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Polycyclic aromatic hydrocarbons (PAHs) in atmospheric PM2.5 around2013 Asian Youth Games period in Nanjing
Xuxu Li b,⁎, Shaofei Kong a,b,⁎, Yan Yin a,b,⁎, Li Li b, Liang Yuan b, Qi Li b, Hui Xiao b, Kui Chen b
a Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science and Technology, Nanjing 210044, Chinab Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration, Nanjing University of Information Science & Technology, Nanjing 210044, China
⁎ Corresponding authors at: Nanjing University of InforNingliu Road 219, Nanjing, China. Tel./fax: +86 25 58731
Article history:Received 7 October 2015Received in revised form 23 December 2015Accepted 11 January 2016Available online 25 January 2016
Eighteen polycyclic aromatic hydrocarbons (PAHs) in PM2.5 collected near the Nanjing Olympic Sports Centeracross the Asian Youth Games (AYG) period (from August 2 to August 28, 2013) were analyzed using GC-MS.Their levels, sources and health risks to human were discussed. Results showed that the total concentrations ofPAHs in PM2.5were 9.43, 7.21 and8.83ngm−3 for pre- (August 3–15), during- (August 16–24) and post- (August25–28) AYGperiods, respectively. Theywere dominated by 5-ring and 6-ring PAHs. Total PAHs concentrations inPM2.5 during AYG period decreased by 24%, when compared with those for pre-AYG period. For combustion-derived PAHs and carcinogenic PAHs, they decreased by 26% and 21%, respectively. It implied that the pollutioncontrol measures implemented during the AYG can effectively reduce the emission of PAHs fromvarious sources.The poor correlations between PAHs and meteorological parameters also favored that the variations of PAHswere raised by the changes of emission sources. Diagnostic ratios and principal component analysis revealedthat vehicle emission and coal combustion were the predominant contributors, with minimal effects from bio-mass burning and petroleum. The health risks for human exposed to PAHs in PM2.5 were quantitatively assessedby BaP equivalent concentration (BaPeq) and the incremental lifetime cancer risk (ILCR). The estimated ILCRvalue of PAHs during the AYG periods decreased by 23% and 27% for children and adults when compared withthose for the pre-AYG, respectively. It indicated that the pollution control measures reduced the risks of PAHsto sportsmen or human gathered around the Olympic Sport Center.
Source identificationHealth riskPollution control measuresMega event
1. Introduction
As one type of carcinogenic organic compounds (WHO, 2003), poly-cyclic aromatic hydrocarbons (PAHs) widely exist in the atmosphere,water and soil and pose a potential carcinogenic and mutagenic threatto human health. They are mainly derived from incomplete combustionor pyrolysis of organic materials such as petroleum and coal (Changet al., 2006; Galarneau, 2008; Wang et al., 2008; Kim et al., 2013;Li et al., 2014; Wu et al., 2014a,b). Their gas/particle partitioning, size-distribution, spatial–temporal variation and health risks of PAHs havebeen widely investigated (Kong et al., 2015a).
Since the Beijing Olympic Games in 2008, temporary pollutioncontrol for improving air quality has been a frequent practice in China.The effects of pollution control measures on atmospheric pollutantsare widely discussed. While plenty of studies have been conducted toinvestigate the effects of pollution control measures on particle massconcentrations (Wang et al., 2010; Dai et al., 2012; Li et al., 2012a;
Huang et al., 2013; Liu et al., 2013; Chen et al., 2013; Yuan et al., 2014)and inorganic components, such as ions (Liu et al., 2011; Okuda et al.,2011; Guo et al., 2011; Zou et al., 2014) and carbonaceous species(Wu et al., 2009; Pan et al., 2010; Huang et al., 2012; Ding et al., 2012;Wang et al., 2014) duringmega-events, very few studies focused on or-ganic components (Yang et al., 2011). Kong et al. (2015b) investigatedeighteen PAHs in PM2.5 at a subway construction site of Nanjing, andindicated that the construction workers were exposed to 10 timeshigher BaPeq concentrations than the background site. Meanwhile, pre-vious studies mainly focused on the overall air quality in the city level(Zhang et al., 2013) and very few were concerned with the air qualityaround the competition venue. It is necessary to investigate the ambientPM2.5, especially the hazardous components around the competitionvenue and assess their possible sources and health risks.
During the 2008 Olympic Games in Beijing, temporary transporta-tion control measures were implemented to reduce emissions fromvehicles (Wang and Xie, 2009; Zhou et al., 2010). Compared with thenon-Olympic period, the PAHs concentrations in PM2.5 (Yang et al.,2011; Wu et al., 2014b), PM10 (Wang et al., 2011) and TSP (Okudaet al., 2011) during the Olympic period all decreased significantly, espe-cially for 4-ring PAHs from heavy-duty diesel vehicles. Similar emissioncontrol policieswere also adopted during the 2009 AsianGames (AG) in
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Guangzhou and the concentrations of PAHs were slightly lower in theAG periods, mainly contributed by motor vehicle emissions (Xu et al.,2013). It is essential to investigate the levels of PAHs around themega-event periods to check the effects of pollution control measureson PAHs reduction and further evaluate their health risks, which willhelp making strategies from the view of protecting the health of sports-men. However there is no relevant research studying the levels, sourcesand risks of PAHs during a major sporting event around sport centers inChina till now.
