To understand the deposition and transport of PAHs in southern China, a measurement campaign was conducted at a high-elevation site (the summit of Mount Heng, 1269 m A.S.L.) from April 4 to May 31, 2009, and a total of 39 total suspended particulate samples were collected for measurement of PAH concentrations. The observed particulate-bound PAHs concentrations ranged from 1.63 to 29.83 ng/m3, with a mean concentration of 6.03 ng/m3. BbF, FLA, and PYR were the predominant compounds. Good correlations were found between individual PAHs and meteorological parameters such as atmospheric pressure, relative humidity, and ambient temperature. The backward trajectory analysis suggested that particulate samples measured at the Mount Heng region were predominantly associated with the air masses from southern China, while the air masses transported over northern and northwestern China had relative higher PAHs concentrations. Based on the diagnostic ratios and factor analysis, vehicular emission, coal combustion, industry emission, and unburned fossil fuels were suggested to be the PAHs sources at Mount Heng site. However, the reactivity and degradation of individual PAHs could influence the results of PAH source profiles, which deserves further investigations in the future.
Polycyclic aromatic hydrocarbons (PAHs) are a group of widespread environmental contaminants, originating from both natural (e.g., forest fires and volcanoes) and anthropogenic sources (e.g., incomplete combustion and pyrolysis of fossil fuels or organic materials). Between the two sources, human activities (i.e., anthropogenic sources) contribute the most to PAHs emissions. This is particularly the case in urban area or industrial areas, where the PAHs sources can be entirely anthropogenic [
Once released into the atmosphere, PAHs can partition between vapor and particle phases, which is dependent on temperature and vapor pressure of the chemicals [
Although a considerable number of studies have been conducted on measurements of PAHs in urban environment, little work has been done in rural sites. Remote mountain regions, particularly with altitude in the free troposphere, are the unique environments for the study of atmospheric pollution load over continental areas, and the study at remote mountain regions can help to get full assessment of the role of the atmosphere in the global distribution of PAHs [
The Mount Heng is located in Hunan Province, south China, and it is between two major polluted industrial/urban areas—the Pearl River and Yangtze River deltas. There are two big cities, Shanghai and Guangzhou, situated 900 km to the east and 400 km to the south of the Mount Heng, respectively. The sampling site was located at a meteorological station (27°18′N, 112°42′E), which was set up in the 1937 at the summit of Mount Heng (1269 m A.S.L.) (Figure
Geographical location of Mount Heng (cited from [
The sampling period was carried out from April 4 to May 31, 2009. Total suspended particulate (TSP) samples were collected on glass fibre filters by a middle-volume air sampler (KC-300, Qingdao Laoshan Electronic Instrument Company) daily (22 hours, from 10 a.m. to 8 a.m.). The sampler was operated at a flow rate of 225 L/min and a total of 39 TSP samples were collected. Prior to sampling, all the glass fibre filters were combusted at 450°C in an oven for 6 h to volatilize any organic contaminants. After sampling, the glass fibre filters were wrapped in aluminum foils and frozen at −20°C, and PAHs analysis was then conducted within two weeks after sampling.
The glass fibre filters were extracted by Accelerated Solvent Extractor (Dionex ASE 300) with acetone/
The abbreviations for PAH compounds and their detection limits.
PAHs | Abbreviation | Detection limit (ng) |
---|---|---|
Acenaphthylene | ACY | 4 |
Acenaphthene | ACE | 5 |
Fluorene | FLU | 5 |
Phenanthrene | PHE | 3 |
Anthracene | ANT | 4 |
Fluoranthene | FLA | 7 |
Pyrene | PYR | 4 |
Benz[a]anthracene | BaA | 2 |
Chrysene | CHR | 7 |
Benzo[b]fluoranthene | BbF | 3 |
Benzo[k]fluoranthene | BkF | 4 |
Benzo[a]pyrene | BaP | 4 |
Dibenz[a,h]anthracene | DahA | 6 |
Benzo[g,h,i]perylene | BghiP | 4 |
Indeno[1,2,3-cd]pyrene | IcdP | 5 |
Deuterated perylene-d12 was spiked to all the samples to monitor procedural performance. The mean recoveries based on surrogates in samples were
Field and method blanks were analyzed using the same procedure as particulate samples, and all the PAHs concentrations were corrected for blanks. The control calibration standards were measured regularly to ensure the performance of instrument during sample analysis.
