Relationship of polycyclic aromatic hydrocarbons with oxy(quinone) and nitro derivatives during air mass transport

Promotive effects of marine-derived dimethyl sulfoxide on the photodegradation of phenanthrene in the atmosphere

Dimethyl sulfoxide (DMSO), a versatile medium, is a particular component in the marine atmosphere that possibly causes polycyclic aromatic hydrocarbons (PAHs) to degrade differently than they do in the continental atmosphere. In this study, phenanthrene (Phe) was used as a model PAH in batch photochemical experiments to investigate the chemical actions of DMSO and the underlying mechanisms. The photodegradation of Phe in aqueous solutions with DMSO volume fractions from 0 % to 100 % was initiated by ultraviolet (UV) radiation and promoted by singlet oxygen, which was consistent with pseudo-first-order kinetics. Phe photodegraded faster in a mixture of DMSO and water than in water or DMSO alone, and the rate constant showed a unimodal distribution over the DMSO fraction range, peaking at 33 % DMSO (0.0333 ± 0.0009 min-1) and 40 % DMSO (0.0199 ± 0.0005 min-1) under 254 nm and 302 nm UV radiation, respectively. This interesting phenomenon was attributed to the competition of DMSO for UV radiation and singlet oxygen and changes in dissolved oxygen and free water contents caused by the interaction between DMSO and water molecules. In addition, 9,10-phenanthrenequinone (9,10-PhQ) with high cytotoxicity was the main photodegradation product of Phe under various conditions. The photodegradation rate of Phe in the mixtures of DMSO and water was comparable to its reaction rate with OH radicals, suggesting that 9,10-PhQ can be rapidly generated in the marine atmosphere, driven by a mechanism different from that in the continental or urban atmosphere. Under the presented experimental conditions, UV intensity and DMSO fraction were the primary factors that affected the photodegradation rate of Phe and 9,10-PhQ and altered their integrated toxicity. The findings of this study support the conclusion that the marine atmosphere is an essential field in the atmospheric transport of PAHs, in which DMSO is an important component that affects their photodegradation.

The shifting research landscape for PAH bioremediation in water environment: a bibliometric analysis on three decades of development

Polycyclic aromatic hydrocarbons (PAHs) with their carcinogenic, teratogenic, and mutagenic effects can cause great damage to the ecosystem and public health when present in water. With bioremediation, PAH contamination in water environment can be greatly reduced in an eco-friendly manner. It has thus become the research focus for many environmental scientists. In this study, a bibliometric analysis on three-decade (1990-2022) development of PAH bioremediation in water environment was conducted from temporal and spatial dimensions using CiteSpace. A total of 2480 publications, obtained from Web of Science core collection database, were used to explore the basic characteristics, hotspots, and prospects of the research area. The results showed that (1) bioremediation/biodegradation of PAHs in water environment has been getting researchers' attention since 1990, and is gaining even more traction as time goes on. (2) In terms of countries, China and the USA were the major contributors in this research area, while at the institutional level, the Chinese Academy of Sciences has produced the most research results. However, international cooperation across regions was lacking in the field. (3) Environment Science and Technology, Chemosphere, Applied and Environment Microbiology, Journal of Hazardous Materials, and Environment Pollution were the 5 most cited journals in this field. (4) There were three major stages the field has gone through, each with distinct research hotspots, including initial stage (1990-1994), mechanism investigation (1995-2000), and application exploration (2001-2010; 2011-2022). Finally, research perspectives were proposed, covering three directions, namely, bioavailability, immobilization, and viable but nonculturable (VBNC) bacteria.

