Physiochemical characteristics of aerosol particles in the typical microenvironment of hospital in Shanghai, China

STOTEN-21532; No of Pages 9 Science of the Total Environment xxx (2016) xxx–xxx

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Physiochemical characteristics of aerosol particles in the typical microenvironment of hospital in Shanghai, China Rui Li a, Hongbo Fu a,b,⁎, Qingqing Hu a, Chunlin Li a, Liwu Zhang a, Jianmin Chen a, Abdel Wahid Mellouki c a b c

Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Department of Environmental Science & Engineering, Fudan University, Shanghai 200433, China Collaborative Innovation Center of Atmospheric Environment and Equipment Technology (CICAEET), Nanjing University of Information Science and Technology, Nanjing 210044, China ICARE-CNRS, 1C Avenue de la Recherche scientifique, 45071 Orleans, Cedex 02, France

H I G H L I G H T S

G R A P H I C A L

A B S T R A C T

• The mean concentrations of PM1 and PM2.5 decreased with floors as a whole. • Trace metals in the first floor were mainly concentrated in the coarse particles. • Minerals, soot, fly ash, sulfate, biogenic particles, Fe-rich and Zn particles were observed in the hospital.

Mineral particles, soot, and Fe-rich particles were mainly concentrated in the first floor, indicating the impacts of walking of patients, traffic emissions, and food cooking. Sulfate particles were internally mixed with soot, fly ash and Fe-rich particles in the second floors, which suggested that these sulfate particles probably underwent aging processes during atmospheric long-range transport. In the fourth floor, fly ash, sulfate particles, Zn-rich particles, and biogenic particles were identified under the TEM.

a r t i c l e

i n f o

Article history: Received 1 November 2016 Received in revised form 2 December 2016 Accepted 2 December 2016 Available online xxxx Editor: D. Barcelo Keywords: Air quality Hospital Pm Trace metals Tem Hospital

a b s t r a c t Health risk of populations dwelling in the hospital has been a global concern, but has not been adequately examined. PM2.5 and PM1 samples were collected in two indoor locations (outpatient department and inpatient department) and one outdoor location (courtyard) of the hospital in Shanghai. The concentrations of sizefractionated trace metals and the morphology of single particles were determined to accurately assess the health risk for populations in the hospital. The results indicated that the mean concentrations of PM2.5 and PM1 were in the order of outpatient department N courtyard N inpatient department. The mean concentrations of PM1 decreased with floors (first floor: 78.0 μg/m3, second floor: 64.1 μg/m3, fourth floor: 48.4 μg/m3). However, the mean PM2.5 concentrations were in the order of first floor (124.0 μg/m3) N fourth floor (91.4 μg/m3) N second floor (90.6 μg/m3), which was likely associated with the number of patients. The PM2.5 and PM1 concentrations have begun to increase rapidly from 9:00 am and decreased after 15:00 pm in the first floor, whereas they remain relatively stable in the second and fourth floor. The abundance of Mg, Ca, Al and K in the fine particles and coarse particles were both higher than other elements for all floors. The concentrations of trace metals (e.g., Zn, Ba, Fe, Mn, Cr, Ca, Ti, Na, and K) except Mg and Al in the coarse particles (N 2.5 μm) decreased with floors, whereas Zn, Ba, Fe, and Cr in the fine particles (b2.5 μm) displayed opposite variation. Trace metals in the first floor were mainly concentrated in the N2.5 μm and 1–2.5 μm, whereas they chiefly peaked at 0.25–0.5 μm and below 0.25 μm in the

⁎ Corresponding author at: Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Department of Environmental Science & Engineering, Fudan University, Shanghai 200433, China. E-mail address: [email protected] (H. Fu).

http://dx.doi.org/10.1016/j.scitotenv.2016.12.011 0048-9697/© 2016 Published by Elsevier B.V.

Please cite this article as: Li, R., et al., Physiochemical characteristics of aerosol particles in the typical microenvironment of hospital in Shanghai, China, Sci Total Environ (2016), http://dx.doi.org/10.1016/j.scitotenv.2016.12.011

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second and fourth floor. Single particles analysis showed that mineral particles, soot, and Fe-rich particles were mainly concentrated in the first floor, indicating the impacts of walking of patients, traffic emissions, and food cooking, respectively. Sulfate particles were internally mixed with soot, fly ash and Fe-rich particles in the second floor, which suggested that these sulfate particles probably underwent aging processes during the atmospheric long-range transport. In the fourth floor, fly ash, sulfate particles, Zn-rich particles, and biogenic particles were identified under the transmission electron microscopy (TEM). Higher abundance of sulfates and absence of chlorate hinted existence of heterogeneous reactions during long-range transport with the Cl− replaced by SO2− 4 . The index of average daily intake (ADI), hazard quotient (HQ), and carcinogenic risks (CR) indicated that Cr pose carcinogenic risks to the surrounding populations, while non-carcinogenic risks of Mn, Zn, and Cr were not remarkable. © 2016 Published by Elsevier B.V.

