characteristics and relationships between indoor and ... · 24 h, and then weighed by an electronic...

Aerosol and Air Quality Research, 16: 2386–2395, 2016 Copyright © Taiwan Association for Aerosol Research ISSN: 1680-8584 print / 2071-1409 online doi: 10.4209/aaqr.2015.12.0682

Characteristics and Relationships between Indoor and Outdoor PM2.5 in Beijing: A Residential Apartment Case Study Yingjie Han1, Xinghua Li1*, Tianle Zhu1**, Dong Lv1, Ying Chen1, Li’an Hou2, Yinping Zhang3,

Mingzhong Ren4 1 School of Space and Environment, Beihang University, Beijing 100191, China 2 Engineering Design and Research Institute of the Second Artillery Corps, Beijing 100011, China 3 Department of Building Science, Tsinghua University, Beijing 100084, China 4 South China Institute of Environmental Sciences, Ministry of Environmental Protection, Guangzhou 510655, China ABSTRACT

In order to understand the characteristics and relationships between indoor and outdoor PM2.5 during the heating period of 2014 in Beijing, the investigation of PM2.5 and associated species including organic and elemental carbon (OC/EC), water soluble ions, metal elements and trace organic matter (OM) were undertaken at a residential apartment. The average PM2.5 concentration was 55.2 ± 47.3 µg m–3 for indoor and 100.4 ± 82.1 µg m–3 for outdoor, and the indoor PM2.5 was found to be mainly from outdoors. OM and (NH4)2SO4 were the dominated components of PM2.5, accounted for 71.5% in indoor PM2.5 and 52.4% in outdoor PM2.5, followed by fine soil and NH4NO3 (23.7% and 27.9%). The polycyclic aromatic hydrocarbons (PAHs) concentration was 187.3 ng m–3 and 387.0 ng m–3, and the phthalic acid esters (PAEs) concentration reached 1054.2 ng m–3 and 515.3 ng m–3, for indoor and outdoor, respectively. Hexachlorobenzene (HCB) only existed indoors (5.5 ng m–3). HCB and most PAEs in indoor PM2.5 were dominated by indoor sources whereas other species were greatly influenced by outdoor sources especially during the pollution period.

Keywords: Indoor/outdoor PM2.5; Chemical composition; Trace organic matter; Heating period. INTRODUCTION

Fine particle (PM2.5) has attracted worldwide attention in the past few decades. Previous epidemiological and toxicological studies has linked PM2.5 to cardiovascular- and respiratory-based disease and premature mortality on a global scale (Pope III and Dockery, 2006; Russell and Bert, 2009; Apte et al., 2015; Lelieveld et al., 2015). Beijing, the capital of China, is one of the cities experiencing serious atmospheric PM2.5 pollution. In 2014, the annual average concentration of PM2.5 in Beijing reached 85.9 µg m–3, 2.5 times of the China National Ambient Air Quality Standard (35 µg m–3). At present, the serious atmospheric PM2.5 pollution has become one of the factors influencing population health and restricting sustainable economic development, social harmony, and stability for Chinese society. * Corresponding author. Tel.: +86-10-82316160; Fax: +86-10-82314215 E-mail address: [email protected]

** Corresponding author. Tel.: +86-10-82314215; Fax: +86-10-82314215 E-mail address: [email protected]

In order to control the serious PM2.5 pollution, Chinese government has implemented a variety of polices and measures (Zhang et al., 2012). The characteristics, sources and control measures of PM2.5 pollution have also been intensively researched in recent years (Zheng et al., 2005; Yang et al., 2011; Wang et al., 2013a; Zhang et al., 2013; Zhao et al., 2013; Huang et al., 2014). In contrary to the extensive attention towards outdoor PM2.5 pollution, only a little attention has been paid to PM2.5 pollution in indoor air. Considering the general facts that there exists a significant difference in air quality between indoor and outdoor, and people spend the majority of their time indoors (Jahn et al., 2013), monitoring and improving the indoor air quality is even more important.

In general, indoor PM2.5 is influenced by direct emissions from indoor sources (e.g., cooking, smoking, and candle burning) (Jones et al., 2000; Dacunto et al., 2013), ventilation supplies from outdoor sources (Zhao et al., 2015), and transport or transformation processes within indoor environments (e.g., mixing, inter-zonal transport, re-suspension, coagulation, and phase change) (Nazaroff, 2004). The indoor/outdoor relationship studies of PM species showed that major chemical components, including organic and elemental carbon (OC/EC), water soluble ions, and metal elements in indoor PM2.5 were greatly influenced by outdoor sources

Han et al., Aerosol and Air Quality Research, 16: 2386–2395, 2016 2387

(Lim et al., 2011; Cao et al., 2012; Hassanvand et al., 2014). For trace organic matter (OM), however, polycyclic aromatic hydrocarbons (PAHs) were affected by both outdoor sources and heating processes inside apartments (Romagnoli et al., 2014), and phthalic acid esters (PAEs) were dominated by indoor sources (Zhang et al., 2014). Although the pollution of PM2.5 in indoor environment has obtained increasing concern in recent years, few studies have been conducted to investigate the characteristics and relationship between indoor and outdoor PM2.5 during different pollution periods. Besides, the simultaneous analysis of different kinds of species in PM2.5, including OC/EC, water soluble ions, metal elements and trace OM is scarce.