Nanjing, located in Yangtze River Delta Region of Eastern China, issuffering from serious air pollution problem, due to the rapid growthof industrial activities, traffic density and urbanization development.Guo et al. (2016) found that the PM1.1 pollution in Nanjing is deteriorat-ing, with the aggravation of industrialization. Zou et al. (2014) indicatedthat fine particle concentrations in Nanjing are in an uptrend in recentyears, leading to the deterioration of air quality and resulting in visibilitydeclining and frequent occurrence of haze (Yuan et al., 2014; Kong et al.,2015c). The 2nd session of the Asian YouthGames (AYG)was held fromAugust 16 to August 24 in 2013 in Nanjing. In order to ensure the airquality and guarantee the success of the Asian Youth Games, localgovernment formulated a series of temporary control measures, includ-ing shutting down or limiting the productions of 60 enterprises andsuspending more than 3000 construction activities sites (NanjingMunicipal Government, NMG, 2013). Temporary traffic controls werealso adopted to mitigate vehicle emissions, including forbidding the
Fig. 1. Location of the
use of high-duty social vehicles especially for yellow-labeled vehiclesand prohibiting sailing of high-pollution vehicles in the main districts.
To directly study the effects of these measures on PAHs concentra-tions in PM2.5 and assess their health risks to sportsmen, PM2.5 samplesare collected at a site near the Nanjing Olympic Center and analyzed foreighteen PAHs around the AYG period. The main objectives are toanalyze the variations of PAHs levels and sources for pre, during andafter the sport periods. The health risks for PAHs to sportsmen andhumans concentrated in the sport center are also assessed, to raiseattentions and establishmore strict rules for air pollutant control duringmega-event periods.
2. Methodology
2.1. Sampling
PM2.5 samples were collected at a site (118°46′E, 32°03′N) (Fig. 1)near the Nanjing Olympic Center from August 2 to August 28, 2013,with a medium-volume sampler (TH-150C, manufactured by WuhanTianhong Ltd., China). The areas numbered by 1, 2, 3, 4 and 5 in Fig. 1are the central districts of Nanjingmetropolis. The sampling site is locat-ed in the vicinity of city center and is far from industrial sites, facing totwo roads with heavy traffic at the southeast and southwest direction(within 100 m). There are few tall buildings around the sampling site.
observation site.
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The samplingflow ratewas 100 L/min. PM2.5 sampleswere collected for24 h, starting at 08:00 am each day.
The sampling campaign lasted for 26 days. The data at 11th, 12th and15th are missing due to the failure of power supply. At last, twenty-three samples were obtained. The samples were collected using quartzfiber filters (Whatman Company, UK; Ø 90 mm, baked at 800 °C for2 h before sampling). The filters are weighed with an analytical balance(Ohaus Discovery DV214CD) with balance sensitivity of ±0.010 mg,after being stabilized for 48 h under constant temperature (22 °C) andhumidity (35%). Then allfilterswere sealed by aluminum foil and storedat−20 °C until chemical analysis.
2.2. PAHs analysis
The quartz fiber filters are cut into pieces, put into 10 mL centrifugetubes and ultrasonically extracted with dichloromethane for 30 min.Then the extracts are concentrated by a rotary evaporator, purifiedwith a silica gel cleanup technique and re-concentrated using rotaryevaporation. Subsequently, the concentrated solution is condensed toexactly 1mL under a gentle nitrogen stream in 60 °Cwater bath. Finally,the extracts are transferred into two ampoule bottles and stored in arefrigerator until analysis. Gas chromatography coupled with massspectrometry (GC-MS) is used to analyze the extracts. Detailed analysisprocedures of GC-MS could be found in our previous works (Kong et al.,2012; Wu et al., 2014a; Kong et al., 2015a).
Eighteen PAH species are detected including naphthalene (NaP),acenaphthylene (Acy), acenaphthene (Ace), fluorene (Fl), phenan-threne (Phe), anthracene (Ant), fluoranthene (Flu), pyrene (Pyr),benzo[a]anthracene (BaA), chrysene (Chr), benzo[b]fluoranthene(BbF), benzo[k]fluoranthene (BkF), benzo[a]pyrene (BaP),Benzo(e)pyrene (BeP), dibenz[a,h]anthracene (DBA), indeno[1,2,3-cd]pyrene (InP), benzo[ghi]perylene (BghiP) and coronene (Cor). Theyare classified by the number of aromatic rings: 2-ring (NaP); 3-ring(Acy, Ace, Fl, Phe, Ant); 4-ring (Flu, Pyr, BaA, Chr); 5-ring (BbF, BkF,BaP, BeP); 6-ring (InP, DBA, BghiP); 7-ring (Cor). Then they were classi-fied into lower molecular weight (LMW) (2- and 3-ring PAHs), middle
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molecular weight (MMW) (4-ring PAHs) and higher molecular weightPAHs (HMW) (5-, 6- and 7-ring PAHs).
For quality assurance and control, the recovery test is performed bymatrix-spiked samples and the spikedfilter is analyzed by the samewayas mentioned above. The recovery experiment is repeated four times.The recoveries for these PAHs are in the range of 86%–95%, with the rel-ative standard deviation less than 10%. Field blanks are placed un-opened next to the sampler for the duration of sampling, andprocessed with the same procedure as other samples. Concentrationsof PAHs in blank samples are deducted from the filed samples. Forevery set of 10 samples, laboratory blanks (clean filters) are extractedand analyzed to check the interference and cross-contamination. Thelimits of detection (LODs) for the 18 kinds of PAHs are in the range of3.0–10.0 ng.
