An overview of possible processes able to account for the occurrence of nitro-PAHs in Antarctic particulate matter

Nitro-PAHs: Occurrences, ecological consequences, and remediation strategies for environmental restoration

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) are persistent pollutants that have been introduced into the environment as a result of human activities. They are produced when PAHs undergo oxidation and are highly resistant to degradation, resulting in prolonged exposure and significant health risks for wildlife and humans. Nitro-PAHs' potential to induce cancer and mutations has raised concerns about their harmful effects. Furthermore, their ability to accumulate in the food chain seriously threatens the ecosystem and human health. Moreover, nitro-PAHs can disrupt the normal functioning of the endocrine system, leading to reproductive and developmental problems in humans and other organisms. Reducing nitro-PAHs in the environment through source management, physical removal, and chemical treatment is essential to mitigate the associated environmental and human health risks. Recent studies have focused on improving nitro-PAHs' phytoremediation by incorporating microorganisms and biostimulants. Microbes can break down nitro-PAHs into less harmful substances, while biostimulants can enhance plant growth and metabolic activity. By combining these elements, the effectiveness of phytoremediation for nitro-PAHs can be increased. This study aimed to investigate the impact of introducing microbial and biostimulant agents on the phytoremediation process for nitro-PAHs and identify potential solutions for addressing the environmental risks associated with these pollutants.

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.

Predictive Models of Gas/Particulate Partition Coefficients (KP) for Polycyclic Aromatic Hydrocarbons and Their Oxygen/Nitrogen Derivatives

Polycyclic aromatic hydrocarbons (PAHs) and their oxygen/nitrogen derivatives released into the atmosphere can alternate between a gas phase and a particulate phase, further affecting their environmental behavior and fate. The gas/particulate partition coefficient (KP) is generally used to characterize such partitioning equilibrium. In this study, the correlation between log KP of fifty PAH derivatives and their n-octanol/air partition coefficient (log KOA) was first analyzed, yielding a strong linear correlation (R2 = 0.801). Then, Gaussian 09 software was used to calculate quantum chemical descriptors of all chemicals at M062X/6-311+G (d,p) level. Both stepwise multiple linear regression (MLR) and support vector machine (SVM) methods were used to develop the quantitative structure-property relationship (QSPR) prediction models of log KP. They yield better statistical performance (R2 > 0.847, RMSE < 0.584) than the log KOA model. Simulation external validation and cross validation were further used to characterize the fitting performance, predictive ability, and robustness of the models. The mechanism analysis shows intermolecular dispersion interaction and hydrogen bonding as the main factors to dominate the distribution of PAH derivatives between the gas phase and particulate phase. The developed models can be used to predict log KP values of other PAH derivatives in the application domain, providing basic data for their ecological risk assessment.

Past, present, and future perspectives on the assessment of bioavailability/bioaccessibility of polycyclic aromatic hydrocarbons: A 20-year systemic review based on scientific econometrics

Bioaccessibility/bioavailability (bioac-bioav) is an important criterion in the risk assessment of polycyclic aromatic hydrocarbons (PAHs), especially in the restoration of contaminated sites. Although, the bioac-bioav concept is widely employed in PAH risk assessment for both humans and wildlife, their growth and integration in risk assessment models are seldom discussed. Consequently, the relevant literature listed on Web of Science (WOS)™ was retrieved and analyzed using the bibliometric software Citespace in order to gain a comprehensive understanding of this issue. Due to the limitations of the literature search software, we manually searched the articles about PAHs bioac-bioav that were published before 2000. This stage focuses on research on the distribution coefficient of PAHs between different environmental phases and laid the foundation for the adsorption-desorption of PAHs in subsequent studies of the bioac-bioav of PAHs. The research progress on PAH bioac-bioav from 2000 to the present was evaluated using the Citespace software based on country- and discipline-wise publication volumes and research hotspots. The development stages of PAH bioac-bioav after 2000 were divided into four time segments. The first three segments (2000-2005, 2006-2010, and 2011-2015) focused on the degradation of PAHs and their in vivo (bioavailability)-in vitro (bioaccessibility) evaluation method and risk assessment. Meanwhile, the current (2016-present) research focuses on the establishment of analytical methods for assessing PAH derivatives at environmental concentrations and the optimization of various in vitro digestion methods, including chemical optimization (sorptive sink) and biological optimization (Caco-2 cell). The contents are aimed at supplying researchers with a deeper understanding of the development of PAH bioac-bioav.

Method development for simultaneous analyses of polycyclic aromatic hydrocarbons and their nitro-, oxy-, hydroxy- derivatives in sediments

It is important to establish an available analytical method for polycyclic aromatic hydrocarbons (PAHs), nitrated PAHs (nitro-PAHs), oxygenated forms of PAHs (oxy-PAHs), and hydroxy-PAHs (OH-PAHs) in sediment samples due to the fact that they co-exist in various environmental mediates, particularly in sediment. In this study, an analytical method has been developed and validated for the quantification of PAHs, nitro-PAHs, oxy-PAHs, and OH-PAHs in sediment samples. The sediment samples were extracted by accelerated solvent extraction and cleaned up with SPE alumina-n combining with aminopropyl cartridges. The extracts were further fractionated by using different solvents. The fractionated extracts were analyzed via gas chromatography of single and triple quadrupole mass spectrometry in the electron ionization and negative ion chemical ionization with selective ion monitoring and selective reaction monitoring mode and liquid chromatography-triple quadrupole mass spectrometry. Each group of analytes was determined by different instrument modes such as GC-EI-SIM for PAHs, GC-NICI-SRM for nitro-PAHs, GC-EI-SRM for the oxy-PAHs and LC-ESI-MS/MS for OH-PAHs. A total of 44 analytes (16 PAHs, 14 nitro-PAHs, 9 oxy-PAHs, and 5 OH-PAHs) and 6 deuterated surrogates were performed. Most of recovery percentage varied from 52.8% up to 114.1% for the targeted analytes verified at three concentration levels (100 ng/g, 400 ng/g and 1000 ng/g for PAHs and 10 ng/g, 50 ng/g and 400 ng/g for their derivatives). The repeatability determined by the relative standard deviation percentage of triplicate trials was less than 10% for most analytes. The limit of detection ranged from 0.01 to 0.02 ng/g for PAHs, 0.002-0.067 ng/g for nitro-PAHs, 0.01-0.1 ng/g for oxy-PAHs, and 0.003-0.006 ng/g for OH-PAHs. Most of the compounds were detectable in the sediments collected from a local River, which illustrates the developed method could be a practical and suitable technique for detection of PAHs and their derivatives in real sediment samples.

