Deposition Of Polycyclic Aromatic Hydrocarbons Research Articles

One year of active moss biomonitoring in the identification of PAHs in an urbanized area-prospects and implications.

Classical monitoring of air pollution provides information on environmental quality but involves high costs. An alternative to this method is the use of bioindicators. The purpose of our work was to evaluate atmospheric aerosol pollution by selected polycyclic aromatic hydrocarbons conducted as part of annual active biomonitoring ("moss-bag" technique) with the use of three moss species: Pleurozium schreberi, Sphagnum fallax, and Dicranum polysetum. The gas chromatography-mass spectrometry (GC-MS) was utilized to determine certain 13 polycyclic aromatic hydrocarbons (PAHs). Three seasonal variations in PAH concentrations have been observed as a result of the study. A fire on the toilet paper plant caused an increase of five new compounds: benzo(k)fluoranthene (BkF), benzo(a)pyrene (BaP), indeno(1.2.3)-cd_pyrene (IP), dibenzo(a.h)anthracene (Dah), and benzo(g.h.i)perylene (Bghi) in proximity after 8months of exposure compared to previous months. The effect of meteorological conditions on the deposition of PAHs (mainly wind direction) in mosses was confirmed by principal component analysis (PCA). Dicranum polysetum moss accumulated on average 26.5% more PAHs than the other species, which allows considering its broader use in active biomonitoring. The "moss-bag" technique demonstrates its feasibility in assessing the source of PAH air pollution in a long-term study. It is recommended to use this biological method as a valuable tool in air quality monitoring.

Investigation of 200 anthropogenic activities in a representative alpine peatland in the Altay Mountains, northwestern China.

Peatlands records can be used to reconstruct and understand the history of environmental evolution, as well as a more accurate reflection of human activities. The black carbon (BC) and polycyclic aromatic hydrocarbons (PAHs) are ideal natural archives of anthropogenic activities. To identify the information of anthropogenic activities recorded by peatlands in the middle and high latitudes of the alpine mountains in the arid and semi-arid regions of China. this study analyzed the concentrations of BC, δ13C ratios of BC, PAHs, and molecular diagnostic ratios of PHAs (including Benzo(a) anthracene (BaA), Chrysene (Chr), fluoranthene (Flt), anthracene (Ant), phenanthrene (Phe), Benzo(a) pyrene (BaP), and pyrene (Pyr) in a 30-cm peat profile from the Altay Mountain, northwestern China. Our results revealed concentrations of BC from 11.71 to 67.5mg·g-1, and PAHs from 168.09 to 263.53ng·g-1. The δ13CBC value ranged from - 31.37 to - 26.27‰, with an average of - 29.54‰, indicating that the BC mainly comes from biomass combustion. The ratios of BaA/(BaA + Chr), Flt/(Flt + Pyr), and Ant/(Ant + Phe) exceeded 0.35, 0.5, and 0.1, respectively, revealing that the PAHs pollutants mainly originated from the combustion of biomass and fossil fuel burning. Furthermore, based on these findings and our knowledge of social development in Altay, industrial transport and tourism have influenced the emission, transport, and deposition of BC and PAH in peatlands in the Altay mountains since the 1980s. After 1980, pollutant concentrations decreased with the implementation of environmental policies. The results not only reveal the influence of anthropogenic activities on the sedimentary characteristics of peatlands in the Altay Mountains, but also provide an important theoretical basis for the conservation of fragile mountain peatlands.

