Polycyclic Aromatic Compounds Emissions Research Articles

Emission characteristic, spatial distribution, and health risk of polycyclic aromatic compounds (PAHs, NPAHs, and OPAHs) from light-duty gasoline and diesel vehicles based on on-road measurements

Vehicle exhaust is the primary source of polycyclic aromatic compounds (PACs). Real road tests using a portable vehicle measurement system on light-duty gasoline vehicles and light-duty diesel trucks were conducted to investigate gas- and particle-phase polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs (NPAHs), and oxy-PAHs (OPAHs) in vehicle exhaust with different emission standards, fuel types, and altitudes. The results showed that with the tightening of emission standards, the overall emission factors (EFs) of PACs decreased. Compared with China V diesel vehicles, the emissions of PAHs, OPAHs, and NPAHs from China VI diesel vehicles were 75.1 %, 84.4 %, and 61.2 % lower, respectively. With a ∼100 m increase in altitude, the EFs of PAHs, OPAHs, and NPAHs of diesel vehicles increased 1.88, 1.92, and 1.59 times due to incomplete combustion. In addition, the EFs of PAHs and OPAHs in gasoline vehicles were lower than those in diesel vehicles. In contrast, the proportion of PAHs with highly toxic components, such as dibenzo[a,h]anthracene (DahA) and benzo[a]pyrene (BaP), and the EFs of gas-phase NPAHs in gasoline vehicles were higher than those in diesel vehicles. Furthermore, the emissions of 1,8-DNP from diesel vehicles cannot be disregarded. 1,8-DNP was the main gas-phase NPAHs emitted by China VI and China V diesel vehicles, accounting for 49.3 % and 26.0 %, respectively. Moreover, gas-phase PACs contributed more to the EFs than particle-phase PACs, whereas particle-phase PACs have greater toxic effects. Although the EFs of PAHs are more than 100 times those of NPAHs, the toxic equivalent concentrations (TEQBaP) of PAHs in diesel and gasoline vehicles were approximately 6.5 times and 35 times those of NPAHs. The spatial distribution characteristics revealed that PACs emissions were mainly concentrated in urban areas and highways, and the differences in the toxicity of PACs emissions between different cities depended on the proportion of diesel vehicles. The average TEQBaP of PAHs and NPAHs in Haidong, Haibei, Huangnan, Hainan, Guoluo, and Yushu was 8.42 μg/m3 and 0.36 μg/m3, respectively, while those of Xining and Haixi were 0.24–0.29 μg/m3 and 0.09–0.108 μg/m3 higher, respectively. This study provides a comprehensive understanding of the emission characteristics, health risks, and spatial distribution of PACs from diesel and gasoline vehicle PACs in urban areas.

Air-soil cycling of oxygenated, nitrated and parent polycyclic aromatic hydrocarbons in source and receptor areas

Polycyclic aromatic hydrocarbons (PAHs) and their oxygenated and nitrated derivatives, OPAHs and NPAHs, are semivolatile air pollutants which are distributed and cycling regionally. Subsequent to atmospheric deposition to and accumulation in soils they may re-volatilise, a secondary source which is understudied.We studied the direction of air-soil mass exchange fluxes of 12 OPAHs, 17 NPAHs, 25 PAHs and one alkylated PAH in two rural environments being influenced by the pollutant concentrations in soil and air, by season, and by land cover. The OPAHs and NPAHs in samples of topsoil, of ambient air particulate and gas phases and in the gas-phase equilibrated with soil were analysed by GC-APCI-MS/MS. The pollutants soil burdens show a pronounced seasonality, a winter maximum for NPAHs and PAHs and a summer maximum for OPAHs. One order of magnitude more OPAH and parent PAH are found stored in forest soil than in nearby grassland soil. Among a number of 3–4 ring PAHs, the OPAHs benzanthrone and 6H-benzo(c,d)pyren-6-one, and the NPAHs 1- and 2-nitronaphthalene, 9-nitrophenanthrene and 7-nitrobenz(a)anthracene are found to re-volatilise from soils at a rural background site in central Europe in summer. At a receptor site in northern Europe, net deposition of polycyclic aromatic compounds (PACs) prevails and re-volatilisation occurs only sporadic.Re-volatilisation of a number of PACs, including strong mutagens, from soils in summer and even in winter indicates that long-range atmospheric transport of primary PAC emissions from central Europe to receptor areas might be enhanced by secondary emissions from soils.

