In this work, we developed and optimized a method for the analysis of PAHs and nitro-PAHs in atmospheric particulate matter (PM) samples by using thermal desorption gas chromatography coupled with ...electron ionization single quadrupole mass spectrometry (TD-GC-(EI)-MS). The method uses thermal desorption from a PM on a filter sample as means of sample introduction to a column and obviates the need for complex extraction procedures, which are time-consuming and require environmentally unfriendly solvents. Moreover, the possibility of systematic errors is minimized and a significantly smaller amount of sample is required compared to traditional techniques requiring a pre-extraction step (approx. 10-times). Thirteen PAHs and three nitro-PAHs were used during method development. Although Tenax cartridges are typically used to capture volatile pollutants from the air, we found that glass-wool liner is the most suitable trap for the examined analytes after desorption from a quartz filter. Among the various instrument parameters which were tested and optimized, TD desorption flow and hold time, and temperature of the cooled injection system (CIS) proved to be most critical. We also found out that the matrix effect is especially pronounced in the case of high PM loadings, which should be kept in mind when planning the analysis. After the optimization, standard reference materials (ERM-CZ100 and NIST 1648a) were used for partial method validation and finally, real PM10 and PM2.5 samples from two Slovenian cities were successfully analyzed.
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•Simultaneous PAH and nitro-PAH determination in ambient PM without extraction.•Thermal desorption gas chromatography with electron ionization mass spectrometry.•Nitro-PAHs are successfully analyzed with TD-GC-(EI)-MS for the first time.•Much smaller amount of sample is needed compared to traditional methods.•Green method is suited for a better time resolution and SOA formation studies.
Phenols, and especially their nitrated analogues, are ubiquitous pollutants and known carcinogens which have already been linked to forest decline. Although nitrophenols have been widely recognized ...as harmful to different aquatic and terrestrial organisms, we could not find any literature assessing their toxicity to terrestrial plants. Maize (monocot) and sunflower (dicot) were exposed to phenolic pollutants, guaiacol (GUA) and 4-nitroguaiacol (4NG), through a hydroponics system under controlled conditions in a growth chamber. Their acute physiological response was studied during a two-week root exposure to different concentrations of xenobiotics (0.1, 1.0, and 10 mM). The exposure visibly affected plant growth and the effect increased with increasing xenobiotic concentration. In general, 4NG affected plants more than GUA. Moreover, sunflower exhibited an adaptive response, especially to low and moderate GUA concentrations. The integrity of both plant species deteriorated during the exposure: biomass and photochemical pigment content were significantly reduced, which reflected in the poorer photochemical efficiency of photosystem II. Our results imply that 4NG is taken up by sunflower plants, where it could enter a lignin biosynthesis pathway.
Methylnitrocatechols (MNCs) are secondary organic aerosol (SOA) tracers and major contributors to atmospheric brown carbon; however, their formation and aging processes in atmospheric waters are ...unknown. To investigate the importance of aqueous-phase electrophilic substitution of 3-methylcatechol with nitronium ion (NO2 +), we performed quantum calculations of their favorable pathways. The calculations predicted the formation of 3-methyl-5-nitrocatechol (3M5NC), 3-methyl-4-nitrocatechol (3M4NC), and a negligible amount of 3-methyl-6-nitrocatechol (3M6NC). MNCs in atmospheric PM2 samples were further inspected by LC/(−)ESI-MS/MS using commercial as well as de novo synthesized authentic standards. We detected 3M5NC and, for the first time, 3M4NC. In contrast to previous reports, 3M6NC was not observed. Agreement between calculated and observed 3M5NC/3M4NC ratios cannot unambiguously confirm the electrophilic mechanism as the exclusive formation pathway of MNCs in aerosol water. However, the examined nitration by NO2 + is supported by (1) the absence of 3M6NC in the ambient aerosols analyzed and (2) the constant 3M5NC/3M4NC ratio in field aerosol samples, which indicates their common formation pathway. The magnitude of error one could make by incorrectly identifying 3M4NC as 3M6NC in ambient aerosols was also assessed, suggesting the importance of evaluating the literature regarding MNCs with special care.