The COVID-19 Pandemic: Quantification of Temporal Variations in Air Pollutants Before, During and Post the Lockdown in Jeddah City, Saudi Arabia

The government of Saudi Arabia imposed a strict lockdown between March and July 2020 to stop the spread of the coronavirus disease (COVID-19), which has led to a sharp decline in economic activities. The daily temporal variations of PM10, PM2.5, carbon monoxide (CO), nitrogen dioxide (NO2), and ozone (O3) were used to investigate the changes in air quality in response to COVID-19 lockdown control measures from January to December 2020 in Jeddah, Saudi Arabia. Meteorological parameters (wind speed, direction, temperature, relative humidity) were also analyzed to understand the changes during the pandemic. As a result, significant reductions in the concentrations of NO2 (- 44.5%), CO (- 41.5%), and PM2.5, PM10 (- 29.5%, each) were measured in the capital city of Jeddah during the quarantine compared to the pre-lockdown average. In contrast, the lockdown caused a significant increase in O3 by 41%. The changes in air quality during the COVID-19 outbreak by comparing the average pollutant concentration before lockdown (January 1-March 21, 2020) and the following 12 weeks during the partial lockdown (March 22-July 28, 2020), reveal a very significant decrease in pollutants, and consequently a significant improvement in air quality. Observed differences are attributable to changes in point source emissions associated with changes in localized activities, possibly related to decreased economic and industrial activity in response to the lockdown. The results of the present study show during the study period indicated a positive response to lockdown during the COVID-19 pandemic. Furthermore, the results can be used to establish future control measures and strategies to improve air quality.

Polycyclic aromatic hydrocarbons and their oxygenated derivatives in urban aerosol: levels, chemical profiles, and contribution to PM2.5 oxidative potential

The concentrations of polycyclic aromatic hydrocarbons (PAHs) and quinones, a subgroup of oxygenated PAHs (oxy-PAHs), were measured in PM_2.5 samples collected during warm (May-June 2019) and cold (February-March 2020) seasons in the city of Bologna, Italy. Total PAHs concentration was nearly double in winter (6.58 ± 1.03 ng m^-3) compared with spring (3.16 ± 0.53 ng m^-3), following the trend of the PM_2.5 mass concentration. Molecular diagnostic ratios suggested that, together with traffic, biomass burning was the dominant emission source contributing to the peaks of concentration of PM_2.5 registered in the cold season. Quinone level was constant in both seasons, being 1.44 ± 0.24 ng m^-3, that may be related to the increased secondary formation during warm season, as confirmed by the higher Σoxy-PAHs/ΣPAHs ratio in spring than in winter. The oxidative potential (OP) of the PM_2.5 samples was assessed using acellular dithiothreitol (DTT) and ascorbic acid (AA) assays. The obtained responses showed a strong seasonality, with higher volume-normalized (OP_V) values in winter than in spring, i.e., OP_V^DTT: 0.32 ± 0.15 nmol min^-1 m^-3 vs. 0.08 ± 0.03 nmol min^-1 m^-3 and OP_V^AA: 0.72 ± 0.36 nmol min^-1 m^-3 vs. 0.28 ± 0.21 nmol min^-1 m^-3. Both OP_V^DTT and OP_V^AA responses were significantly associated with total PAHs, as a general descriptor of redox-active PAH derivatives, associated with co-emission from burning sources or secondary atmospheric oxidation of parent PAHs. Otherwise, only winter OP_V^DTT responses showed a significant correlation with total Ʃoxy-PAHs concentration.

Size-dependent in vitro inhalation bioaccessibility of PAHs and O/N PAHs - Implications to inhalation risk assessment