Performance evaluation of four sampling techniques and source apportionment for the atmospheric deposition fluxes of polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are primarily emitted into the atmosphere through anthropogenic activities and can be transported to receptor sites at varying distances. In this study, the atmospheric PAH deposition was investigated using a dry deposition plate (DDP) with Mylar, a dry deposition disk (DDD) with Velcro, a resin bulk deposition sampler (Resin-BDS), and a water bulk deposition sampler (Water-BDS) in Ulsan, South Korea, during May–October 2013. Additionally, ambient PAH concentrations were monitored using high-volume air samplers. The mean deposition fluxes of Σ13 PAHs were 8.62 ± 1.44, 36.9 ± 6.81, 56.9 ± 9.74, and 63.8 ± 8.04 μg/m2/d for the DDP, DDD, Resin-BDS, and Water-BDS, respectively. The DDD was more effective than the DDP because it could collect high molecular weight (HMW) PAHs from dry deposition, which are more toxic than low molecular weight PAHs. The Water-BDS had the highest fluxes of Σ13 PAHs; however, the Resin-BDS may be more suitable for collecting HMW PAHs from both dry and wet deposition due to relatively constant values for the deposition velocity of PAHs. Furthermore, the PAH fluxes in the Resin-BDS samples were significantly positively correlated with the gaseous and total (gaseous + particulate) concentrations of ambient PAHs. Hence, the fluxes obtained by the Resin-BDS were further used to apply principal component analysis, multiple linear regression, and backward air trajectory simultaneously to identify the emission sources of the deposited PAHs. The results indicate that the combustion of fossil fuels and biomass was the major source. In particular, the industrial complexes using petroleum and coal on the city's east coast and vehicular exhausts were the main local sources. Meanwhile, long-range sources may be forest fires, harbors, and industrial activities in nearby countries. Our study suggests that BDS, considering both dry and wet deposition, can be selectively used for research on PAH deposition.

Sources, spatial-distributions and fluxes of PAH-contaminated dusts in the Athabasca oil sands region

Atmospheric deposition of polycyclic aromatic hydrocarbons (PAHs) has increased in northern Alberta, Canada, due to industrial development in the Athabasca oil sands region (AOSR). However, the sources, summertime deposition fluxes and associated spatial patterns are poorly characterized, and the magnitude of contamination has not been directly contrasted with comparable measurements around large Canadian cities. PAHs were measured in Sphagnum moss collected from 30 bogs in the AOSR and compared with reference moss collected from various remote, rural and near-urban sites in Alberta and Ontario. At all 39 locations, strong correlations between depositional fluxes of PAHs and accumulation rates of ash (n = 117, r = 0.877, p < 0.001) implied that the main source of PAHs to moss was atmospheric deposition of particles. Average PAH concentrations at near-field AOSR sites (mean [SD], 62.4 [24.3] ng/g) were significantly higher than at far-field AOSR sites (44.9 [20.8] ng/g; p = 0.038) or the 7 reference sites in Alberta (20.6 [3.5] ng/g; p < 0.001). In fact, average PAH concentrations across the entire AOSR (7,850 km2) were approximately twice as high as in London, Ontario, or near petroleum upgrading and major traffic corridors in Edmonton, Alberta. A chemical mass balance model estimated that both delayed petcoke (33 % of PAHs) and fine tailings (38 % of PAHs) were the major sources of PAHs in the AOSR. Over the 2015 summer growing season, we estimate that 101–110 kg of PAHs (on 14,300–17,300 tonnes of PAH-containing dusts) were deposited to the AOSR within a 50 km radius of surface mining. Given that the highest PAH deposition was to the northern quadrant of the AOSR, which includes the First Nations community of Fort MacKay, further dust control measures should be considered to protect human and environmental health in the region.

