Nitrated Polycyclic Aromatic Hydrocarbons Research Articles

Existence, removal and transformation of parent and nitrated polycyclic aromatic hydrocarbons in two biological wastewater treatment processes

Polycyclic aromatic hydrocarbons (PAHs) and nitrated polycyclic aromatic hydrocarbons (NPAHs) are pollutants commonly present in the environment. Some NPAHs are considered to have more severe toxic effects than their parent PAHs. The existence of 16 PAHs (678.5–3817.8 ng/L in wastewater, 499.9 ng/g-1239.6 ng/g in sludge) and 5 NPAHs (175.8–1392.4 ng/L in wastewater, 483.5 ng/g-2763.1 ng/g in sludge) was determined in a biological wastewater treatment plant (WWTP) in Qingdao, China. Anthracene and naphthalene were the predominant PAHs, and 2-nitrofluorene and 9-nitroanthracene were the predominant NPAHs. Petroleum, liquid fossil fuel combustion and exhaust emissions were the main sources of PAHs and NPAHs in this study. In both the sequencing batch reactor/moving-bed biofilm (SBR/MBBR) and the anaerobic-anoxic-aerobic (A2O) process, low-molecular-weight PAHs were mainly removed through volatilization and biodegradation/biotransformation. Meanwhile, the removal of high-molecular-weight PAHs and NPAHs depended on adsorption and sedimentation. The transformation from PAHs to NPAHs mainly occurred in the aqueous-phase, especially in summer and that was confirmed by mass flow and ratios variation. Overall, the removal capacity of the A2O process for PAHs and NPAHs was better than that of the SBR/MBBR process. Tertiary treatment processes had little effect or even a negative effect on the removal of PAHs and NPAHs.

Determination of nitrated polycyclic aromatic hydrocarbons in particulate matter 2.5 by laser ionization mass spectrometry using an on-line chemical-reduction system.

Nitrated polycyclic aromatic hydrocarbons (NPAHs) were separated by gas chromatography (GC) and were introduced into a reactor consisting of an inner-seal Y-connector for the on-line chemical reduction of NPAH using hydrazine monohydrate as a chemical reducing agent. The reduced forms of amino polycyclic aromatic hydrocarbons (APAHs) were then determined by multiphoton ionization time-of-flight mass spectrometry (MPI/TOF-MS) using a femtosecond laser as the ionization source. Three standard samples of NPAHs, i.e., 9-nitroanthracene (9-NANT), 3-nitrofluoranthene (3-NFLU), and 1-nitropyrene (1-NPYR), were confirmed to be completely reduced to the corresponding APAHs, i.e., 9-aminoanthracene (9-AANT), 3-aminofluoranthene (3-AFLU), and 1-aminopyrene (1-APYR). The sensitivity of the method was improved by 2-8 fold by converting the NPAHs to APAHs. This analytical technique was applied to a sample extracted from PM2.5 collected in Fukuoka. The signal enhancement and background reduction by the chemical reaction resulted in the NPAHs in the actual sample being more efficiently measured, and the concentrations of 9-NANT, 3-NFLU, and 1-NPYR were determined to be 25, 305, and 217 pg m-3, respectively.

Spatiotemporal variation of atmospheric nitrated polycyclic aromatic hydrocarbons in semi-arid and petrochemical industrialized Lanzhou City, Northwest China.