2.3. Meteorological data and backward trajectory calculations
Continuous meteorological parameters including temperature (°t),relative humidity (RH, %), wind speed (m s−1), wind direction (°),atmospheric pressure (hPa) and visibility (km) are recorded simulta-neously at the sampling site, which is also the environmental observa-tion station set by Nanjing environmental monitoring center. Fig. 2shows the time series of the meteorological parameters during the ob-servation period. Affected by the subtropical high system, there was apreponderance of high temperature days especially in the first half ofAugust. In the latter half of August, the temperature decreased slightlyand humidity rise due to the influence of a short-time afternoon thun-dershower and outer cloud systems associated with a tropical cyclone.During the sampling period, the average temperature and RH were31.9 °3 and 58.5%, respectively. The highest temperature and humidityduring the sampling period was 41.0 °1 and 88.9%. The maximumwind speed was smaller than 4 m s−1 and was unfavorable to diffusionand transport of pollutants. 72-h air mass backward trajectories werecalculated using NOAA Air Resource Lab HYSPLIT model with theGDAS dataset (1° × 1°). The starting height was set as 500 m abovethe ground. Themixing layer height (MLH)was obtained by theNOAA's
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READY ArchivedMeteorology online calculating program (http://ready.arl.noaa.gov/READYamet.php) (Kong et al., 2015a).
2.4. Principal component analysis
Principal component analysis (PCA) was adopted to identify thesources of PAHs in PM2.5 during thewhole samplingperiod. ThePCA cal-culations are executed by the varimax normalized rotation methodusing SPSS 13.0 software. The main function is to transfer the multivar-iate data into a smaller set of variables. Variables with higher factorloadings are considered relevant and indicate possible emission sources(Han et al., 2011; He et al., 2014; Wu et al., 2014a,b).
2.5. Health risk assessment
BaP equivalent concentration (BaPeq) was adopted to assess thehealth risk of PAHs. It is calculated by multiplying the mass concentra-tion of specific PAHs species with their corresponding toxic equivalentfactor (TEF). The total carcinogenic potency of PAHs can be evaluatedby the sum of the BaPeq of each PAHs as Eq. (1) (Kong et al., 2015a).
Health risk can be estimated using PAH exposure through inhalation(Jamhari et al., 2014; Kong et al., 2015a). The incremental lifetimecancer risk (ILCR) in human beings can be quantitatively calculated bythe lifetime average daily dose (LADD) of PAHs. The equations used tocalculate LADD and ICLR are as follows:
LADD ¼ C� IR � ED� EF= BW� ALTð Þ ð2Þ
ILCR ¼ LADD� CSF ð3Þ
where C is the PAHs concentration in PM2.5 (mgm−3); IR is the air inha-lation rate (m3 day−1, 20 and 7.6 for adult and children, respectively);ED is the lifetime exposure duration (52 and 6 years for adult and
Table 1Mass concentrations of PAHs species in PM2.5 before, during and after the Asian Youth Games
Lowermolecularweight (LMW) contains 2 and3-ring PAHs;middlemolecularweight (MMW)PAHs. COMPAHs: combustion derived PAHs including Flu, Pyr, Chr, BbF, BkF, BaA, BeP, BaP, INDAYG/Pre-AYG: the ratios of PAHs concentrations for the days of AYG and the days before AYG.AYG/Post-AYG: the ratios of PAHs concentrations for the days of AYG and the days after AYG.
children, respectively); EF is the exposure frequency (2 days year−1);BW is the body weight (70 kg and 15 kg for adult and children); ALTis the average lifetime for carcinogens (70 years × 365 day year−1 =25, 550 days); and CSF is the cancer slope factor and is set as3.14 mg kg−1 day−1 for BaP from inhalation. The total BaPeq valuesare used to calculate LADD instead of C (Jamhari et al., 2014).
3. Results and discussion
3.1. PAHs concentrations
3.1.1. Differences of PAHs before, during and after the 2013 Asian YouthGames
The total concentrations of PAHs were in the range of 3.77–15.59 ng m−3 (8.35 ± 3.35 ng m−3) during the sampling period, with2-ring eliminated because of its high volatility. Table 1 shows themass concentrations of PAHs species in PM2.5 in the periods of before,during and after AYG. The contents of LMW, MMW and HMW were inthe ranges of 0.51–1.70 ng m−3, 0.58–3.25 ng m−3 and 2.23–11.1 ng m−3, respectively. The ratio of LMW, MMW and HMW-PAHswas approximately 1:1.6:5, indicating that the dominance of HMW(44%–81%). The concentrations of HMW-PAHs for during-AYG were0.81 and 0.85 times of those for pre-AYG and post-AYG period, respec-tively. And the concentrations of MMW-PAHs for during-AYG periodwere 0.64 and 0.70 times of those for pre-AYG and post-AYG period,respectively.
