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Some ideas about the sources of PM10
ATMOSPHERIC ENVIRONMENT PERGAMON
Atmospheric Environment 35 Supplement No. 1 (2001) $23-$33 www.elsevier.com/locate/atmosenv
Some ideas about the sources of PM10 P. Lenschow, H.-J. Abraham, K. Kutzner, M. Lutz*, J.-D. PreuB, W. Reichenbficher Department of Urban Development, Berlin, Germany Received 3 May 2000; received in revised form 18 January 2001; accepted 24 January 2001
Abstract In Berlin, about 50% of the urban background PM10 concentration is due to long range transport--mainly secondary aerosols (ammonium nitrate and ammonium sulphate) and natural sources. At kerbside sites on main streets the PM10-concentration is up to 40% higher than the urban background. Half of this additional pollution is due to motor vehicle exhaust emission and tyre abrasion and the other half is due to resuspended soil particles. On the basis of comparison of the main chemical components at stations in the regional and urban background and a station at the kerbside of a busy street, we estimate the source apportionment for the main source groups. Possible reduction measures are discussed. © 2001 Elsevier Science Ltd. All rights reserved. Keywords. Source apportionment; Chemical composition; Secondary aerosols; Resuspension by traffic; Measures of reduction
1. Introduction Concentrations of airborne particles have been measured in Berlin over almost 30 years. Exposure to huge emissions of sulphur dioxide and particulate matter in the 1970s and 1980s, especially in the then East Berlin and in the surrounding industrial agglomerations of East Germany, created a strong need to measure these and other pollutants at up to 43 measuring sites (SenStadt, 1998). Recorded series of air pollution data showed strikingly high levels of total suspended particulates (TSP) and sulphur dioxide concentration until the early 1990s, which led to smog alarms and traffic bans in the western part of the then divided city of Berlin. So, public pressure on the need for abatement of air pollution became strong and so was the necessity for identifying the sources of air pollution where control measures would have to be taken. Hence, surveys on the emission from all sectors led to a rather detailed
*Corresponding author. Present address: Senatsverwaltung fuer Stadtentwicklung-IX D-, Brueckenstrasse 6, D-10173 Berlin, Germany. E-mail address: [email protected] (M. Lutz).
emission register of Berlin for all major pollutants which has been updated regularly (SenStadt, 1998). The reunification of the city in 1989 led to a total reconstruction of the heating systems in the east, to an abandonment of high-sulphur lignite as a fuel in this part of the city as it had already been since 1981 in the western part, a total restructuring of the industrial and electricity sector in east Germany and so to an accelerated reduction of emissions of particulate matter and sulphur dioxide from these sources. The situation thus looks a lot better than illustrated in OECD (1999), one of the rare comparisons of air pollution between a larger number of cities in the world. Since 1993 the levels of suspended particulates have again fallen by about one third and the concentration of sulphur dioxide has dropped far below the limit values of EC-Directive 99/30/EC (EC, 1999). However, as shown in this paper, it is still necessary to assess sources of air pollution-especially as regards the levels of fine particles smaller than 10pro (PM10). Among other things, the above mentioned Directive sets tough limits for PM10 for 2005 and a further preliminary set of even tougher limit values for 2010. As these new limit values were based on recent findings on health effects from exposure to fine particles they are by far more stringent than those in the previous legislation. Together with the Air Quality
1352-2310/01/$-see front matter © 2001 Elsevier Science Ltd. All rights reserved. PII: S 1 352-23 1 0(0 1)00 1 22-4