Polyurethane foam-based passive air sampler (PUF-PAS) and passive dry deposition sampler (PAS-DD) were adopted, for thefirst timeever in China, to investigate the atmospheric levels and spatial-temporal distributions of air burdens and dry deposition fluxes of 12 nitrated polycyclic aromatic hydrocarbons (NPAHs) during winter and summer seasons in a multiple site field campaign in a petrochemical industrialized capital city in Northwest China. The results showed that the highest air concentration and dry deposition fluxes of ∑12NPAHs occurred at a heavy traffic site among 18 sampling sites in both winter and summer season. The lowest air concentration and dry deposition fluxes were observed at the background site. The mean concentrations of ∑12NPAHs in the ambient air were 8.6 ± 8.1ngm-3 in winter and 15 ± 11ngm-3 in summer. The mean dry deposition fluxes of ∑12NPAHs were 1.8 × 103 ± 1.9 × 103ng(m2day)-1 in winter and 1.4 × 103 ± 1.3 × 103ng(m2day)-1 in summer, respectively. The total concentration of 12 NPAHs was mainly dominated by 1-nitro-naphthalene (1N-NAP) and 2-nitro-naphthalene(2N-NAP) in air, accounting for 32% in winter and 45% in summer of ∑12NPAHs. 7-Nitro-benzo [a] anthracene (7N-BaA) made the largest contribution to dry deposition fluxes of ∑12NPAHs, accounting for 28% in winter and 24% in summer. The ratios of ∑12NPAHs/∑15pPAHs (parent polycyclic aromatic hydrocarbons) were calculated to identify potential sources of NPAHs across the city. The results revealed that the main atmospheric air concentration and dry deposition fluxes of 12 NPAHs could be attributed to the primary emissions in winter and the secondary reaction formation in summer. The sources of primary emissions could be traced back to petrochemical, steel mills, as well as aluminum industries in winter and vehicle exhaust in summer. Higher ∑12NPAH/∑15pPAH concentration ratios in summer indicated that the oxidation of pPAHs contributed to the secondary formation of NPAHs via atmospheric chemical reactions in this petrochemical industrialized mountain-valley city.

Photochemical degradation of nitrated PAHs in snow

Nitrated polycyclic aromatic hydrocarbons (NPAHs) are derived from PAHs, which are ubiquitous in the aqueous and atmospheric environments, and whose mutagenicity and carcinogenicity are much higher than that of PAHs. Therefore, their environmental transformation has attracted a lot of attention. In the present study, direct and indirect UV photodegradation kinetics of two NPAHs (1-nitropyrene and 1,8-dinitropyrene) in snow were investigated. It was found that the kinetics followed the pseudo-first-order kinetics with the photochemical degradation rate 0.3773 h−1 for 48.98 nM 1-NP and 0.3653 h−1 for 41.00 nM 1,8-DNP. Photosensitizers (hydrogen peroxide and nitrate) promoted the photodegradation of NPAHs. Considering the lower temperature and less microorganisms in snow environment, the photodegradation can be a key factor in determining the fate of NPAHs in sunlit surface snow. To the best of our knowledge, this is the first report on the photodegradation of NPAHs in snow.

Role of Human Aldo-Keto Reductases in the Metabolic Activation of the Carcinogenic Air Pollutant 3-Nitrobenzanthrone.

3-Nitrobenzanthrone (3-NBA) is a potent mutagen and suspected human carcinogen detected in diesel exhaust particulate and ambient air pollution. It requires metabolic activation via nitroreduction to promote DNA adduct formation and tumorigenesis. NAD(P)H:quinone oxidoreductase 1 (NQO1) has been previously implicated as the major nitroreductase responsible for 3-NBA activation, but it has recently been reported that human aldo-keto reductase 1C3 (AKR1C3) displays nitroreductase activity toward the chemotherapeutic agent PR-104A. We sought to determine whether AKR1C isoforms could display nitroreductase activity toward other nitrated compounds and bioactivate 3-NBA. Using discontinuous enzymatic assays monitored by UV-HPLC, we determined that AKR1C1-1C3 catalyze three successive two-electron nitroreductions toward 3-NBA to form the reduced product 3-aminobenzanthrone (3-ABA). Evidence of the nitroso- and hydroxylamino- intermediates were obtained by UPLC-HRMS. Km, kcat, and kcat/ Km values were determined for recombinant AKR1C and NQO1 and compared. We found that AKR1C1, AKR1C3, and NQO1 have very similar apparent catalytic efficiencies (8 vs 7 min-1 mM-1) despite the higher kcat of NQO1 (0.058 vs 0.012 min-1). AKR1C1-1C3 possess a Km much lower than that of NQO1, which suggests that they may be more important than NQO1 at the low concentrations of 3-NBA to which humans are exposed. Given that inhalation represents the primary source of 3-NBA exposure, we chose to evaluate the relative importance of AKR1C1-1C3 and NQO1 in human lung epithelial cell lines. Our data suggest that the combined activities of AKR1C1-1C3 and NQO1 contribute equally to the reduction of 3-NBA in A549 and HBEC3-KT cell lines and together represent approximately 50% of the intracellular nitroreductase activity toward 3-NBA. These findings have significant implications for the metabolism of nitrated polycyclic aromatic hydrocarbons and suggest that the hitherto unrecognized nitroreductase activity of AKR1C enzymes should be further investigated.