Gasoline vehicles were themajor sources of HMW-PAHs emission insummer in China (Okuda et al., 2011). The averaged PAHs concentra-tions in this study were lower than the PAHs levels measured in otherChinese cities (Zheng and Fang, 2000; Lee et al., 2001; Wang et al.,2010; Wu et al., 2014b; He et al., 2014). It can be explained as that theemission restriction policies conducted before and during the AYG peri-od effectively reduced the PAHs concentrations. However, it should benoted that the PAHs concentrations in this study are still higher whencompared with some cleaner regions (Kendall et al., 2001; Mantiset al., 2005; Vasilakos et al., 2007; Kume et al., 2007; Amodio et al.,2009; Kong et al., 2015b).
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The combustion-derived PAHs (COMPAHs) was defined as a combi-nation including Flu, Pyr, BaA, Chr, BbF, BkF, BaP, InP, and BghiP (Roggeet al., 1993; Sienra et al., 2005). They were in the range of 2.07–9.61 ng m−3, accounting for 47.3%–61.4% of the total PAHs. And theCOMPAHs concentrations for pre-, during- and post-AYG periods were5.44 ± 2.42 ng m−3, 4.02 ± 1.52 ng m−3 and 5.12 ± 2.52 ng m−3,respectively. They decreased by 26% and 21% for during-AYG periodwhen compared with those for pre-AYG and post-AYG periods. It signi-fied the reduction of combustion sources. After AYG, there was a slightrebound of COMPAHs concentrations due to the increase of humanactivities such as restart of industrial and construction works andmore traffics on the road. It can be concluded that the emission controlpolicies reduced the traffic, industrial activities and improved the airquality effectively.
Carcinogenic PAHs (C-PAHs) include BaA, Chr, BbF, BkF, BaP, InP, andDaA (He et al., 2014). In this study the C-PAHs concentrations ranged in1.79–8.89 ng m−3, accounting for 36%–57% of the total PAHs. The C-PAHsdecreased by 24% and19% for during-AYGperiod,when comparedwith those for pre-AYG and post-AYG periods. It might be related to thechanges of emission sources for particles during AYG, with reduceddiesel vehicle emissions, industrial and construction activities. BaPwas considered as an indicator of the whole PAHs carcinogenicity(Hassanien and Abdel-Latif, 2008; Shi et al., 2010). In this paper, BaPconcentration ranged from 0.22 to 1.32 ng m−3, accounting for up to9% of the total PAHs. The health risk during the AYG period was low,since the concentration of BaP in thewhole sampling days didn't exceedtheupper limit (2.5 ngm−3) of the Chinese ambient air quality standardfor BaP issued in 2012, andwere slightly higher than the air quality stan-dard (1.0 ng m−3) set by the World Health Organization.
The individual PAH mass percentages in PM2.5 are presented inFig. 3. The average concentrations of the 18 types of PAHs during thewhole sampling periods varied from 0.02 ng m−3 (Acy) to1.30 ng m−3 (BbF). The most abundant PAHs were BbF, BghiP, InP,BaP and BeP, totally accounting for 56% of all the PAHs, indicating theobvious influence of traffic exhaust. Almost all PAHs decreased by up
Fig. 3.Mass percentages of 18 kinds of individual PAHs in PM2.5 in three periods (a: before the Ac: after Asian Youth Games (Aug. 25–Aug. 28)).
to 50% of those for pre- and post-AYG period. Li et al. (2012b) suggestedthat BaA, Chr, BkF, BbF, and BaP were indicators of petroleum combus-tion. Flu, Pyr, BbF, and BkF were widely used as tracers for heavy-dutydiesel vehicles (Kulkarni and Venkataraman, 2000). BghiP, BaP, BbF,BkF, DBA and InP have been recognized as tracers of vehicular emissions(Harrison et al., 1996; Jamhari et al., 2014). BeP, BghiP and Cor werecharacteristic of diesel and gasoline engine emission sources (Fanget al., 2004; Sklorz et al., 2007); Flu, Chr, InP, BghiP and Cor were usedto identify gasoline vehicle emission (Caricchia et al., 1999). Conclusioncould be drawn that during the periods of AYG, themain contributors toPAHs concentrationswere gasoline vehicles, related to the concentratedtraffic flows around the venue.
3.1.2. The composition of PAHsFig. 4 shows the time series of ring distribution of PAHs. 5-ring
(39.5 ± 4.8% of total PAHs) and 6-ring PAHs (22.8 ± 3.4%) were themost abundant species, then followed by 4-ring (18.0 ± 4.4%), 3-ring(11.1 ± 3.4%), 7-ring (5.7 ± 2.0%) and 2-ring species (1.48 ± 0.76%),indicating the dominance of high molecular weight PAHs. When com-pared with PAHs concentrations before and after the AYG, the masspercentages of 3- and 4-ring PAHs during the AYG decreased by 2.0%and 0.1%, 3.2% and 2.0%, respectively. While 2-, 6- and 7-ring PAHsmass percentages increased by 0.6% and 0.2%, 1.5% and 3.1%, 1.2% and0.7%, respectively. The mass percentage of 5-ring PAHs during the AYGwas slightly higher than pre-AYG by 2.0% and lower than post-AYG by1.9%. This was different from those observed by Okuda et al. (2011)that decreased trends of 6- and 7-ring PAHs were found during the Bei-jing Olympic Game period. Previous studies indicated that gasoline ve-hicles emit more HMW-PAHs, about five times of those from dieselvehicles (Ho et al., 2009). The sampling site in this study was close tothe Nanjing Olympic Center (approximately 1.3 km), the measuredPAHs profiles were more representative of that around the venue. Theslight increase of 6-ring and 7-ring PAHs can be attributed to thedense gasoline traffic flows around the venue. The mean temperatureand humidity for the pre-AYG period were 34 °4 and 50%, and were
sian Youth Games (Aug. 3–Aug. 15); b: during the Asian Youth Games (Aug. 16–Aug. 24);
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31 ° and 63%, for the during-AYG period, respectively. The enhanced 2-ring concentrations may be attributed to the uptrend humidity and de-crease in temperature during theAYGperiod, and itwould be elaborate-ly discussed in Section 3.1.3.