In the present study, PM2.5 mass concentrations were continuously monitored inside and outside an apartment in Beijing’s urban area to understand the temporal variations and indoor/outdoor relationships during the different pollution periods. On the other hand, the contents of OC/EC, water soluble ions, metal elements and trace OM including 16 kinds of PAHs, 6 kinds of PAEs and hexachlorobenzene (HCB) in PM2.5 were investigated based on filter-based sampling and subsequent analysis, and the indoor/outdoor relationships of these species were established. METHODS Site and Sampling

Samples and data were collected on the 9th floor of a residential apartment building in Haidian district, Beijing, approximately 50 meters from a two-way road. The sampling site is located in the cultural and educational zone, and there is not any big industrial air pollution source around. The apartment’s three occupants are non-smokers and cook two times daily, which represents typical working families in urban Beijing. The indoor sampling site was in the living room (approximately 1.5 m above the floor), and the outdoor sampling site was located outside the north bedroom window. During the sampling period, the apartment windows were only opened on clean air days for approximately half an hour a day.

Real-time mass concentrations of indoor and outdoor PM2.5 were continuously monitored from January 30 to February 25, 2015 using SDM 805 laser particle monitors (Jinan Nuofang electronic technology Ltd, China) with 5 minute counting intervals. A parallel test between the laser particle monitor and Tapered Element Oscillating Microbalance (TEMO) (Thermal Fisher) was conducted before monitoring. The regression equation obtained from the test was y = 1.02x + 1.33 (R2 = 0.999). In this expression, x and y is the real-time 1-h PM2.5 mass concentration based on TEMO and laser particle monitor, respectively.

Filter-based PM2.5 samples at each sampling site were collected by using two parallel Mini-volume samplers (Airmetrics, USA) on Whatman 47 mm quartz and Teflon filters from December 15, 2014 to March 7, 2015. Each sampling cycle lasted 48 h, and the sampling flow rate was 5 L min–1. Before sampling, the quartz filters were pre-heated at 500°C for 4 h to remove carbonaceous contaminants. After 48-hour sampling period, the loaded filters were stored

in a refrigerator below 0°C before the gravimetric and chemical analysis.

Meteorological data including wind speed (WS) and wind direction (WD) were obtained from China Meteorological Data Sharing Service System. The real-time PM2.5 mass concentration monitoring data was communicated from the sampling devices to the computer over wireless. Gravimetric and Chemical Analysis

Before and after sampling, Teflon filters were equilibrated in a controlled chamber (T = 20 ± 1°C, RH = 50 ± 5%) for 24 h, and then weighed by an electronic balance with a detection limit of 2 µg (CPA-26P, Sartorius, German).

Teflon filters were analyzed for both water soluble ions and metal elements. Half of each filter was extracted once in 10 mL Milli-Q water using an ultrasonic bath for 30 min, and then filtered through a 0.45 µm polytetrafluoroethylene (PTFE) syringe filter. Part of the filtrate was analyzed for anions of SO4

2–, NO3– and Cl– using ion chromatography

(IC) (792 Basic IC, Metrohm, Switzerland), and part was determined for NH4

+ according to Nessler’s reagent colorimetric method formulated by Ministry of Environmental Protection of People’s Republic of China (2009). The rest of Teflon filter was firstly digested in a Teflon vessel using a mixture of HNO3, HClO4, and HF at 170°C for 4.5 h. After the mixed acids in the extract were evaporated, the extract was diluted to 10 mL using Milli-Q water. The 13 metal elements (Na, Mg, Al, Ca, Ti, Mn, Fe, Ni, Cu, Zn, Sr, Mo, and Pb) were analyzed using inductively coupled plasma mass spectrometry (ICP-MS) (Agilent 7500a, Agilent Technologies, USA). Field blank values were subtracted from sample concentrations.

A 0.5 cm2 punch from each quartz filter was analyzed for OC and EC using a Model 2001 Thermal/Optical Carbon Analyzer (Atmoslytic Inc., Calabasas, CA, USA), following the IMPROVE thermal/optical reflectance (TOR) protocol (Chow et al., 1993). Again, field blank values were subtracted from sample concentrations. Half of each quartz filter was extracted three times in 5mL dichloromethane (DCM) using an ultrasonic bath for 20 min, then the extract was concentrated to approximately 2 mL using a rotary evaporator, meanwhile the solvent was exchanged to hexane, and finally the extract was concentrated to 100 µL by nitrogen blow-down. The trace OM of PAHs, PAEs and HCB were analyzed using gas chromatographic mass spectrometry (GC-MS) (Trace GC Polaris Q, Thermo Scientific, USA), operated in selected ion monitoring mode. The 16 kinds of PAHs include naphthalene (Nap) with 2-rings, acenaphthylene (Acy), acenaphthene (Ace), fluorene (Fl), phenanthrene (Phe) and anthracene (An) with 3-rings, fluoranthene (Flu), pyrene (Pyr), benzo[a]anthracene (BaA) and chrysene (Chr) with 4-rings, benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), benzo[a]pyrene (BaP) and dibenzo[a,h]anthracene (DBA) with 5-rings, indeno[1,2,3-cd]pyrene (InP) and benzo[g,h,i]perylene (BghiP) with 6-rings. The 6 kinds of PAEs include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), butyl benzyl phthalate (BBP), di-2-ethyl hexyl phthalate (DEHP) and di-n-octyl phthalate (DNOP).


The recovery rates of trace OM were evaluated by injecting standard mixtures formulated to mimic real sample concentrations into three blank filters respectively and conducting the entire pretreatment and analysis process. The recovery rates of most trace OM were in the range of 80–125%, whereas that of NaP only reached 60% because of its strong volatility.