Descriptive statistics for all valid observations of PAHs concentrations in particulate samples collected at Mount Heng are summarized in Table
Statistical description of PAH concentrations in particulate samples at Mount Heng.
Species | PAHs concentrations (ng/m3) | ||
---|---|---|---|
Range | Mean | SD | |
ACY | Nd-0.11 | 0.02 | 0.03 |
ACE | Nd-0.56 | 0.10 | 0.15 |
FLU | Nd-0.85 | 0.22 | 0.23 |
PHE | 0.17–2.83 | 0.74 | 0.71 |
ANT | Nd-0.41 | 0.12 | 0.12 |
FLA | 0.15–4.88 | 0.77 | 0.97 |
PYR | 0.13–3.62 | 0.60 | 0.72 |
BaA | 0.05–1.68 | 0.27 | 0.33 |
CHR | Nd-3.80 | 0.52 | 0.80 |
BbF | Nd-4.24 | 0.86 | 0.88 |
BkF | 0.11–1.25 | 0.36 | 0.30 |
BaP | 0.08–1.47 | 0.35 | 0.31 |
IcdP | Nd-1.80 | 0.39 | 0.39 |
DahA | Nd-0.53 | 0.07 | 0.11 |
BghiP | 0.21–2.60 | 0.64 | 0.51 |
PAHs | 1.63–29.83 | 6.03 | 5.87 |
The observed PAHs concentrations at the Mount Heng are comparable with our previous studies done at the Mount Tai (fine particles, 6.88 ng/m3; Table
Comparison of particulate-bound PAH levels between Mount Heng and other studies.
Sampling site | Sample type | Altitude (m A.S.L.) |
|
PAHs concentrations (ng/m3) | Reference |
---|---|---|---|---|---|
Mount Heng, China | TSP | 1269 m |
|
6.03 | This research |
Mount Tai, China | PM2.5 | 1534 m |
|
6.88 | [ |
Waliguan, China | TSP | 3810 m |
|
2.08 | [ |
High Mountain Regions, Europe | TSP | 2240 m–2413 m |
|
0.07–1.10 | [ |
MBO, US | TSP | 2763 m |
|
<4 | [ |
Far East Asia | TSP | NA |
|
0.32 | [ |
North Pacific Ocean | TSP | NA |
|
0.14 | [ |
Arctic | TSP | NA |
|
0.48 | [ |
Beijing, China | PM10 | NA |
|
44.9 | [ |
Northern Plain, China | TSP | NA |
|
346 | [ |
Guangzhou, China | TSP | NA |
|
19.5 | [ |
The meteorological conditions are important factors that can affect the deposition levels of pollutants [
The correlation coefficients between particulate bound-PAH concentrations and meteorological parameters.
Press. (Pa) |
|
RH (%) | |
---|---|---|---|
PAHs | 0.627 | −0.639 | 0.226 |
ACY | 0.551 | −0.764 |
0.665 |
ACE | −0.025 | −0.234 | 0.940 |
FLU | −0.078 | −0.166 | 0.938 |
PHE | 0.389 | −0.554 | 0.700 |
ANT | 0.472 | −0.641 | 0.621 |
FLA | 0.541 | −0.571 | 0.119 |
PYR | 0.555 | −0.564 | 0.076 |
BaA | 0.572 | −0.537 | 0.050 |
CHR | 0.531 | −0.475 | 0.015 |
BbF | 0.688 | −0.644 | 0.174 |
BkF | 0.733 |
−0.718 |
0.233 |
BaP | 0.722 |
−0.706 | 0.221 |
IcdP | 0.767 |
−0.783 |
0.336 |
DahA | 0.626 | −0.656 | 0.363 |
BghiP | 0.751 |
−0.784 |
0.310 |
Significance level:
In previous studies, atmospheric samples always have higher deposition concentrations when they came from the more polluted area [
Based on the analysis, four major trajectory categories were classified for the samples: N/NW, continental air masses from northern and northwestern China, the most polluted region of China; EA, air masses from eastern China, where Shanghai and its surrounding cities located here; S, air masses from the Southern China, transported through the Pearl River Delta region; and L, samples with looped and short trajectories that stayed within a radius of 500 km of sampling site (Figure
Classified pathway of each trajectory category.
