both DB spills. In contrast, the members of Actinobacteria reduced with time. The microbial shifts coincided with the changes of PAHs in the waters at both temperatures. A comparison of the physical properties and chemical compositions of fresh and weathered DBs at both temperatures showed that the oil had undergone weathering that increased oil density and viscosity due to losing the light oil fraction with boiling points < 204 °C and emulsifying with water. This corresponded to losses of 19.0 wt% and 17.2 wt% of the fresh DB at 15 °C and 2 °C tests, respectively. For organic compounds in the DB with boiling points > 204 °C, there were small losses of saturates and 2- & 3-ring PAH aromatics (more during the 15 °C test than the 2 °C test), and negligible losses in the subfractions of resins and asphaltenes by the ends of the tests. <1.0 wt% of the DB was recovered from the bottom sediment, regardless of the temperature.

SPATIO-TEMPORAL OCCURRENCE, SOURCES, AND HUMAN HEALTH RISK OF 16-POLYCYCLIC AROMATIC HYDROCARBONS IN ANTHROPOGENIC VECTORED SOILS

This study determined the spatiotemporal distribution, sources, and human health hazards of sixteen polycyclic aromatic hydrocarbons (PAHs) in land-use soils. PAHs were determined by a gas chromatography-mass spectrometer (GC-MS). Total PAHs concentrations ranged from 125.3 to 2587.16 µgkg-1 showing concentrations in the order of topsoil &lt; subsoil and wet season &gt; dry season. PAHs occurrence exceeded the DPR-EGAPSIN target and intervention value in 33.3% and 11% of the samples. This study established variable concentrations of HPAHs relative to LPAHs with a predominance of carcinogenic 5-ring PAHs. The highest concentrations of total PAHs were at Warri military checkpoint. The cancer risk for infants was higher than for adults, and permissible target values, thus signifying human on-spot exposure risk. The results established that the source of PAHs is pyrogenic and petrogenic low-temperature combustion of petroleum fractions and high-temperature combustion of wood, grass, biomass, diesel, and vehicular traffic particulate emissions. The results demonstrated considerable concentration variation and potential for ecological and human health exposure risks. The results show PAHs exposures risk in military checkpoints and related catchments elsewhere.

Toxicity and distribution of polycyclic aromatic hydrocarbons in leachates from an unlined dumpsite in Nnewi, Nigeria

ABSTRACT Leachates from dumpsites have been known to pollute the environment with deleterious effects. The study examined the levels of the sixteen United States Environmental Protection Agency polycyclic aromatic hydrocarbons (PAHs) in leachates from an unlined solid waste dumpsite using a gas chromatography incorporated with a flame ionisation detector (GC-FID). Possible sources of the PAHs were identified using diagnostic pair ratios. Toxicity and mutagenic health-related risk were extrapolated. The average levels of PAHs ranged from 0.03–147.85 µg/L. The anthracene value of 147.85 µg/L was the maximum PAH concentration recorded. The lowest PAH observed was 0.03 µg/L, which was found in benzo(k)fluoranthene. The 3 – ring PAHs matrix was the highest PAH observed and it followed a ring size decreasing order of 3 > 4 > 5 > 2 > 6 in the leachate sample. The diagnostic pair ratio suggested mixed sources with a slightly dominant petrogenic source identified. The cluster analysis showed different sources of the congeners in the leachate. The benzo(a)pyrene toxic and mutagenic risk quotients showed that the greater concentrations of benzo(a)pyrene and dibenz(a,h)anthracene can induce carcinogenic and non-carcinogenic related health risks to a living organism.

Atmospheric Deposition of Polycyclic Aromatic Hydrocarbons (PAHs) in the Coastal Urban Environment of Poland: Sources and Transport Patterns.