Magnetic halloysite nanotube/polyaniline/copper composite coupled with gas chromatography-mass spectrometry: A rapid approach for determination of nitro-phenanthrenes in water and soil samples

A fast, sensitive and reliable ultrasound-assisted magnetic dispersive solid-phase microextraction (UAMDSPME) setup was developed and evaluated for the enrichment of nitro- phenanthrenes compound in environmental samples prior to GC-MS determination. A new type of nanocomposite sorbent was made based on halloysite nanotubes (HNTs). HNTs is a type of natural material, have attracted great interest because of their large surface area and high chemical and thermal stability. The hybrid nanocomposite (magnetic HNT@PANI@Cu) was obtained by coating the magnetic HNTs by polyaniline (PANI) and afterwards decorating with metalic copper. Its morphology and surface properties were characterized using Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, energy dispersive spectroscopy and vibrating sample magnetometry. In this work several factors that may affect the extraction efficiencies such as desorption solvent type and its volume, sonication times for extraction and desorption, sorbent amount, organic modifier content, salt concentration and matrix effect were investigated in detail. Under the optimal conditions, the limit of detection (S/N = 3) was 0.25 ng L^-1 and the linearity was in the range of 0.01-100 μg L^-1. The method precision expressed as relative standard deviations (RSDs%) were 4.6-6.1% (intra-day), and 7.2-9.6% (inter-day). Finally, the presented method was successfully applied to the rapid determination of trace levels of nitro-phenanthrenes in spiked water and soil samples.

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) in the environment - A review

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) are derivatives of PAHs with at least one nitro-functional group (-NO₂) on the aromatic ring. The toxic effects of several nitro-PAHs are more pronounced than those of PAHs. Some nitro-PAHs are classified as possible or probable human carcinogens by the International Agency for Research on Cancer. Nitro-PAHs are released into the environment from combustion of carbonaceous materials (e.g. fossil fuels, biomass, waste) and post-emission transformation of PAHs. Most studies on nitro-PAHs are about air (gas-phase and particulate matter), therefore less is known about the occurrence, concentrations, transport and fate of nitro-PAHs in soils, aquatic environment and biota. Studies on partition and exchange of nitro-PAHs between adjacent environmental compartments are also sparse. The concentrations of nitro-PAHs cannot easily be predicted from the intensity of anthropogenic activity or easily related to those of PAHs. This is because anthropogenic source strengths of nitro-PAHs are different from those of PAHs, and also nitro-PAHs have additional sources (formed by photochemical conversion of PAHs). The fate and transport of nitro-PAHs could be considerably different from their related PAHs because of their higher molecular weights and considerably different sorption mechanisms. Hence, specific knowledge on nitro-PAHs is required. Regulations on nitro-PAHs are also lacking. We present an extensive review of published literature on the sources, formation, physico-chemical properties, methods of determination, occurrence, concentration, transport, fate, (eco)toxicological and adverse health effects of nitro-PAHs. We also make suggestions and recommendations about data needs, and future research directions on nitro-PAHs. It is expected that this review will stimulate scientific discussion and provide the basis for further research and regulations on nitro-PAHs.

Diurnal variation of nitrated polycyclic aromatic hydrocarbons in PM10 at a roadside site in Xiamen, China

Intensive daytime and nighttime sampling was carried out from 23 Oct to 31 Dec 2008 to investigate the occurrence of nitrated polycyclic aromatic hydrocarbons (NPAHs) in PM10 at a roadside site in Xiamen, China. At the same time, six PM10 samples were collected from a nearby roadway tunnel for comparison. Six NPAHs, namely 9-nitroanthracene, 2- and 3-nitrofluoranthene, 1-nitropyrene, 7-nitrobenz[a]anthracene, and 6-nitrobenzo[a]pyrene, were identified and quantified using GC/MS in negative ion chemical ionization mode. The average total concentration of six NPAHs (sigmaNPAHs) in the cold season (26 Nov-31 Dec) was 2.3 (daytime) and 9.9 (nighttime) times higher than those in the warm season. Significant statistical difference (p < 0.01, 2-tailed) of sigmaNPAHs between daytime and nighttime was found during both the warm and cold seasons. NPAHs were significantly positively correlated with their parent PAHs and nitrogen dioxide but negatively correlated with ambient temperature. The ratio of 2 + 3-nitrofluoranthene to 1-nitropyrene exhibited a similar diurnal pattern as sigmaNPAHs and was generally greater than 5, indicating the importance of secondary atmospheric formation. The diurnal variations of NPAHs were all influenced by the diurnal variations of PAHs, nitrogen dioxide, sunlight, and temperature. The daily inhalable exposure to the six NPAHs in the tunnel was much higher than the roadside values in the warm season but only slightly higher than those in the cold season.