Wet deposition of polycyclic aromatic hydrocarbons in a remote area of Central South China from 2014 to 2017

AbstractIn recent years, there has been a notable increase in the consumption of fossil energy, leading to a significant rise in environmental pollution, particularly in China due to its rapid development. This has resulted in the frequent occurrence of large‐scale fog and haze weather, highlighting the urgent need for environmental protection measures. To gain insights into the atmospheric conditions in China, an analysis was conducted on the wet deposition of polycyclic aromatic hydrocarbons (PAHs) in a remote region of Central South China from 2014 to 2017. The study revealed that the average concentrations and peak values of Ʃ16PAHs in 2014 and 2015 were considerably higher than those observed in 2016 and 2017. Furthermore, it was found that five‐ring PAH species were the predominant components during 2014 and 2015, indicating a shift in the main sources of PAHs. The peaks of Ʃ16PAHs were predominantly detected in samples collected during light rain in the winter, specifically on days without heavy rainfall. This can be attributed to the absence of heavy rain, which would otherwise reduce the concentration of air pollutants. Consequently, contaminants accumulated in the air are easily enriched in rainwater. The concentrations of Ʃ15Alkyl‐PAHs also exhibited a significant correlation with the number of rainfall days. Notably, a much higher annual average concentration of Ʃ15Alkyl‐PAHs was observed in 2017, which experienced fewer rainfall days. Coal combustion, petroleum sources, and vehicular emissions accounted for 58%, 12%, and 30% of the PAHs in the air, respectively. Despite improvements in air quality in China since 2016, it is crucial to address the elevated concentrations of PAHs in the atmosphere, particularly under adverse meteorological conditions characterized by reduced rainfall.

A century-long record of polycyclic aromatic hydrocarbon deposition in the Old Yellow River Estuary, China

Polycyclic aromatic hydrocarbons (PAHs) are potential geochemical indicators for assessing the impact of human activities and can be used to reconstruct historical human activities. This study collected a 108 cm sediment core from the 5th lobe of the Yellow River Delta for the first time and analyzed the historical distribution characteristics of PAHs in this area. The results showed that the sedimentation history of the core was from 1908 to 2014. The average value of PAHs was 28.93 ng/g. Biomass and coal combustion sources were the main sources of PAHs in the low-value areas, while oil spill sources were the main sources in the significantly higher PAHs areas in the 1960s, mid-1980s, late 1990s, and late 2010s, which was consistent with the development history of Shengli Oilfield. Compared with global estuaries, the historical industrial activity intensity in this area was weaker.

Atmospheric occurrences and health risk assessment of polycyclic aromatic hydrocarbons and their derivatives in a typical coking facility and surrounding areas

Coking facilities release large quantities of polycyclic aromatic hydrocarbons (PAHs) and their derivatives into the ambient air. Here we examined the profiles, spatial distributions, and potential sources of atmospheric PAHs and their derivatives in an industrial coking plant and its surrounding environment (gaseous and particulate). The mean concentrations of PAHs, nitrated PAHs (NPAHs), chlorinated PAHs (ClPAHs), and brominated PAHs (BrPAHs) in the air of the coking facility were 923, 23.8, 16.7 and 4.25 ng m−³, respectively, 1–2 orders of magnitude higher than those in the surrounding area and the control area. Linear regressions between contaminant concentrations and distance from the coking facility suggested that the concentrations of PAHs (r2 = 0.82, p < 0.05), NPAHs (r2 = 0.77, p < 0.01), and BrPAHs (r2 = 0.62, p < 0.01) were negatively correlated with distance. Additionally, the particle-bound fractions of PAHs and their derivatives were significantly correlated with their molecular weights (p < 0.01). Based on the calculation of the gas/particle partitioning coefficients (log KP) for PAHs and their derivatives and the corresponding subcooled liquid vapor pressures (log PL), the slope values for PAHs, NPAHs, ClPAHs, and BrPAHs ranged from −1 to −0.6, indicating that deposition of PAHs and their derivatives occurred through both adsorption and absorption. Five emissions sources were identified by positive matrix factorization (PMF), including coking emissions, oil pollution, industrial and combustion sources, secondary formation, and traffic emissions, with coking emissions accounting for more than 50% of total emissions. Furthermore, the results of the health risks assessment suggested that atmospheric PAHs and their derivatives in the coke plant and surrounding area negatively impacted human health.