Size segregated samples (<0.49, 0.49-0.95, 0.95-1.5, 1.5-3.0, 3.0-7.2 and > 7.2 μm) of atmospheric particulate matter (APM) were collected at a traffic site in the urban agglomeration of Thessaloniki, northern Greece, during the cold and the warm period of 2020. The solvent-extractable organic matter was analyzed for selected organic contaminants including polycyclic aromatic hydrocarbons (PAHs), and their nitro- and oxy-derivarives (NPAHs and OPAHs, respectively). Mean concentrations of ∑₁₆PAHs, ∑₆NPAHs and ∑₁₀OPAHs associated to total suspended particles (TSP) were 18 ng m^-3, 0.2 ng m^-3 and 0.9 ng m^-3, respectively, in the cold period exhibiting significant decrease (6.4, 0.2 and 0.09 ng m^-3, respectively) in the warm period. The major amount of all compounds was found to be associated with the alveolar particle size fraction <0.49 μm. The inhalation bioaccessibility of PAHs and O/N PAHs was measured in vitro using two simulated lung fluids (SLFs), the Gamble's solution (GS) and the artificial lysosomal fluid (ALF). With both SLFs, the derived bioaccessible fractions (BAFs) followed the order PAHs > OPAHs > NPAHs. Although no clear dependence of bioaccessibility on particle size was obtained, increased bioaccessibility of PAHs and PAH derivatives in coarse particles (>7.2 μm) was evident. Bioaccessibility was found to be strongly related to the logK_OW and the water solubility of individual compounds hindering limited mobilization of the most hydrophobic and less water-soluble compounds from APM to SLFs. The lifetime cancer risk due to inhalation exposure to bioaccessible PAHs, NPAHs and OPAHs was estimated and compared to those calculated from the particulate concentrations of organic contaminants.

NPAHs and OPAHs in the atmosphere of two central European cities: Seasonality, urban-to-background gradients, cancer risks and gas-to-particle partitioning

Derivatives of polycyclic aromatic hydrocarbons (PAHs) such as nitrated- and oxygenated-PAHs (NPAHs and OPAHs) could be even more toxic and harmful for the environment and humans than PAHs. We assessed the spatial and seasonal variations of NPAHs and OPAHs atmospheric levels, their cancer risks and their gas-to-particle partitioning. To this end, about 250 samples of fine particulate matter (PM2.5) and 50 gaseous samples were collected in 2017 in central Europe in the cities of Brno and Ljubljana (two traffic and two urban background sites) as well as one rural site. The average particulate concentrations were ranging from below limit of quantification to 593 pg m-3 for Σ9NPAHs and from 1.64 to 4330 pg m-3 for Σ11OPAHs, with significantly higher concentrations in winter compared to summer. In winter, the particulate levels of NPAHs and OPAHs were higher at the traffic site compared to the urban background site in Brno while the opposite was found in Ljubljana. NPAHs and OPAHs particulate levels were influenced by the meteorological parameters and co-varied with several air pollutants. The significance of secondary formation on the occurrence of some NPAHs and OPAHs is indicated. In winter, 27-47% of samples collected at all sites were above the acceptable lifetime carcinogenic risk. The gas-particle partitioning of NPAHs and OPAHs was influenced by their physico-chemical properties, the season and the site-specific aerosol composition. Three NPAHs and five OPAHs had higher particulate mass fractions at the traffic site, suggesting they could be primarily emitted as particles from vehicle traffic and subsequently partitioning to the gas phase along air transport. This study underlines the importance of inclusion of the gas phase in addition to the particulate phase when assessing the atmospheric fate of polycyclic aromatic compounds and also when assessing the related health risk.

Occurrence, fates, and carcinogenic risks of substituted polycyclic aromatic hydrocarbons in two coking wastewater treatment systems