Data Analysis

PM2.5 mass concentrations were reconstructed using the method adopted by Li et al. (2013). The PM2.5 chemical compositions were classified into six major chemical components: NH4NO3, (NH4)2SO4, OM, EC, fine soil and others in this research. The NH4NO3 mass was estimated by multiplying the NO3

– mass by a factor of 1.29 and the (NH4)2SO4 mass was estimated by multiplying the SO4

2– mass by a factor of 1.38. The OM concentration was derived from multiplying the OC concentrations by a factor of 1.4 to account for unmeasured atoms (Xing et al., 2013).

The fine soil mass was estimated using factors associated with common oxides of soil elements (Al2O3, SiO2, CaO, FeO, Fe2O3, and TiO2), and calculated as follows (Chan et al., 1997):

[fine soil] = 2.20[Al] + 2.49[Si] + 1.63[Ca] + 2.42[Fe] + 1.94[Ti] (1)

Given a lack of data for Si, the Si mass was estimated using the Al mass, multiplied by a factor of 3.36 (Rudnick and Gao, 2003). RESULTS AND DISCUSSION Temporal Variations of Indoor and Outdoor PM2.5

Fig. 1 provides time series of real-time 1-h PM2.5 mass concentrations, measured both inside and outside the apartment, together with meteorological parameters. The

arrow length represents WS with a range of 0–9 m s–1 and the arrow direction represents WD. Daily PM2.5 concentrations ranged from 4.5 to 193.1 µg m–3 for indoor with an average of 55.2 ± 47.3 µg m–3, and ranged from 5.9 to 298.9 µg m–3 for outdoor with an average of 100.4 ± 82.1 µg m–3. Compared against World Health Organization (WHO) guidelines, the average indoor and outdoor PM2.5 concentration was almost 2 and 4 times of the daily outdoor limit (25 µg m–3), respectively. In addition, approximately 41% of the indoor and 56% of the outdoor daily mean values exceeded the limit value of PM2.5 (75 µg m–3) stipulated by the China National Ambient Air Quality Standards (GB 3095-2012).

As shown in Fig. 1, there were six pollution cycles during the monitoring period, with duration of 3 to 6 days for each cycle. For each cycle, the PM2.5 concentrations kept at a low level for 1–2 days firstly, then rose slowly over a few days, and finally fell abruptly to the valley value in a few hours. This cyclical pattern has also been observed by Jia et al. (2008). Based on PM2.5 concentration variation, each cycle can be divided into three periods: a clean air period, a PM2.5 accumulation period, and a PM2.5 decline period. As illustrated in Fig. 1, the clean air period came along with the wind from north, northwest, or northeast with an average speed of 3.1 m s–1 that favors the transport and diffusion of air pollutants. During the PM2.5 accumulation period, the winds were mainly from south or southwest with a low WS of less than 1.7 m s–1, which resulted in the accumulation and formation of secondary pollutants, as described by Wang et al. (2013b). The sudden drop during PM2.5 decline period could be attributed to the gale from north or northwest with a speed exceeding 4.0 m s–1.

Indoor/Outdoor Relationships of PM2.5 during Different Periods

Indoor/Outdoor (I/O) ratios and regression lines were analyzed to compare indoor/outdoor relationships of PM2.5 during the clean air period, PM2.5 accumulation period and

Fig. 1. Time series of real-time mass concentrations of indoor and outdoor PM2.5 and meteorological parameters.


PM2.5 decline period. In this study, the average I/O ratio was 0.60 during the clean air period and 0.51 during the PM2.5 accumulation period, and the correlation coefficient (r) was 0.746 and 0.944, respectively, which indicated that indoor PM2.5 was greatly influenced by outdoor sources. The concentrations of PM2.5 between indoor and outdoor PM2.5 can be expressed by linear regression equation as follows: Cin = FinCout + Cṡ (2)

In this expression, Cin is the indoor PM2.5 concentration

based on both indoor and outdoor sources; Cout is the outdoor PM2.5 concentrations; Fin is the infiltration factor; and Cṡ is the indoor PM2.5 concentration contributed by indoor sources, as described in Chen and Zhao (2011).

It can be seen from Fig. 2 that during the clean air period, the PM2.5 from indoor sources (Cṡ) was 4.90 µg m–3 and the corresponding average indoor PM2.5 concentration (Cin) was 10.53 µg m–3, suggesting that approximately 47% of the indoor PM2.5 came from indoor sources. The intercept during the PM2.5 accumulation period was less than zero (–7.50 µg m–3), which might be attributed to some species’ decomposition in indoor PM2.5. In this study, the I/O ratios for NH4NO3 and NH4Cl were about 0.28 and 0.32, respectively, much lower than 0.67 for (NH4)2SO4. The result proved that part decomposition of NH4NO3 and NH4Cl inside the apartment did occur, which could be attributed that indoor temperature was higher than outdoor one during the heating period.

As also shown in Fig. 2, Fin was estimated as 0.29 for the clean air period and 0.56 for the PM2.5 accumulation period, showing that the infiltration of PM2.5 during the PM2.5 accumulation period occurred more easily. This result might be due to the fact that during the PM2.5 accumulation period, quite a number of outside PM2.5 were secondary aerosols (e.g., sulfate, nitrate, ammonium, secondary organic carbon) with size less than 1 µm (John et al., 1990; Pandis et al., 1993), which have better infiltration performance, compared with particles of other sizes (Long et al., 2001).