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o f 100 km 2. The city is situated in the N o r t h e r n G e r m a n Lowlands less than 100km west o f G e r m a n y ' s border with Poland and a r o u n d 200 km northwest o f the more industrialised so-called "Black Triangle" o f the borders o f G e r m a n y , Poland and the Czech Republic. It has a m o d e r a t e climate with 50% winds from Southwest to N o r t h w e s t (mainly maritime influence) and 30% winds f r o m Southeast to N o r t h e a s t (mainly continental influence), average wind speed o f 3 m s 1 ( 1 0 m above r o o f tops in the built up area) and yearly mean temperature o f 8.8°C ( - 0 . 5 ° C in January, 17.9°C in July). The n u m b e r o f passenger cars and light duty vehicles (LDV) totalled 1.1 million at the end o f 1999 which means 323 cars per 1000 inhabitants (73% with threeway catalytic converter, 15% diesel) and the n u m b e r o f heavy duty vehicles (HDV) is 100000. This is still a rather low vehicle density in c o m p a r i s o n with other cities o f similar size. There are 13 bigger c o m b i n e d power and heating plants with a capacity o f 2800 M W electrical power run with coal, oil and natural gas. They all meet the G e r m a n emission limits. The coal and oil p o w e r plant are equipped with flue gas desulphurisation, denitrification and filters. One domestic waste incineration plant exists with a capacity o f 376000 tonnes waste per a n n u m equipped with flue gas filters o f a very high technical standard. There is nearly no heavy industry. Fuel used for domestic heating consists o f 30% natural gas, 20%
F r a m e w o r k Directive 96/62/EC (EC, 1996) authorities in n o n - a t t a i n m e n t z o n e s are required to assess PM10 pollution, including investigation into the origins o f air pollution, its major sources, and pollution which might be i m p o r t e d from other regions. F o r Berlin, the following questions arise: Will the PM10-1imits be met in 2005 without additional action or are the current reduction regulations sufficient? If not: • •
•
W h a t are the major sources (industry, transport, domestic, agriculture etc.)? H o w do sources inside the agglomeration which are directly accessible to the local authorities contribute to the PM10 pollution? W h a t sort o f additional action should be taken at regional, national, EC or U N - E C E levels?
This paper aims to get first answers for those questions and to identify further areas o f investigation so as to gain a more reliable basis for a b a t e m e n t plans and programmes.
2. Some basic information about Berlin and its monitoring network With a surface area o f 8 9 0 k m 2 and 3.4 million inhabitants Berlin is G e r m a n y ' s largest single c o n u r b a tion. 1.12 million people live in the inner city in an area
Table 1 Annual emissions of various source sectors in Germany and Berlin (1998)a'b Particles PM10
Plants subjected to licensing Domestic heating Households Small industries Traffic (motorvehiclesonly) Resuspension by traffic Traffic (other) Use of soIvents Agriculture (cattle) Agriculture (fertilize0 Other sources (construction,etc) Sum of all sources
Sulphur dioxide
Oxides of nitrogen
Volatile organiccompounds
Ammonia
Gerlnany
Berlin
Germany
Berlin
Germany
Berlin
Germany
Berlin
Germany
kt
%
kt
kt
%
kt
%
kt
%
kt
%
kt
%
kt
%
kt
%
95
38.8
1.9 20.3 1119
86.6
7.9
71.3 564
31.7
7.5
24.8
140
8.2
2.2
3.8
8
1.3
29
11.8
0.5 5.3
102
7.9
2.5
22.6 103
5.8
3.0
9.9
1.0
1.7
5
2.0
0.1
37
2.9
0.0
0.4
38
2.1
1.0
3.3
3.3 0.3
10.0 10.0
17.2 17.2
43
17.6
2,4 25.6 30
2.3
0.5
4.5
856
48.1
17.0 56.3 409
24.0
28.0
48.3
43
17.6
2,4 25.6
20
8.2
0,2 2.6
0.4
0.1
1.3
220
12.4
1.7
3.1 58.7
2.8
4.8 525
84.0
70
l 1.2
22
3.5
11 245
4.5
%
1.5
5
0.0
1.8 19.2 9.4
1292
11.1
0.0
0.0 1780
30.2
5.6
0.0
56 5
53 I000
42 1705
2.5
4.0 58.0
6.9
625
~Remarks: (1) All emissions extrapolated from data of 1995, (2) natural emissions not included, (3) use of solvents in Berlin is included in households and light industry. bData sources: Berlin: Senatsverwaltung fuer Stadtentwicklung, Germany: according to Umweltbundesamt Berlin and minutes of expert hearing III 2.2 H 50231-18/11 and Ehrlich et al. (2000).