Polycyclic aromatic hydrocarbons (PAHs) in air, foliage, and litter in a subtropical forest: Spatioseasonal variations, partitioning, and litter-PAH degradation

Forest canopies play a vital role in scavenging airborne semi-volatile organic compounds. The present study measured polycyclic aromatic hydrocarbons (PAHs) in the understory air (at two heights), foliage, and litterfall in a subtropical rainforest (the Dinghushan mountain) in southern China. ∑17PAH concentrations in the air ranged from 2.75 to 44.0 ng/m3 (mean = 8.91 ng/m3), showing a spatial variation depending on the forest canopy coverage. Vertical distributions of the understory air concentrations also indicated PAH inputs from the above-canopy air. The concentrations of PAHs in fresh litter (with a mean of 261 ± 163 ng/g dry weight (dw)) were slightly lower than those in the foliage (362 ± 291 ng/g dw). Unlike the stable air PAH concentrations for most of the time of the year, the temporal variations of foliage and litter concentrations were remarkable but generally similar. Higher or comparable leaf/litter-air partition coefficients (KLA) in fresh litter compared with living KLA in leaves suggest that the forest litter layer is an efficient storage media for PAHs. Degradation of three-ring PAHs in litter under the field conditions follows first-order kinetics (R2 = 0.81), while the degradation is moderate for four-ring PAHs and insignificant for five- and six-ring PAHs. The yearly net cumulative deposition of PAHs through forest litterfall in the whole Dinghushan forest area over the sampling year was about 1.1 kg, 46% of the initial deposition (2.4 kg). This spatial variations study provides the results of in-field degradation of litter PAHs and makes a quantitative assessment of the litter deposition of PAHs, deducing their residence dynamics in the litter layer in a subtropical rainforest.

Deposition of atmospheric polycyclic aromatic hydrocarbons in rural areas: Current data and historical record from an ombrotrophic peatland

Atmospheric concentrations of 18 polycyclic aromatic hydrocarbons (PAHs) were measured in a rural area in northern Spain. Both the gas phase and particulate fraction were determined to evaluate the types and abundance of PAHs taken up by vegetation and the historical record of PAH deposition in an ombrotrophic peatland over the last 300 years. The total atmospheric PAH concentration was ca. 2.5 ng m−3, a value that is slightly lower value than those found in other rural areas, consistent with those of remote areas (Pyrenees, Alps, and Caledonian Mountains), and much lower than those recorded in urban areas. The particulate fraction showed a greater content of high molecular weight PAHs, whereas the gas phase was enriched in low molecular weight homologues. The concentration of total PAHs in the gas phase was higher than that in the particulate fraction (ca. 80%) and similar to that found in other localities in remote areas. PAHs showed seasonal variability. In this regard, the highest concentrations in the gas phase occurred in winter and autumn, whereas in the particulate fraction they were found in winter and spring. Of note, the concentrations of PAHs increased in the particulate fraction during the years in which fires occurred. The PAH content in peat-forming plants in this area showed a similar distribution to that of the gas phase. The historical record of the depositional fluxes of PAHs in an ombrotrophic peatland in the study area, which was dated radiometrically, allowed to reconstruct the changes in pollutant content between 1775 and the present. In general, the PAHs detected were of pyrogenic origin (fossil fuels and wood combustion). The concentrations of these pollutants increased from uniform background levels at the turn of the second half of the 19th century, which were linked to industrial development, to maximum values during the first half of the 20th century until the beginning of the 21st century, when the extraction and combustion of coal was extensive close to the study area. In contrast, in the uppermost part of the record, PAH concentrations decreased. This reduction is attributed to the implementation of environmental policies, although the concentrations of these pollutants were still greater than during the preindustrial period. To gain a detailed understanding of the deposition and evolution of PAHs in the study area, here it is reported on a new method that integrates current atmospheric data on PAHs with information on their accumulation in plants and the historical peat record of a rural area in Spain. The methodology described herein could be applied to other scenarios in the context of PAH pollution.