Unlike the I/O ratios (< 1) during the clean air period and PM2.5 accumulation period, the I/O ratio during the PM2.5 decline period reached 1.26, which was attributed to the fact that the drop in indoor PM2.5 concentration was later than that in outdoor PM2.5 concentration, and the PM2.5 falling rate for indoor (15.0 µg m–3 h–1) was lower than that for outdoor (29.4 µg m–3 h–1). In this case, fine particulates might travel from inside to outside.

Chemical Compositions of Indoor/Outdoor PM2.5

Fig. 3 shows the reconstructed indoor/outdoor PM2.5 chemical compositions during all days, normal days and Chinese Spring Festival, calculated based on material balance. The Spring Festival lasted from the eve of lunar New Year (February 18, 2015) to lantern festival (March 5, 2015). The frequent burning of firework during this period has adverse effects on air quality (Wang et al., 2007). The number at the top of each column is the corresponding average PM2.5 concentration for each period. For the total sampling period, the proportion of different components in PM2.5 is

as follows: OM (52.0% for indoor and 37.5% for outdoor), (NH4)2SO4 (19.5% for indoor and 14.9% for outdoor), NH4NO3 (8.3% for indoor and 15.3% for outdoor), fine soil (15.4% for indoor and 12.6% for outdoor), EC (4.7% for indoor and 4.2% for outdoor).

Compared with the result for outdoor, the proportion of OM for indoor increased 14.5%, which might be attributed to the presence of more OM sources in indoor environment. The average concentration of OC was 18.3 µg m–3 for indoor and 27.9 µg m–3 for outdoor. It is noted that the percentage of OC to total carbon (TC) (OC/TC) in indoor and outdoor environment reached 90% and 87%, respectively, higher than the values (67%–86%) previously reported in Chinese urban areas (including Beijing, Hongkong, Guangzhou, Shenzhen, Zhuhai and Xi’an) (Cao et al., 2003; Cao et al., 2005; Peng et al., 2009; Cao et al., 2012). This result might be due to the intensive OC emissions from coal burning during heating period. Despite significant efforts made in Beijing, scattered coal stoves were still widely used in the suburban area.

The proportion of NH4NO3 for indoor decreased 7.0%, compared to that for outdoor, which could be attributed to the decomposition of NH4NO3 inside the apartment where the temperature was relatively high, compared with that of outdoor. It is noted that the NO3

–/SO42– ratio in outdoor

environment was 1.1, considerably higher than 0.49 in the winter of 2001–2003 in Beijing (Wang et al., 2005). In fact, NO3

–/SO42– ratio is used to indicating the relative importance

of mobile and stationary sources (Yao et al., 2002), and the value suggested the dominance of mobile sources over stationary ones at present.

Compared with the results during normal days, the indoor and outdoor PM2.5 concentrations during Spring Festival were much higher. For outdoor environment, the concentrations of fine soil, (NH4)2SO4, NH4NO3 during Spring Festival were 5.2, 2.3 and 1.1 times of those during normal days, respectively. For indoor environment, the corresponding times were 5.7, 1.9 and 2.1. These results were due to the firework burning during Spring Festival. According to Wang et al. (2007), firework burning will generate primary components of K, Ba, Sr, Cl–, Pb, Mg, Al, Cu, Mn and promote the formation of secondary components of SO4

2– and NO3–. The

outdoor concentration of Cl–, Pb, Mg, Al, Cu, Mn, SO42–

and NO3– during Spring Festival in this study was found to

be 2.5, 4.5, 12.7, 7.8, 10.6, 3.5, 2.3 and 1.1 times of those during normal days, respectively. K, the most important characteristic element for firework burning, was not detected in this study because the presence of argon ion would cause a big error in the detection of K when ICP-MS uses argon as a carrier gas. On the contrary, the indoor and outdoor concentration of OM during Spring Festival decreased 14% and 24%, compared to those during normal days, respectively, which was attributed to the significant decrease in the emissions from traffic, industry and cooking during Spring Festival when population and anthropogenic activities decreased a lot in this city. Indoor/Outdoor Relationships of OC, EC, Water Soluble Ions and Total Metal Elements

Linear regression analysis was used to investigate the


Fig. 2. I/O ratios and regression lines during the clean air period, PM2.5 accumulation period and PM2.5 decline period.


Fig. 3. Reconstructed chemical compositions of indoor and outdoor PM2.5 organized by material balance during different periods.

indoor/outdoor relationships of OC, EC, water soluble ions and total metal elements during the sampling period. As Table 1 shows, the indoor and outdoor concentrations of OC, EC, Cl–, SO4

2– and NH4+ were all strongly correlated

with r of 0.79–0.99, indicating that outdoor sources had a considerable impact to indoor PM2.5. The intercept in Table 1 indicated that approximately 27% of indoor OC was from indoor sources, and the value was 5% for indoor EC. The result was consistent with He et al. (2004) and Cao et al. (2012). It is noted that the intercepts for Cl– and NH4

+ were both below zero. In general, most of NH4

+ in PM2.5 are in the form of (NH4)2SO4 and NH4NO3. According to the charge balance between NH4

+ and acidic ions, the stoichiometric ratio for [NH4

+] and [SO42– + NO3

–] was 1.18, which suggested

that extra NH4+ would be in the form of NH4Cl. Thus the

negative intercept was due to the decomposition of NH4Cl and NH4NO3 inside the apartment where the temperature was relatively high, compared with that of outdoor (Lunden et al., 2003).

