Development of a sequential supercritical fluid extraction method for the analysis of nitrated and oxygenated derivatives of polycyclic aromatic hydrocarbons in urban aerosols

Investigation of PAHs, nitrated PAHs and oxygenated PAHs in PM10 urban aerosols. A comprehensive data analysis

Polycyclic aromatic compounds (PACs) in particulate matter contribute considerably to the health risk of air pollution. As such, we have optimized a method to determine the levels of polycyclic aromatic hydrocarbons, especially nitrated and oxygenated polycyclic aromatic hydrocarbons, in samples of PM₁₀ particulate matter using microwave-assisted extraction (MAE) and gas chromatography coupled to a triple quadrupole mass spectrometer (GC-MS/MS). The proposed method was applied to the analysis of real samples collected in the urban area of Ciudad Real (Spain) during one year. The median total concentrations of eighteen PAHs (∑PAHs) and seven OPAHs (∑OPAHs) were 0.54 and 0.23 ng m^-3, respectively, with the corresponding value for NPAH (∑NPAHs) being 0.03 ng m^-3 (only detected in 40% of samples). A clear seasonal trend was observed, with higher levels in the cold season and lower in the warm season for ∑PAHs. The same effect was observed for ∑OPAHs, which exhibited a median concentration of 0.72 ng m^-3 in the cold season and 0.10 ng m^-3 in the warm season, and for ∑NPAH, which exhibited a median of 0.04 ng m^-3 in the cold season but were not detected in the warm season. Molecular diagnostic ratios and PCA (principal component analysis) showed a predominantly traffic origin for PACs. The sources of PAHs also depend on meteorological conditions and/or atmospheric reactions, as confirmed by means of statistical analysis. The ∑OPAH/∑PAH and ∑NPAH/∑PAH ratios were higher in the cold season than the warm season, thus suggesting that PAH derivatives originated from primary combustion emission sources together with their parent PAHs. The concentration range found for benzo(a)pyrene was 0.006-0.542 ng m^-3, which is below the threshold value of 1 ng m^-3 established in European legislation as the annual average value. The lifetime lung risk from inhalation of PM₁₀-bound PACs was estimated to be six cancer cases per million people using the World Health Organization method.

Ambient air levels and health risk assessment of benzo(a)pyrene in atmospheric particulate matter samples from low-polluted areas: application of an optimized microwave extraction and HPLC-FL methodology

A new methodology involving a simple and fast pretreatment of the samples by microwave-assisted extraction and concentration by N2 stream, followed by HPLC with fluorescence detection, was used for determining the concentration of benzo(a)pyrene (BaP) in atmospheric particulate matter (PM10 fraction). Obtained LOD, 1.0 × 10(-3) ng/m(3), was adequate for the analysis of benzo(a)pyrene in the samples, and BaP recovery from PAH in Fine Dust (PM10-like) certified reference material was nearly quantitative (86%). The validated procedure was applied for analyzing 115 PM10 samples collected at different sampling locations in the low-polluted area of Extremadura (Southwest Spain) during a monitoring campaign carried out in 2011-2012. BaP spatial variations and seasonal variability were investigated as well as the influence of meteorological conditions and different air pollutants concentrations. A normalized protocol for health risk assessment was applied to estimate lifetime cancer risk due to BaP inhalation in the sampling areas, finding that around eight inhabitants per million people may develop lung cancer due to the exposition to BaP in atmospheric particulates emitted by the investigated sources.

Determination of oxygenated and native polycyclic aromatic hydrocarbons in urban dust and diesel particulate matter standard reference materials using pressurized liquid extraction and LC-GC/MS

The objective of this study was to develop a novel analytical chemistry method, comprised of a coupled high-performance liquid chromatography-gas chromatography/mass spectrometry system (LC-GC/MS) with low detection limits and high selectivity, for the identification and determination of oxygenated polycyclic aromatic hydrocarbons (OPAHs) and polycyclic aromatic hydrocarbons (PAHs) in urban air and diesel particulate matter. The linear range of the four OPAHs, which include 9,10-anthraquinone, 4H-cyclopenta[def]phenanthrene-4-one, benzanthrone, and 7,12-benz[a]anthraquinone, was 0.7 pg-43.3 ng with limits of detection (LODs) and limits of quantification (LOQs) on the order of 0.2-0.8 and 0.7-1.3 pg, respectively. The LODs in this study are generally lower than values reported in the literature, which can be explained by using large-volume injection. The recoveries of the OPAHs spiked onto glass fiber filters using two different pressurized liquid extraction (PLE) methods were in the ranges of 84-107 and 67-110 %, respectively. The analytical protocols were validated using the following National Institute of Standards and Technology standard reference materials: SRM 1649a (Urban Dust), SRM 1650b (Diesel Particulate Matter), and SRM 2975 (Diesel Particulate Matter, Industrial Forklift). The measured mass fractions of the OPAHs in the standard reference materials (SRMs) in this present study are higher than the values from the literature, except for benzanthrone in SRM 1649a (Urban Dust). In addition to the OPAHs, 44 PAHs could be detected and quantified from the same particulate extract used in this protocol. Using data from the literature and applying a two-sided t test at the 5 % level using Bonferroni correction, significant differences were found between the tested PLE methods for individual PAHs. However, the measured mass fractions of the PAHs were comparable, similar to, or higher than those previously reported in the literature.