A 150 years record of polycyclic aromatic compounds in the Sihailongwan Maar Lake, Northeast China: impacts of socio-economic developments and pollution control.

The geochemical composition of sediment cores can serve as a proxy for reconstructing past human and nature-driven environmental and climatic changes. We investigated the temporal variation in the concentrations and fluxes of polycyclic aromatic compounds (PACs) which include polycyclic aromatic hydrocarbons (PAHs), oxygenated PAHs, and azaarenes in the Sihailongwan Maar Lake and found that they remained low before 1950. The PAC concentrations and fluxes increased substantially since 1950, which was in good agreement with the fast socio-economic development, industrialization, and associated growth in fossil fuel consumption in China, particularly since the 1980s. After 2010, the PAC fluxes decreased, which was consistent with the implementation of air pollution control policies in China at that time. The concentration ratios of the sums of low to high molecular weight PAHs (LMW-PAHs/HMW-PAHs), benzo[e]pyrene/benzo[a]pyrene, and benzo[a]anthracene-7,12-dione/benzo[a]anthracene all decreased from bottom to top of the sediment core, reflecting the rapidly increasing contribution of emissions derived from high-temperature fossil fuel combustion (energy, transport and industry) to the PAC emissions in recent times at the expense of biomass burning. In addition, these data reflect the increasing local sources of PACs in more recent times because of the enhanced human activities in the area surrounding the Maar lake. Our results demonstrate that PAC fluxes and concentrations in sediment cores reflect the regional and national economic development and the efficiency of pollution control measures.

Atmospheric emissions estimation of polycyclic aromatic compounds from an oil sands tailings pond using passive air samplers

A mapping study targeting emissions of polycyclic aromatic compounds (PACs) from an oil sands tailings pond was undertaken in the Athabasca Oil sands Region (AOSR). Ten passive air samplers comprising polyurethane foam (PUF) disks were deployed around the perimeter of Suncor Tailings Pond 2/3 for a five-week period to generate time-integrated concentrations in air for PACs, which included ∑unsubstituted polycyclic aromatic hydrocarbons (PAHs), ∑alkylated PAHs (alk-PAHs), and ∑dibenzothiophenes (DBTs) (both unsubstituted and alkylated). Concentrations in air ranged from 13 to 70, 220–970, and 30–210 ng/m3, respectively, and were elevated in samplers downwind of the tailings pond. PAC emissions to air from the pond were estimated using only the air-side concentration information by applying a simplified Gaussian dispersion model and found to be 896 μg/m2/day. ∑alk-PAHs and ∑DBTs had the highest contribution to the total PAC fluxes (79% and 16%, respectively). This flux estimate for PACs is equivalent to 460 kg on an annual basis and 35 000 kg/year when scaled to represent all tailings ponds in the region. The results generally agree with fluxes estimated from coupled high volume air sampling data and tailings pond water concentrations from the same field study but which are complicated due to uncertainties associated with the use of pure water Henry's Law values for tailings pond water as well as the potential for surface oily films on the tailings ponds to impact water-air exchange of PACs. Overall, these findings support the use of relatively simple and electricity-free PUF disk samplers for mapping and estimating emissions from area sources such as tailings ponds, using only air-side concentration information.

Fugitive emissions of polycyclic aromatic compounds from an oil sands tailings pond based on fugacity and inverse dispersion flux calculations.

