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2 JOUR NAL O F E N V I R ONM E NT AL S C I E NC ES 87 (202 0) 1 – 9
100 nm could reach up to 30,000 cm −3 in the urban area of environment and regional climate, but also have an important
Beijing, which is much higher than Wu's studies hazard to human health.
−3
(27,000 cm ) (Wu et al., 2008). It is known that aerosols can Prior research on the chemical composition of particles in
not only reduce the visibility, but also have an adverse effect Beijing was mainly focused on fine particles, and it was also
on the human respiratory and cardiovascular systems. The mainly focused on some specific species in China and abroad
World Health Organization (WHO) estimated that air pollu- in recent years (Pathak et al., 2009; Ianniello et al., 2011), the
tion was associated with approximately 300,000 premature size distribution of aerosol chemical species (Guo et al., 2010;
deaths per year in China (Duan et al., 2014). Li et al., 2012), particle number concentration (Yue et al., 2011)
Beside the mass concentration and the particle size, the and new particle formation processes (Gao et al., 2012) have
concentration of potential toxic metals of aerosols plays a also been discussed. There were few measurements of PM 10 ,
decisive role for the assessment of atmospheric pollution and especially comprehensive analysis of the different chemical
the hazards to human health (Limbeck et al., 2012; Sato et al., compositions of particles. To fully understand concentrations
2008). Atmospheric heavy metals are continually being and chemical compositions of atmospheric particles in
deposited into the ground by dry and wet deposition, from Beijing, daily PM 10 samples were collected at an urban site in
where they could be absorbed by plant roots and stems or Beijing during December, 2014–January, 2015. The concentra-
impact soil enzyme activity, biological activity and biodiver- tions of major components, their characteristics and compar-
sity, resulting in persistent negative impacts on the ecosys- ison in hazy and non-hazy days of PM 10 were discussed in
tem biogeochemical cycles. The long-term existence of heavy detail. The studies presented are expected to be useful in
metals may pose a great potential threat to the environment, making future PM pollution control policies.
it can invade the respiratory system, induce heart disease,
lung disease, reduce lung function, and even cause cancer
(Fang, 2010). As, Cr, Ni, Pb and Cd have some carcinogenic 1. Experimental design
capacity, As and Cd have potential teratogenic effects on the
human body, and Pb and Hg are toxic to the fetus (Hu et al., 1.1. Sample collection
2012). High anthropogenic emissions of heavy metals enter
into the biosphere in China, and these emissions far exceed The sampling site was located on the roof of an office building
those of other countries with increasing trend (Pacyna and at the IAP (Institute of Atmospheric Physics, Chinese Acad-
Pacyna, 2001). Studies have shown that about 70%–80% of emy of Sciences) campus (116°22′ E, 39°58′ N) in the Haidian
metal elements in the atmosphere are adsorbed on fine District, Beijing, which is about 6 m above the ground. The site
particles (Lv et al., 2005; Mohanra et al., 2004). is in the middle of the North Third Ring Road and the North
The scattering and extinction effects of atmospheric Fourth Ring Road in Beijing, which is about 150 m eastern
aerosols are affected by its own physical properties (including from the east–west urban traffic main road, North Tucheng
particle size distribution, mass concentration, etc.) and Road, and is about 200 m from the Badaling Expressway
chemical composition. Water-soluble compounds (nitrates, (Fig. 1). It is surrounded by high-density roads, residential
sulfates, ammonium salts, etc.), organic and elemental carbon buildings and office buildings. There are no obvious industrial
(OC and EC) are the main chemical components that reduced sources of aerosols in the vicinity. Therefore, it can be
visibility in hazy days. Nitrates and sulfates are one of the considered as a typical urban site.
most important extinction components in the atmosphere, Sampling was conducted from December 29, 2014 to
the visibility will significantly reduce with the increasing of January 22, 2015 by a sampler (VFC-PM10, Thermo, USA).
concentration. Concentrations of nitrates and sulfates have a There was no precipitation during observation period. The
close relationship with the acidity of atmospheric precipita- quartz filters were baked at 800°C for 3 hr before using to
tion. Water-soluble ions have strong hygroscopic property; remove absorbed organic vapors. The sampling duration was
they can promote the formation of cloud condensation nuclei, 24 hr and filters were changed at about 9:00 am. Two sets of
and also affect the size, composition, number, acidity and life samplers were used to take samples in turn. After collecting,
time of aerosols due to their strong hygroscopic property the sampler was ultrasonically cleaned and dried, and was left
(Xiang et al., 2017). In the case of high relative humidity, the for use the next day. The concentrations of all species were
moisture-absorbing growth of water-soluble ions will en- calculated by mass divided by sampling air flow rate.
hance the extinction effect of aerosols, which will lead to a
decrease in visibility. 1.2. Chemical analysis
Carbonaceous species are also important fraction in PM 10 .
Based on thermal and optical properties, carbonaceous After sampling, all the samples were wrapped in aluminum
aerosols can be divided into EC and OC. OC is emitted by foil and stored in a refrigerator (−18°C) to avoid sunlight and
fossil fuel combustion or is formed by a complex process of analyzed for chemical species in less than a month. Prior to
secondary formation, including of a vast array of individual extraction and digestion, each filter was cut into three equal
organic species, such as formaldehyde, acetone and PAHs parts. One of them was digested with nitric acid, hydrogen
(Cao et al., 2003; Tang et al., 2006; Yang et al., 2011). EC, which peroxide, and hydrofluoric acid at 180°C for 6 hr. The reagents
is important for radiative forcing, can be emitted directly by were all Merk ultra-pure reagents (6 mL HNO 3 +2mL
incomplete combustion of e.g., biomass and fossil fuel (Xiang H 2 O 2 + 0.1–1 mL HF Mixed acid system). After the permeation
et al., 2017), mainly from primary emissions. Carbonaceous solution passed through a filter (pore size: 0.45 μm,
species have a significant impact on the atmospheric Membrana, Germany, Micro PES), an inductively coupled