To investigate the indoor/outdoor relationship at different pollution levels, samples were divided into two categories according to the standard daily mean value of 75 µg m–3 for PM2.5 (China National Ambient Air Quality Standard, GB3095-2012). Ones were samples of clean period with outdoor PM2.5 concentrations less than or equal to 75 µg m–3, and the others were samples of pollution period with outdoor PM2.5 concentrations higher than 75 µg m–3. I/O ratios, r and P values (through paired-sample t-tests) during the clean

Table 1. Indoor/outdoor relationships of OC, EC, water soluble ions, total metal elements, PAHs with different rings and DMP (regression equation: µg m–3 for the first seven species and ng m–3 for the others).

Regression equation

(n = 24) rb

Clean period (n = 12) Pollution period (n = 12) rb I/Oc Pd rb I/Oc Pd

OC y = 0.48x + 5.01 0.987a 0.883a 0.92 0.045 0.972a 0.63 0 EC y = 0.51x + 0.11 0.968a 0.958a 0.54 0 0.887a 0.54 0 Cl– y = 0.48x – 0.82 0.944a 0.846a 0.35 0 0.967a 0.29 0

NO3– y = 0.21x + 0.53 0.798a 0.639a 0.29 0 0.562a 0.27 0

SO42– y = 0.49x + 1.49 0.944a 0.897a 0.69 0.007 0.925a 0.65 0.007

NH4 + y = 0.38x – 0.21 0.885a 0.970a 0.26 0 0.715a 0.36 0

Total metal elements y = 0.76x – 0.72 0.807a 0.045 0.67 0.037 0.933a 0.67 0.01 2-ring PAH y = 0.61x + 1.30 0.606a 0.556a 0.88 0.172 0.648a 1.06 0.605 3-ring PAHs y = 0.34x + 6.65 0.881a 0.931a 0.7 0.002 0.873a 0.56 0.011 4-ring PAHs y = 0.17x + 12.53 0.923a 0.960a 0.24 0 0.911a 0.23 0.035 5-ring PAHs y = 0.25x + 18.82 0.914a 0.971a 0.52 0.001 0.920a 0.48 0.104 6-ring PAHs y = 0.30x + 6.24 0.883a 0.975a 0.33 0.002 0.892a 0.6 0.132

DMP y = 0.18x + 4.41 0.371 0.297 0.47 0 0.484 0.55 0 a P < 0.05. b Correlation coefficients. c Indoor/outdoor concentration ratios. d P values were calculated from paired-sample t-test, comparing the indoor and outdoor concentrations.


period and pollution period were computed for the target components. The concentrations of OC, EC, water soluble ions and total metal elements for indoor were significantly (P < 0.05) lower than those for outdoor. On the other hand, the indoor and outdoor concentrations of most species were in good correlation (r > 0.6). These results indicated these indoor species were greatly influenced by outdoor sources. It is also noted that the indoor/outdoor correlation of most pollutants (OC, Cl–, SO4

2– and metal elements) were better during pollution period, which aligned with the fact that the outdoor PM2.5 infiltration during pollution period was stronger than that during clean period. The I/O ratios of Cl–, NO3

–, and NH4+ were much lower than that for SO4

2–, which could be attributed to the decomposition of NH4NO3 and NH4Cl, as has been mentioned before. In fact, SO4

2– often serves as the characteristic component to evaluate PM2.5 infiltration performance for its high stability at

ambient temperatures (Jeremy et al., 2002).

Characteristics and Indoor/Outdoor Relationships of Trace Organic Matter

During the sampling period, the PAHs concentration was 187.3 ng m–3 for indoor and 387.0 ng m–3 for outdoor, and the outdoor value was around 1.7-fold of that detected in 2001 winter (228.9 ng m–3) and comparable to that detected in 2008 winter in Beijing (407.6 ng m–3) (Huang et al., 2006; Wang et al., 2008). In indoor environment, 4-ring PAHs accounted for 38.0% of the total PAHs mass, followed by 5-ring PAHs (36.2%), 6-ring PAHs (12.1%), 3-ring PAHs (11.2%) and 2-ring PAH (2.4%). In outdoor environment, 4-ring PAHs made up 52.2% of PM2.5 mass, followed by 5-ring PAHs (29.3%), 6-ring PAHs (9.4%), 3-ring PAHs (7.9%) and 2-ring PAH (1.2%). Fig. 4 shows the distributions of PAHs and PAEs in indoor and outdoor samples during

Fig. 4. PAHs and PAEs distributions during different periods.


different periods. The number at the top of each column was corresponded to the concentration of PAHs or PAEs. Compared with the results during normal days, the PAHs concentration in indoor and outdoor during Spring Festival decreased about 50% and 58%, respectively, which could also be attributed to the significant decrease in the emission from traffic, industry and cooking, as has been mentioned before.