Nitroaromatic compounds (NACs) as important constituents of atmospheric humic-like substances (HULIS) and brown carbon (BrC) affect the Earth's climate and pose a serious environmental hazard. We ...investigated seasonal size-segregated NACs in aerosol samples from the urban background environment in Ljubljana, Slovenia. Total concentrations of twenty NACs in PM15.6 were on average from 0.51 ng m−3 (summer) to 109 ng m−3 (winter), and contributed the most to submicron aerosols (more than 74%). Besides 4-nitrocatechol (4NC) as the prevailing species, methylnitrocatechols (MNCs) and nitrophenols (NPs), we reported on some very rarely mentioned, but also on five novel NACs (i.e., 3H4NBA: 3-hydroxy-4-nitrobenzoic acid, 3MeO4NP: 3-methoxy-4-nitrophenol, 4Et5NC: 4-ethyl-5-nitrocatechol, 3Et5NC: 3-ethyl-5-nitrocatechol and 3MeO5NC: 3-methoxy-5-nitrocatechol). Concentrations of 3MeO5NC, 4Et5NC and 3Et5NC were enhanced during cold seasons, contributing up to 11% to total NAC in winter. In cold season, NAC size distributions were characterized with the peaks in the broader size range of 0.305–1.01 μm (accumulation mode), with 4NC and alkyl-nitrocatechols (∑(M/Et)NC) as the most abundant, followed by 4-nitrosyringol, nitrophenols and nitroguaiacols. In spring, a pronounced peak of ∑(M/Et)NC was observed in the accumulation mode (0.305–0.56 μm) as well as in the coarse one. A strong correlation of all NACs with ∑(M/Et)NC and levoglucosan indicates that primary emissions of wood burning were the most important source of NACs, but their secondary formation (e.g., aqueous-phase at higher ambient RH) in cold season could also be a significant one. In warmer season, NACs may be mostly derived from traffic-related aromatic VOCs. The contribution of NACs to the light absorption of the aqueous extracts was up to 10-times higher (contribution to Abs365 up to 31%) than their mass contributions to WSOC (up to 3%) of corresponding size-segregated aerosols, confirming that most of the identified NACs are strong BrC chromophores.
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•Extensive study on seasonal size-segregated nitroaromatics (NACs) in ambient aerosol.•Besides NACs usually reported, five novel NACs unambiguously quantified.•Seasonal variability of NACs with the highest contribution to submicron fraction.•Wood burning and traffic were the most important sources.•NACs contribution to WSOC light absorption up to 10-times higher than to WSOC mass.
Particulate matter (PM) is the major environmental pollutant. Its elemental composition is routinely monitored. Inductively coupled plasma mass spectroscopy (ICPMS) is commonly applied after a PM ...sample has been digested by an acid during a microwave treatment. In this case, sample preparation procedure is laborious, sometimes incomplete and produces toxic waste. In this paper we show that direct sample introduction to ICPMS by laser ablation (LA-ICPMS) is of huge advantage. Minimal quantity of a sample is required for the analysis (<1 cm2) and no chemical waste is produced. The study focused on the most universal and widely used quartz fibre filter samples and we show that LA-ICPMS can be successfully applied for the determination of the elemental composition of such samples. Some effort is, however, still needed to develop an autosampler for the LA-ICPMS system and to provide commercial matrix-matched standards for this application to be implemented in environment laboratories worldwide.
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•A new method for the direct analysis of PM on quartz fibre filters is presented.•No pre-treatment step is required and no waste chemicals are produced.•By LA-ICPMS, more than 20 elements can be measured at a time with low LODs.•Based on the homogeneity assessment less than 1 cm2 of filter sample is required.•LA-ICPMS proved itself at least as accurate as the current standard method.
The ultimate goal in the understanding of complex chemical processes is a complete description of the underlying reaction mechanism. In the present study and for this purpose, a novel experimental ...platform is introduced that builds upon electrochemistry capable of generating reactive intermediate species at the electrode surface. The atmospherically relevant nitration of catechols is taken as a case example. First, we confirm the recently proposed nitration mechanism, advancing the understanding of atmospheric brown carbon formation in the dark. We are able to selectively quantify aromatic isomers, which is beyond the limits of conventional electroanalysis. Second, we identify a new pathway of nitrocatechol hydroxylation, which proceeds simply by oxidation and the addition of water. This pathway can be environmentally significant in the dark aqueous-phase formation of secondary organic aerosols. Third, the developed methodology is capable of selectively detecting a wide range of nitroaromatics; a possible application in environmental monitoring is proposed.
