Roughly, the regional geology of China can be divided into five domains (realms), which are (Cheng, 2000):
• Tianshan–Hinggan domain
• Tarim–North China domain
• Kunlun–Qiling domain
• Sichuan–Yunnan–Qinghai–Xizang domain
• South China domain
The area around Beijing belongs to the North China domain. In the follow-ing, the most important features are briefly described according to Cheng (2000).
Precambrian rocks in the Yanshan area north of Beijing are mainly composed of gneisses and granulites with banded iron formation. The Middle Protero-zoic rocks occurring in the Yanshan Mountains are clastic and carbonate de-posits intercalated with intermediate-basic to acid volcanic rocks. Carbonates and argilaceous-arenaceous sediments were deposited in the Cambrian and are widespread in distribution. The Carboniferous System in the North China region is widespread in distribution and is composed mainly of clastic rock formation with a few beds of carbonate rocks. The clastic rocks are coal-bearing. Permian formations are made up mainly of continental deposits and triassic rocks are made up of inland basin deposits. Intermontane basin clastic-volcanic rocks are found in the Jurassic strata. Widespread continental deposits are found in the Tertiary formations. In the Quaterny, alluvial-proluvial deposits were sedimentated. Fur-thermore, aeolian deposits are common. Consequently, a widespread variety of different rock types can be considered as sources for geogenic particles around Beijing.
Chapter 3
Methodology
3.1 Sampling sites and sampling procedure
3.1.1 Location and description of the sampling sites
Five sampling sites (site 1–5) were located along a transect from NW to SE through Beijing. These sites were operated during the main sampling period (period A), which comprised two years, from Sep-05 to Aug-07. Additionally, two other sites, labelled as site CUG and site CRAES were established. Site CUG was operated during the whole period A and additionally during an inten-sive sampling campaign in spring 2007 (period B, 27th of March to 16th of April 2007) and the Olympic period (period C, Oct-07–Dec-09). Site CRAES was es-tablished for the Olympic sampling period C. The location of the sampling sites is shown in Figure 3.1. A short description of the sampling sites and their main characteristics is summarized in Table 3.1.
3.1.2 Active sampling
During the main sampling period (period A, Sep-05–Aug-07), weekly PM2.5 samples were collected with Mini-Volume samplers (Leckel, Berlin) at flow rates of 200 L/h at six sampling sites (sites 1–5, site CUG, Figure 3.1). At site 1 to site 5, weekly sampling was carried out separately for day- and night-time (from 7 a.m. to 7 p.m. and 7 p.m. to 7 a.m., respectively). At site CUG, sampling was performed continuously for a whole week. Additionally, weekly TSP samples were collected at site 4 with a TSP sampler at flow rates of 1 m3/h. All samples were collected on quartz fibre filters (QF-filters). These QF-filters had a diameter of 50 mm (Macherey & Nagel) or 47 mm (Whatman), respectively.
20 CHAPTER 3. METHODOLOGY
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Figure 3.1: City map of Beijing with the location of the sampling sites (source of the map: http://beijing2008.go2map.com). Sites 1 – 5 operated from Sep-05 to Aug-07 (sampling period A), site CRAES from Oct-08 to Feb-09 (sampling period C), and site CUG from Apr-05 to Oct-09 (sampling periods A, B, and C).
The Olympic rings mark the Olympic park (“Olympic Green”), where the Beijing National Stadium and other Olympic sites are located.
In spring 2007, during a short-term intensive measurement period (period B from the 27th of March to the 16th of April 2007), 12-hourly PM2.5 and PM10 samples were collected at site CUG. Samples were collected on small QF-filters (Whatman, d = 25 mm) and the 12-hourly sampling intervals were from 7 a.m.
to 7 p.m. and from 7 p.m. to 7 a.m., respectively.