Effects of humidity and [NO3]/[N2O5] ratio on the heterogeneous reaction of fluoranthene and pyrene with N2O5/NO3/NO2

Atmospheric 2-nitrofluoranthene (2-NFL) and 2-nitropyrene (2-NPY) were two important nitro-polycyclic aromatic hydrocarbons (NPAHs). Especially, 2-NFL was recognized to be the most abundant particle-associated NPAH (Ramdahl et al., 1986). In previous studies, these two products were observed in the gas-phase reaction between N2O5/NO3/NO2 and their parent polycyclic aromatic hydrocarbons (PAHs), while the heterogeneous reaction generated other nitro-PAH isomers (1, 3, 7, 8-NFL and 1-NPY) (Atkinson et al. 1990). To clarify the possible reasons for this difference, the heterogeneous reactions of suspended fluoranthene (FL) and pyrene (PY) particles under different relative humidity (RH; 0.5%-43%) and [NO3]/[N2O5] ratios were carried out. Under low humidity (0.5% RH) or a relatively high ratio of [NO3]/[N2O5], 2-NFL and 2-NPY were observed as the major nitro-FL isomers for the first time in the heterogeneous reaction. Decreasing the humidity or increasing the [NO3]/[N2O5] ratio in the reaction essentially increases the concentration radio of [NO3(g)]/[NO2(+)(aq)] on the particle surface (NO2(+) is derived from the ionization of N2O5). Thus, it can be concluded that under different atmospheric conditions, the change of [NO3(g)]/[NO2(+)(aq)] in the particle surface has an influence on the product distribution of FL and PY in the atmosphere. The experimental results provide evidence for the heterogeneous formations of particle-bound 2-NFL and 2-NPY. However, relative to the gas-phase formation, they will be negligible in the real atmosphere. 2-NFL and 2-NPY observed in the ambient particles should mainly derive from deposition of gas-phase reactions. Additionally, this study also clarifies the reason for different nitro-PAHs isomers observed between gas and particulate reactions.

Atmospheric reactions of 9,10-anthraquinone

The probably carcinogenic compound 9,10-anthraquinone is mainly existing in the atmosphere in the particulate phase and is often detected and measured among other oxygenated PAHs in atmospheric samples. Its fate, once released or formed in the atmosphere, still remains unknown. In this work, heterogeneous chemical oxidation processes of 9,10-anthraquinone were investigated with ozone (O3), nitrogen dioxide (NO2) and hydroxyl radical (OH). The study of 9,10-anthraquinone adsorbed on silica particles showed no reactivity with O3 and NO2. On the other hand, the reaction with OH radicals was observed and led to the formation of 1-hydroxy-9,10-anthraquinone, another oxidation product recognized as possibly carcinogenic to humans. This study showed that reactions with ozone and nitrogen dioxide are unlikely to contribute to atmospheric degradation of 9,10-anthraquinone, whereas reactions with OH radicals could be involved in 9,10-anthraquinone degradation processes, even if such reaction is probably very slow under ambient conditions.

Polycyclic aromatic hydrocarbons study in atmospheric fine and coarse particles using diagnostic ratios and receptor model in urban/industrial region

Atmospheric fine and coarse particles were collected in Teflon filters in three cities of the region of the Lower Sinos River Basin of Rio Grande do Sul in the year 2010. The filters were Soxhlet extracted, and 14 priority PAHs were analyzed using a gas chromatograph coupled to a mass spectrometer (GC/MS). The principal emission sources of these compounds were assessed by using diagnostic ratios and receptor model: positive matrix factorization (PMF 3.0) of the US Environmental Protection Agency. The results of PAHs concentration for the studied year showed significant levels of high molecular weight (HMW) PAH, Ind, and BghiP, in PM2.5 in the winter season, showing the influence of mobile sources. The application of receptor model PMF 3.0 revealed that the main sources of PAHs were vehicle fleet (both diesel and gasoline), followed by coal combustion, wood combustion, and resuspension of dust. The results of the receptor modeling are in agreement with the data obtained by the ratio diagnostic.