1. Introduction Particulate matter (PM) has been widely investigated due to their adverse effects on human health. Many studies showed that inhalable particles were significantly linked with respiratory and cardio-vascular diseases (Araujo, 2011; Kim et al., 2015). As the fine particles, PM2.5 and PM1 has been paid more attention because they are inclined to affect the respiratory health through penetrating deeply into the respiratory tree (Uysal and Schapira, 2003; Ghio and Huang, 2004). Moreover, they were generally correlated with deaths resulting from lung cancer and cardiopulmonary disease (Riediker et al., 2004). On the other hand, these particles can act as CCN to govern the heat transfer properties of atmosphere, thereby altering the cloud formation process and rainfall patterns (Carslaw et al., 2013; Kalkavouras et al., 2017). The occurrence of hazy days has been increasing since 2005, particularly in some megacities of China (Tong et al., 2007). Formation mechanism of aerosol particles, namely nucleation and growth by multi chemical processes, is an important reason for the formation of severe haze days (Guo et al., 2014a, 2014b). Thus, it is necessary to investigate the pollution levels of PM. Trace metals are important components in the PM, even though they just constitute a small portion of these particles. Some trace metals, such as Zn, Cr and Ti, pose significant threats on the human and animal carcinogens (Wang et al., 2006a, 2006b). Schell et al. (2006) reported that maternal mice exposure to Pb increases the risk of abortion and inhibits the fetal growth. Memory disturbances, blurred vision and unclarified speech have been observed after the exposure of some trace metals (Ratnaike, 2003). Damek-Poprawa and Sawicka-Kapusta (2003) concluded that trace metals increase the risk of kidney damage and nephrocalcinosis. Besides, trace metals control the chemical and optical properties of particles, consequently impacting the global radiation balance (Huang et al., 2012). Moreover, trace metals play significant roles on the formation of haze all over China because they can catalyze the production of nitrate and sulfate, which was a key factor contributing to the formation of haze (Li et al., 2011a, 2011b). There are many researches on the PM outdoors, mainly focusing on the pollution levels, components, source and morphology (Hu et al., 2015; Liu et al., 2015; Yang et al., 2016). However, there are few reports on the air quality of indoors, especially for hospitals. Hospital is regarded as an important and special type of indoor public place because it is considered as an important sink of pollutants. Hospital is generally situated close to main thoroughfares so that they were vulnerable to the effects of vehicle emissions, industrial manufacture and other human activities (Loupa et al., 2016). Wang et al. (2006a, 2006b) observed that the concentrations of PM2.5 indoors were markedly correlated to that outdoors. Jung et al. (2015) reported that indoor/outdoor ratios of PM2.5 in the hospitals were below 1 and concluded that traffic emissions outdoors promote the elevation of PM2.5 indoor the hospitals. Meanwhile, hospital is also a major source of pollutants due to the existence of large amount of human activities. Many people walked in and out of hospitals frequently, leading to the resuspension of particles deposited on the

surface (Wang et al., 2006a, 2006b). Furthermore, ventilation pattern in some hospitals is not conducive to the spread of pollutants, consequently resulting in the accumulation of particles indoors (Monn et al., 1995). In addition, hospitals were generally filled with many people, particularly patients who were more susceptible to respiratory distress and other related disorders due to their suppressed immune system (Lomboy et al., 2015). Therefore, hospital was ideal place to investigate the PM levels and assess their risks to the occupants' exposure to airborne particles. A growing body of studies on PM have been conducted in the hospital. Most of them centered on the pollution levels, source, and influence factors of PM indoors. Verma and Taneja (2011) analyzed the concentrations of PM1, PM2.5, and PM10 in the hospital and observed that their concentrations were remarkably higher than the WHO standards. Brown et al. (2012) showed that hospitals were exposed of the impacts of vehicle emissions, although they possessed lowest PM2.5 concentrations compared with other indoor microenvironments. Wang et al. (2006a, 2006b) concluded that outdoor air conditions, ventilation types and indoor human activities are main factors that affecting the PM2.5 concentrations in the hospital. Due to the existence of inhalable particles in the hospital, exposure risks assessment has been conducted in a Portuguese hospital (Slezakova et al., 2014). The results suggested that As and Cr pose high risk to all age of groups. Up to date, the size distribution and morphology of particles inside the hospital was seldom mentioned in Shanghai, which is necessary to exactly evaluate the risk of particles to human health. Thus, the objectives of this study are to (1) investigate the PM2.5 and PM1 levels in various zones of hospitals and compare with studies representative of other areas, (2) decipher the concentrations of trace metals in PM and their size distribution, and (3) penetrate into the morphology of single particles in the hospital. The quantification of the pollution levels, components, size distribution and morphology of particles can raise the awareness of authorities about the air quality in the hospital and seek to obtain appropriate strategies to protect patients and employees from air pollution. 2. Materials and methods 2.1. Sampling sites description The samples were collected in the Shanghai pulmonary hospital, which is located in Zhengmin road of Yangpu district, Shanghai. National Container Processing Company and Baoshan steel factory are located 15 and 24 km north of the sampling site. Two waste incineration facilities Jiangqiao and Yuqiao were located 17 km to the west and 19 km to the south, respectively. Besides, the sampling site was located in the densely populated commercial areas and close to heavy traffic road. Outpatient department in the hospital is approximately 10 m away from Wudong road and 18 m from bus stop. The service of first floor is registration and payment, while second floor is site many people receive laboratory sheets. The first and second floor of outpatient

Please cite this article as: Li, R., et al., Physiochemical characteristics of aerosol particles in the typical microenvironment of hospital in Shanghai, China, Sci Total Environ (2016), http://dx.doi.org/10.1016/j.scitotenv.2016.12.011

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department are occupied by patients all day. The fourth floor was disease treatment area, where patients are relatively lesser than those in the first and second floor. The surveyed hospital is cooled by windowtype air conditioners or central air conditioners and the windows are open all day. Inpatient department and courtyard do not adjoin to the road compared with outpatient department. The number of patients in the inpatient department is significantly lower than that in the outpatient department. The windows in the inpatient department were open all day. The hospital forbid smoking indoors and frequent housecleanings are done in the inpatient department.