The deposition mapping of polycyclic aromatic hydrocarbons in megacity Shanghai, China.

The deposition of polycyclic aromatic hydrocarbon (PAHs) has far-reaching impacts on Earth's surface system and human health. However, a comprehensive understanding of PAHs' deposition in a high urbanized area is still lacking because of limited field measurements data and rough resolution of current models. In this research, a deposition map of PAHs with a resolution of 2×2km in megacity Shanghai, China was established. Gridded annual total deposition of PAHs from July 2020 to June 2021 ranged from 385 to 10,631ng/(m2·d), with a mean value of 2,611ng/(m2·d). The highest PAHs deposition was found over the downtown Shanghai, which received 4.3 times the deposition flux of outlying areas. About 77 % of area in Shanghai was dominated by wet deposition which accounted for 62 % of total deposition in Shanghai. The total deposition showed a trend of summer>fall>spring>winter, which was similar to that of the amount of rain. Source apportionment and geographically weighted regression analysis showed that built-up land and human activities are key driving factors of PAHs' deposition in Shanghai. Our results suggest that intensive human activities could alter the PAHs deposition distribution in Shanghai, and improve the understanding of PAHs' environmental behavior in high urbanized area.

Chronology of PAH and PCB pollution using sediment core in the Golden Horn estuary (Sea of Marmara)

The sources and depositional history of 16 polycyclic aromatic hydrocarbons (PAHs) and 18 polychlorinated biphenyl (PCBs) congeners in the Golden Horn estuary (İstanbul) were investigated using a dated sediment core for the period between 1880 and 2012. The concentrations of PAHs and PCBs were calculated for every 4 cm slices of the sediment core and ranged from 1203.5 to 3441.4 ng/g and 5.4 to 41.4 ng/g, respectively. The diagnostic ratios indicated that the maximum PAH values correspondence to combustion after a crude oil-carrying Romanian tanker (Independenta) accident in the İstanbul Strait in 1979. The historical deposition of PAHs and PCBs in the Golden Horn was influenced by municipal effluent and heavy industrial dischargers approximately 50 years. When the Silahtarağa thermal power plant (TPP) was operating, PCB pollution rose; however, after a thorough rehabilitation effort and the outlawing of PCB use in the 1990s, pollution levels significantly tended to decrease.

Association of polycyclic aromatic hydrocarbons in moss with blood biomarker among nearby residents in Portland, Oregon.

Polycyclic aromatic hydrocarbons (PAHs) are air pollutants that are costly to measure using traditional air-quality monitoring methods. We used an epiphytic bio-indicator (moss genus: Orthotrichum) to cost-effectively evaluate atmospheric deposition of PAHs in Portland, Oregon in May 2013. However, it is unclear if measurements derived from these bioindicators are good proxies for human exposure. To address this question, we simultaneously, measured PAH-DNA adducts in blood samples of non-smokers residing close to the sites of moss measurements. We accounted for individual determinants of PAH uptake that are not related to environmental air quality through questionnaires, e.g., wood fires, consumption of barbecued and fried meats. Spearman rank correlation and linear regression (to control for confounders from the lifestyle factors) evaluated the associations. We did not observe evidence of an association between PAH levels in moss and PAH-DNA adducts in blood of nearby residents (e.g., all correlations p≥0.5), but higher level of adducts were evident in those who used wood fire in their houses in the last 48 hours. It remains to be determined whether bio-indicators in moss can be used for human health risk assessment.