Characterization and Risk Assessment of Atmospheric PM2.5 and PM10 Particulate-Bound PAHs and NPAHs in Rwanda, Central-East Africa.

Exposure to airborne particulates is estimated as the largest cause of premature human mortality worldwide and is of particular concern in sub-Saharan Africa where emissions are high and data are lacking. Particulate matter (PM) contains several toxic organic species including polycyclic aromatic hydrocarbons (PAHs) and nitrated PAHs (NPAHs). This study provides the first characterization and source identification for PM10- and PM2.5-bound PAHs and NPAHs in sub-Saharan Africa during a three-month period that spanned dry and wet seasons at three locations in Rwanda. The 24-h mean PM2.5 and PM10 concentrations were significantly higher in the dry than the wet season. PAH and NPAH concentrations at the urban roadside site were significantly higher than the urban background and rural site. Source identification using diagnostic ratio analysis and principal component analysis (PCA) revealed diesel and gasoline-powered vehicles at the urban location and wood burning at the rural location as the major sources of PAHs and NPAHs. Our analysis demonstrates that PM concentrations and lifetime cancer risks resulting from inhalation exposure to PM-bound PAHs and NPAHs exceed World Health Organization safe limits. This study provides clear evidence that an immediate development of emission control measures is required.

Quantification of nitrated-polycyclic aromatic hydrocarbons in atmospheric aerosol samples with in-injection port thermal desorption-gas chromatography/ negative chemical ionization mass spectrometry method

In-injection port thermal desorption (TD) was extended in determination of particulate phase nitrated-polycyclic aromatic hydrocarbons (N-PAHs) on filter samples coupled with a gas chromatography/negative ion chemical ionization-mass spectrometry (GC/NCI-MS). The experimental and analytical parameters were optimized with standard testing and ambient samples. Fourteen of the most abundant N-PAHs in ambient airs were included for their quantification. A desorption temperature of 280 °C for 10 min was sufficient to transfer entire target compounds from injection port to the analytical system. Good linearity (R2 >0.995) on the calibrations for each analyte was achieved. The limit of detections (LODs) ranged from 46.5 to 152.3 pg per filter sample, which were 4–66% better than solvent extraction (SE) approach. Method precision, repeatability and reproducibility, determined by replicate analyses of calibration standards and ambient samples, were less than 6% for target compounds. Validation of the method were conducted with two batches of a total of 30 ambient aerosol-loaded filters using our TD and the traditional SE approaches. Reasonably good agreement (R2 = 0.98) by the two methods was demonstrated for most of N-PAHs, except for 9-nitrophenanthrene and 6-nitrobenzo(a)pyrene. The in-injection port TD can improve laboratory efficiency and reduce solvent-based costs for the measurement of N-PAHs.

Study on formation of nitrated polycyclic aromatic hydrocarbons from different roasting condition in coffee.

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) are organic, carcinogenic and mutagenic compounds that originate from the reaction of PAHs with NOx and OH radicals. In this study, an analytical method was developed, for the determination of seven nitro-PAHs and the method was applied to quantify the nitro-PAHs, in coffee model systems, prepared with coffee beans produced from three distinct locations and under various roasting conditions. Also, experiments were performed to study the effect of adding various amino acids on the formation of nitro-PAHs. The free radicals produced, were quantified by electron spin resonance (ESR), to assess their correlation with the formed nitro-PAHs. After extraction and cleanup, the nitro-PAHs in coffee were analyzed by gas chromatography/mass selective detection. In all heated coffee model systems, the addition of the amino acids, significantly increased the nitro-PAHs compared to the control. The ESR results were consistent with previous outcomes on the formation of nitro-PAHs.