2.2. Sample collection The PM2.5 and PM1 samples were collected from indoor and outdoor on quartz filters by a MiniVol sampler (America, USA) with an airflow of 51 min−1. The samples of outpatient department and courtyard were taken from 9:00 am to 17:00 pm during the period of March 7thMarch 18th, 2016. Indoor and outdoor particulate samples were collected simultaneously at all of the observed sites to evaluate the relationship between indoor and outdoor particulates. Samples were collected at each sampling site for three days. The collected samples were immediately put in a polyethylene plastic box and then stored in a refrigerator under 4 °C until analysis. Single particles were collected directly onto the 300-mesh copper TEM grids coated with carbon films using a single-stage cascade impactor for the TEM analysis. Sampling periods ranged between 30 and 300 s, depending on particle loading. The collected samples were put in plastic carriers and then stored in a desiccator to preserve them for further analysis. More detailed information about sampling process was shown in the previous work (Fu et al., 2014).

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2.5. Enrichment factor, geochemical index method and health risk assessment Crustal enrichment factors (EF) for each element in various sizes of particles were calculated as presented in Eq. (1), considering Al as reference element: EF ¼ ðMe=AlÞaerosol =ðMe=AlÞbackground

ð1Þ

where (Me/Al)aerosol was the ratio of trace metal and Al concentrations in the aerosol, while (Me/Al)background was calculated based on the concentrations of trace metal and Al in the continental crust (Taylor, 1964). Geochemical indexes for each element were calculated based on Eqs. (2), (3), and (4): ½MeL ¼ ½AlS  ðMe⁄AlÞB

ð2Þ

½MeP ¼ ½MeT −½MeL

ð3Þ

Anthropogenic Me ð%Þ ¼ ½MeP =½MeT  100%

ð4Þ

where [Me]P is the concentrations of anthropogenic trace metals; [Me]T is the total concentrations of trace metals; [Me]L is the concentrations of natural trace metals; [Al]S is the total concentrations of samples; (Me⁄Al)B represents the ratio of target trace metal and Al background values. Human health risks for adults and children were evaluated based on the average daily intake (ADI), hazard quotient (HQ), and carcinogenic risks (CR). Three elements, i.e., Mn, Zn, and Cr are selected in our study as possible carcinogens based on the International Agency for Research on Cancer. The formulas for calculating ADI, HQ, and CR are as follows: ADI ¼ ðC  IR  EF  EDÞ=ðBW  ATÞ

ð5Þ

2.3. Trace element measurements

HQ ¼ ADI=RfD

ð6Þ

Particle-loaded filters were punched using a special round handpunch made of high purity molybdenum. Particles on the filters were dissolved in 3 mL of ultrapure concentrated HNO3, 1 mL of ultrapure concentrated HCl, and 1 mL of ultrapure concentrated HF for digestion. One of the diluted digests was then analyzed by an inductively coupled plasma atomic emission spectrometry (ICP-AES, ULTIMA, JOBIN-YVON Company, France) and to determine trace elements in the particles. Based on the measurement of the reference materials (S44001000241) and repeated samples, the relative standard deviation was below 3%. The recovery of the reference materials ranged from 95 to 105%.

CR ¼ ADI  SF

ð7Þ

where C (mg m− 3) is the concentration of metal, including the total concentration in all size fractions except N2.5 μm; IR is the exposure time (adults: 16.5 m3 d−1; children: 5.6 m3 d−1); EF is the exposure frequency (d y−1); ED is the exposure duration (adults: 24 years; children: 6 years); BW is the average body weight (adults: 70 kg; children: 15 kg); AT is the averaging time; RfD is the reference dose, calculated with reference concentrations (Mn: 0.14, Zn: 0.30, Cr: 0.003); SF is the inhalation slope factor (Cr: 42 kg d mg−1) (Huang et al., 2016). 2.6. Statistical analysis

2.4. TEM analysis The aerosols sampled on the TEM grids were investigated with a JEOL-2010F field emission high-resolution TEM (FE-HRTEM) equipped with an Oxford energy-dispersive X-ray spectrometer (EDS) to obtain the morphology and composition at a single particle level. EDS were recorded in TEM image mode and then quantified using ES Vision software that uses the thin-foil method to convert X-ray counts of each element into atomic or weight percentages. EDS were collected for 30 s in order to minimize radiation exposure and potential beam damage. To ensure that the analyzed particles were representative of the entire size range, three to four areas were chosen from the center and periphery of the sampling spot on each grid. Elemental compositions were determined semi-quantitatively by using EDS that can detect elements heavier than carbon. High resolution TEM (HRTEM) was also used in the present study to examine the structure of typical crystalline particles (Fu et al., 2014).

One-Way ANOVA (Fisher Test, p b 0.05) was used to identify the significant difference of the concentrations of PM2.5, PM1, and trace metals in the different sampling sites. All of statistical analysis and figures in this study was performed by the software package SPSS 16.0 and Origin 8.0 for Windows. 3. Results and discussion 3.1. PM2.5 and PM1 levels 3.1.1. Comparation of PM2.5 and PM1 at the different zones in the hospital The concentrations of PM2.5 and PM1 in various zones of hospital are shown in Table 1. The mean concentrations of PM2.5 and PM1 were both in the order of outpatient department N courtyard N inpatient department. However, the standard deviation displayed highest values in courtyard, which could be affected by meteorological factors. In outpatient department, the mean PM2.5 concentrations were in the order of ones at first floor (124.0 μg/m3) N fourth floor (91.4 μg/m3) N second

Please cite this article as: Li, R., et al., Physiochemical characteristics of aerosol particles in the typical microenvironment of hospital in Shanghai, China, Sci Total Environ (2016), http://dx.doi.org/10.1016/j.scitotenv.2016.12.011