From Oct-07 to Feb-09 (period C) sampling was continued at site CUG and additional samples were collected at a new site labelled CRAES. Site CRAES, at the roof of the Chinese Research Academy of Environmental Sciences (CRAES) is located 4 km north of the 5th ring road, 15 km from the city center, and 5.8 km from the National Olympic Stadium, the so-called “Bird’s Nest”, (Wang et al.,
3.1. SAMPLING SITES AND SAMPLING PROCEDURE 21 Table 3.1: Description of the sampling sites (AGL: above ground level; CUG:
China University of Geosciences, Beijing; CRAES: Chinese Research Academy of Environmental Sciences).
Site Location Height AGL Period Samples Remarks
1 N40◦04.102’ 1.5 m A PM2.5 agricultural
E116◦06.586’ inside patio
2 N40◦00.436’ 40 m A PM2.5 residential
E116◦20.280’ tall buildings
3 N39◦53.586’ 6 m A PM2.5 old Hutong quarter
E116◦23.059’ few traffic
4 N39◦48.394’ 1.5 m A PM2.5 much traffic
E116◦28.131’ TSP (4th ring road)
5 N39◦47.197’ 1.5 m A PM2.5 Hotel area
E116◦38.552’ few traffic
CUG Xueyuan Road 29 1.5 m A PM2.5 University entrance
APM(2.5−80) much traffic
B PM2.5 (4th ring road)
PM10 sheltered by vegetation
C PM2.5
CRAES 8 Yangfang Anwai 20 m C TSP Roof of the Academy
PM2.5 5.8 km distance to PM1 Olympic Stadium
2010b). This sampling period was further divided into the time before (period C1, 07–Jul-08), during (period C2, Jul-08–Sep-08), and after (period C3, Oct-08–Feb-09) the Olympic Games. In periods C1 and C3, samples were collected on a weekly basis at site CUG and site CRAES. During period C2, the time-resolution was increased to 24-hourly intervals for TSP and PM1 samples at site CRAES and PM2.5 samples at site CUG, and to 12-hourly intervals for PM2.5 samples at site CRAES.
During sampling period A, 23% of TSP samplings were interrupted by exter-nal errors such as interruption of power supply, but only three weeks were without any record. These occasions are listed in Table 3.2 together with the share of the weeks during which the sampling operated. The weeks with sampling interrup-tions for PM2.5 samples are listed in Table 3.3.
22 CHAPTER 3. METHODOLOGY Table 3.2: List of all TSP sampling weeks of period A and the percentage of sampling duration for the corresponding weeks. (N: number; w/o: without; PCT:
percentage).
N PCT Calendar weeks
weeks of total (ww/yy)
Weeks w/o sampling 3 2.9 06/06, 11/07, 29/07
Weeks< 25% operation 9 8.7 21/06, 41/06, 48/06, 15/07, 18/07, 20-23/07 Weeks> 25% operation 12 11.5 36/05, 44/05, 13/06, 16-18/06,
22/06, 07-09/07, 19/07, 30/07
Weeks w/o errors 80 76.9 all others
Total weeks 104 100 35/05–34/07
Table 3.3: List of all PM2.5sampling weeks of period A during which operational errors occurred.
N of weeks Calendar weeks
w/o samples (ww/yy)
Site 1 – day 8 28–33/06, 21–22/07
Site 1 – night 9 20/06, 28–33/06, 21–22/07 Site 2 – day 19 39/05, 17–30/06, 05–08/07
Site 2 – night 15 16–30/06
Site 3 – day 8 37/05, 03–08/07, 24/07
Site 3 – night 7 37/05, 03–08/07
Site 4 – day 0 –
Site 4 – night 2 17–18/06
Site 5 – day 7 21/06, 29/06, 44–47/06, 22/07 Site 5 – night 8 21/06, 29/06, 44–47/06, 50/06, 22/07
3.1.3 Passive sampling
Passive sampling with a Sigma-2 device according to VDI-Guideline 2119 (VDI, 1997) was performed during all three sampling periods (A, B, and C) at site CUG (Figure 3.1). Normally, two samples were collected each week (three and four days of exposure time for each sample, respectively). During sampling period B and during the Olympic Games (period C2), the time resolution was higher with 12- and 24-hour intervals. The particles were deposited as single particles in the stilling section at the bottom of the sampler on a transparent adhesive collection plate. Further details about the method can be found in Dietze et al. (2006).