Diurnal variability of polycyclic aromatic compound (PAC) concentrations: Relationship with meteorological conditions and inferred sources

Alam, Mohammed S.; Keyte, Ian J.; Yin, Jianxin; Stark, Christopher; Jones, Alan M.; Harrison, Roy M.

doi:10.1016/j.atmosenv.2015.09.050

Cited by 50 publications

(20 citation statements)

References 34 publications

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“…The OPCs were deployed at two urban background locations in Birmingham. The first was the Birmingham Air Quality Supersite at Elms Road (BAQS; 52.4554 • N, 1.9286 • W), which is located on the University of Birmingham campus (Alam et al, 2015) and will hereafter be referred to as "Bham BAQS". The second site was the Tyburn Road air monitoring station, which is part of the UK Automatic Rural Urban Network (AURN), and will hereafter be referred to as "Bham Tyburn".…”

Section: Birmingham United Kingdommentioning

confidence: 99%

Effect of aerosol composition on the performance of low-cost optical particle counter correction factors

et al. 2020

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Abstract. There is considerable interest in using low-cost optical particle counters (OPCs) to supplement existing routine air quality networks that monitor particle mass concentrations. In order to do this, low-cost OPC data need to be comparable with particle mass reference instrumentation; however, there is currently no widely agreed upon methodology to accomplish this. Aerosol hygroscopicity is known to be a key parameter to consider when correcting particle mass concentrations derived from low-cost OPCs, particularly at high ambient relative humidity (RH). Correction factors have been developed that apply κ-Köhler theory to correct for the influence of water uptake by hygroscopic aerosols. We have used datasets of co-located reference particle measurements and low-cost OPC (OPC-N2, Alphasense) measurements, collected in four cities on three continents, to explore the performance of this correction factor. We provide evidence that the elevated particle mass concentrations, reported by the low-cost OPC relative to reference instrumentation, are due to bulk aerosol hygroscopicity under different RH conditions, which is determined by aerosol composition and, in particular, the levels of hygroscopic aerosols (sulfate and nitrate). We exploit measurements made in volcanic plumes in Nicaragua, which are predominantly composed of sulfate aerosol, as a natural experiment to demonstrate this behaviour in the ambient atmosphere; the observed humidogram from these measurements closely resembles the calculated pure sulfuric acid humidogram. The results indicate that the particle mass concentrations derived from low-cost OPCs during periods of high RH (>60 %) need to be corrected for aerosol hygroscopic growth. We employed a correction factor based on κ-Köhler theory and observed that the corrected OPC-N2 PM2.5 mass concentrations were within 33 % of reference measurements at all sites. The results indicated that a κ value derived in situ (using suitable reference instrumentation) would lead to the most accurate correction relative to co-located reference instruments. Applying a κ values from the literature in the correction factor also resulted in improved OPC-N2 performance, with the measurements being within 50 % of the reference values. Therefore, for areas where suitable reference instrumentation for developing a local correction factor is lacking, using a literature κ value can result in a reasonable correction. For locations with low levels of hygroscopic aerosols and low RH values, a simple calibration against gravimetric measurements (using suitable reference instrumentation) would likely be sufficient. Whilst this study generated correction factors specific for the Alphasense OPC-N2 sensor, the calibration methodology developed is likely amenable to other low-cost PM sensors.

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Section: Birmingham United Kingdommentioning

confidence: 99%

Effect of aerosol composition on the performance of low-cost optical particle counter correction factors

et al. 2020

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“…However, these ratios should be used with caution, because the degradation products of compounds may vary with time in the atmosphere 14 . Nitro-PAHs are formed directly from combustion processes such as those in diesel and gasoline engines, as well as by oxidants in the atmosphere through both gas-phase and heterogeneous reactions of PAHs, and are also useful as tracers for the identification of air pollution sources and photochemical pathways 15 , 16 . These pathways include reactions of the parent PAH with OH or NO 3 radicals in the gas phase, and with N 2 O 5 or HNO 3 when the parent PAH is in the aerosol phase 17 .…”

Section: Introductionmentioning

confidence: 99%

Concentration, source identification, and exposure risk assessment of PM2.5-bound parent PAHs and nitro-PAHs in atmosphere from typical Chinese cities