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Table 1 The concentrations of PM2.5 and PM1 in the hospital. Sites Outpatient department

First floor Second floor Fourth floor

Inpatient department

Sickroom Office Lobby

Courtyard

Grassland

Mean Std Mean Std Mean Std Mean Std Mean Std Mean Std Mean Std

PM1 (μg/m3)

PM2.5 (μg/m3)

PM1/PM2.5

78.0 45.4 64.1 7.5 48.4 5.2 45.0 2.5 29.0 3.0 36.0 2.0 59.2 30.8

124.0 56.1 90.6 17.1 91.4 17.0 51.0 3.0 33.0 2.0 42.0 2.0 86.3 35.2

0.55 0.73 0.60 0.88 0.88 0.86 0.69

floor (90.6 μg/m3). However, the mean concentrations of PM1 decreased with floors and displayed the highest value of PM1 (78 μg/m3) in the first floor, followed by ones at second floor (64.1 μg/m3) and fourth floor (48.4 μg/m3). Such results were ascribed to that patients in the first floor were markedly higher than those in the second and fourth floor. Frequent human activities might lead to the elevation of PM2.5 and PM1 concentrations. The standard deviation exhibited similar variation to the mean concentrations. The highest and lowest values of inpatient department occurred in sickroom and office, respectively, which was also likely associated with the number of patients. The concentrations of PM2.5 in the first, second, and fourth floor of outpatient department were around 1.91, 1.39, and 1.41 times of the standard recommended by USEPA (65 μg/m3), which suggested health risk existed in the outpatient department. The concentrations of PM2.5 in the courtyard were 1.32 times of the standard value. However, the PM2.5 concentrations in the inpatient department were lower than the standard value. The PM2.5 concentrations in the hospital were significantly lower than those in the hospitals of Guangzhou (Wang et al., 2006a, 2006b), Atlanta (Brown et al., 2012), while they were remarkably higher than those of Portuguesa (Slezakova et al., 2012; Slezakova et al., 2014), Philippines (Lomboy et al., 2015), Taiwan (Jung et al., 2015), Greek (Loupa et al., 2016), which was probably associated with the number of patients, ventilation patterns, and ambient environment (Lomboy et al., 2015; Loupa et al., 2016). The I/O ratio is an indicator to distinguish the difference between indoor and outdoor levels. I/O ratio N 1.0 implied the presence of sources of pollutants indoors. However, I/O ratio b 1.0 suggested that pollutants indoors derived from outdoor sources (Lomboy et al., 2015). The I/O ratio of PM2.5 varied between 0.74 and 1.56 for outpatient department and between 0.57 and 0.74 for inpatient department, which are close to the results conducted in the hospitals of Guangzhou (Wang et al., 2006a, 2006b), Philippines (Lomboy et al., 2015) and Greece (Loupa et al., 2016). The I/O ratio of PM1 ranged from 0.73 to 1.57 for outpatient department and from 0.64 to 0.79 for inpatient department. Inpatient department may be strongly influenced by the particles outdoors because the I/O ratio for PM2.5 and PM1 were considerable higher than 0 but lower than 1.0. Chan (2002) reported that the infiltration ratio of pollutants outdoors reached 70% with full air conditioning, which was remarkably higher than that in the present study. The results of outpatient department indicated that outpatient department was affected by the common effects of indoors and outdoors. Generally, hospitals were located in close proximity to a heavy-traffic road where a lot of vehicles might emit PM2.5 and PM1. On the other hand, cooking activities and patient's walking probably elevated the concentrations of particles indoors. However, the I/O ratio for PM2.5 and PM1 in the inpatient department were significantly lower than those in the outpatient department, which was possibly attributed to the difference of ventilation patterns. Many sickrooms are equipped with window-type air conditioners or

exhaust fans for ventilation. Particles in the ambient air can be filtered through mechanical ventilation air conditioning (Wang et al., 2006a, 2006b). In contrast, human activities could play a significant role on particulate generation indoors considering that the patient density in the hospital was several times higher than that in other indoor environment. Large-scale human activities such as walking and working released PM indoors, leading to the higher I/O ratio (Chao and Wong, 2002). The mean ratios of PM1/PM2.5 were 0.63, 0.87 and 0.69 in outpatient department, inpatient department, and courtyard, respectively (Table 1). They were significantly higher than 0.5, hinting the existence of large amount of fine particles, whereas they were slightly lower than those in a hospital of Portuguesa (PM 1/PM2.5: 0.93) (Slezakova et al., 2012). The highest values occurred in inpatient department because air conditioners are used to filter the amounts of coarse particles (Verma and Taneja, 2011). The mean ratios of PM1/ PM2.5 were 0.55, 0.73, and 0.60 in the first, second, and fourth floor of outpatient department, respectively. The first floor displayed lowest values probably due to the impacts of human activities. The patient density in the first floor was markedly larger than those in other floors, contributing to the resuspension of many coarse particles (Wang et al., 2006a, 2006b).

3.1.2. Diurnal variation of PM2.5 and PM1 in the outpatient department The diurnal variation of PM2.5 and PM1 in the outpatient department is summarized in Fig. 1. The PM2.5 and PM1 concentrations have begun to increase rapidly from 9:00 am in the first floor. There are two reasons accounting for this phenomenon. The first reason is that hospitals were exposed of the impacts of traffic emissions, food cooking, and industrial activities since they become more frequent after 9:00 am. On the other hand, patients in the hospital increased significantly after 9:00 am, leading to the elevation of particle concentrations. The PM2.5 and PM1 concentrations in the first floor decreased sharply after 15:00 pm as the result of the decrease of patients. Compared with the diurnal variation of PM concentrations in the first floor, the PM2.5 and PM1 concentrations displayed relatively stable variation in the second floor and fourth floor, which was attributed to relatively fewer patients than those in the first floor. Furthermore, second floor and fourth floor were less affected by the emission from outdoors than first floor because first floor was close to the main road. Zheng et al. (2012) confirmed that sites with lower altitude are vulnerable to local pollutants, whereas sites in the higher altitude are usually affected by long-range transport of pollutants.