This paper reports for the first time the occurrence, fates, and carcinogenic risks of 20 substituted polycyclic aromatic hydrocarbons (SPAHs) and 16 priority PAH species in two coking wastewater treatment plants (WWTPs) (plant E and central WWTP). The measured total concentrations of PAHs and SPAHs in raw wastewater of coking plant E were 3700 and 1200 μg·L^-1, respectively, with naphthalene (1400 μg·L^-1), and fluoranthene (353 μg·L^-1) as dominant PAH species and 2-methylnaphthalene (167 μg·L^-1), anthraquinone (133 μg·L^-1), and 1-methylnaphthalene (132 μg·L^-1) as dominant SPAHs. For the 11 methyl-PAHs (MPAHs), 4 oxygenated-PAHs (OPAHs), and 5 nitrated-PAHs (NPAHs) investigated, the biological wastewater treatment process removed 98.6% MPAHs, 83.9% OPAHs, and 89.1% NPAHs. Mass balance analysis result revealed that transformation was the major mechanism to remove low-molecular-weight (LMW) MPAHs (59.9-77.3%), a large part of OPAHs, including anthraquinone, methylanthraquinone, and 9-fluorenone (46.7-49.6%), and some NPAHs, including 2-nitrofluorene and 9-nitroanthrancene (52.9-59.1%). Adsorption by activated sludge mainly accounted for removing high-molecular-weight (HMW) SPAHs (59.6-71.01%). The relatively high concentrations of SPAHs in excess sludge (15,000 μg·g^-1) and treated effluent (104 μg·L^-1) are of great concern for their potential adverse ecological impacts. SPAHS exhibited similar behaviors in central WWTP, though the influent concentrations were much lower. The concentration levels of SPAHs in the ambient air of coking plant E and central WWTP may also pose potential lung cancer risks (LCR) to the workers through inhalation, where all studied SPAHs except 3-nitrofluoranthene and 7-nitrobenz[a]anthracene exceeded the acceptable cancer risk standards (>10^-6) recommended by U.S EPA. This study could help identify the ecological and healthy risks during coking wastewater treatment and provide useful information for policy-making.

On the nature of polycyclic aromatic hydrocarbons associated with sporting walkways dust: Concentrations, sources and relative health risk

Sporting walkways (SW) are a new innovation which may prove popular in many cities. As there is currently no information on possible health risks associated with their use, concentrations of polycyclic aromatic hydrocarbons (PAHs) associated with deposited dust sampled on SW in Jeddah, Saudi Arabia, have been measured and interpreted in relation to sources and cancer risk. The average ∑PAHs (16 compounds) ranged between 1357 ng/g in residential areas and 3764 ng/g in central urban areas, with suburban areas between. The congener profile and diagnostic ratios of PAHs indicate a predominant source associated with petroleum combustion (pyrogenic source), most probably vehicular emissions. Carcinogenic potential is estimated from the sum of carcinogenic compound concentrations weighted by their individual potency relative to benzo(a)pyrene, and is found to be similar to household dust sampled in the same city, and lower than many other indoor and outdoor (road) dusts sampled across the world.

Lockdowns and reduction of economic activities during the COVID-19 pandemic improved air quality in Alexandria, Egypt

Parallel reductions in atmospheric aerosols (particulate matter (PM)) and nitrogen dioxide (NO₂) accompanied the drastic measures that were adopted to limit the spread of COVID-19. The results of this preliminary study conducted in northern Egypt revealed that ambient PM₁₀, PM_2.5, and NO₂ levels decreased by 22.8%, 29.3%, and 25.9%, respectively, after the lockdown started on March 13, 2020. These reductions in concentrations significantly (p ˂ 0.01) correlated with the decrease in transportation and industrial and other economic activities. Furthermore, PM and NO₂ concentrations radically reduced during the full lockdown on Easter, Ramadan, and Eid Al-Fitr. The findings of this study will help the World Health Organization (WHO) and other health regulators to combat COVID-19 in the world. This study is part of an ongoing research related to the current pandemic.

Polycyclic Aromatic Hydrocarbons: Occurrence, Electroanalysis, Challenges, and Future Outlooks

The past several decades have seen increasing concern regarding the wide distribution of polycyclic aromatic hydrocarbons (PAHs) in environmental matrices. Primary toxicological data show PAHs' persistent characteristics and possible toxicity effects. Because of this pressing global issue, electroanalytical methods have been introduced. These methods are effective for PAH determination in environmental waters, even outclassing sophisticated analytical techniques such as chromatography, conventional spectrophotometry, fluorescence, and capillary electrophoresis. Herein, the literature published on PAHs is reviewed and discussed with special regard to PAH occurrence. Moreover, the recent developments in electrochemical sensors for PAH determination and the challenges and future outlooks in this field, are also presented.