Among all environmental pollutants, particulate matter (PM) poses the major threat to our health. These tiny airborne particles vary in shape and composition, which is reflected in their hazardous ...potential. The particles are small enough to penetrate deep into the lungs and even enter the bloodstream, causing severe diseases. Therefore, their regular monitoring is required. Toxic metals and other elements are often measured by regulatory agencies as well as in research laboratories, either to compare ambient concentrations with prescribed limit values or to study provenance of air pollution sources in order to target PM pollution mitigation strategies. The most established method for the determination of regulated Pb, Cd, As, Ni and other elements in PM is microwave digestion inductively coupled plasma mass spectrometry (MW/ICPMS), whereas X-ray fluorescence (XRF) techniques have also often been used, especially in research. In this review paper we critically assess these two and three other analytical techniques (i.e., LA-ICPMS, PIXE and INAA) for element determination in PM deposited on filter media. All aspects from sample treatment to measurement range and limitations, costs and waste management are considered. In conclusion we identify XRF and LA-ICPMS as two promising surface techniques for the analysis of a PM deposit on a filter, which could replace the laborious wet MW/ICPMS method, which is – considering its wide use, very incriminating to the environment. In short, EDXRF is the cheapest, simplest for use and already customized for PM samples, whereas LA-ICPMS is promising, but still needs some development in the direction of autosamplers and matrix-matched standards for calibration.
Airborne particulate matter (PM) is a vector of many toxic pollutants, including polyaromatic hydrocarbons (PAHs) and their derivatives. Especially harmful is the fine fraction (PM2.5), which ...penetrates deep into the lungs during inhalation and causes various diseases. Amongst PM2.5 components with toxic potential are nitrated PAHs (NPAHs), knowledge of which is still rudimentary. Three of the measured NPAHs (1-nitropyrene (1-nP), 9-nitroanthracene (9-nA), and 6-nitrochrysene (6-nC)) were detected in ambient PM2.5 from Ljubljana, Slovenia, along with thirteen non-nitrated PAHs. The highest concentrations of pollutants, which are closely linked with incomplete combustion, were observed in the cold part of the year, whereas the concentrations of NPAHs were roughly an order of magnitude lower than those of PAHs throughout the year. Further on, we have evaluated the toxicity of four NPAHs, including 6-nitrobenzoapyrene (6-nBaP), to the human kidney cell line, HEK293T. The most potent was 1-nP (IC50 = 28.7 µM), followed by the other three NPAHs, whose IC50 was above 400 or 800 µM. According to our cytotoxicity assessment, atmospheric 1-nP is the most harmful NPAH among the investigated ones. Despite low airborne concentrations of NPAHs in ambient air, they are generally considered harmful to human health. Therefore, systematic toxicological assessment of NPAHs at different trophic levels, starting with cytotoxicity testing, is necessary in order to accurately evaluate their threat and adopt appropriate abatement strategies.
Aromatic compounds contribute significantly to the budget of atmospheric pollutants and represent considerable hazard to living organisms. However, they are only rarely included into atmospheric ...models which deviate substantially from field measurements. A powerful experimental-simulation tool for the assessment of the impact of low- and semi-volatile aromatic pollutants on the environment due to their atmospheric aqueous phase aging has been developed and introduced for the first time. The case study herein reveals that remote biotopes might be the most damaged by wet urban guaiacol-containing biomass burning aerosols. It is shown that only after the primary pollutant guaiacol has been consumed, its probably most toxic nitroaromatic product is largely formed. Revising the recent understanding of atmospheric aqueous phase chemistry, which is mostly concerned with the radical nitration mechanisms, the observed phenomenon is mainly attributed to the electrophilic nitrogen-containing reactive species. Here, their intriguing role is closely inspected and discussed from the ecological perspective.
Kohlrabi (Brassica oleracea L. var. gongylodes L.) was biofortified with selenium (Se), as selenite and selenate, and iodine (I), as iodide and iodate, and their combinations through foliar spraying, ...to study absorption of these elements by the plants, separately and in combination. The effects on selected physiological and morphological traits and optical characteristics were monitored. Treatments with Se positively affected total chlorophylls and carotenoids, and leaf stomata dimensions. Addition of I decreased total chlorophylls and increased anthocyanins. In reflectance spectra of the leaves, specific colour regions differed significantly due to the different treatments. Reflectance in the UV correlated positively with Se and I contents of the leaves, which indicated lower demand for production of phenolic compounds. Differences in reflectance in UV part of the spectra could be a consequence of changes in the cuticle. The Se and I levels increased markedly in leaves and tubers, without loss of biomass or yield. Se had antagonistic effects on accumulation of I in leaves. The similar levels of Se and I in the leaves and tubers suggest that the transport of both elements in these plants occurs from the leaves to the tubers through the phloem. According to the Se and I contents in the kohlrabi tubers, biofortification with both elements simultaneously is feasible for human nutrition.
•I and Se affect the biochemical and anatomical characteristics of treated kohlrabi.•I and Se increase reflectance in different part of the spectra.•Increased reflectance in UV part could be due to changes in the cuticle.•It is feasible to add I and Se to kohlrabi simultaneously.
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