Fig. 1. Diurnal variation of PM2.5 and PM1 in the outpatient department.

Please cite this article as: Li, R., et al., Physiochemical characteristics of aerosol particles in the typical microenvironment of hospital in Shanghai, China, Sci Total Environ (2016), http://dx.doi.org/10.1016/j.scitotenv.2016.12.011

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3.2. The concentrations and size distributions of trace metals in the outpatient department 3.2.1. The comparison of trace metal concentrations among the different floors The ratio of total trace metals in the fine particles (b2.5 μm) to PM2.5 in the first, second and fourth floor was 10.4%, 10.9%, and 13.0%, respectively, which was higher than the results determined in the hospitals of Guangzhou (Wang et al., 2006a, 2006b) and Greece (Loupa et al., 2016). The abundance of Mg, Ca, Al and K in both the fine particles and coarse ones was higher than the other elements (Fig. 2). Ca was thought to stem from the cement fly ash of construction sites because calcite is frequently used as filler in concrete (Kaegi, 2004), which can be transported into hospitals through wind. In addition, human activities such as walking and working probably contribute to the accumulation of Ca. K has been widely used as a tracer for biomass burning (Hays et al., 2005). Food cooking and the burning of strawberry can promote the accumulation of K (Robinson et al., 2006). Al and Si were the main crustal elements and originated from frictional work from construction sites and wind-blowing soil dust in ambient environment (Li et al., 2017). All of the trace metals in the coarse particles (N2.5 μm) displayed the highest values in the first floor because trace metals in the coarse particles primarily resulted from ground dusts (Huang et al., 2011). The population density was significantly higher in the first floor where their walking even the mere presence of people at room who conduct ordinary activities lead to the dust resuspension (Wang et al., 2006a, 2006b). In addition, the dusts in the main road might be transported into the first floor indoors. However, the concentrations of Zn, Ba, Fe and Cr in the fine particles increased with the floors. The previous studies concluded that Zn was linked with the abrasion of tyre, while Ba, Cr and Fe were probably associated with brake wear (Sanders et al., 2003;

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Birmili et al., 2006). Apart from the traffic source, Moffet et al. (2008) reported that waste incineration can release large amount of Zn to the atmosphere. Ba has been indicated as a potential fingerprint for contaminated roadside soils (Schauer et al., 2006). Guo et al. (2014a, 2014b) observed that steelwork is a dominant source of Fe in the fine particles. Cr probably reflects numerous pollution sources, such as coal combustion and sewage sludge incineration (Nriagu and Davidson, 1986). Trace metals contributed by anthropogenic source in fine particles were easily deposited in the higher altitude via long-range transport (Bing et al., 2014), leading to the higher accumulation of Zn, Ba and Cr, particularly in the fourth floor. 3.2.2. Enrichment characteristics and quantitative source identification of trace metals Enrichment factor is an important indicator to reflect the mass balance of trace metals and consequently distinguish natural process from anthropogenic source. Trace metals with EFs (enrichment factor) b10 were generally considered to have a major natural source, while species with higher EFs were regarded as contaminated by anthropogenic sources (Huang et al., 2011). In the coarse particles, the enrichment factor of Zn was higher than 10 except in the fourth floor, indicating the impacts of anthropogenic source (Table 2). Thorpe and Harrison (2008) concluded that Zn in the coarse particles is commonly linked with tyre wear emissions. However, the other trace metals in the coarse particles displayed lower EFs values, which suggested that they were primarily sourced from natural processes. In the fine particles, the mean EF values of Zn, Ba, Fe, K and Cr were all above 10 and even the EF values of Zn reach 470 in the fourth floor, confirming the contribution of human activities. Most of EFs values of trace metals in the coarse particles decreased with the floors except Cr, Mg and Ca, which is identical to the variation of concentrations. This result was probably

Fig. 2. Size distribution of trace metals in three floors of outpatient department (1: N2.5 μm, 2: 1–2.5 μm, 3: 0.5–1 μm, 4: 0.25–0.5 μm, 5: b0.25 μm).

Please cite this article as: Li, R., et al., Physiochemical characteristics of aerosol particles in the typical microenvironment of hospital in Shanghai, China, Sci Total Environ (2016), http://dx.doi.org/10.1016/j.scitotenv.2016.12.011

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Table 2 Enrichment factor of trace metals in coarse and fine particles of different floors. Element Coarse mode (N2.5 μm)

Zn Ba Fe Mn Cr Mg Ca Ti Na K

Fine mode (b2.5 μm)