Determination of nitro-polycyclic aromatic hydrocarbons in atmospheric aerosols using HPLC fluorescence with a post-column derivatisation technique

The objective of this study was to develop an efficient and sensitive analytical protocol for the determination of nitrated polycyclic aromatic hydrocarbons (NPAHs) in aerosol samples. The separation of 16 NPAH (mono-and dinitro-PAH) was achieved by reversed-phase high-performance liquid chromatography (HPLC) followed by on-line reduction of the NPAHs to their corresponding amino polycyclic aromatic hydrocarbons (APAHs) and quantification by fluorescence detection. The main factors affecting the on-line reduction efficiency, such as the flow rate, the temperature, the position and packing of the reduction column were evaluated and optimised. The optimal conditions obtained were: packing of the reduction column with Pt-Al(2)O(3); a reduction column oven temperature of 90 degrees C; a flow rate of 0.8 mL min(-1). The resulting detection limits of the method ranged between 0.06 (2 NN) and 1.25 microg L(-1) (1.8 DNN), with an uncertainty of about 6%. The lifetime of the reduction column was identical to that of a typical analytical column. This analytical method was applied to particulate matter samples collected during December 2005 and August 2006 in Strasbourg (Alsace, eastern France). The NPAH concentrations observed for this urban site showed that the compounds are more abundant during winter (average of 534 pg m(-3)) than during summer (average of 118 pg m(-3)). 1-Nitropyrene was the predominant NPAH species, independent of season.

Sources, fate, and toxic hazards of oxygenated polycyclic aromatic hydrocarbons (PAHs) at PAH-contaminated sites

In this paper we show that oxygenated polycyclic aromatic hydrocarbons (oxy-PAHs) are important cocontaminants that should be taken into account during risk assessment and remediation of sites with high levels of PAHs. The presented data, which have been collected both from our own research and the published literature, demonstrate that oxy-PAHs are abundant but neglected contaminants at these sites. The oxy-PAHs show relatively high persistency and because they are formed through transformation of PAHs, their concentrations in the environment may even increase as the sites are remediated by methods that promote PAH degradation. Furthermore, we show that oxy-PAHs are toxic to both humans and the environment, although the toxicity seems to be manifested through other effects than those known to be important for polycyclic aromatic compounds in general, that is, mutagenicity and carcinogenicity. Finally, we present data that support the hypothesis that oxy-PAHs are more mobile in the environment than PAHs, due to their polarity, and thus have a higher tendency to spread from contaminated sites via surface water and groundwater. We believe that oxy-PAHs should be included in monitoring programs at PAH-contaminated sites, even if a number of other toxicologically relevant compounds that may also be present, such as nitro-PAHs and azaarenes, are not monitored. This is because oxy-PAH levels are difficult to predict from the PAH levels, because their environmental behavior differs substantially from that of PAHs, and oxy-PAHs may be formed as PAHs are degraded.

Development of analytical methods for polycyclic aromatic hydrocarbons (PAHs) in airborne particulates: a review

In the present work, the different sample collection, pretreatment and analytical methods for polycyclic aromatic hydrocarbons (PAHs) in airborne particulates is systematacially reviewed, and the applications of these pretreatment and analytical methods for PAHs are compared in detail. Some comments on the future expectation are also presented.

Cavity ring-down spectroscopy for detection in liquid chromatography: extension to tunable sources and ultraviolet wavelengths

In earlier studies, it was demonstrated that the sensitivity of absorbance detection in liquid chromatography (LC) can be improved significantly by using cavity ring-down spectroscopy (CRDS). Thus far, CRDS experiments have been performed using visible laser light at fixed standard wavelengths, such as 532 nm. However, since by far most compounds of analytical interest absorb in the ultraviolet (UV), it is of utmost importance to develop UV-CRDS. In this study, as a first step towards the deep-UV region, LC separations with CRDS detection (using a previously described liquid-only cavity flow cell) at 457 and 355 nm are reported for standard mixtures of dyes and nitro-polyaromatic hydrocarbons (nitro-PAHs), respectively. For the measurements in the blue range a home-built optical parametric oscillator (OPO) system, tunable between 425 and 478 nm, was used, achieving a baseline noise of 2.7 x 10(-6) A.U. at 457 nm, improving upon the sensitivity of conventional absorbance detection (typically around 10(-4) A.U.). An enhancement of the sensitivity can be seen at 355 nm as well, but the improvement of the baseline noise (1.3 x 10(-5) A.U.) is much less pronounced. The sensitivity at 355 nm is limited by the quality of the UV-CRDS mirrors that are currently available: whereas the ring-down times as obtained at 457 nm are around 70-80 ns for the eluent, they are only 20-25 ns at 355 nm. Critical laser characteristics for LC-CRDS measurements, such as pulse length and mode structure, are given and prospects for going to shorter wavelengths are discussed.

Analysis of nitrated polycyclic aromatic hydrocarbons

Many nitrated polycyclic aromatic hydrocarbons (NPAH) that are present in low concentrations in the environment and in emission sources have been shown to be mutagenic and/or carcinogenic. This paper reviews the current methods of analysis of these compounds with the emphasis on NPAH measurements in ambient particulate matter samples.

Nitrated Polycyclic Aromatic Hydrocarbons in the Environment: Formation, Occurrences and Analysis

A review is presented on the formation and occurrence in the atmosphere of nitrated polycyclic aromatic hydrocarbons. Some analytical methodologies (covering various matrices) are also considered.