Comparison of polycyclic aromatic compounds in air measured by conventional passive air samplers and passive dry deposition samplers and contributions from petcoke and oil sands ore

Abstract. Conventional passive air samplers (PAS) and passive dry deposition samplers (PAS-DD) were deployed along a 90 km south–north transect at five sites in the Athabasca oil sands region (AOSR) during October to November 2015. The purpose was to compare and characterize the performance of the two passive sampling methods for targeted compounds across a range of site types. Samples were analyzed for polycyclic aromatic compounds (PACs), nitrated polycyclic aromatic hydrocarbons (NPAHs), and oxygenated PAHs (OPAHs). ΣPAC and ΣNPAH concentrations were highest in PAS and PAS-DD samplers at site AMS5, which is the closest sampling site to surface mining and upgrading facilities. The OPAHs were elevated at site AMS6, which is located in the town of Fort McMurray, approximately 30 km south of the main mining area. PAS-DD was enriched relative to PAS in particle-associated target chemicals, which is consistent with the relatively more open design of PAS-DD intended to capture particle-phase (and gas-phase) deposition. Petroleum coke (petcoke) (i.e., the carbonaceous byproduct of bitumen upgrading) and oil sands ore (i.e., the material mined in open-pit mines from which bitumen is extracted) were assessed for their potential to be a source of PACs to air in the oil sands region. The ore samples contained ∼ 8 times and ∼ 40 times higher ΣPACs concentrations (dry weight basis) than delayed and fluid petcoke, respectively. The residue analysis of ore and petcoke samples also revealed that the chemical 4-nitrobiphenyl (4-NBP) can be used to track gas-phase emissions to air. A comparison of chemical residues in ore, petcoke, and air samples revealed that the ore is likely a major contributor to volatile PACs present in air and that both ore and petcoke are contributing to the particle-associated PACs in air near open-pit mining areas. The contribution of petcoke particles in passive air samples was also confirmed qualitatively using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS).

Novel method for in situ investigation into graphene quantum dots effects on the adsorption of nitrated polycyclic aromatic hydrocarbons by crop leaf surfaces

Nitrated polycyclic aromatic hydrocarbons (NPAHs) are PAH derivatives with more toxic effects to ecosystem, and the partitioning of NPAHs in crop system constitutes the potential exposure to human health through the dietary pathway. In the present study, a novel method for in situ detection of 9-nitroanthracene (9-NAnt) and 3-nitrofluoranthene (3-NFla) adsorbed onto the leaf surfaces of living soybean and maize seedlings was established based on the fiber-optic fluorimetry combined with graphene quantum dots (GQDs) as a fluorescent probe. The detection limits for the in situ quantification of the two adsorbed NPAHs ranged from 0.8 to 1.6 ng/spot (spot represents determination unit, 0.28 cm2 per spot). Using the novel method, the effects of GQDs on the adsorption of individual 9-NAnt and 3-NFla by the living soybean and maize leaf surfaces were in situ investigated. The presence of GQDs altered the adsorption mechanism from the sole film diffusion to the combination of film diffusion and intra-particle diffusion, and shortened the time required to achieving adsorption equilibrium by 15.8–21.7%. Significant inter-species and inter-chemical variability existed in terms of the equilibrated adsorption capacity (qe) with the sequence of soybean > maize and 3-NFla > 9-NAnt. The occurrence of GQDs enlarged the qe values of 9-NAnt and 3-NFla by 22.8% versus 28.7% for soybean, and 16.2% versus 20.3% for maize, respectively, which was largely attributed to GQDs-induced expansion to the surface area for adsorbing NPHAs and the stronger electrostatic interaction between the -NO2 of NPAH molecules and the functional groups (e.g., -COOH, -OH) of GQDs outer surfaces. And, the varied enhancement degrees in the order of 3-NFla > 9-NAnt might be explained by the steric effects that resulted in the easier accessibility of -NO2 of 3-NFla to the outer surface of GQDs. Summarily, the GQDs increased the retention of NPAHs on crop leaf surfaces, potentially threatening the crop security.