This study combines an interseasonal variation of deposition profiles of fine-particulate-bound polycyclic aromatic hydrocarbons (PM2.5-bound PAHs) with source apportionment analysis. Comprehensive measurements were conducted in four representative periods of 2019 in the coastal urban region of the Baltic Sea in Poland. The mean daily deposition flux of Σ13PAHs was 229 ng m-2 day-1, which was lower than in other urban/industrial sites of Europe and Asia. The seasonal PAHs distribution exhibited a clear U-shaped pattern, reaching maximum values in January and December and the minimum in June. A strong influence of local/regional anthropogenic emissions and meteorological factors (precipitation, ambient temperature, wind regimes) was observed. The contribution of medium molecular weight PAHs (fluoranthene, pyrene, benzo(a)anthracene, chrysene) to the total sum of PAHs deposition fluxes increased from 24% in spring to 38% in summer, as a result of photochemistry, urban traffic, and shipping emissions. The highest contribution of 5- and 6-ring PAHs occurred primarily in autumn (55%), followed by winter (39%), spring (35%), and summer (26%). Benzo(a)pyrene (human carcinogenic compound) had a relatively high deposition flux in winter, which was almost 14 and 20 times higher than the values registered in spring and summer, respectively. The FLEXTRA dispersion model was used to study potential pollution regions for PM2.5-bound PAHs and to investigate changes in the PAH deposition regime in different seasons. This study reveals that the winter contribution of PAHs was mostly impacted by local urban activities (i.e., residential heating and coal-fired power plants). Winter PAH deposition fluxes were particularly associated with atmospheric particles transported from surrounding areas and industrially impacted regions of SE-S-SW Poland and Europe.

Novel eco-friendly methodology to determine polycyclic aromatic hydrocarbons in polyurethane foam for air monitoring: Application to spatial and temporal distribution survey

This study aimed at developing a new method for the extraction of polycyclic aromatic hydrocarbons (PAHs) in polyurethane foam (PUF). In the field of PAH monitoring, passive samplers using PUF disks are widely used. However, current extraction methods are time and solvent consuming. This new method employs 3 times a sixteenth of the PUF disk, with method detection limits (MDL) values below 5 and 13 ng/sampler for 3- and 4-rings PAHs, respectively. The use of only parts of the disk allows extraction by ultrasounds using exclusively 120 mL of ethanol, making it environmentally friendly. Ethanolic extracts are then purified and concentrated using microextraction by packed sorbent (MEPS) before GC-MS analyses. This method was applied for an environmental survey in a French urban area with an oceanic climate. Variations in PAH concentrations were observed depending on the site studied (urban, traffic, periurban and rural), as well as temporal variations.

Evolution of PAHs in the mobile phase of low-rank coal during medium–low-temperature pyrolysis

The generation and release of polycyclic aromatic hydrocarbons (PAHs) during coal pyrolysis have been extensively studied, yet the evolution process of PAHs in the mobile phase is poorly understood. In this study, Yulin (YL) subbituminous coal and its solid products (YL350–700) obtained by pyrolysis at ∼350–700 °C were treated with dichloromethane, and the extracted PAHs were analyzed by gas chromatography and mass spectrometry. The total PAH concentration in the YL350–700 mobile phase was found to increase and then decrease with increasing pyrolysis temperature, and peak in the YL380 sample. The concentrations of alkylated PAHs were found to be the main contributors to the total PAH concentrations among the YL350–700 samples. YL coal was dominated by 4-ring PAHs, while YL350–700 samples were all dominated by 2-ring PAHs (naphthalene and alkylated naphthalenes). Variations in the proportion of 2-ring PAHs and the degree of naphthalene alkylation in YL350–700 indicated that alkylated naphthalenes were the main component of PAHs generated during YL coal pyrolysis at medium–low temperatures. This may suggest that the condensed aromatic units in the macromolecular structure of YL coal mainly consist of low-ring PAHs. Finally, an evolutionary process for PAHs in the mobile phase of YL subbituminous coal during pyrolysis at medium–low temperatures was proposed.

Light intensity affects tolerance of pyrene in Chlorella vulgaris and Scenedesmus acutus

The impact of light intensity on the toxicity of pyrene, a 4-ring polycyclic aromatic hydrocarbon (PAH), was studied in Chlorella vulgaris and Scenedesmus acutus. Both species were cultured under low light, LL [50-60 µmol(photon) m-2 s-1], and high light, HL [100-110 µmol(photon) m-2 s-1] conditions to study the effects of pyrene (PYR) toxicity on growth parameters, the content of biomolecules, chlorophyll content, and photosynthetic efficiency. In the presence of PYR, S. acutus could grow well in LL and HL intensity. On the other hand, C. vulgaris showed a drastic decrease in growth and photosynthesis during HL conditions due to PYR toxicity. Regulation of nonphotochemical and photochemical quenching was responsible for the survival of S. acutus under PYR toxicity in LL and HL conditions. Thus, S. acutus seems to be a more promising candidate for pyrene degradation under varying light conditions.