Alberta's oil sands tailings ponds are suspected to be a source of fugitive emissions of polycyclic aromatic compounds (PACs) to the atmosphere. Here we report, for the first time, fluxes of 6 parent and 21 alkylated PACs based on the measured co-located air and water concentrations using a two-film fugacity-based model (FUG), an inverse dispersion model (DISP) and a simple box model (BOX). Air samples were collected at the Suncor Tailings Pond 2/3 using a high volume air sampler from the "pond" and towards the pond ("non-pond") directions separately. Mean ∑27PACs in air from the "pond" direction was greater than the "non-pond" direction by a factor of 17. Water-air fugacity ratio of 20PACs quantifiable in water indicated net volatilization from water. Dispersion and box model results also indicated upward fluxes of 22PACs. Correlation between the estimated flux results of BOX and DISP model was statistically significant (r=0.99 and p<0.05), and correlation between FUG and DISP results ranged from 0.54 to 0.85. In this first-ever assessment of PAC fluxes from tailings pond, the three models confirmed volatilization fluxes of PACs indicating Suncor Tailings Pond 2/3 is a source of PAC emissions to the atmosphere. This study addressed a key data gap identified in the Joint Oil Sands Monitoring Emissions Inventory Compilation Report (Government of Alberta and Canada, 2016) which is the lack of consistent real-world tailings pond fugitive emission monitoring of organic chemicals. Our findings highlight the need for measurements from other tailings ponds to determine their overall contribution in releasing PACs to the atmosphere. This paper presents a practical method for estimating PAC emissions from other tailings ponds, which can provide a better understanding of these fugitive emissions, and thereby help to improve the overall characterization of emissions in the oil sands region.

Polycyclic aromatic compounds (PACs) in the Canadian environment: Sources and emissions.

Twenty-five years after the first look at polycyclic aromatic compounds (PACs) in Canada, this article presents current knowledge on Canadian PAC emission sources. The analysis is based on national inventories (the National Pollutant Release Inventory (NPRI) and the Air Pollutant Emissions Inventory (APEI)), an analysis of Canadian forest fires, and several air quality model-ready emissions inventories. Nationally, forest fires continue to dominate PAC emissions in Canada, however there is uncertainty in these estimates. Though forest fire data show a steady average in the total annual area burned historically, an upward trend has developed recently. Non-industrial sources (home firewood burning, mobile sources) are estimated to be the second largest contributor (∼6-8 times lower than forest fires) and show moderate decreases (25%-65%) in the last decades. Industrial point sources (aluminum production, iron/steel manufacturing) are yet a smaller contributor and have seen considerable reductions (90%+) in recent decades. Fugitive emissions from other industrial sources (e.g. disposals by the non-conventional oil extraction and wastewater sectors, respectively) remain a gap in our understanding of total PAC emissions in Canada. Emerging concerns about previously unrecognized sources such as coal tar-sealed pavement run-off, climate change are discussed elsewhere in this special issue. Results affirm that observations at the annual/national scale are not always reflective of regional/local or finer temporal scales. When determining which sources contribute most to human and ecosystem exposure in various contexts, examination at regional and local scales is needed. There is uncertainty overall in emissions data stemming in part from various accuracy issues, limitations in the scope of the various inventories, and inventory gaps, among others.

Emission characteristics and temporal variation of PAHs and their derivatives from an ocean-going cargo vessel

Polycyclic aromatic hydrocarbons (PAHs), nitro- (NPAHs) and oxy-derivatives (OPAHs) are of considerable concern due to their toxicity and carcinogenic hazards. Ships are recognized as an important emission source of these compounds. Marine diesel oil (MDO) and heavy fuel oil (HFO) are the two most commonly used fuels. The emission characteristics and toxicities of PM2.5-bound PAHs, NPAHs and OPAHs due to HFO and MDO combustion in atypical ocean-going vessel were investigated. The EF variability of polycyclic aromatic compounds (PACs) varied considerably with the fuel formulation (HFO and MDO) and engine loading (20%–100%). The concentration of ΣPACs was 0.63 mg/kWh for MDO and ranged from 2.14 to 9.80 mg/kWh for HFO. Compared to HFO-20%, the EFs of ΣPAHs, ΣNPAHs and ΣOPAHs from MDO-20% were reduced by 97%, 77% and 73%, respectively. As identified through the coefficient of divergence, the profile of HFO-20% was notably different from those under the other three engine loadings for HFO. In addition, the emissions of ΣPAHs and ΣOPAHs showed a significant correlation with PM2.5, while they were relatively weak for ΣNPAHs. However, the CO and PAC emissions were not highly correlated. Furthermore, the BaPeq-ΣPAHs values were 0.010 mg/g for MDO and ranged from 0.092 mg/g to 0.306 mg/g for HFO, and the reduction ranged from 89% to 97% by substituting MDO for HFO. These data highlight the importance of improving fuel quality in close proximity to port areas and are useful for enhancing relevant databases.