Characterization of PM2.5-bound nitrated and oxygenated polycyclic aromatic hydrocarbons in ambient air of Langfang during periods with and without traffic restriction

PM2.5-bound nitrated polycyclic aromatic hydrocarbons (nPAHs) and oxygenated polycyclic aromatic hydrocarbons (oPAHs) in ambient air were analysed in Langfang during periods with and without traffic restriction. During traffic restriction periods, 20% of gasoline vehicles and all diesel vehicles were restricted to travel within downtown. The 2-nitrofluoranthene/1-nitropyrene ratios obtained during the sampling periods implied that direct emission, especially from diesel vehicles, is the main source for the nPAHs in Langfang. The primary sources of nPAHs and oPAHs, including diesel vehicle emissions and gasoline vehicle emissions, were reduced in the P2 period. Thus, the concentrations of 1-nitropyrene, 3-nitrobenzanthrone, 9-nitrophenanthrene, 2-nitrofluorene, 7-nitrobenz[a]anthracene, 9,10-anthraquinone and benzanthrone were reduced up to 73.3% under this traffic restriction policy. However, the concentrations of 2-nitrofluoranthene and 9-fluorenone formed from gas phase reactions increased slightly. Meanwhile, the chemical profiles of nPAHs and oPAHs changed with traffic fleet variation, and cancer risk levels decreased under the traffic restriction policy. Hence, the traffic restriction policy did effect the ambient concentrations of nPAHs and oPAHs.

Development of Prediction Models for the Mutagenicity of Nitrated-PAHs Based on Multiple Linear Regression

Nitrated polycyclic aromatic hydrocarbons (NPAHs) are a family of toxicants wide spreading in the environment. In this study, quantitative structural-activity relationship (QSAR) models were developed for the prediction of mutagenicity of NPAHs. Structural descriptors were screened and multiple linear regression (MLR) were performed for developing the QSAR models. Totally 1706 descriptors were obtained based on structural optimization using density functional theory (DFT) at the CPCM-B3LYP/6-311+g (d,p) theoretical level in water. External and leave-one-out cross validation were performed to confirm the predictive ability and the models robustness, respectively. Totally 33 QSAR models were generated using one to eight descriptors, in which the model consisting of 4 descriptors, including Eelec, SIC2, RDF040v and GATS4v, has the highest correlation coefficient (R2=0.8755). This study will contribute to not only the prediction of the mutagenicity of NPAHs, but also the development of QSAR modeling methods of toxicants.

Dispersive liquid–liquid microextraction for the simultaneous determination of parent and nitrated polycyclic aromatic hydrocarbons in water samples

A new method for simultaneous extraction and quantification of 6 nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) and 16 parent polycyclic aromatic hydrocarbons (PAHs) in water matrices was optimized and validated. The extraction procedure was based on dispersive liquid-liquid microextraction technique, followed by gas chromatography-mass detection. The optimum conditions of extraction (volume of the extraction solvent, dispersive solvents and amount of salt) were selected using central composite design. The best results were found by using 200 μL of acetonitrile as dispersive solvent, 60 μL of chloroform as extraction solvent, and 10% (w/v) NaCl. Excellent linearity was observed in the range of 10–150 ng L−1 with correlation coefficients (r2) ranging between 0.9996 and 0.9999 for nitro-PAHs and in the range of 5–150 ng L−1 with r2 ranging from 0.9998 to 1.000 for PAHs. The limits of detection for the nitro-PAHs studied ranged from 0.82 to 3.37 ng L−1, whereas for PAHs ranged from 0.62 to 3.48 ng L−1. The intra- and inter-day precisions for nitro-PAHs were in the range of 0.45 to 19.54% and 0.43 to 19.62%, respectively, and for PAHs ranged between 0.45 to 17.42% and 0.38 to 18.97%, respectively. The proposed method was successfully applied in analyses of groundwater, sea, rain water and river water, being appropriate for routine analyses.

Analysis of trace-level nitrated polycyclic aromatic hydrocarbons in water samples by solid-phase microextraction with gas chromatography and mass spectrometry.

