Gas-particle Partitioning Of Polycyclic Aromatic Hydrocarbons Research Articles

Polycyclic Aromatic Hydrocarbons in the Marine Atmosphere from the Western Pacific to the Southern Ocean: Spatial Variability, Gas/Particle Partitioning, and Source Apportionment.

The spatial variability of polycyclic aromatic hydrocarbons (PAHs) in the marine atmosphere contributes to the understanding of the global sources, fate, and impact of this contaminant. Few studies conducted to measure PAHs in the oceanic atmosphere have covered a large scale, especially in the Southern Ocean. In this study, high-volume air samples were taken along a cross-section from China to Antarctica and analyzed for gaseous and particulate PAHs. The data revealed the spatial distribution, gas-particle partitioning, and source contributions of PAHs in the Pacific, Indian, and Southern Oceans. The median concentration (gaseous + particulate) of ∑24PAHs was 3900 pg/m3 in the Pacific Ocean, 2000 pg/m3 in the Indian Ocean, and 1200 pg/m3 in the Southern Ocean. A clear latitudinal gradient was observed for airborne PAHs from the western Pacific to the Southern Ocean. Back trajectories (BTs) analysis showed that air masses predominantly originated from populated land had significantly higher concentrations of PAHs than those from the oceans or Antarctic continents/islands. The air mass origins and temperature have significant influences on the gas-particle partitioning of PAHs. Source analysis by positive matrix factorization (PMF) showed that the highest contribution to PAHs was from coal combustion emissions (52%), followed by engine combustion emissions (27%) and wood combustion emissions (21%). A higher contribution of PAHs from wood combustion was found in the eastern coastal region of Australia. In contrast, engine combustion emissions primarily influenced the sites in Southeast Asia.

Emission Characteristics of Gas-and Particle-Phase Polycyclic Aromatic Hydrocarbons from Cooking

Polycyclic aromatic hydrocarbons (PAHs) play a key role in the formation of secondary organic areole and ozone. This study sampled three commercial Chinese restaurants and a food plant in Shenzhen to analyze the emission characteristics of PAHs, especially the alkyl PAHs in both gas and particle phases. The results showed that the ρ(total PAHs)in the particle and gas phase were (1381.6±140.5) ng·m-3, (1030.2±116.4) ng·m-3, (908.3±111.9) ng·m-3, and (838.0±93.5) ng·m-3 in the food plant, Sichuan, Cantonese, and Zhejiang restaurants, respectively. More than 60% of the PAHs were distributed in the gas phase, especially the lower molecular weight PAHs (lower than Chrysene). The gas phase proportion of naphthalene was the highest, with over 75% of it distributed in the gas phase. However, the PAHs with a higher molecular weight than that of benzo(b)fluorescence were mainly distributed in the particle phase. The total concentration of alkyl PAHs emitted from cooking was much lower than that of the corresponding parent PAHs, and the distribution characteristics of alkyl PAHs were quite different from those of other emission sources. The linear fitting of lgKp and lgPL showed that the slopes of the three commercial restaurants ranged from -0.25 to -0.28, whereas for the food plant, the value was -0.18, which indicates that the gas-particle partitioning of PAHs were not in equilibrium.

Seasonal variations of atmospheric polycyclic aromatic hydrocarbons (PAHs) surrounding Chaohu Lake, China: Source, partitioning behavior, and lung cancer risk

The gas-particle partitioning, source, and lung cancer risk of atmospheric polycyclic aromatic hydrocarbons (PAHs) in different seasons were investigated in a megacity of China with coal dominating the energy structure over one year period. The total concentrations of 16 U.S. EPA priority PAHs (Σ16PAHs) were highest in winter (gaseous: 36.6 ± 1.89 ng m−3; PM phase: 16.9 ± 10.2 ng m−3) and lowest in summer (gaseous: 4.78 ± 1.48; PM phase: 2.28 ± 1.26), and followed the sequence of urban site > tourist site > rural site. In addition, rural site had higher particulate PAH concentrations in summer, autumn, and winter than other sites, primarily due to the extensive biomass burning. Low molecular weight (LMW) PAHs (2- and 3-ring PAHs) were the dominating compounds in gaseous phase, which was quite different from the high molecular weight (HMW) PAHs (4- to 6-ring PAHs) predominating in the particulate phase. The fractions of LMW PAHs showed a declining trend with the decrease of particle size for all seasons. The gas-particle partitioning of PAHs was controlled by organic carbon absorption and primarily influenced by the particle sizes. Petrogenic, traffic emission, biomass burning, and coal combustion were the main sources of atmospheric PAHs, which contributed to 33%, 35%, 32%, and 32% in spring, summer, autumn, and winter, respectively. The overall population attributable fraction (PAF) for lung cancer due to inhalation exposure to PAHs was 0.78‰ (interquartile range (IR) = 0.17–2.4‰), corresponding to the excess annual lung cancer incidence rates of 6.6 × 10−8, 1.2 × 10−8, and 2.0 × 10−7 for children, adolescents, and adults, respectively.