As shown in Fig. 5, the highest value of total PAHs concentrationwasfound on August 6th with high proportion of 4- and 5-ring PAHs, espe-cially for DBA, BaA, Chr, Pyr, BaP and BkF. DBA was associated withthermal power plant that used coal as fuel (Fang et al., 2004). BaA,Chr, BkF, BbF and BaP were related to petroleum combustion sources(Li et al., 2012b). The highest value occurred with lower mixing layerheight of 556 m, wind speed of 1.18 m s−1 and PM2.5 mass concentra-tion of 31.6 μg m−3, favoring the accumulation of PAHs. The predomi-nant wind direction was S–SW.
PAHs with 3 or 4 rings are semi-volatile ones and partition signifi-cantly in both the gas and the particle phase, while PAHs with morerings are roughly non-volatile and mostly reside in the particle phase(Huang et al., 2006). Ratio of PAHs (3 + 4)/PAHs (5 + 6) is usually
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used in evaluating the origin of PAHs, and higher ratio implies a longerdistance of transport; while lower ratio suggests that the PAHsmight bemostly produced from local emissions (Hou et al., 2006; Wang et al.,2008; Tan et al., 2011). The ratios of PAHs (3+ 4)/PAHs (5+ 6) duringthe sampling period varied from 0.25 to 1.35, indicating that PAHs dur-ing the sampling periods might be mostly from local sources. And thecorrelation coefficient between PAHs (3 + 4)/PAHs (5 + 6) and tem-perature was lower than 0.3. Furthermore, the ratios of PAHs (3 + 4)/PAHs (5 + 6) were 0.55, 0.42 and 0.46 for pre-AYG, during-AYG andpost-AYG periods, respectively. The slightly lower ratio during AYG ver-ified the conclusion that the decrease in PAHs for the sport period wasattributed to the emission reduction measures. The highest value oc-curred on Aug. 9th, with a mixing layer height of 633 m, a wind speedof 1.17m s−1 and a PM2.5mass concentration of 39.6 μgm−3. Accordingto the cruising monitoring results in the surrounding area of Nanjing(Zhang et al., 2014), there were extremely high SO2 and NO2 concentra-tions on Aug. 9th, implying the influence of coal consumptions from the
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Table 2Correlations between meteorological parameters and different rings of PAHs.
RH: relative humidity; WD: wind direction; WS: wind speed; VS: visibility.⁎⁎ Correlation is significant at the 0.01 level (2-tailed).⁎ Correlation is significant at the 0.05 level (2-tailed).
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southwest of Jiangsu Province. In conclusion, the extreme value in Au-gust 9th may be affected by the long-distance transportation of pollut-ants from the southwest region of Jiangsu Province.
3.1.3. Relations between meteorological parameters and PAHsconcentrations
High temperature and strong radiation in summer may increasePAHs partitioning from particulate phase into vapor phase. Besides,the strong photochemical decomposition, deeper mixing layer, strongthermal circulations (Mantis et al., 2005), rain's washing out effectand the summer monsoon (Karar and Gupta, 2006) can also lead tolower PAHs concentrations in summer than other seasons (Kong et al.,2010; He et al., 2014).
Influences of meteorological parameters on the variation of PAHsconcentrations were investigated using Pearson's correlation analysis(Table 2). Higher temperature would not only increase the partitioningof PAHs in the vapor phase but also raise more degradation (He et al.,2014). In this study, there was no linear relationship between tempera-ture and total PAHs concentrations (R b 0.12), mainly because of thelimited samples collected in a single season.
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Different from the results of Chetwittayachan et al. (2002) and Hienet al. (2007), who found that therewas remarkable negative correlationbetween PAHs concentrations and RH, the correlation between RH andPAHs concentrations in this study was not significant. Our conclusionwas consistent with those in Fang et al. (2004) and Kong et al.(2015b). Therefore, the differences in PAHs concentrations here canbe mainly attributed to the variations of emissions.
In this study, 2-ring PAHs correlated positively with humidity andnegatively with temperature. 2-ring PAHs were semi-volatile organiccomponents. He et al. (2014) found that LMW levels were higher insummer than in other seasons. Okuda et al. (2011) also observed thatin summer, low molecule weight PAHs (2-ring and 3-ring) were moreinclined to be volatile and distributed mainly in gas phase, and part ofit can be absorbed on particles. We considered that the high RH andrelative low temperature favor the partitioning of semi-volatile compo-nents into particle phase, butwe still need further and concrete analysis.