P. Lenschow et al. / Atmospheric Environment 35 Supplement No. 1 (2001) $23-$33
light oil (sulphur content less than 0.2%) and 15% lignite (sulphur content less than 1%). 30% are supplied by district heating and 5% by electricity. The annual mean emissions are shown in Table 1 together with German total emission data. In 1999 the Berlin air pollution monitoring network (Berliner Luftguete Messnetz, BLUME) consisted of 21 stations. Particulate matter is currently measured at 18 stations (see Fig. 1). A majority of 12 automatic instruments (radiometric monitors Eberline FH62IN) still measure TSP as was required by the recently repealed Directive 80/779/EEC (EC, 1980). The automatic network has been fitted to gravimetric TSP-measurement in 1988 with a constant factor (1.34) after gravimetric reference measurements at nine collocated background stations with about 100 daily samples each and correlation coefficients of 0 . 9 4 < r < 0 . 9 8 (TUEV, 1989). Gravimetric reference measurements of PM10 were performed during a measuring campaign in 1996 at three urban background stations and three stations near streets with 72-100 daily samples (Air Consult, 1997). The gravimetric reference measurements are made using low volume samplers (Kleinfilterger/it GS050) and high volume samplers (Digitel DHA80). After the elimination of 8% of data with PM 10/TSP less than 0.5 or more than 1.2 comparison of PM10 and TSP series resulted in conversion factors of 0.76-0.79 at the investigated urban background sites and slightly higher values of 0.82-0.85 at the three traffic sites with correlation coefficients of 0.953 < r < 0.967. Taking into account the uncertainties of the measurement techniques, the low correlation and the microlocation of measuring instruments an overall factor of 0.8 is considered as an appropriate approximation when estimating PM10 concentrations on the basis of TSP measurements with the Berlin BLUME network. The same factor has been used by federal institutions in Germany to gain an overview of the PM10 pollution. There have been two campaigns to measure and chemically analyse PM10 and PM2.5. The first was from November 1989 to October 1990 at an urban background station (and three other stations) in Berlin and the rural EMEP station Waldhof, about 180 km west of the town (Israel et al., 1992). The second was in 1998 at one urban background and one traffic station in Berlin (Abraham, 1999). These measurements have been made with teflon filters on Dichotomous Samplers (PM10 and PM2.5) and quartz filters on Digital DHA80 (TSP) in 1989/1990 and with quartz filters on Kleinfiltergeraet GS050 (PM10 and PM2.5) in 1998. Before and after exposure the filters are stored for more than 24h at 40 50% relative humidity and temperatures of 20 _+ 2°C. The methods used for chemical analysis were ion chromatography after extraction with ethanol or acetone and water for the ions and three step thermography (350°C and 620°C with helium, 700°C with
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(a) " "
1999 a n n ~ M l O (PMIO~
concentrations ~'/,,, PMIO=O,8xTSP) ~ r o 2 "
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(PM10 measurementin bold/italics, otherval~JesPMlO=O,SxTSP) ~
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Windroses of suspended particulates
Fig. I. Spatial distribution of suspended particulates in Berlin (1999). helium plus 20% oxygen) for elemental carbon (EC) and organic carbon (OC). The organic material (OM) is derived by multiplying OC with a factor 1.2 (Israel et al., 1992; VDI, 1999). In this paper all ions are displayed without their charges. Since no chemical analyses were available in the regional background in 1998 these values are estimated from 1996 data (Umweltbundesamt, 1997) and lowest
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concentrations of carbonaceous material measured at other stations in the region. There are differences between the results of the continuous automatic measurements and the results of the measuring campaigns that are mainly due to small sample size of the campaigns. Therefore, we avoid cross comparisons that could be affected by these differences.