First floor

Second floor

Fourth floor

First floor

Second floor

Fourth floor

40.75 5.03 2.42 2.45 1.43 1.34 1.37 0.28 3.89 3.33

20.14 3.32 2.19 2.40 5.13 0.53 2.08 0.27 1.65 2.04

6.97 1.15 1.93 2.30 1.96 1.61 1.61 0.15 0.56 0.72

101.39 13.49 6.39 7.15 5.46 2.00 1.38 0.72 2.25 6.80

295.13 31.90 10.15 9.08 22.50 2.68 3.81 1.14 3.90 12.62

470.13 58.34 18.91 19.27 31.56 1.16 3.65 1.90 9.71 19.20

attributed to that coarse particles were mainly sourced from the dust and controlled by the number of patients. However, the EFs of trace metals in the fine particles displayed different distribution from those in the coarse particles. EFs of all the trace metals (e.g., Zn, Ba, Fe, Mn, Cr, Ti, Na, and K) except Mg and Ca in the fine particles increased with the floors, suggesting that higher floors have become important sink of external input of trace metals in the fine particles. Even though the EFs values can be used to isolate crustal elements from anthropogenic source, contribution of natural and anthropogenic source is still unknown. Therefore, geochemical index method was used to calculate the anthropogenic contribution of trace metals. Particle-bound trace metals were classified into two groups according to their contribution ratio (Table 3). The first group was composed of all the crustal elements, such as Mg, Ca, Ti, and Na. Their anthropogenic contributions were significantly lower than natural contributions and even reached zero for Ti. The second group comprised of Zn, Ba, Fe, Mn, Cr, and K. It is interesting to note that the anthropogenic contribution of Mn was above 50%, which is in contrast to previous conclusion because Mn was regard as typical crustal element from soil dust. However, the iron and steel industry consumes nearly 90% of the Mn, representing most significant pollution source of Mn (Bouaziz et al., 2011). Besides, K was considered as a mixed element, affected by dust suspension and biomass burning (Thorpe and Harrison, 2008). In our study, the contribution ratio of K was about 80%, indicating primary contribution of biomass burning. The anthropogenic contribution of Zn, Ba, Fe, Mn, Cr, and K increased with floors, displaying similar variation to their concentrations in the fine particles. 3.2.3. Size distribution of trace metals in the different floors Size distribution of particle-bound trace metals varied with different floors. Most of trace metals appeared to enrich slightly more in fine particles with increasing heights. Trace metals in the first floor were mainly concentrated in the coarse particles (N2.5 μm), and 1–2.5 μm, whereas they chiefly peaked at 0.25–0.5 μm and below 0.25 μm in the second and fourth floor (Fig. 2). Particle-bound trace metals were categorized

into three groups based on their size distribution at different floors. The first group was enriched with some elements from Fe, Cr, and Mn. These trace metals exhibited unimodal size distributions with highest values below 0.25 μm in the first, second, and fourth floors. This finding was in agreement with the size distribution characteristics of other locations, such as Guangzhou (Huang et al., 2016), New Jersey (Song and Gao, 2011), and Helsinki (Pakkanen et al., 2003). This finding was ascribed to that Fe and Cr originated from anthropogenic source were dominant in the fine particles (Guo et al., 2014a, 2014b). Manganese alloyed with silicon and iron can form silicomanganese and ferromanganese and their residues were usually enriched in fine particles (Lucas et al., 2015). The second group consists of Zn, Ba, and K, which displayed different size distribution from other anthropogenic elements in the group 1. The peaks of Zn and Ba shifted from 0.5–1 μm and 1– 2.5 μm to 0.25–0.5 μm and below 0.25 μm with the increasing floors, although they displayed bimodal distribution in all the floors. This result was possibly associated with different deposition velocities for sizefractionated particles because fine particles usually underwent longrange transport from industrial or residential zones (Zhang et al., 2001). The third group include some crustal elements, such as Mg, Ca, Ti, Al, and Na, which was characterized by three peaks primarily concentrated in coarse particles including N 2.5 μm, 1–2.5 μm, and 0.5–1 μm. This indicated that the dust in the main road probably play significant roles in their accumulation. 3.3. Single particles analysis 3.3.1. Classification of single particles and morphology characteristics The collected particles were classified into seven major categories: mineral particles, soot, fly ash, sulfate, biogenic particles, Fe-rich particles, and Zn-rich particles (Fig. 3). The coarse particles were mainly concentrated in the first floor, while the fine particles were enriched in the fourth floor. The coarse and fine particles were distributed uniformly in the second floor. This result is in accordance to the distribution of PM and trace metals. In the first floor, mineral particles, soot, and Fe-rich particles can be observed through TEM analysis. Mineral particles were characterized by irregular shape and relatively stable under the electron beam. Both SAED and EDS data together suggested the mineral particles consisted of clay, feldspar, quartz, dolomite, and calcite. The EDS data indicated that most of mineral particles were mixed with Ca, O, and S, and thus were most likely CaSO4. CaSO4 is prone to contribute by local source, such as coal combustion and construction (Kodavanti et al., 1998). Apart from the impacts of industries around the hospital, many business streets were built in the north section of the hospital during the sampling period. Therefore, the hospital was more or less influenced by the construction source. Meanwhile, many sulfur-bearing substances such as SO2 and SO24 − existed in the atmosphere, which probably react with CaO and Ca(OH)2 produced from construction source, leading to the formation of CaSO4. Soot particles displayed chain-like appearance of carbon-containing spheres. The soot spheres under the high-

Table 3 Percentage of anthropogenic trace metals in the particles of different floors. First floor (%)

Zn Ba Fe Mn Cr Mg Ca Ti Na K

Second floor (%)

Fourth floor (%)

Natural

Anthropogenic

Natural

Anthropogenic

Natural

Anthropogenic

1.9 14.9 31.7 29.6 20.1 96.3 77.1 100 92.5 26.8

98.1 85.1 68.3 70.4 79.9 3.67 22.9 0 7.54 73.2

1.1 9.5 30.4 26.2 16.9 98.7 41.1 100 43.9 18.3

98.9 90.5 69.6 73.8 83.1 1.31 58.9 0 56.1 81.7

1.0 8.2 20.8 18.9 18.9 74.6 51.9 100 40.2 14.7

99.0 91.8 79.2 81.1 81.1 25.4 48.1 0 59.8 85.3

Please cite this article as: Li, R., et al., Physiochemical characteristics of aerosol particles in the typical microenvironment of hospital in Shanghai, China, Sci Total Environ (2016), http://dx.doi.org/10.1016/j.scitotenv.2016.12.011