A solid-phase microextraction coupled with gas chromatography and mass spectrometry method has been developed for the determination of ten nitrated polycyclic aromatic hydrocarbons in water samples. Five different kinds of commerical fibers were used to compare the extraction efficiency, including 65μm polydimethylsiloxane/divinylbenzene, 100μm polydimethylsiloxane, 30μm polydimethylsiloxane, 7μm polydimethylsiloxane, and 85μm polyacrylate fibers. Five factors were also selected to optimize conditions, including extraction temperature, time, stirring speed, salt concentration, and headspace volume. Taguchi design was applied to design the experiments and obtain the best parameters. The results show that 65μm polydimethylsiloxane/divinylbenzene fiber directly immersed into aqueous solution for 35min at 55°C with a constant stirring rate of 1150rpm were the optimal conditions. Under these conditions, the limits of quantification were 0.007-0.063μg/L, and the relative standard deviation based on six replicates ranged from 2.8 to 9.5%. The spiked recoveries ranged from 69.1 to 110.1%. Intra- and inter day relative standard deviations at three concentration levels were less than 12%, and the recoveries were 66.4-111.5%. The proposed method is reliable for analyzing nitrated polycyclic aromatic hydrocarbons in different water samples.

Chemical speciation, including polycyclic aromatic hydrocarbons (PAHs), and toxicity of particles emitted from meat cooking operations

We assessed the chemical properties and oxidative stress of particulate matter (PM) emissions from underfired charbroiled meat operations with and without the use of aftertreatment control technologies. Cooking emissions concentrations showed a strong dependence on the control technology utilized, with all emission rates showing decreases with the control technologies compared to the baseline testing. The organic acids profile was dominated by the saturated nonanoic, myristic, palmitic, and stearic acids, and the unsaturated oleic, elaidic, and palmitoleic acids. Cholesterol was also found in relatively high concentrations. Lower and medium-weight polycyclic aromatic hydrocarbons (PAHs) were the dominant species for all cooking experiments. Heavier PAHs were also detected in high concentrations, especially in the particle-phase. For the nitrated PAH emissions (nitro-PAHs), low molecular weight compounds dominated the cooking emissions. Under the present experimental conditions, the heterocyclic aromatic amines (HAAs) showed very low concentrations, which suggests these species are rarely formed in meat cooking PM. The most efficient control technology for reducing the majority of the toxic pollutants was the electrostatic precipitator, which resulted in total emissions reductions on the order of 95%, 79%, 90%, 96%, 90%, and 94%, respectively, for particle-phase PAHs, gas-phase PAHs, particle-phase nitro-PAHs, gas-phase nitro-PAHs, particle-phase HAAs, and gas-phase HAAs compared to the baseline testing. Our experiment showed that cooking aerosol contained higher levels of prooxidants in the particle-phase and the corresponding vapors contained higher levels of electrophiles. Overall, the use of control technologies reduced the redox and electrophilic activities of cooking PM.

Gasoline Particulate Filters as an Effective Tool to Reduce Particulate and Polycyclic Aromatic Hydrocarbon Emissions from Gasoline Direct Injection (GDI) Vehicles: A Case Study with Two GDI Vehicles.

We assessed the gaseous, particulate, and genotoxic pollutants from two current technology gasoline direct injection vehicles when tested in their original configuration and with a catalyzed gasoline particulate filter (GPF). Testing was conducted over the LA92 and US06 Supplemental Federal Test Procedure (US06) driving cycles on typical California E10 fuel. The use of a GPF did not show any fuel economy and carbon dioxide (CO2) emission penalties, while the emissions of total hydrocarbons (THC), carbon monoxide (CO), and nitrogen oxides (NOx) were generally reduced. Our results showed dramatic reductions in particulate matter (PM) mass, black carbon, and total and solid particle number emissions with the use of GPFs for both vehicles over the LA92 and US06 cycles. Particle size distributions were primarily bimodal in nature, with accumulation mode particles dominating the distribution profile and their concentrations being higher during the cold-start period of the cycle. Polycyclic aromatic hydrocarbons (PAHs) and nitrated PAHs were quantified in both the vapor and particle phases of the PM, with the GPF-equipped vehicles practically eliminating most of these species in the exhaust. For the stock vehicles, 2-3 ring compounds and heavier 5-6 ring compounds were observed in the PM, whereas the vapor phase was dominated mostly by 2-3 ring aromatic compounds.