Distribution and gas-particle partitioning of polycyclic aromatic hydrocarbons over the East China Sea and Yellow Sea in spring: Role of atmospheric transport transition

To elucidate the variations in the East Asian monsoon system during seasonal changes and their impacts on continental outflow of polycyclic aromatic hydrocarbons (PAHs), sixteen integrated air samples were collected during a research cruise covering the Yellow Sea (YS) and East China Sea (ECS) in mid-spring of 2017. The concentrations of total suspended particle (TSP), aerosol-phase PAH fractions, ratios of organic to elemental carbon (OC/EC) and gas-particle partitioning of atmospheric PAHs exhibited clear regional differences associated with variations in the monsoon regime. The total concentrations of 16 USEPA priority PAHs (Σ16PAHs) varied from 3.11 to 13.4 ng/m3 throughout the cruise, with medium-to-high molecular weight (MW) PAHs more enriched over the YS and north ECS than the south ECS. Together with the relatively low gaseous PAH fraction over the YS and north ECS (78 ± 4%) relative to the south ECS (95 ± 13%), this result indicates the pattern of regional atmospheric transport. The ratio of organic to elemental carbon varied significantly between the south ECS (lower than 4) and the YS and north ECS (greater than 4), indicating contributions from vehicle emissions and coal combustion or biomass burning, respectively, following different atmospheric input pathways of carbonaceous aerosols, as supported by backward trajectory analysis. Considering the gas-particle partitioning of PAHs, soot adsorption was the main partitioning mechanism in the study region; while high-MW PAHs in the YS and north ECS were influenced by both absorption and adsorption. The Koa absorption model provided better predictions for high-MW PAHs when continental air masses prevailed, despite underestimating the partition coefficients (kp) of low-MW PAHs. Meanwhile, predicted kp for medium MW PAHs was better estimated over the YS and ECS when Ksa was included.

Emission characteristics for gaseous- and size-segregated particulate PAHs in coal combustion flue gas from circulating fluidized bed (CFB) boiler

The partitioning behavior of polycyclic aromatic hydrocarbons (PAHs) between gaseous and particulate phases from coal-fired power plants (CFPPs) is critically important to predict PAH removal by dust control devices. In this study, 16 US-EPA priority PAHs in gaseous and size-segregated particulate phases at the inlet and outlet of the fabric filter unit (FFs) of a circulating fluidized bed (CFB) boiler were analyzed. The partitioning mechanisms of PAHs between gaseous and particulate phases and in particles of different size classes were investigated. We found that the removal efficiencies of PAHs are 45.59% and 70.67–89.06% for gaseous and particulate phases, respectively. The gaseous phase mainly contains low molecular weight (LMW) PAHs (2- and 3-ring PAHs), which is quite different from the particulate phase that mainly contains medium and high molecular weight (MMW and HMW) PAHs (4- to 6-ring PAHs). The fractions of LMW PAHs show a declining trend with the decrease of particle size. The gas-particle partitioning of PAHs is primarily controlled by organic carbon absorption, in addition, it has a clear dependence on the particle sizes. Plot of log (TPAH/PM) against logDp shows that all slope values were below −1, suggesting that PAHs were mainly adsorbed to particulates. The adsorption effect of PAHs in size-segregated PMs for HMW PAHs is more evident than LMW PAHs. The particle size distributions (PSDs) of individual PAHs show that most of PAHs exhibit bi-model structures, with one mode peaking in the accumulation size range (2.1–1.1 μm) and another mode peaking in coarse size range (5.8–4.7 μm). The intensities of these two peaks vary in function of ring number of PAHs, which is likely attributed to Kelvin effect that the less volatile HMW PAH species preferentially condense onto the finer particulates. The emission factor of PAHs was calculated as 3.53 mg/kg of coal burned, with overall mean EFPAH of 0.55 and 2.98 mg/kg for gaseous and particulate phase, respectively. Moreover, the average emission amount of PAHs for the investigated CFPP was 1016.6 g/day and 371073.6 g/y, respectively.