Although no significant correlations were found between RH, tem-perature, wind speed and PAH concentrations, there were strong corre-lations between wind direction and 2-, 3-, 4-ring PAHs. Kong et al.(2015a) found that NaP was mainly derived from petroleum evapora-tion. Ravindra et al. (2006) indicated that the major source for 3- and
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1.0
1.5
2.0
2.5
1.0
1.5
2.0
2.50.0
22.5
45.0
67.5
90.0
112.5
135.0
157.5180.0
202.5
225.0
247.5
270.0
292.5
315.0
337.5
1.0
1.5
2.0
2.5
Concentration(ng m
-3)
0.000
0.045
0.090
0.135
0.180
Concentration(ng m
-3)
(d)
(b)
0.00
0.75
1.50
2.25
3.00
s (a), 2-ring (b), 3-ring (c) and 4-ring (d) PAHs concentrations.
Table 4Factor loadings of PCA analysis.
Component
0.0
0.1
0.2
0.3
0.4
0.5
0.6 Before the AYG During the AYG After the AYG Petroleum
combustion
Petroleum Biomass coal and
petroleum combustion
Flu/
(Flu
+Py
r)
Ant/(Ant+Phe)
Petroleum
Biomass and coal combustion
OC
CC
(a)
0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20
0.1 0.2 0.3 0.4 0.50.20
0.25
0.30
0.35
0.40
0.45
0.50 Before the AYG During the AYG After the AYG Biomass and
coal combustion
Petroleumcombustion
PetroleumcombustionB
aA/(
BaA
+C
hr)
InP/(InP+BghiP)
PetroleumBiomass and coal combustion
OC
CC
(b)
Fig. 7. Graphic illustration of the diagnostic ratios for the sources of PAHs (OC: the openceremony; CC: the close ceremony).
92 X. Li et al. / Atmospheric Research 174–175 (2016) 85–96
4-ring PAHs is coal combustion. Fig. 6 shows the predominance of southwind during thewhole sampling period. As shown in Fig. 6, the concen-trations of total PAHs, 3-ring and 4-ring PAHs increased from ESE to SWdirection, while the concentrations of 2-ring PAHs exhibited the oppo-site tendency. The increased 3- and 4-ring PAHs concentrations can beattributed to the air masses from coal-combustion factories in theSSW direction. Strong wind can bring pollutants from outside of thesampling area (Hong et al., 2007). In this study, the concentrations ofPAHs increased more obviously with wind speed increasing when thewind was from the SSW direction. It could verify the effects of long-range transportation. The above explanation could be further elaborat-ed by the cruising monitoring results (Zhang et al., 2014), indicatingthe importance of coal combustion activities at the southwest to theair quality of Nanjing.
3.2. Source identification
3.2.1. Diagnostic ratiosDiagnostic ratios have been applied to identify the possible sources
of PAHs (Tsapakis and Stephanou, 2005; Hong et al., 2007; Vasilakoset al., 2007; Kong et al., 2010). Table 3 lists the widely used diagnosticratios for PAHs. It is identified as the petroleum source if the ratio ofFlu/(Flu + Pyr) is lower than 0.40, and as petroleum combustion if itis between 0.40 and 0.50 and biomass and coal combustion if it exceed0.5 (Li et al., 2009; Gu et al., 2010; Han et al., 2011). For the ratio of Ant/(Ant+ Phe), 0.1 is taken as a dividing line to distinguish petroleum andcombustion sources (Han et al., 2011). Ant/(Ant + Phe) less than 0.1 isconsidered to be petroleum source. As for InP/(InP + BghiP), a ratio of0.18, 0.35 and 0.56 signals gasoline engine, diesel engine, and coal burn-ing sources, respectively (Sienra et al., 2005;Wang et al., 2008; Ravindraet al., 2008; Kong et al., 2010). The BaA/(BaA + Chr) ratio ranging in0.38–0.64 is considered as good markers for diesel and 0.22–0.55 forgasoline emissions (Shi et al., 2014). From Table 3, it is difficult to distin-guish PAHs sources by a single ratio as the overlapping of them for somesources, such as Flu/(Flu + Pyr) and BaA/(BaA + Chr). Therefore, thecombination of Flu/(Flu + Pyr) v.s. Ant/(Ant + Phe) and BaA/(BaA + Chr) v.s. InP/(InP + BghiP) are widely adopted.
In the present study, the scatter plot (Fig. 7a) showed that Flu/(Flu + Pyr) ratios ranged from 0.06 to 0.48, suggesting the dominanceof petroleum during the sampling periods. For Ant/(Ant+ Phe), the ra-tios ranged from0.05 to 0.18, indicating that petroleum(with 26% of thedata values smaller than 0.1) and petroleum combustion (with 74% ofthe data values higher than 0.1) both contributed to PAHs in PM2.5.