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7

Fig. 3. Various types of individual particles in the outpatient department identified using TEM/EDS.

resolution TEM exhibited a discontinuous onion-like structure of graphitic layers. Most of soot adhere to the mineral particles, which suggested the impacts of traffic emissions (Fu et al., 2014). Besides, food cooking can also generate a small amount of soot, which probably collide with mineral particles. Fe-rich particles were mainly characterized by spherical-shaped with high contents of Fe and O and minor amount of Zn, Ca and Na. Zn existed in lubrication oil and tyre wear, and Ca was commonly associated with the wear of brake pads (Hu et al., 2015). Furthermore, the sampling site in the present study was situated close to the main road. Thus, Fe-rich particles mainly result from traffic source. In addition, spherical-shaped particles can be produced by a gas-toparticle transformation followed by condensational growth under a high-temperature environment (Ault et al., 2012). The Baoshan steel manufacturing enterprise is situated approximately 24 km to the north of the sampling site. Therefore, it was supposed that the Fe-rich particles could be ascribed to the iron and steelwork emissions. In the second floor, mineral, “sulfate + soot”, “sulfate + fly ash”, and “sulfate + Fe-rich” particles were shown under the TEM. Sulfate particles were sensitive to the electron beam, indicating a soluble nature (Li et al., 2013a, 2013b). Some sulfate particles such as (NH4)2SO4 and NH4NO3 were usually transformed from SO2 andNO2 reacted with NH3 in the atmosphere with the relative RH N 80% (Li et al., 2013a, 2013b). In our study, sulfate particles were internally mixed with soot, fly ash and Fe-rich particles, which suggested that these sulfate particles probably underwent aging processes during atmospheric long-range transport because chemical reactions tend to happen on the surfaces of Ferich particles. Li et al. (2011a, 2011b) conducted the single particle analysis at a high-elevation mountain and observed that the spherical sulfate particles increased with the altitude. In the fourth floor, fly ash, sulfate particles, Zn-rich particles, and biogenic particles were identified under the TEM. Fly ash and sulfate

particles were mainly characterized by spherical morphologies. Spherical fly ash is usually the result of molten nature of the material at high temperatures during steel production (Ault et al., 2012). Zn-rich particles were primarily amorphous. Apart from the impacts of traffic source, non-ferrous metal metallurgy released Zn-rich particles to atmosphere. It is well known that minor Pb-bearing compounds generally existed in the Zn-rich particles generated from non-ferrous smelter because Pb is concomitant to Zn in ores (Choel et al., 2006). However, Pb was not observed in the Zn-particles, which suggested that the sampling site was not exposed of non-ferrous smelter. EDS indicated that Zn-rich particles possessed minor amount of Na and Cl, implicating the effects of waste incineration. Two waste incineration facilities Jiangqiao and Yuqiao were located 17 km to the west and 19 km to the south, respectively. Thus, this result suggested that waste incineration made non-negligible contributions to the accumulation of Zn-rich particles in the fourth floors (Moffet et al., 2008). Biogenic particles are a special type of organic particles, ranging in size from tens of nanometers to millimeters. The presence of minor P, S, Si and Cl can be regarded as the fingerprint of biogenic materials (Geng et al., 2010; Pósfai and Buseck, 2010). Biogenic particles in our study presented bar-like morphology with diameters around 500 nm, which had some functional elements such as P, N, and S. 3.3.2. Relative abundances of the particles The relative abundances of particles in different floors are shown in Fig. 4. The relative abundances of particles in the mineral, soot, sulfate, fly ash, biogenic particles, Fe-rich particles, Zn-rich particles were 44.2%, 27.3%, 10.5%, 4.5%, 0%, 13.5%, and 0% for the first floor, 10.7%, 11.9%, 45.4%, 20.1%, 7.4%, 2.7%, and 1.8% for the second floor, and 19.0%, 13.7%, 33.7%, 21.1%, 2.4%, 2.1%, and 8% for the fourth floor, respectively. The abundances of mineral particles, soot and Fe-rich particles in the first floor were significantly higher than those in the second and

Please cite this article as: Li, R., et al., Physiochemical characteristics of aerosol particles in the typical microenvironment of hospital in Shanghai, China, Sci Total Environ (2016), http://dx.doi.org/10.1016/j.scitotenv.2016.12.011

8

R. Li et al. / Science of the Total Environment xxx (2016) xxx–xxx

Fig. 4. The relative abundances of major chemical species in the samples collected in Shanghai.

floors. HQ and CR are indicators to assess the non-carcinogenic and carcinogenic risk of trace metals on human health, respectively. The HQ values and CR values for adults were significantly higher than those for children. Compared with adults, children have a higher susceptibility of exposure to contaminants due to behavioral and physiological characteristics (Li et al., 2014). Similar findings can be observed in the studies of Zota et al. (2011) and Qu et al. (2012). The hazard quotients of trace metals were in the order of Cr N Zn N Mn, which was mainly controlled by RfD. The HQ of Cr, Zn, and Mn were remarkably lower than 1.0, hinting no obvious health risk for surrounding populations. The HQ values of Zn and Cr displayed the highest values in the fourth floor, which was similar to the variation of ADI. However, the variation of HQ for Mn was not consistent with that of ADI for Mn, which was ascribed to relatively lower RfD for Mn. Due to lack of the SF for Mn and Zn, the CR of Mn and Zn could not be calculated. However, the CR of Cr for adults and children were significantly higher than the threshold value (10−4), which suggested that Cr pose carcinogenic risks to the surrounding populations. The CR of Cr increased with the floors, which is similar to the results of ADI and HQ. 4. Conclusions