Liu

Lin

Syed

et al. 2017

Sci Rep

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Sixteen parent PAHs and twelve nitro-PAHs were measured in PM2.5 samples collected over one year (2013–2014) at nine urban sites in China. During the sampling period, concentrations of individual nitro-PAHs were one or two orders of magnitude lower than their parent PAHs. Typical seasonal variations in parent PAH concentrations, which increased 10- to 80- fold in winter compared to summer, were observed in this study. Conversely, the mean atmospheric concentrations of nitro-PAHs were similar in all four seasons, with the exception of 9-nitroanthracene (9n-Ant). Compared to other nitro-PAHs which were secondary formation products, 9n-Ant had a higher concentration and made up a larger proportion of total nitro-PAHs. Positive matrix factorization results indicated that 9n-Ant sources included biomass burning (20%), vehicle exhaust emissions (43%), and secondary formation (30%). Overall, the elevated concentrations of parent PAHs observed in winter correlated with the contribution from coal combustion at all sites, especially in north China (>80%). The contribution of secondary formation products to total nitro-PAHs was measured during the summer, and was especially high in the larger cities such as Shanghai (84%), Beijing (76%), Guangzhou (60%), and Chengdu (64%), largely due to the summer concentrations of parent PAHs were markedly lower than in winter.

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“…PC2 did not reveal additional PAH sources and confirmed inputs from the PP coal burning (Phe, Flu, and 9-Flu) and diesel exhaust (4-NBip, 1-and 2-NNap, 2+3-NFlt, Hu et al, 2013;Keyte et al, 2013;Alam et al, 2015). Moreover, PC2 revealed a 325 negative correlation of LMW PAHs, namely 4-NBip, 2-NNap, Phe, Flu, 1-NNap, 9-Flu, and Acy (in loading order) with https://doi.org/10.5194/acp-2020-142 Preprint.…”

Section: Adventdalenmentioning

confidence: 69%

Polycyclic aromatic hydrocarbons (PAHs), oxy- and nitro-PAHs in ambient air of Arctic town Longyearbyen, Svalbard

Drotikova¹,

Ali²,

Halse³

et al. 2020

Preprint

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Abstract. Polycyclic aromatic hydrocarbons (PAHs) are not declining in Arctic air despite reductions in their global emissions. In Svalbard, the Longyearbyen coal-fired power plant is considered to be one of the major local source of PAHs. Power plant stack emissions and ambient air samples, collected simultaneously 1 km (UNIS) and 6 km (Adventdalen) transect distance, were analyzed (gaseous and particulate phases separately) for 22 nitro-PAHs, 9 oxy-PAHs and 16 parent PAHs by GC/ECNI/MS and GC-MS/MS. Results confirm low level of PAH emissions (∑16 PAHs = 1.5 µg kg−1 coal) from the power plant. Phenathrene, 9,10-anthraquinone, 9-fluorenone, fluorene, fluoranthene, and pyrene accounted for 85 % of the plant emission (not including naphthalene). A dilution effect was observed for the transect ambient air samples, 1.26 ± 0.16 and 0.63 ± 0.14 ng m−3 sum all 47 PAH derivatives for UNIS and Adventdalen, respectively. The PAH profile was homogeneous for these recipient stations with phenathrene and 9-fluorenone being most abundant. Principal component analysis, in combination with PAH diagnostic ratios and literature data on different source-specific markers, confirmed coal combustion, gasoline, and diesel traffic as the predominant sources of PAHs. Secondary atmospheric formation of 9-nitroanthracene and 2+3-nitrofluoranthene was evaluated and concluded. Results also indicate that ambient PAH concentrations were affected by precipitation events, and specific humidity is an essential parameter influencing PAH scavenging from the air. The present study contributes important data which can be utilized to eliminate uncertainties in model predictions that aim to assess the extent and impacts of Arctic atmospheric contaminants.

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Diurnal variability of polycyclic aromatic compound (PAC) concentrations: Relationship with meteorological conditions and inferred sources

Cited by 50 publications

References 34 publications

Effect of aerosol composition on the performance of low-cost optical particle counter correction factors

Effect of aerosol composition on the performance of low-cost optical particle counter correction factors

Concentration, source identification, and exposure risk assessment of PM2.5-bound parent PAHs and nitro-PAHs in atmosphere from typical Chinese cities

Polycyclic aromatic hydrocarbons (PAHs), oxy- and nitro-PAHs in ambient air of Arctic town Longyearbyen, Svalbard

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