Indoor air pollution from gas cooking in five Taiwanese families

There is a high lung cancer prevalence in females in Taiwan with a relatively low number of smokers. Exposure to air pollution from cooking (APC) has been suspected as one of the major risk factors for lung cancer since cooking is one of the major sources of particulate matter (PM) and polycyclic aromatic hydrocarbons (PAHs) in household buildings. Many studies have demonstrated that occupational exposure (40 h per week) to APC in commercial kitchens and restaurants could cause a cancer risk higher than 10−6. However, currently the data of exposure to APC in household kitchens are relatively few in Taiwan. Therefore, we conducted a health risk assessment for exposure to APC in five household kitchens in northern Taiwan during 2010–2011.Twenty-four-hour monitoring of the particle concentration shows that particle number concentrations during non-cooking hours ranged from 1220 to 6200 particles/cm3 and increased to 1,400,000 particles/cm3 during cooking hours, and most of these particles are ultrafine ones. Some of the measurement results (PM10 > 80 μg/m3 at 3 kitchens) exceed the current indoor air quality standards of Taiwan. The gas-particle partitioning of PAHs in household APC indicates that most of the low molecular PAHs (2 and 3 rings) are in the gas phase, while the high molecular PAHs (more than 4 rings) are particle-bound. The particulate-phase PAHs contribute more than 95% of the benzo[a]pyrene equivalent concentration. The incremental lifetime cancer risk resulting from exposure to the household APC could be higher than the acceptable level of 10−6, and thus of health concerns.

Estimation of Gas-particle partitioning Coefficients (Kp) of Carcinogenic polycyclic Aromatic hydrocarbons in Carbonaceous Aerosols Collected at Chiang - Mai, Bangkok and hat-Yai, Thailand

To assess environmental contamination with carcinogens, carbonaceous compounds, water-soluble ionic species and trace gaseous species were identified and quantified every three hours for three days at three different atmospheric layers at the heart of Chiang-Mai, Bangkok and Hat-Yai from December 2006 to February 2007. A DRI Model 2001 Thermal/Optical Carbon Analyzer with the IMPROVE thermal/optical reflectance (TOR) protocol was used to quantify the organic carbon (OC) and elemental carbon (EC) contents in PM10. Diurnal and vertical variability was also carefully investigated. In general, OC and EC mass concentration showed the highest values at the monitoring period of 21.00-00.00 as consequences of human activities at night bazaar coupled with reduction of mixing layer, decreased wind speed and termination of photolysis at nighttime. Morning peaks of carbonaceous compounds were observed during the sampling period of 06:00-09:00, emphasizing the main contribution of traffic emission in the three cities. The estimation of incremental lifetime particulate matter exposure (ILPE) raises concern of high risk of carbonaceous accumulation over workers and residents living close to the observatory sites. The average values of incremental lifetime particulate matter exposure (ILPE) of total carbon at Baiyoke Suit Hotel and Baiyoke Sky Hotel are approximately ten times higher than those air samples collected at Prince of Songkla University Hat-Yai campus corpse incinerator and fish-can manufacturing factory but only slightly higher than those of rice straw burning in Songkla province. This indicates a high risk of developing lung cancer and other respiratory diseases across workers and residents living in high buildings located in Pratunam area. Using knowledge of carbonaceous fractions in PM10, one can estimate the gas-particle partitioning of polycyclic aromatic hydrocarbons (PAHs). Dachs-Eisenreich model highlights the crucial role of adsorption in gas-particle partitioning of low molecular weight PAHs, whereas both absorption and adsorption tend to account for gas-particle partitioning of high molecular weight PAHs in urban residential zones of Thailand. Interestingly, the absorption mode alone plays a minor role in gas-particle partitioning of PAHs in Chiang-Mai, Bangkok and Hat-Yai.