fourth floor, whereas sulfate particles, fly ash, biogenic particles and Znrich particles displayed opposite variation. Higher abundances of mineral particles in the first floor was attributed to a large number of patients whose walking contribute to the dust resuspension (Wang et al., 2006a, 2006b), whereas the number of patients was lower in the second and fourth floor. Traffic emissions were main sources of soot and Fe-rich particles, which were inclined to enter the first floor because the outpatient department was situated close to main road. Besides, the canteen was situated in the first floor, which probably emit soot to the indoor air. Although traffic emissions were an important source of Zn, Zn-rich particles were even absent in the first floor, which was not in agreement with the distribution of Fe-rich particles. This result indicated that local human activities were likely not main contributors to Zn-rich particles. Besides the impacts of vehicle emissions, municipal solid waste incineration and industrial combustion can release a large amount of Zn, which are far away from our sampling sites. It was thus concluded that Zn-rich particles undergoing long-range transport tend to settle into the sites with higher altitude. In the same way, sulfate particles, fly ash, and biogenic particles were prone to deposit into the higher floors. 3.4. Health risk assessment of trace metals Among all the investigated trace metals, people are most exposed to Mn, Zn, and Cr because of their high concentrations in the ambient atmosphere and low RfD values. Therefore, health risk assessment of Mn, Zn, and Cr were conducted in the present study. ADI of trace metals is an indicator to reflect the health risk to human (Table 4). The ADI values of trace metals were around three times for adults than those for children. The ADI values of Zn and Cr increased with the floors because the concentrations of Zn and Cr were higher in the first floor. However, the ADI of Mn were relatively stable in three Table 4 Health risk of trace metals in particulate matters from different floors of hospital. Elements

ADI

HQ

CR

Mn Zn Cr Mn Zn Cr Mn Zn Cr

First floor

Second floor

Fourth floor

Adults

Children

Adults

Children

Adults

Children

0.002 0.013 0.001 0.017 0.044 0.462 – – 0.058

0.001 0.004 0.000 0.006 0.015 0.154 – – 0.019

0.002 0.013 0.001 0.017 0.042 0.461 – – 0.058

0.001 0.004 0.000 0.006 0.014 0.154 – – 0.019

0.002 0.017 0.002 0.015 0.058 0.555 – – 0.070

0.001 0.006 0.001 0.005 0.019 0.185 – – 0.023

The mean concentrations of PM1 and PM2.5 were in the order of outpatient department N courtyard N inpatient department. The mean concentrations of PM1 decreased with floors, whereas the mean PM2.5concentrations were in the order of first floor N fourth floor N second floor, which was influenced by walking and working of occupants in the hospital. The I/O ratio of PM1 ranged from 0.73 to 1.57 for outpatient department and from 0.64 to 0.79 for inpatient department. The mean ratios of PM1/PM2.5 were 0.55, 0.73, and 0.60 in the first, second, and fourth floor of outpatient department, respectively, which suggested that fine particles were main components in the aerosols. The PM2.5 and PM1 concentrations have begun to increase rapidly from 9:00 am and decreased after 15:00 pm in the first floor, whereas they remain relatively stable in the second and fourth floor. The abundance of Mg, Ca, Al and K in the fine particles and coarse particles were both higher than other elements for all floors. The concentrations of all the trace metals except Mg and Al in the coarse particles (N 2.5 μm) decreased with floors, whereas Zn, Ba, Fe, and Cr in the fine particles (b 2.5 μm) displayed opposite variation. Trace metals in the first floor were mainly concentrated in the N2.5 μm and 1–2.5 μm, whereas they chiefly peaked at 0.25–0.5 μm and below 0.25 μm in the second and fourth floor. Single particles analysis showed that mineral particles, soot, and Ferich particles were main components in the first floor, indicating the impacts of walking of patients, traffic emissions, and food cooking. Sulfate particles were internally mixed with soot, fly ash and Fe-rich particles in the second floors, which suggested that these sulfate particles probably underwent aging processes during atmospheric long-range transport. In the fourth floor, fly ash, sulfate particles, Zn-rich particles, and biogenic particles were identified under the TEM. The ADI, HQ, and CR of trace metals were significantly higher for adults than those for children. The HQ values of Zn and Cr displayed highest values in the fourth floor, while those of Mn peaked in the first floor. The index of ADI, HQ, and CR indicated that Cr pose carcinogenic risks to the surrounding populations, while non-carcinogenic risk of Mn, Zn, and Cr were not obvious. Our findings point to the necessity of further research of physicochemical characteristics and their health risk assessment of aerosol particles in the hospital in order to protect patients from atmospheric pollutants. Acknowledgements This work was supported by National Natural Science Foundation of China (Nos. 21577022, 21190053, 40975074), Ministry of Science and Technology of China (2016YFC0203700), and International cooperation project of Shanghai municipal government (15520711200).

Please cite this article as: Li, R., et al., Physiochemical characteristics of aerosol particles in the typical microenvironment of hospital in Shanghai, China, Sci Total Environ (2016), http://dx.doi.org/10.1016/j.scitotenv.2016.12.011

R. Li et al. / Science of the Total Environment xxx (2016) xxx–xxx

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Please cite this article as: Li, R., et al., Physiochemical characteristics of aerosol particles in the typical microenvironment of hospital in Shanghai, China, Sci Total Environ (2016), http://dx.doi.org/10.1016/j.scitotenv.2016.12.011