The PAEs concentrations ranged from 301.6 to 2606.8 ng m–3 for indoor with an average of 1054.2 ng m–3, and ranged from 122.3 to 1658.3 ng m–3 for outdoor with an average of 515.3 ng m–3, which was comparable with those collected from 13 homes in Tianjin (14.9–1591.3 ng m–3 for indoor and 7.3–1244.2 ng m–3 for outdoor) (Zhang et al., 2014) and those collected from 10 offices in Hangzhou (1375.8 ng m–3 for indoor) (Min et al., 2015). Among the 6 kinds of PAEs, DBP and DEHP were the dominant species, accounting for 46% and 43% of the total indoor PAEs mass, and 12% and 81% of the outdoor PAEs mass, which could be attributed to the wide use of DBP and DEHP as additives in China’s industrial production (up to 90% of total output) (Wang et al., 2008). Unlike PAHs, the indoor concentration of DEP, DBP, BBP, DEHP and DNOP was approximately 2.0, 7.9, 70.9, 1.1 and 4.8 times of the outdoor concentrations, respectively. Clearly, there existed considerable PAEs sources in the apartment, such as cosmetics, personal care products and resin products (e.g., polyvinyl chloride plastics, polyvinyl acetate, polyurethane) (Gómez-Hens and Aguilar-Caballos, 2003). HCB was detected only in the indoor samples and the average concentration was 5.5 ng m–3, which indicated the predominant contribution of indoor sources (e.g., rubber, aluminum products, dyes, wood preservatives) (Kümmling et al., 2001).

The indoor/outdoor relationships of PAHs with different rings and DMP were also investigated (shown in Table 1). PAHs with rings of 3, 4, 5 and 6 were in good positive correlation with r of 0.88–0.93, suggesting outdoor sources had a great influence on these species. Whereas, the r of 2-ring PAH and DMP was only 0.606 and 0.371, which suggested the definite effect from indoor sources. According to the research conducted by Batterman et al. (2012) and Guerrero and Corsi (2012), the indoor sources of 2-ring PAH include the mothball in closets and deodorizer in toilet bowls. As discussed by Gómez-Hens and Aguilar-Caballos (2003), cosmetics, personal care products and resin products are the indoor sources of DMP. Compared with the result during the clean period, the indoor and outdoor concentrations of 2-ring PAH and DMP during the pollution period were better correlated, which could be attributed to the stronger infiltration of outdoor PM2.5 during the pollution period as mentioned before. CONCLUSIONS

This study presented the results of real-time PM2.5 concentrations and chemical composition of PM2.5 inside and outside an apartment in urban Beijing during heating period. The average PM2.5 concentration from January 30 to February 25, 2015 was 55.2 ± 47.3 µg m–3 for indoor

and 100.4 ± 82.1 µg m–3 for outdoor, revealing there existed a serious PM2.5 pollution in Beijing and indoor PM2.5 was mainly from outdoor sources. OM and (NH4)2SO4 were the dominated components of PM2.5, accounted for 71.5% in indoor PM2.5 and 52.4% in outdoor PM2.5, followed by fine soil and NH4NO3 (23.7% and 27.9%). The PAHs concentration was 187.3 ng m–3 for indoor and 387.0 ng m–3 for outdoor, and PAEs concentration was 1054.2 ng m–3 and 515.3 ng m–3 for indoor and outdoor, respectively. HCB was detected only in the indoor samples (5.5 ng m–3). Higher concentrations of Cl–, Pb, Mg, Al, Cu, Mn, SO4

2– and NO3–

were observed during Spring Festival, compared with normal days, which could be attributed to the firework burning. HCB and most PAEs in indoor PM2.5 were dominated by indoor sources whereas other species were greatly influenced by outdoor sources especially during the pollution period. Effective measures should be taken to control the infiltration of outdoor pollutants especially during heavy pollution period. ACKNOWLEDGMENTS

This work was supported by Chinese Ministry of Environmental Protection (201409080) and National Natural Science Foundation of China (41275121). REFERENCES Apte, J.S., Marshall, J.D., Cohen, A.J. and Brauer, M.

(2015). Addressing global mortality from ambient PM2.5. Environ. Sci. Technol. 49: 8057–8066.

Batterman, S., Chin, J.Y., Jia, C., Godwin, C., Parker, E., Robins, T., Max, P. and Lewis, T. (2012). Sources, concentrations, and risks of naphthalene in indoor and outdoor air. Indoor Air 22: 266–278.

Cao, J.J., Lee, S.C., Ho, K.F., Zhang, X.Y., Zou, S.C., Fung, K., Chow, J.C. and Watson, J.G. (2003). Characteristics of carbonaceous aerosol in Pearl River delta region, China during 2001 winter period. Atmos. Environ. 37: 1451–1460.

Cao, J.J., Wu, F., Chow, J.C., Lee, S.C., Li, Y., Chen, S.W., An, Z.S., Fung, K.K., Watson, J.G. and Zhu, C.S. (2005). Characterization and source apportionment of atmospheric organic and elemental carbon during fall and winter of 2003 in Xi’an, China. Atmos. Chem. Phys. 5: 3127–3137.

Cao, J.J., Huang, H., Lee, S.C., Chow, J.C., Zou, C.W., Ho, K.F. and Watson, J.G. (2012). Indoor/outdoor relationships for organic and elemental carbon in PM2.5 at residential homes in Guangzhou, China. Aerosol Air Qual. Res. 12: 902–910.

Chan, Y., Simpson, R., McTainsh, G.H., Vowles, P.D., Cohen, D. and Bailey, G. (1997). Characterisation of chemical species in PM2.5 and PM10 aerosols in brisbane, Australia. Atmos. Environ. 31: 3773–3785.

Chen, C. and Zhao, B. (2011). Review of relationship between indoor and outdoor particles: I/O ratio, infiltration factor and penetration factor. Atmos. Environ. 45: 275–288.

Chow, J.C., Watson, J.G., Pritchett, L.C., Pierson, W.R.,


Frazier, C.A. and Purcell, R.G. (1993). The dri thermal/optical reflectance carbon analysis system: description, evaluation and applications in U.S. air quality studies. Atmos. Environ. 27: 1185–1201.