Polycyclic aromatic compounds (PAHs, oxygenated PAHs, nitrated PAHs and azaarenes) in soils from China and their relationship with geographic location, land use and soil carbon fractions

The assessment of risks arising from polycyclic aromatic compounds (PACs), particularly from the polar PACs [azaarenes (AZAs), oxygenated PAHs (OPAHs), nitrated PAHs (NPAHs)] requires us to understand the drivers of their spatial distribution. We determined the concentrations of 29 PAHs, 4 AZAs, 15 OPAHs and 11 NPAHs and their relationships with land use (urban vs. rural and forest vs. agriculture), climate (Qinghai-Tibetan plateau, temperate, sub tropical and tropical) and three C fractions (soil organic C, char, soot) in 36 mineral topsoils (0–5 cm) of China. The average concentrations±standard deviation of the Σ29PAHs, Σ16PAHs, Σ4AZAs, Σ15OPAHs and Σ11NPAHs were 352 ± 283, 206 ± 215, 5.7 ± 3.7, 108 ± 66.8 and 3.2 ± 3.4 ng g−1, respectively. PAH, OPAH, NPAH and AZA concentrations were frequently not correlated within or across the regions reflecting different sources and turnover of PAHs and their derivatives. Temperate urban soils showed the highest and tropical rural soils the lowest concentrations of PACs. Forest soils had higher PACs concentrations than agricultural soils. Longitude correlated positively with the ∑29PAHs concentrations, because of increasing emissions of PAHs from East to West. The tropical and plateau regions with the lowest PAH concentrations, were dominated by low molecular weight PAHs (LMW-PAHs) with LMW/high molecular weight (HMW)-PAHs ratios >1, while the other two climatic regions with more industrial sites showed the opposite. Latitude correlated with NPAHs likely because of enhanced formation by photochemical reactions during transport in the atmosphere. The concentrations of the ∑29PAHs, ∑4AZAs, ∑15OPAHs, ∑11NPAHs and their individual components were only occasionally correlated with those of carbon fractions (soil organic C, soot and char) suggesting a small role of soil C pool properties in driving PACs concentrations. Our results demonstrate that the strongest drivers of PACs concentrations are land use and distance to PAC emission sources followed by climate and size and properties of the soil organic C pool.

Emission of oxygen, sulphur and nitrogen containing heterocyclic polyaromatic compounds from lignite combustion

Maritza–East Bulgarian lignite was burnt in an atmospheric fluidised bed pilot plant, laboratory scale, at conditions close to the real ones used in power generation (850 °C, 3% oxygen excess, limestone with ratio Ca/S=3.25) in order to analyse in a qualitative way the polycyclic aromatic compounds (PAC) emissions. The samples studied were collected by flowing an aliquot of the combustion gases through a sampling system, consisting of cyclones, nylon and teflon filters and an XAD-2 resin. Before sample analysis by gas chromatography with mass spectrometry detection (GC-MS), ligand exchange chromatography on PdCl 2 impregnated silicagel was used to separate PAC with different heteroatoms, concretely, oxygen (O-PAC), sulphur (S-PAC) and nitrogen (N-PAC) of the polycyclic aromatic hydrocarbon (PAH) fraction. For all samples studied, the highest PAC emissions were due to compounds containing three and four aromatic rings in their structure. The O-PAC constituted carbonyl-containing compounds Z(O)=−18 to −22, with carbon numbers n=13–17; anthraquinones, Z(O 2)=−20, n=14 and 15, phenols, phenanthroaldehyde, and furans, Z(O)=−22, n=16, where concentration of quinones far predominated. A peculiar group of C 19–C 23 alkylbenzones, with a maximum at C 20–C 21, was found as well. Dibenzothiophenes, phenanthrothiophene and benzonaphthothiophenes, Z(S)=−16 to −20, were the major constituents of the S-PAC, while the N-PAC were determined at trace levels.