Polycyclic aromatic hydrocarbons in Fildes Peninsula, maritime Antarctica: Effects of human disturbance

This study provides the first data on the distribution, sources, and transport dynamics of polycyclic aromatic hydrocarbons (PAHs) in Fildes Peninsula, Antarctica via summertime analyses of lakes, seawater, snow, and air in 2013. Relatively high PAH levels and similar composition profiles (dominance of two- and three-ring PAHs) in the investigated marine and terrestrial environmental matrices were found, indicating substantial primary emissions of petrogenic PAHs. This result was corroborated by nonequilibrium partitioning of atmospheric PAHs caused by release of anthropically-derived lighter PAHs and air mass movement trajectories mainly originated from the Antarctic marginal seas. Notable geographical disparities of PAH pollution in the various types of samples consistently suggested impacts of station-related activities, rather than long-range atmospheric transport, on PAHs in Fildes Peninsula. The lack for temperature dependence for gas-phase concentrations and various molecular diagnostic ratios of atmospheric PAHs demonstrated that the impact of local anthropogenic inputs on air PAH variability supersedes the re-emission effect. The derived air–water and air–snow exchanges of PAHs in this remote region indicated a disequilibrium state, partially associated with intense local emissions of PAHs. PAH outgassing from, and absorption into, lake and marine waters were both observed, probably due to differences in anthropogenic influences among sites, while the net deposition of gaseous PAHs into snow prevailed. The results of this study shed lights on the major importance of native anthropogenic sources in the footprint and fate of PAHs in the Fildes Peninsula, which merits further monitoring.

Polycyclic Aromatic Hydrocarbons in the Snow Cover in the City of Tyumen (Western Siberia, Russia).

Some of Russia's large industrial cities are sources of hazardous contamination in the environment. Tyumen is one of the most rapidly developing cities in Siberia due to oil and gas extraction in the northern Tyumen Region. Concentrations of 14 polycyclic aromatic hydrocarbons (PAH)s deposited with the particulate matter (PM) of snow in the city of Tyumen were determined by liquid chromatography. In the background area, the rate of atmospheric particulate deposition was shown to be low, and the mean total content of 14 PAHs had a value of 6.2 ng L-1, which is lower than many unpolluted areas on Earth. In the city of Tyumen, the mean content of PM was five times higher and the mean total content of 14 PAHs was twenty times higher as compared to the background. The contents of chrysene, benzo(k)fluoranthene, and benzo(a)pyrene were increased by multiples of 78, 77, and 32, respectively. The rates of ∑14 PAH deposition with airborne PM over the winter ranged from 1.1 to 65.5 μg m-2. Calculations of BaP toxic equivalent showed maximal toxicity within the transport zone. Both analysis of spatial distribution and diagnostic ratios showed that the PAHs were mainly from coal combustion and vehicle emissions.

Deposition effect of inhaled particles in the human: Accurate health risks of personal exposure to PAHs and their derivatives from residential solid fuel combustion

The drastic household clean heating renovation has been undertaken in rural northern China since 2017. A method incorporating the deposition efficiency of particulate matters (PMs) in the human respiratory tract is firstly introduced into the personal exposure (PE) study which is more accurately assess the health risks of homemakers inhaling PM-bound four subclasses polycyclic aromatic hydrocarbons (PAHs) emitted from different solid fuels (i.e., biomass, raw coal chunk, and clean coal). Homemakers using clean coal show the lowest exposure levels of all PAH subclasses (parent, alkylated, oxygenated, and nitro PAHs) and total quantified PAHs (ΣPAHs). Remarkable reductions of 93.9% and 89.0% on ΣPAHs in PE PM2.5 are observed with the substitutions of the raw coal chunk and biomass fuel by the clean coal, respectively. 86.8–96.8% of ΣPAHs are inhaled by the human body, while approximately 22.4–44.8% are deposited in the respiratory tract. The deposition concentrations (DC) of ΣPAHs in the biomass and raw coal chunk groups are 12 and 5 times the clean coal group, respectively. PAHs in coarse mode PE particles with an aerodynamic size between 2.5 and 100 μm mostly deposit in the head airway (HA) (98%). Moreover, the PAHs in fine particles (i.e., with aerodynamic size less than 2.5 μm) mainly deposit in the alveolar region (AR), accounting for 20–70% of ΣPAHs. Replacing biomass and raw coal chunk with clean coal reduced incremental lifetime cancer risks (ILCR) by 91% and 92%, respectively. This study improves the understanding of the PM-bound PAHs deposition in the human respiratory system and contributes to the promotion of domestic energy transition in rural northern China.