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.

Insights into the error bypass of 1-Nitropyrene DNA adduct by DNA polymerase ι: A QM/MM study

The error bypass mechanism of DNA polymerase ι toward N-(deoxyguanosin-8-yl)-1-aminopyrene adduction was studied by using quantum mechanics/molecular mechanics method. The most favorable mechanism highlights three elementary steps: proton transfer from dC to dATP, phosphoryl transfer, and deprotonation of dAMP. The phosphoryl transfer step was found to be rate-determining. The calculated average barrier (23.8kcalmol−1) is in accordance with the experimental value (21.5kcalmol−1). Electrostatic influence analysis indicates that residues Asp126 and Lys207 significantly suppress the error bypass while Glu127 facilitates the process. These results highlight the origins of the mutagenicity of nitrated polycyclic aromatic hydrocarbons in molecular detail.

An Integrated Ultrasonic Extraction and Cleanup Procedure for Determining PAHs and NPAHs in Ambient Air Particulates

An analytical method was developed for the determination of 16 polycyclic aromatic hydrocarbons (PAHs) and 15 nitrated PAHs (NPAHs) in ambient air particulates by applying an in-house built integrated ultrasonic extraction device followed by gas chromatography coupled with mass spectrometry (GC–MS). After integrated ultrasonic extraction in the extraction cell, the extract solution was released through the opened valve into a purification tube containing adsorbents for purification, then concentrated and analyzed by GC–MS. Compared to previously reported methods, such as Soxhlet extraction and accelerated solvent extraction, this method has greatly shortened the pretreatment time, simplified the pretreatment process, and reduced experimental costs. A series of experimental conditions, including extraction solvent, adsorbents, and elution solvent, were systematically studied and optimized. Owing to its superior ability in purifying particulate matter samples, a combination of flower-like-texture Mg–Al layered double oxide (Mg–Al-LDO) and silica gel was selected as the optimized adsorbent. To our knowledge, few reports on this combination of materials exist. The limits of detection (LODs) of 16 PAHs and 15 NPAHs ranged from 0.018 to 1.7 and from 0.035 to 0.60 ng g−1, respectively. Limits of quantifications (LOQs) were from 0.061 to 5.7 and 0.12 to 2.0 ng g−1 for 16 PAHs and 15 NPAHs, respectively. Recoveries at three spiked concentration levels ranged from 81.6 to 116%. The relative standard deviations (RSDs) were less than 6.5% in all cases. The proposed analytical method was proved to be practical and suitable technique for PAH and NPAH analysis in real ambient air particulate samples.

Urban air pollution and health risks of parent and nitrated polycyclic aromatic hydrocarbons in two megacities, southwest China

Ambient air pollution in China has a significant spatial variation due to the uneven development and different energy structures. This study characterized ambient pollution of parent and nitrated polycyclic aromatic hydrocarbons (PAHs) through a 1-year measurement in two megacities in southwest China where regional PM2.5 levels were considerably lower than other regions. Though the annual average BaP levels in both two cities were below the national standard of 1.0 ng/m3, however, by taking other PAHs into account, PAHs pollution were serious as indicated by high BaP equivalent concentrations (BaPEQ) of 3.8 ± 2.6 and 4.4 ± 1.9 ng/m3, respectively. Risk assessment would be underestimated by nearly an order of magnitude if only using BaP in risk assessment compared to the estimation based on 26 PAHs including 16 priority and 10 non-priority isomers targeted in this study. Estimated incremental lifetime cancer risks (ILCR) were comparable at two cities, at about 330–380 persons per one million, even though the mass concentrations were significantly different. Nitrated PAHs showed distinct temporal and site differences compared to the parent PAHs. High cancer risks due to inhalation exposure of PAHs and their polar derivatives in the low PM2.5-pollution southwest China suggest essential and effective controls on ambient PAHs pollution in the region, and controls should take potential health risks into account instead of solely mass concentration.