During the whole observation period, InP/(InP + BghiP) variedbetween 0.44 and 0.5, implying the dominance of petroleum combus-tion and vehicle emission for PAHs. The values of BaA/(BaA+ Chr) var-ied from 0.26 to 0.47 which were in accordance with 0.22–0.55,
Table 3Diagnostic ratios of PAHs for ambient samples in previous works.
a Han et al., 2011.b The citation “Li et al., 2009” has been changed to “Li et al., 2010” to match the author
name/date in the reference list. Please check if the change is fine in this occurrence andmodify the subsequent occurrences, if necessary Li et al., 2010.
c Gu et al., 2010.d Sarkaret al., 2010.e Sienra et al., 2005.f Wang et al., 2008.g Ravindra et al., 2008.h Kong et al., 2010.i Shi et al., 2014.
suggesting gasoline emissions. In summary, gasoline and diesel emis-sions and petroleum were the main sources of PM2.5-bound PAHs.Rogge et al. (1993) determined that COMPAH/ΣPAHs ratio is 0.4, 0.5and 0.3 for non-catalyst, catalyst-equipped automobiles and heavy-duty diesel trucks, respectively. The conclusion could be verified bythe COMPAHs concentrations which accounted for 47.3%–61.4% of thetotal PAHs, suggesting the dominance of vehicle emission of PAHs inthis study.
93X. Li et al. / Atmospheric Research 174–175 (2016) 85–96
3.2.2. Principal component analysisPrincipal component analysis (PCA) is a widely used multivariate
statistical technique to identify the major sources of air pollutants(Harrison et al., 1996). It is carried out using the statistical software(SPSS 13.0) by the method of varimax rotated factor matrix, based onthe orthogonal rotation criterion maximizing the variance of thesquared elements in the column of a factor matrix (Li et al., 2013). Var-iables with similar characteristics are grouped into specific factorswhich indicate the correlation between pollutant species (Ho and Lee,2002).
Table 4 shows the factor loadings of PAHs for the whole period. Fac-tor 1 explained 55.5% of the total variance, with high loadings of BaA,Chr, BbF, BkF, BaP, DBA, InP and BghiP. Previous studies suggested thatBbF, BkF, BaP, InP, BghiP, BeP, and Cor are markers of vehicular such asdiesel and gasoline combustion sources (Harrison et al., 1996; Fanget al., 2004). Li et al. (2012b) concluded that species including BaA,Chr, BkF, BbF, and BaP were associated with petroleum combustion.High molecular weight PAHs, such as BaP, BeP, InP, DBA, BghiP andCor were widely used as tracers for gasoline and diesel exhaust in for-mer studies (Chang et al., 2006; Wang et al., 2008; Lai et al., 2013; Li
Pre-AYG
Fig. 8. 72-h cluster-mean air parcel backward trajector
et al., 2013; Wu et al., 2014b). Considering the surrounding environ-ment of the sampling site, factor 1 was defined as vehicle emission.
Factor 2 (19.6% of the total variance) was interpreted as coal com-bustion with higher loadings of Ant and Flu. Fl and Ant were the indic-atory PAHs for stationary sources such as power plant, cement,incineration or coke production (Chang et al., 2006; Kong et al., 2011;Kong et al., 2015a). NaP, Acy Ace, Flu, Phe and Ant were associatedwith coal tar/coal combustion (Sofowote et al., 2008). Ant has beenidentified in coal combustion and coke production (Guo et al., 2003a;Akyüz and Çabuk, 2008). Consequently, PM2.5-bound PAHs around thesport centermainly attributed to thedominant contributionof vehicularexhaust, and the contribution of coal combustion should also not be ig-nored. It is in accordance with the results of diagnostic ratio analysis inSection 3.2.1. It was associated with the enhanced use of automobilesaround the center and the shutdown of industrial factories with coalas fuels during the AYG.
Factor 3, with high loadings of NaP, Ace, Acy and Cor, explained 9.7%of the total variance. Factor 4was predominatelyweighted in NaP. Konget al. (2015a) found that NaP and Ace were related with joss paperburning activities at the temples of Mt. Huang. NaP was mainly derived
AYG
Post-AYG
ies for the periods of pre-AYG, AYG and post-AYG.
Table 5Mass concentrations of PAHs for air masses from different directions (ng m−3).
94 X. Li et al. / Atmospheric Research 174–175 (2016) 85–96
frompetroleumevaporation (Kong et al., 2015a). Therefore, factor 3 andfactor 4 were defined as biomass burning and petroleum sources re-spectively, contributing 15.4% of PAHs sources.
3.2.3. Differences of PAHs from different air massesDifferent air masses from different origins can bring clean or pollut-
ed air into the sampling site, influencing PAHs concentrations. Thus,back-trajectories analysis was employed to illustrate the air masses or-igins arriving at the observation site for the pre-AYG, AYG and post-AYGperiods, respectively. According to the cluster analysis results in Fig. 8,the airmasses for different periods can be classified into 3 categories, in-cluding: SW—air masses from southwest of the sampling site (cluster 1of pre-AYG); SE—airmasses from southeast China (cluster 2 of pre-AYG,cluster 1 of AYG and cluster 2 of post-AYG); and S—air masses from sea(cluster 2, 3, 4 of AYG and cluster 1, 3 of post-AYG).
Total PAHs concentrations showed decreasing trend as SW(11.42 ng m−3) N SE (7.54 ng m−3) N S (7.29 ng m−3) (Table 5). MostPAHs species also exhibited the trend of SW N SE N S. It implied thatmore serious PAHs pollution occurred when air masses were from thesouthwest direction, transporting across the Ningwu–Luo River–
8/16
8/17
8/18
8/19
8/20
8/21
8/22
8/23
8/24
8/25
0.0
0.5
1.0
1.5
BaP
eq C
once
ntra
tion
s(ng
m-3)
(a)
Samplin
1
1
ILC
R
Fig. 9. BaP equivalent (BaPeq) concentrations and incremental lifetim
Cheng metallogenic belt in central China where intensive nonferrousmetal industries with huge coal or petroleum consumptions werelocated.