Effect of Aquatic Organic Matter and Global Warming on Accumulation of PAHs in Lakes, East China

AbstractThe sedimentary records of organic matter in lakes can reflect the response of lakes to global warming. Multiple organic proxies in the sediment core samples collected from Luoma Lake and Hongze Lake in Jiangsu were used to expound the effects of global warming and anthropogenic activities on lacustrine productivity and deposition of polycyclic aromatic hydrocarbons (PAHs). Total organic carbon, algal organic matter proxies (S2 and hydrogen index), and nutrients such as total phosphorus and total nitrogen were measured. The source apportionment modeling and the principal component analysis demonstrated that algal organic matter and bacteria organic matter showed an upcore increasing trend and an obvious enrichment effect on PAHs, which was also related to the increasing temperature and algal productivity in the lakes. Global warming enhanced the lacustrine productivity and the accumulation of PAHs in sediments. Therefore, the organic geochemical indicators in lake sediments can effectively reflect the impact of climate warming on the lacustrine productivity and the accumulation of PAHs, and provide data support for the management of lakes.

Atmospheric Deposition of Polycyclic Aromatic Hydrocarbons (PAHs) in the Coastal Urban Environment of Poland: Sources and Transport Patterns.

This study combines an interseasonal variation of deposition profiles of fine-particulate-bound polycyclic aromatic hydrocarbons (PM2.5-bound PAHs) with source apportionment analysis. Comprehensive measurements were conducted in four representative periods of 2019 in the coastal urban region of the Baltic Sea in Poland. The mean daily deposition flux of Σ13PAHs was 229 ng m-2 day-1, which was lower than in other urban/industrial sites of Europe and Asia. The seasonal PAHs distribution exhibited a clear U-shaped pattern, reaching maximum values in January and December and the minimum in June. A strong influence of local/regional anthropogenic emissions and meteorological factors (precipitation, ambient temperature, wind regimes) was observed. The contribution of medium molecular weight PAHs (fluoranthene, pyrene, benzo(a)anthracene, chrysene) to the total sum of PAHs deposition fluxes increased from 24% in spring to 38% in summer, as a result of photochemistry, urban traffic, and shipping emissions. The highest contribution of 5- and 6-ring PAHs occurred primarily in autumn (55%), followed by winter (39%), spring (35%), and summer (26%). Benzo(a)pyrene (human carcinogenic compound) had a relatively high deposition flux in winter, which was almost 14 and 20 times higher than the values registered in spring and summer, respectively. The FLEXTRA dispersion model was used to study potential pollution regions for PM2.5-bound PAHs and to investigate changes in the PAH deposition regime in different seasons. This study reveals that the winter contribution of PAHs was mostly impacted by local urban activities (i.e., residential heating and coal-fired power plants). Winter PAH deposition fluxes were particularly associated with atmospheric particles transported from surrounding areas and industrially impacted regions of SE-S-SW Poland and Europe.

Spatial origin analysis on atmospheric bulk deposition of polycyclic aromatic hydrocarbons in Shanghai

Atmospheric deposition of polycyclic aromatic hydrocarbons (PAHs) onto soil threatens terrestrial ecosystem. To locate potential source areas geographically, a total of 139 atmospheric bulk deposition samples were collected during 2012–2019 at eight sites in Shanghai and its surrounding areas. A multisite joint location method was developed for the first time to locate potential source areas of atmospheric PAHs based on an enhanced three dimensional concentration weighted trajectory model. The method considered spatial and temporal variations of atmospheric boundary layer height and homogenized all results over the eight sites via geometric mean. Regional transport was an important contributor of PAH atmospheric deposition while massive local emissions may disturb the identification of potential source areas. Northwesterly winds were associated with elevated deposition fluxes. Potential source areas were identified by the multisite joint location method and included Hebei, Tianjin, Shandong and Jiangsu to the north, and Anhui to the west of Shanghai. PM and SO2 data from the national ground monitoring stations confirmed the identified source areas of deposited PAHs in Shanghai.