Formation and Lifetime of Polycyclic Aromatic Compounds During a National-Scale Transient Pollution Episode

Concentrations of selected particle-borne parent, alkylated, oxygenated, and nitrated polycyclic aromatic compounds (PACs) have been monitored before, during, and after a large national-scale wood-burning pollution episode (5 November 1994 and 4-5 November 1995). Toluene-modified supercritical CO 2 was used for the extraction of PACs from the collected particulate matter. Analysis was performed using an on-line multidimensional chromatographic technique using coupled liquid and gas chromatography (LC-GC) with loop interface. Comparison of average urban and wood smoke particulate PAC profiles identified a marked change in the ambient PAC profile for the pollution episode period, caused by the change in emission source from predominantly vehicular to wood smoke. A chemical mass balance model has been used to calculate the relative contributions from general urban and wood smoke PAC sources and from them, an estimation of the atmospheric life-time of the PAC emissions has been made. When monitored with 24 hr resolution in 1994, the concentrations of quinone-PAC oxidation products were found to peak 1 day after the maximum concentrations in the parent PAH were recorded, consistent with photochemically driven reactions with singlet state molecular oxygen. When concentrations were monitored on a more frequent basis in 1995, the concentrations of oxygenated species were seen to begin increasing in concentration before sunrise but still peaking after the maximum concentrations of parent PAH were recorded. The nighttime rise in product PAC suggests dark reactions with ozone or the NO 3 radical also may be occurring.

Cytotoxic and mutagenic effects, particle size and concentration analysis of diesel engine emissions using biodiesel and petrol diesel as fuel.

Diesel engine exhaust particles (DEP) contribute substantially to ambient air pollution. They cause acute and chronic adverse health effects in humans. Biodiesel (rapeseed oil methyl ester. RME) is used as a "green fuel" in several countries. For a preliminary assessment of environmental and health effects of RME, the particulate-associated emissions from the DEP of RME and common fossil diesel fuel (DF) and their in vitro cytotoxic and mutagenic effects were compared. A test tractor was fuelled with RME and DF and driven in a European standard test cycle (ECE R49) on an engine dynamometer. Particle numbers and size distributions of the exhausts were determined at the load modes "idling" and "rated power". Filter-sampled particles were extracted and their cytotoxic properties tested using the neutral red assay. Mutagenicity was tested using the Salmonella typhimurium/microsome assay. Despite higher total particle emissions, solid particulate matter (soot) in the emissions from RME was lower than in the emissions from DF. While the size distributions and the numbers of emitted particles at "rated power" were nearly identical for the two fuels, at "idling" DF emitted substantially higher numbers of smaller particles than RME. The RME extracts caused fourfold stronger toxic effects on mouse fibroblasts at "idling" but not at "rated power" than DF extracts. The extracts at both load modes were significantly mutagenic in TA98 and TA100. However, extracts of DF showed a fourfold higher mutagenic effect in TA98 (and twofold in TA100) than extracts of RME. These results indicate benefits as well as disadvantages for humans and the environment from the use of RME as a fuel for tractors. The lower mutagenic potency of DEP from RME compared to DEP from DF is probably due to lower emissions of polycyclic aromatic compounds. The higher toxicity is probably caused by carbonyl compounds and unburned fuel, and reduces the benefits of the lower emissions of solid particulate matter and mutagens from RME.