Meanwhile, the weather conditions for air masses from SW favoredthe accumulation of pollutants, with lower MLH (517 ± 183 m), lowerRH (49 ± 7%) and wind speed (1.36 ± 0.32 m s−1). The air masses forSE hold lowest wind speed (0.96 ± 0.14 m s−1) and MLH (509 ±122 m) also favored the accumulation of PM2.5-bound PAHs. For caseS, it held the highest RH (68 ± 7%) andMLH (587 ± 273m). Combinedwith the low PAHs concentrations from the southeast direction asshown in Fig. 6(a), we can draw the conclusion that the relativelyclean air masses from sea diluted PAHs in particles (Kong et al.,2015a) and brought in plentiful water vapor favoring the wet deposi-tion of particle phase PAHs. To conclude, air masses from SW directionshould be paid more attention, which can lead to higher PAHs concen-trations in Nanjing.
3.3. Health risk assessment
Fig. 9(a) shows the total BaP equivalents (BaPeq) for the during-AYGperiod were in the range of 0.42–1.35 ng m−3, with an average of0.84 ng m−3, which was obviously lower than that for a residentialsite (2.80 ng m−3) (Kong et al., 2010), an urban area (7.1 ng m−3)(Wang et al., 2006) and a construction site (1.3 ng m−3) (Kong et al.,2015b). The average BaPeq concentrations during the AYG exhibitedlower levels than those for pre-AYG (1.15 ng m−3) and post-AYG(0.91 ng m−3) periods. The decrease of BaPeq reflected the reductionin vehicle emission and coal combustion. It indicated that the temporalemission reductionmeasures during the AYGwere effective and imper-ative to emancipate people from high health risks of ambient PAHs.BaPeq was significantly correlated with C-PAHs (R2 = 0.97) whichalso elevated by 1.37 and 1.1 times of those for pre-AYG and post-AYGperiods, respectively. It suggested lower potential carcinogenic effectof PAHs during the AYG when compared with other periods.
Excess lifetime cancer risks were shown in Fig. 9(b). Before the AYG,the ILCR values were 1.04 and 5.1 per 1,000,000 exposed children andadults, respectively. During the AYG, the ILCR values were 0.76 and3.71 per 1,000,000 exposed children and adults, which decreased by23% and 27%, respectively when compared with the values for pre-AYG period. These ILCR values indicated that the daily inhalation doseof PAHs and cancer risk to adults and children residing around the sam-pling areas were comparable to the acceptable levels of 10−6 to 10−4 asproposed by the USEPA (Jamhari et al., 2014). It also suggested that thecancer risks to humans were relatively low during the AYG, and thetemporal control measures could efficiently mitigate the health risks.
g period
Pre- AYG During- AYG Post- AYG
E-6
E-5
(b) Children Adult
e cancer risk (ILCR) for children and adult for different periods.
95X. Li et al. / Atmospheric Research 174–175 (2016) 85–96
4. Conclusions
The concentrations of PM2.5-bound PAHs in Nanjing were measuredfrom August 3 to August 28, 2013, across the 2013 Asian Youth Gamesperiod. The total concentration of analyzed PAHs ranged from3.87 ng m−3 to 15.6 ng m−3, with 5-ring PAHs (39.5 ± 4.8% of totalPAHs) and 6-ring PAHs (22.8 ± 3.4%) dominated. The ratio of PAHs(3 + 4) to PAHs (5 + 6) indicated that PAHs might be emitted mostlyfrom the local emissions. The average mass concentrations of PAHswere 9.43, 7.21 and 8.83 ng m−3 for pre-AYG, during-AYG and post-AYG periods, respectively. LMW-PAHs, MMW-PAHs, HMW-PAHs andCOMPAHs for the during-AYG period were all lower than those forpre-AYG and post-AYG periods, due to the emission control measures.The main emission sources of PM2.5-bound PAHs were identified by di-agnostic ratios and principal component analysis, which were gasolinevehicle emissions, coal combustion and petroleum. The estimated life-time cancer risks of PAHs during the Asian YouthGameswere compara-ble to the acceptable levels of 10−6 to 10−4. And they decreased by 23%and 27% for children and adultswhen comparedwith those for pre-AYGperiod, indicating the effectiveness of emission control measures duringAYG period.
Acknowledgments
This work was funded by the National Natural Sciences Foundationof China (no. 41305119), the research funds for Jiangsu Higher Educa-tion Institutions (13KJB170010), Program for Environmental protectionin Jiangsu Province (2014050, 2015017), and the Priority AcademicProgram Development (PAPD) of Jiangsu Higher Education Institution.
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Further Reading
Guo, Z., Sheng, L., Feng, J., Fang, M., 2003b. Seasonal variation of solvent extractable organ-ic compounds in the aerosols in Qingdao, China. Atmos. Environ. 37, 1825–1834.
Liu, Y., Liu, L., Lin, J., Tang, N., Hayakawa, K., 2006. Distribution and characterization ofpolycyclic aromatic hydrocarbon compounds in airborne particulates of East Asia,China. Particuology 4 (7), 283–292.