Polycyclic aromatic hydrocarbons (PAHs) in gas, PM2.5, and frost samples in a severely polluted rural site of the North China Plain: Distribution, source, and risk assessment

The process of frost formation has been studied as an important deposition pathway for removing atmospheric pollutants. However, the removal of organic species during frost formation remains unknown. Gas, PM2.5 and frost samples were collected in Wangdu, a severely polluted rural site in the North China Plain, during the winter of 2018. The concentrations, distributions, sources, and ecological and health risks of the 16 PAHs in the samples were determined. The 24 h-averaged concentrations of PAHs in the air (gas + PM2.5) reached 719 ng m−3, indicating that the local atmosphere was heavily contaminated by PAHs in winter. The average concentrations of PAHs in the frost insoluble reached 27.5 μg g−1, indicating the strong ambient PAHs deposition during the frost process. The distribution patterns of individual PAH species indicated that the PAHs in the gas influenced the frost samples, and the sources of PAHs in frost samples were highly similar to those in PM2.5 samples. The calculated lifetime lung cancer risk (LLCR) via inhalation of ambient PAHs was classified as high risks. The average total Benzo(a)pyrene toxic equivalent quotient (TEQ) of PAHs in the frost samples was estimated as 2.50 μg TEQ g−1, posing a high threat to the ecological environment and health. After the melting of frost, the PAHs are released into the soil. Although the concentrations are diluted, the PAH concentrations could adversely affect the growing vegetation or agricultural activities. The extremely high PAH concentrations and their ecological and health risks require special attention and strict regulation.

Spatial and seasonal variation and sources of deposition fluxes of polycyclic aromatic hydrocarbons (PAHs) in Shanghai.

Spatial and temporal variations of polycyclic aromatic hydrocarbons (PAHs) deposition fluxes and sources may significantly facilitate risk evaluation and pollution control of super megacity in China. A study on PAHs of wet and dry deposition in Shanghai was conducted from January to December of 2019. Seventeen sampling sites located in four functional areas were set, including the Baoshan iron and steel industry area (BS), Jinshan petrochemical industry area (JS), city center (CC), and Chongming agricultural area (CM). A total of 15 PAHs were determined by gas chromatography-mass spectrometry (GC-MS, Agilent 7890A/5975C). PAHs atmospheric deposition flux in winter was highest (3.12 ± 1.98μg/(m2·day), mostly attributed to local emissions accumulation under adverse meteorological diffusion conditions, as well as pollutants transport from northern China during heating season. PAHs deposition fluxes in industrial area (BS and JS) were 3.75 ± 4.08μg/(m2·day) and 3.18 ± 3.62μg/(m2·day) respectively, which were greater than those in CC and CM, accounting for 1.91 ± 1.06μg/(m2·day) and 1.41 ± 0.61μg/(m2·day) respectively. Proportional composition and isomer ratios of PAHs indicated that the PAHs deposition in winter and spring samples were more homogeneous, whereas those of summer and autumn seemed to be more variable and dispersed. Positive matrix factorization model were employed to identify the potential sources of PAHs in specific functional areas. A dominance of contribution was attributed to coal combustion (46%) at BS, petroleum volatilization (48%) at JS, biomass burning (55%) at CM, and vehicle emission (49%) at CC. This study highlighted that local urbanization and industrialization have a significant contribution to PAHs deposition to specific functional regions in Shanghai.