Dacunto, P.J., Cheng, K.C., Acevedo-Bolton, V., Jiang, R.T., Klepeis, N.E., Repace, J.L., Ott, W.R. and Hildemann, L.M. (2013). Real-Time particle monitor calibration factors and PM2.5 emission factors for multiple indoor sources. Environ. Sci. Processes Impacts 15: 1511–1519.

Gómez-Hens, A. and Aguilar-Caballos, M.P. (2003). Social and economic interest in the control of phthalic acid esters. TrAC, Trends Anal. Chem. 22: 847–857.

Guerrero, P.A. and Corsi, R.L. (2012). Emissions of p-dichlorobenzene and naphthalene from consumer products. J. Air Waste Manage. Assoc. 62: 1075–1084.

Hassanvand, M.S., Naddafi, K., Faridi, S., Arhami, M., Nabizadeh, R., Sowlat, M.H., Pourpak, Z., Rastkari, N., Momeniha, F. and Kashani, H. (2014). Indoor/outdoor relationships of PM10, PM2.5, and PM1 mass concentrations and their water-soluble ions in a retirement home and a school dormitory. Atmos. Environ. 82: 375–382.

He, L.Y., Hu, M., Huang, X.F., Yu, B.D., Zhang, Y.H. and Liu, D.Q. (2004). Measurement of emissions of fine particulate organic matter from Chinese cooking. Atmos. Environ. 38: 6557–6564.

Huang, R.H., Zhang, Y.L., Bozztti, C., Ho K.F., Cao J.J., Han, Y.M., Daellenbach, K.R., Slowik, J.G., Platt, S.M. and Francesco, C. (2014). High secondary aerosol contribution to particulate pollution during haze events in China. Nature 514: 218–222.

Huang, X.F., He, L.Y., Hu, M. and Zhang, Y.H. (2006). Annual variation of particulate organic compounds in PM2.5 in the urban atmosphere of Beijing. Atmos. Environ. 40: 2449–2458.

Jahn, H.J., Kraemer, A., Chen, X.C., Chan, C.Y., Engling, G. and Ward, T.J. (2013). Ambient and personal PM2.5 exposure assessment in the Chinese megacity of Guangzhou. Atmos. Environ. 74: 402–411.

Jeremy, A.S., Christopher, M.L., Petros, K., Brent, A.C., Joel, S. and Helen, H.S. (2002). Using sulfur as a tracer of outdoor fine particulate matter. Environ. Sci. Technol. 36: 5305–5314.

Jia, Y., Rahn, K.A., He, K., Wen, T. and Wang, Y. (2008). A novel technique for quantifying the regional component of urban aerosol solely from its sawtooth cycles. J. Geophys. Res. 113: 6089–6098.

John, W., Wall, S.M., Ondo, J.L. and Winklmayr, W. (1990). Modes in the size distributions of atmospheric inorganic aerosol. Atmos. Environ. 24: 2349–2359.

Jones, N.C., Thornton, C.A., Mark, D. and Harrison, R.M. (2000). Indoor/outdoor relationships of particulate matter in domestic homes with roadside, urban and rural locations. Atmos. Environ. 34: 2603–2612.

Kümmling, K., Gray, D.J., Power, J.P. and Woodland, S.E. (2001). Gas-phase chemical reduction of hexachlorobenzene and other chlorinated compounds: Waste treatment experience and applications. In 6 th International HCH & Pesticides Forum Book, p. 20–22.

Lelieveld, J., Evans, J.S., Fnais, M., Giannadaki, D. and

Pozzer, A. (2015). The contribution of outdoor air pollution sources to premature mortality on a global scale. Nature 525: 367–371.

Li, X., He, K., Li, C., Yang, F., Zhao, Q., Ma, Y., Yuan, C., Ouyang, W. and Chen, G. (2013). PM2.5 mass, chemical composition, and light extinction before and during the 2008 Beijing olympics. J. Geophys. Res. 118: 12158–112167.

Lim, J.M., Jeong, J.H., Lee, J.H., Moon, J.H., Chung, Y.S. and Kim, K.H. (2011). The analysis of PM2.5 and associated elements and their indoor/outdoor pollution status in an urban area. Indoor Air 21: 145–155.

Lin, P., Hu, M., Deng, Z., Slanina, J., Han, S., Kondo, Y., Takegawa, N., Miyazaki, Y., Zhao, Y. and Sugimoto, N. (2009). Seasonal and diurnal variations of organic carbon in PM2.5 in Beijing and the estimation of secondary organic carbon. J. Geophys. Res. 114: 1013–1033.

Long, C.M., Suh, H.H., Catalano, P.J. and Koutrakis, P. (2001). Using time- and size-resolved particulate data to quantify indoor penetration and deposition behavior. Environ. Sci. Technol. 35: 2089–2099.

Lunden, M.M., Revzan, K.L., Fischer, M.L., Thatcher, T.L., Littlejohn, D., Hering, S.V. and Brown, N.J. (2003). The transformation of outdoor ammonium nitrate aerosols in the indoor environment. Atmos. Environ. 37: 5633–5644.

Min, S., Chi, C., Min, G., Wang, X., Cheng, L. and Shen, X. (2015). Pollution levels and characteristics of phthalate esters in indoor air of offices. J. Environ. Sci-China 28: 157–162.

Ministry of Environmental Protection of People’s Republic of China (2009). Air and Exhaust Gas —Determination of Ammonia—Nessler’s Reagent Spectrophotometry, HJ533-2009, China Environmental Science Press, Beijing.