sources like traffic, tram and sandy pavements have high influence at these points. The 90th percentiles (Fig. lb) show nearly the same spatial distribution as the annual means with lowest values at the borderline and highest values in the inner city near streets. As Fig. lc shows, the PM concentration is higher when the wind blows from the east (continental influence) than from the west (maritime influence). In the inner city, the background concentration for the east wind sectors (80-170 °) is higher than the west sectors (250-340 °) by a factor of 1.5-2.0 depending on the year. The measurements show that in 1999 the PM10 limit value of 4 0 g g m -3 as annual average was exceeded at one traffic site (Fig. la). The second PM10 limit value of 50 gg m -3 as 24 h mean not to be exceeded more than 35 times per year is equivalent to a limit for the 90th percentile of 50 ggm -3. As shown in Fig. lb, this limit value is exceeded more frequently throughout the city by up to 35% at stations with high influence of traffic. The situation looks even worse with regard to the indicative limit values for 2010 laid down in ECDirective 99/30/EC (EC, 1999) of 20ggm -3 as annual mean, with not more than seven peaks above 50 ggm 3. This short term limit is equivalent to a limit of the 98th percentile of 501agm 3. In 1999 the measured 98th percentiles go up to 100 lagm -3. It should be noted that in 1998 and 1999 westerly winds were more frequent than normal (and easterly
3. Present situation of P M I O
Fig. 1 shows the annual mean concentrations and relevant percentiles of PM10 as well as windroses of suspended particulate matter (SPM) at 18 automatic stations in Berlin. Six of them (one suburban, two urban background and three kerbside stations) measure PM 10. To give full information about the distribution in the city, the concentrations of the 12 TSP-stations are scaled down to PM10 by the above-mentioned factor of 0.8. As seen in Fig. la, in 1999 the annual mean values of PM10 in Berlin lay between 18 and 2 5 g g m -3 near the border line, 27-33ggm -3 in the inner city and 39-41ggm 3 at the two kerbside stations near main roads ( > 50 000 vehicles per day) in street canyons and 37ggm -3 near the inner city highway ring (180000 vehicles per day). Two stations in the eastern part of the town with 38 and 39ggm -3 do not fit into the concentration field of the background stations. Local
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1996
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Fig. 2. Monthly averages of TSP and S02 in the urban background.
1998
II 0 1999
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winds less frequent). With the usual distribution of winds the concentrations would have been higher than recorded. In order to meet the short-term limit values for 2005 also in hot spots with intense traffic the PM10pollution must drop by at least 27% by 2005. In order to develop an efficient abatement strategy more information is needed about the future trend and the sources of PM10.
4. Long-term changes in the characteristics of suspended particulate matter
Time series of monthly mean values of TSP and SO2 at three urban background stations in the inner city of Berlin show a distinct downward trend (Fig. 2). In summer there was always much more TSP than SO2. However, in winter in the period before 1991 peak levels of both substances were quite similar, while since 1991 much less SO2 than TSP has been found all over the year. A special feature of TSP is that the downward trend seems to remain on a high level with winter peaks sometimes nearly vanishing, whereas SO2 still shows clear winter peaks. The annual averages and the 98th percentiles of TSP concentrations measured in the urban background are
90
:
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This behaviour may be due to better particle filters in plants, less emission of smoke from domestic heating (the use of lignite in domestic heating has been reduced b y a b o u t 90% since 1990), and much better car engines. The lower reduction of EC can be attributed to the relative growth of influence of traffic, the influence of
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a strong reduction by about 50% of unresolved particles (mainly soil particles) and of OM, • a medium reduction of about 20% of SO4 and EC, and • a much smaller reduction of NO3 and NH4. •
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i
80
subject to nearly the same trend (Fig. 3). This is understandable if the main sources are subject to the same trends, or if the main sources react similar to the changes of climate influences. From this we infer that relative changes of annual averages may be taken in the first approximation as representative for the changes of higher percentiles. Table 2 depicts the decrease of TSP, PM10 and PM2.5 between 1990 and 1998 on the basis of annual mean concentrations measured at the urban background stations Fasanenstrasse in 1990 and Nansenstrasse in 1998. The last column of the table shows that the decrease of PM2.5 is less pronounced than of PM 10 and even less than TSP. As shown in Fig. 4, the development of the Berlin urban background since 1990 shows
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Fig. 3. Annual averages and 98-percentilesof daily mean concentration in the urban background.
1999
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One can clearly recognise from Fig. 4 and Table 3 that in the busy street the PM10-pollution is up to 40% higher than in the surrounding urban background. Near the street there is a higher share of EC, OM and soil. It should be mentioned here that the method used to measure carbonaceous material does not perfectly separate EC from OM. Tests with extraction of OM with a mixture of 1 part of toluene and 3 parts of N , N dimethylformamide before thermographic analysis have revealed that about 30M0% of PM10 EC and 50-60% of PM2.5 EC may really be OM. Near streets where high concentrations of EC and OM are measured, the differences are not as distinct as in the background. For the source apportionment we could not take this finding into account.
tyre abrasion and the less restrictive emission limits for HDV in comparison with passenger cars. The lower reduction of SO4, NO3 and NH4 may be due to former limitations in the small scale conversion of SO2 and N O , in the atmosphere and perhaps emissions of NH3 from the growing number of cars with catalytic converters (Kirchner et al., 2000).