Oxygenated and Nitrated Polycyclic Aromatic Hydrocarbons in Ambient Air-Levels, Phase Partitioning, Mass Size Distributions, and Inhalation Bioaccessibility

Among the nitrated and oxygenated polycyclic aromatic hydrocarbons (NPAHs and OPAHs) are some of the most hazardous substances to public health, mainly because of their carcinogenicity and oxidative potential. Despite these concerns, the concentrations and fate of NPAHs and OPAHs in the atmospheric environment are largely unknown. Ambient air concentrations of 18 NPAHs, 5 quinones, and 5 other OPAHs were determined at two urban and one regional background sites in central Europe. At one of the urban sites, the total (gas and particulate) concentrations of Σ10OPAHs were 10.0 ± 9.2 ng/m3 in winter and 3.5 ± 1.6 ng/m3 in summer. The gradient to the regional background site exceeded 1 order of magnitude. Σ18NPAH concentrations were typically 1 order of magnitude lower than OPAHs. Among OPAHs, 9-fluorenone and (9,10)-anthraquinone were the most abundant species, accompanied by benzanthrone in winter. (9,10)-Anthraquinone represented two-thirds of quinones. We found that a large fraction of the target substance particulate mass was carried by submicrometer particles. The derived inhalation bioaccessibility in the PM10 size fraction is found to be ≈5% of the total ambient concentration of OPAHs and up to ≈2% for NPAHs. For 9-fluorenone and (9,10)-anthraquinone, up to 86 and 18%, respectively, were found at the rural site. Our results indicate that water solubility could function as a limiting factor for bioaccessibility of inhaled particulate NPAHs and OPAHs, without considerable effect of surfactant lipids and proteins in the lung lining fluid.

Occurrence of the potent mutagens 2- nitrobenzanthrone and 3-nitrobenzanthrone in fine airborne particles

Polycyclic aromatic compounds (PACs) are known due to their mutagenic activity. Among them, 2-nitrobenzanthrone (2-NBA) and 3-nitrobenzanthrone (3-NBA) are considered as two of the most potent mutagens found in atmospheric particles. In the present study 2-NBA, 3-NBA and selected PAHs and Nitro-PAHs were determined in fine particle samples (PM 2.5) collected in a bus station and an outdoor site. The fuel used by buses was a diesel-biodiesel (96:4) blend and light-duty vehicles run with any ethanol-to-gasoline proportion. The concentrations of 2-NBA and 3-NBA were, on average, under 14.8 µg g⁻¹ and 4.39 µg g⁻¹, respectively. In order to access the main sources and formation routes of these compounds, we performed ternary correlations and multivariate statistical analyses. The main sources for the studied compounds in the bus station were diesel/biodiesel exhaust followed by floor resuspension. In the coastal site, vehicular emission, photochemical formation and wood combustion were the main sources for 2-NBA and 3-NBA as well as the other PACs. Incremental lifetime cancer risk (ILCR) were calculated for both places, which presented low values, showing low cancer risk incidence although the ILCR values for the bus station were around 2.5 times higher than the ILCR from the coastal site.

Street Dust-Bound Polycyclic Aromatic Hydrocarbons in a Saudi Coastal City: Status, Profile, Sources, and Human Health Risk Assessment