Nazaroff, W.W. (2004). Indoor particle dynamics. Indoor Air 14: 175–183.

Pandis, S.N., Wexler, A.S. and Seinfeld, J.H. (1993). Secondary organic aerosol formation and transport—II. Predicting the ambient secondary organic aerosol size distribution. Atmos. Environ. 27: 2403–2416.

Pope III, C.A. and Dockery, D.W. (2006). Health effects of fine particulate air pollution: Lines that connect. J. Air Waste Manage. Assoc. 56: 709–742.

Romagnoli, P., Balducci, C., Perilli, M., Gherardi, M., Gordiani, A., Gariazzo, C., Gatto, M. and Cecinato, A. (2014). Indoor PAHs at schools, homes and offices in Rome, Italy. Atmos. Environ. 92: 51–59.

Rudnick, R.L. and Gao, S. (2003). Composition of the continental crust. In Treatise on Geochemistry, Volume 3, Holland, H.D. and Turekian, K.K. (Eds.), pp. 1–64.

Russell, A.G. and Bert, B. (2009). A focus on particulate matter and health. Environ. Sci. Technol. 43: 4620–4625.

Wang, J., Hu, Z., Chen, Y., Chen, Z. and Xu, S. (2013a). Contamination characteristics and possible sources of PM10 and PM2.5 in different functional areas of Shanghai, China. Atmos. Environ. 68: 221–229.

Wang, P., Wang, S. and Fan, C. (2008). atmospheric distribution of particulate-and gas-phase phthalic esters (PAEs) in a metropolitan City, Nanjing, East China.


Chemosphere 72: 1567–1572. Wang, X.F., Cheng, H.X., Xu, X.B., Zhuang, G.M. and

Zhao, C.D. (2008). A wintertime study of polycyclic aromatic hydrocarbons in PM2.5 and PM2.5–10 in Beijing: Assessment of energy structure conversion. J. Hazard. Mater. 157: 47–56.

Wang, Y., Zhuang, G., Tang, A., Yuan, H., Sun, Y., Chen, S. and Zheng, A. (2005). The ion chemistry and the source of PM2.5 aerosol in Beijing. Atmos. Environ. 39: 3771–3784.

Wang, Y., Zhuang, G., Xu, C. and An, Z. (2007). The air pollution caused by the burning of fireworks during the lantern festival in Beijing. Atmos. Environ. 41: 417–431.

Wang, Y.S., Yao, L., Wang, L.L., Liu, Z.R., Ji, D.S., Tang, G.Q., Zhang, J.K., Sun, Y., Hu, B. and Xin, J.Y. (2013b). Mechanism for the formation of the January 2013 heavy haze pollution episode over central and Eastern China. Sci. China Earth Sci. 57: 14–25.

Xing, L., Fu, T.M., Cao, J.J., Lee, S.C., Wang, G.H., Ho, K.F., Cheng, M.C., You, C.F. and Wang, T.J. (2013). Seasonal and spatial variability of the OM/OC mass ratios and high regional correlation between oxalic acid and zinc in Chinese urban organic aerosols. Atmos. Chem. Phys. 13: 4307–4318.

Yang, F., Tan, J., Zhao, Q., Du, Z., He, K., Ma, Y., Duan, F. and Chen, G. (2011). Characteristics of PM2.5 speciation in representative megacities and across China. Atmos. Chem. Phys. 11: 5207–5219.

Yao, X., Chan, C.K., Fang, M., Cadle, S., Chan, T., Mulawa, P., He, K. and Ye, B. (2002). The water-soluble ionic composition of PM2.5 in Shanghai and Beijing,

China. Atmos. Environ. 36: 4223–4234. Zhang, L., Wang, F., Ji, Y., Jiao, J., Zou, D., Liu, L., Shan,

C., Bai, Z. and Sun, Z. (2014). Phthalate esters (PAEs) in indoor PM10/PM2.5 and human exposure to PAEs Via inhalation of indoor air in Tianjin, China. Atmos. Environ. 85: 139–146.

Zhang, Q., He, K. and Huo, H. (2012). Cleaning China's air. Nature 484: 161–162.

Zhang, R., Jing, J., Tao, J. and Hsu, S.C. (2013). Chemical characterization and source apportionment of PM2.5 in Beijing: Seasonal perspective. Atmos. Chem. Phys. 13: 7053–7074.

Zhao, L., Chen, C., Wang, P., Chen, Z., Cao, S., Wang, Q., Xie, G., Wan, Y., Wang, Y. and Lu, B. (2015). Influence of atmospheric fine particulate matter (PM2.5) pollution on indoor environment during winter in Beijing. Build. Environ. 87: 283–291.

Zhao, P.S., Dong, F., He, D., Zhao, X.J., Zhang, X.L., Zhang, W.Z., Yao, Q. and Liu, H.Y. (2013). Characteristics of concentrations and chemical compositions for PM2.5 in the region of Beijing, Tianjin, and Hebei, China. Atmos. Chem. Phys. 13: 4631–4644.

Zheng, M., Salmon, L.G., Schauer, J.J., Zeng, L., Kiang, C.S., Zhang, Y. and Cass, G.R. (2005). Seasonal trends in PM2.5 source contributions in Beijing, China. Atmos. Environ. 39: 3967–3976.

Received for review, December 13, 2015 Revised, February 20, 2016

Accepted, February 24, 2016

characteristics and relationships between indoor and ... · 24 h, and then weighed by an electronic...

Documents