Gas-Particle Partitioning of PAHs In The Urban Air of Dalian, China: Measurements and Assessments

To evaluate the gas-particle partitioning behavior of polycyclic aromatic hydrocarbons (PAHs) in the urban air of Dalian, China, both gas phase and particle phase ambient air were monitored with active high-volume sampler from November 2009 to October 2010. The average total concentration of 16 US EPA priority monitoring PAHs (particle + gas) (∑PAHs) was 112 ng m−3 and the most abundant PAH was Phenanthrene. ∑PAHs and the gas-particle partitioning coefficients (K p) of PAHs displayed seasonal variation in the order of winter > autumn > spring > summer. ∑PAHs was much higher during the heating period than non heating period. ∑PAHs in gas phase were all higher than those in particle phase in the four seasons. The PAHs sources identification was attempted using diagnostic ratios. The relationship between the concentration of PAHs in the air and meteorology parameters were analyzed using SPSS packages. The concentrations of PAHs in the air decreased with the increase of ambient temperature, and increased with the increase of atmospheric pressure. The gas-particle distribution was examined through several different approaches such as the relationship of logK p with the ambient temperature, with the logarithm of the sub-cooled vapor pressure (logP L 0), and the octanol-air partitioning coefficient (logK oa) of PAHs. The slopes obtained from regressing logK p vs. logP L 0 was −0.687∼−0.821 in heating periods, which was in the range between −0.6 and −1, indicating the partitioning of PAHs to particle phase in the urban air of Dalian was absorption as well as for adsorption mechanism. However, the average slope value was −0.502 in the non heating periods, which was shallower than -0.60, indicating that the absorption mechanisms contributed more to the partitioning process. The exposure risk of PAHs was evaluated with four methods, the results of which indicated that the quality of the urban air of Dalian was better.

Atmospheric concentrations, sources and gas-particle partitioning of PAHs in Beijing after the 29th Olympic Games

A comprehensive sampling campaign was carried out to study atmospheric concentration of polycyclic aromatic hydrocarbons (PAHs) in Beijing and to evaluate the effectiveness of source control strategies in reducing PAHs pollution after the 29th Olympic Games. The sub-cooled liquid vapor pressure ( log P L o ) -based model and octanol-air partition coefficient ( K oa)-based model were applied based on each seasonal dateset. Regression analysis among log K P, log P L o and log K oa exhibited high significant correlations for four seasons. Source factors were identified by principle component analysis and contributions were further estimated by multiple linear regression. Pyrogenic sources and coke oven emission were identified as major sources for both the non-heating and heating seasons. As compared with literatures, the mean PAH concentrations before and after the 29th Olympic Games were reduced by more than 60%, indicating that the source control measures were effective for reducing PAHs pollution in Beijing.

Polycyclic aromatic hydrocarbons in the atmosphere of Shanghai, China

Shanghai is the largest industrial and commercial city in China, and its air quality has been concerned for several years. However, scarce study had been made on the seasonal levels of atmospheric polycyclic aromatic hydrocarbons (PAHs), together with their gas-particle partitioning and potential emission sources. Based on an intensive sampling campaign at urban and suburban areas in Shanghai during four seasons of 2005-2006, this study presented the measurement of PAH concentrations in both particulate and gaseous phases, as well as seasonal and spatial variability. The results showed that the annual PAH levels (gas + particle) were 167 ± 109 ng m⁻³ at the urban site and 216 ± 86.5 ng m⁻³ at the suburban site. Gaseous PAHs (>70%) dominated the total PAH mass at both sites, while particulate PAHs contributed more than 90% of the toxic power according to benzo(a)pyrene-equivalent carcinogenic parameter. Different seasonal trend of PAH concentrations was observed between the two sites, and it may be explained by complicated factors such as sampling heights, local/regional emission sources, and climatic conditions. The gas-particle partitioning of PAHs in all samples was calculated, and strong linear correlations between log K (p) and log P(L)° were observed, with shallower slopes (m(r)) at the suburban site than the urban one and in warm season than the cold months, indicating the different equilibrium conditions of PAHs in spatial and seasonal scales in Shanghai. The slope (m(r) = - 0.96) and correlation coefficient (R² = 0.81) for four-ring PAHs were closest to theoretical equilibrium conditions among compounds with various aromatic rings. Finally, the potential PAH sources were estimated based on principal factor analysis with multiple linear regressions. Ground volatilization dominated the PAH pollutions at both sites, while vehicles and coal consumption were the other main emission sources, which totally contributed 32.0% (suburban) to 49.2% (urban) of PAH mass in Shanghai atmosphere. The effects of wood and biomass burning were also detected, but their contributions to PAHs were negligible.