Profiling and occupational health risk assessment study on coal ashes in terms of polycyclic aromatic hydrocarbons (PAHs)

Profiling and cancer risk assessment on the polycyclic aromatic hydrocarbons (PAHs) content of coal ashes produced by the major coal combustion plants from the eastern coalfield region in India was conducted. Thirteen PAHs were detected on coal ashes collected from ash deposition sites of major thermal power plants and the profiling of the PAHs was done. Benzo[a]pyrene equivalents (BaPeq) for individual PAHs were calculated and applied to the probabilistic assessment model from US EPA (1989). Monte Carlo simulations were conducted to assess the risk of inhabitants exposed to PAHs through the dust of the coal ash deposition site. In fly ash, the range of total amount of carcinogenic PAHs was from 3.50 to 6.72 µg g−1 and for the bottom ash, the range was 8.49 to 14.91 µg g−1. Bottom ashes were loaded with ample amounts of 5- and 6-ring carcinogenic PAHs, whereas fly ashes were dominated by medium molecular weight PAHs. The simulated mean cancer risks from fly ashes were 2.187 E–06 for children and 3.749 E–06 for adults. For the case of bottom ash, the mean risks were 1.248 E–05 and 2.173 E–05 respectively for children and adults. Among all the three exposure routes, dermal contact was the major and caused 81% of the total cancer risk. The most sensitive parameters were exposure duration and relative skin adherence factor for soil, which contributed the most to total variation. The 90% risks calculated from the bottom ashes (2.617 E–05 for children and 4.803 E–05 for adults) are marginally above the acceptable limit (>1.000 E–06) according to US EPA. In this study, a comprehensive risk assessment on carcinogenic PAHs present in coal ashes was done for the first time that may be helpful to develop potential strategies against occupational cancer risk.

Distribution Characteristics and Potential Risks of Polycyclic Aromatic Hydrocarbon (PAH) Pollution at a Typical Industrial Legacy Site in Tianjin, North China

Polycyclic aromatic hydrocarbon (PAH) pollution in the soil of industrial legacy sites is a prominent problem when reusing urban land. To estimate the potential risks of PAHs, this study investigated 16 priority PAHs in the soil at different depths in a typical decommissioned industrial site in Tianjin. PAH concentrations were determined via gas chromatography-(tandem) quadrupole mass spectrometry. Incremental lifetime cancer risk (ILCR) assessment was applied to assess the potential risks to the population after land reconstruction. The total concentrations of PAHs in the soil at different depths ranged from 38.3 ng·g−1 to 1782.5 ng·g−1, which were below the risk control standard for soil contamination of development land (GB 36600-2018). Low-ring (two-three ring) PAHs exhibit a dominant component, and the variations in PAH compositions were closely related to the former production units and soil properties. Compared to silty clay layers, PAHs tended to accumulate in the permeable miscellaneous fill layers. Incremental lifetime cancer risk assessment values associated with different exposure pathways for children, adolescents, and adults were calculated. The results showed potential carcinogenic risks for people of varying ages in this area, but they were still acceptable. In general, this legacy site can meet the demands of sustainable land development.

Exploring the Cumulative Selectivity of Polycyclic Aromatic Hydrocarbons in Phytoplankton, Water, and Sediment in Typical Urban Water Bodies

To understand the interactions among eutrophication, algal bloom, and POPs (persistent organic pollutants) in freshwater ecosystems, the cumulative selectivity of PAHs (polycyclic aromatic hydrocarbons) in phytoplankton, water, and sediment with different eutrophication level waters were identified in a typical plain river network region located in Nanjing City. Results showed that a total of 33 algal species belonging to 27 genera and 4 phyla were identified in 15 sites of urban water bodies, and most of them belonged to the type Cyanobacteria–Bacillariophyta. The eutrophication level of these rivers and lakes led to the sample site specificity of algal composition and abundance. The planktonic algae mainly accumulated the 2-ring and 3-ring PAHs, and the sediment mainly enriched the high-ring PAHs. However, the enrichment capacity of planktonic algae on PAHs was much higher than that of sediment. Cyanophyta and some species of Bacillariophyta and Chlorophyta in mesotrophic (βm) and meso-eutrophic water bodies (ßαm) preferentially accumulated lower-ring PAHs (naphthalene, acenaphthylene, and phenanthrene). Some other specific algae species, such as Euglenophyta, some species of Bacillariophyta, and most Chlorophyta in mesotrophic and moderate eutrophic water bodies, had strong capacities to enrich high-ring PAHs subsuming benzo[a]anthracene, chrysene, and anthracene. The eutrophication level of water bodies affected the cumulative selectivity of PAHs by shaping the site specificity of phytoplankton composition, which may be related to water quality, sediment characteristics, phytoplankton composition, and the algal cell walls.