Polycyclic aromatic hydrocarbons (PAHs) in street dust pose a serious problem threatening both the environment and human health. Street dust samples were collected from five different land use patterns (traffic areas TRA, urban area URA, residential areas REA, mixed residential commercial areas MCRA and suburban areas SUA) in Jeddah, a Saudi coastal city, and one in in Hada Al Sham, a rural area (RUA). This study aimed to investigate the status, profile, sources of PAHs and estimate their human health risk. The results revealed an average concentration of total PAHs of 3320 ng/g in street dust of Jeddah and 223 ng/g in RUA dust. PAHs with high molecular weight represented 83.38% of total PAHs in street dust of Jeddah, while the carcinogenic PAH compounds accounted 57.84%. The highest average concentration of total PAHs in street dust of Jeddah was found in TRA (4980 ng/g) and the lowest in REA (1660 ng/g). PAHs ratios indicated that the principal source of PAHs in street dust of Jeddah is pyrogenic, mainly traffic emission. Benzo(a)anthracene/chrysene (BaA/CHR) ratio suggests that PAHs in street dusts of Jeddah come mainly from emission of local sources, while PAHs in RUA might be transported from the surrounding urban areas. The estimated Incremental Lifetime Cancer Risk (ILCR) associated with exposure to PAHs in street dusts indicated that both dermal contact and ingestion pathways are major contributed to cancer risk for both children and adults. Based on BaPequivalence concentrations of total PAHs, ILCRIngestion, ILCRdermal and cancer risk values for children and adults exposed to PAHs in street dust of different areas in Jeddah were found between 10-6 and 10-4, indicating potential risk. The sequence of cancer risk was TRA > URA > MCRA > SUA > REA. Only exposure to BaP and DBA compounds had potential risk for both children and adults.

Profiling quinones in ambient air samples collected from the Athabasca region (Canada)

This paper presents new findings on polycyclic aromatic hydrocarbon oxidation products-quinones that were collected in ambient air samples in the proximity of oil sands exploration. Quinones were characterized for their diurnal concentration variability, phase partitioning, and molecular size distribution. Gas-phase (GP) and particle-phase (PM) ambient air samples were collected separately in the summer; a lower quinone content was observed in the PM samples from continuous 24-h sampling than from combined 12-h sampling (day and night). The daytime/nocturnal samples demonstrated that nighttime conditions led to lower concentrations and some quinones not being detected. The highest quinone levels were associated with wind directions originating from oil sands exploration sites. The statistical correlation with primary pollutants directly emitted from oil sands industrial activities indicated that the bulk of the detected quinones did not originate directly from primary emission sources and that quinone formation paralleled a reduction in primary source NO_x levels. This suggests a secondary chemical transformation of primary pollutants as the origin of the determined quinones. Measurements of 19 quinones included five that have not previously been reported in ambient air or in Standard Reference Material 1649a/1649b and seven that have not been previously measured in ambient air in the underivatized form. This is the first paper to report on quinone characterization in secondary organic aerosols originating from oil sands activities, to distinguish chrysenequinone and anthraquinone positional isomers in ambient air, and to report the requirement of daylight conditions for benzo[a]pyrenequinone and naphthacenequinone to be present in ambient air.

Atmospheric deposition of polycyclic aromatic compounds and associated sources in an urban and a rural area of Chongqing, China

Monthly bulk (dry + wet) deposition samples were collected at an urban and a rural site in Chongqing, southwestern China during May 2014 to April 2015 for analyzing the contents of parent polycyclic aromatic hydrocarbons (PPAHs) and three types of substituted PAHs (SPAHs) including oxygenated PAHs (OPAHs), nitrated PAHs (NPAHs) and methyl PAHs (MPAHs). Annual average (±standard deviation) deposition fluxes of ΣPPAHs, ΣOPAHs, and ΣMPAHs were 536 ± 216; 221 ± 118, and 131 ± 41.9 ng/m²/d, respectively, in the urban area, and 347 ± 185, 160 ± 112, and 85.2 ± 32.0 ng/m²/d, respectively in the rural area. Deposition of ΣNPAHs (6.01 ± 3.93 and 3.91 ± 4.84 ng/m²/d) were about two orders of magnitude lower than those of ΣPPAHs. In the urban area, temporal variations of PPAHs and MPAHs fluxes were positively correlated with particle deposition, while the trends of OPAHs and NPAHs were probably controlled by secondary formation. In the rural area, SPAHs and PPAHs deposition fluxes had similar temporal trends but differed from particle deposition. High relative humidity in Chongqing likely played an important role in facilitating the partitioning of OPAHs to atmospheric aerosols and resulting in the relatively high OPAHs level in winter. Principle component analysis identified secondary formation (21.7%) and combustion emission (52.7%) as two important contributors to polycyclic aromatic compounds (PACs) deposition fluxes in urban area.