Among the four classified trajectory categories, S happened most frequently, accounting for 42.9% of the total, followed by N/NW (37.1%), EA (14.3%), and L (5.7%). As presented in Figure
PAHs concentrations based on different trajectory categories.
As suggested in prior studies, the concentrations and ratios of some tracer PAHs could be used to identify the contribution of different sources. Four common diagnostic ratios including FLA/(PYR + FLA), IcdP/(BghiP + IcdP), ANT/(PHE + ANT), and BaA/(BaA + CHR) were used to analyze the PAHs in particulate samples, and the results are presented in Figure
Diagnostic PAH ratios for TSP samples collected at Mount Heng.
According to the study of Yunker et al. [
Based on the results of diagnostic ratios analysis, coal combustion and emissions from liquid fossil fuel consumption were suggested to be the dominating sources of particulate-bound PAHs at Mount Heng site. In our previous studies conducted at Mount Tai, the highest mountain in northern China, coal combustion and vehicular emissions were the main sources of PAHs in atmospheric samples as well [
As stated above, several constraints exist when using diagnostic ratios to identify PAHs sources. Factor analysis, which served as an exploratory tool, can be used to quantify the major sources of PAHs. In this present study, the total concentrations of 15 PAHs compounds detected in particulate samples were subjected to factor analysis using SPSS version 16 (SPSS Inc.). Factor analysis was conducted with Varimax rotation, and factors with eigenvalue >1 were considered. The results of rotated factors are listed in Table
Factor analysis for particulate-bound PAHs.
PAHs | Factor 1 | Factor 2 |
---|---|---|
ACY | 0.735 | |
ACE | 0.977 | |
FLU | 0.962 | |
PHE | 0.790 | |
ANT | 0.846 | |
FLA | 0.857 | |
PYR | 0.882 | |
BaA | 0.940 | |
CHR | 0.922 | |
BbF | 0.954 | |
BkF | 0.709 | |
BaP | 0.810 | |
IcdP | 0.851 | |
DahA | 0.895 | |
BghiP | 0.833 | |
% of variance | 70.77 | 15.43 |
Sources | Vehicular and coal combustion emission | Unburned fossil fuels and incense burning |
Two factors were separated, accounting for 86.2% of the total variance in the data. Factor 1, which explained 70.77% of the variance, presented high loading for individual PAHs with higher molecular weight, including FLA, PYR, BaA, CHR, BbF, BkF, BaP, IcdP, DahA, and BghiP. According to previous studies, BbF, BkF, IcdP, and BghiP are the major components of vehicular emission, and the presence of FLA, PYR, BaA, and CHR could point to coal and wood combustion sources [
Based on the results of factor analysis, vehicular emission, coal combustion, industry emission, and unburned fossil fuels were suggested to be the PAHs sources at Mount Heng site. However, as mentioned earlier, the reactivity and degradation of individual PAHs could influence the results for profiles of PAH sources, and thus much work still needs to be conducted in the future.
Particulate-bound PAHs concentrations were investigated at high mountain region in Southern China from April to May 2009. The PAH concentrations ranged from 1.63 to 29.83 ng/m3, with a mean concentration of 6.03 ng/m3. The meteorological parameters including atmospheric pressure, relative humidity, and ambient temperature had good correlations with individual PAHs. The results obtained from air mass back trajectories and PAHs concentrations highlighted the importance of air mass origin. The air masses of N/NW group, transported over the most polluted region of China, had relatively higher PAH concentrations. Both the diagnostic ratio and factor analysis suggested that vehicular emission, coal combustion, industry emission, and unburned fossil fuels were the possible sources of PAHs at Mount Heng site.
The authors declare that there is no conflict of interests regarding the publication of this paper.
The authors are grateful to Mount Heng Meteorological Station for providing meteorological data and other support in the field observation. They thank Jinan Institute of Environmental Protection for the support of sample analysis. They appreciate the assistance from Zaifeng Wang, Houyong Zhang, Likun Xue, Xiaomei Gao, Wei Nie, and Shengzhen Zhou. This study was supported by the National Natural Science Foundation of China (21177073, 41475115), Tianjin 131 creative talents project, and Tianjin High School Science & Technology Fund Planning Project (20140515).