5. Main chemical composition of PMI0 The main chemical components of PMI0 in 1990 and 1998 are shown in Table 3 and Fig. 4. About one third of the mass of PM10 in the urban background is attributable to inorganic secondary aerosols originating from Europe-wide gaseous emissions. Another third is carbonaceous material, mainly emitted by motor vehicles and by lignite and coal combustion in stoves, but also secondary aerosol of organic matter from anthropogenic and natural sources. The remaining third consists of soil and ash particles, sea spray and water.
6. Source apportionment For the first approximation of the source apportionment presented in this paper, assumptions are made in three steps. The field structure of PM10-concentrations in the Berlin region (Fig. 1) suggests that concentrations measured at only one carefully sited station per type can be taken as representative for other stations of the three types "traffic", "urban background" and "regional background" as shown schematically in Fig. 5. So in the first step it is assumed that
Table 2 Average concentrations of TSP, PM10 and PM2.5 in the urban background Fasanenstrasse in 1990 (Israel et al., 1992), Nansenstrasse in 1998 (Abraham, 1999)
TSP PM10 PM2.5
1990 ggm -3
1998 pgm 3
Reduction %
77 58 39
43 38 30
44 34 23
Urban background Nansenstr
•
the kerbside station Frankfurter Allee at a busy main street with a traffic flow of about 60 000 vehicles per day with a HDV-share of 3.4% and a LDV-share of 7.1% is representative of the influence of traffic on air pollution near streets,
Traffic site Frankfurter Allee I
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Difference traffic - urban background I
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III V ~ 6 7
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V
1991 l
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II Eso4 III E]NH4 IV Florganie matter(OM) V Belemental carbon (EC) Vt D soil+water
Fig. 4. Chemical composition of PM10 in the city of Berlin (ggm 3).
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Table 3 Average concentation of PM10 and PM2.5 and main chemical components in the city of Berlin and the regional background ~ Type
UB Berlinb Fasanenstr.
RB Waldhofb
TR Berlin ° Frankfurter All.
UB Berlinc Nansenstr.
RB Neuglobsowd
PM10 (i.tgm-3) OM (gg m -3) EC (~tgm 3) SO4 (ggm -3) N O 3 (ggm 3) NH4(lag m -3) C1 (ggm -3) Unresolved (ggm 3) PM2.5 (ggm 3) OM (I,tgm -3) EC (ggm 3) S O 4 (,t.tgm-3) NO3 (I.tgm 3) NH4 (ggm -3) C1 (ggm 3) Unresolved (gg m -3) Start (MM.JJ) End (MM.JJ) No. of cases Sample (h)
57.6 15.0 6.3 9.3 4.3 3.7 0.7 19.0 39.2 10.1 5.3 7.8 3.3 3.9 0.4 8.8 10,89 10,90 254 12
26.9 5.8 2.1 4.9 3.0 2.4 0.7 8.7 18.6 4.0 1.7 4.2 2.2 2.2 0.2 4.3 10.89 10.90 313 12
51.5 11.0 9.0 5.7 4.6 3.3 0.8 17.9 38.6 9.4 7.7 5.6 4.3 3.8 0.7 7.8 02.98 12.98 33 24
37.7 7.5 5.1 6.1 4.4 3.4 0.7 11.2 30.2 7.0 4.7 5.5 3,7 3.7 0.5 5.6 02.98 12.98 33 24
18.6 3.0 1.8 3.9 2.4 2.0 5.5
01.98 12.98 24
aUB: urban background, RB: regional background, TR: Traffic, Unresolved: mainly metal oxides (soil) and water (Israel et al., 1992). bIsrael et al (1992). ~Abraham (1999). a Guessed after Umweltbundesamt (1997).
In the second step, it is assumed that
1, near traffic station (Frankforter Allee) 2. urban backgroond stations (N ansenstrasse; Fasanenstrage) 3. regional background stations (Waldhof; Neuglobsow)
•
PM [pg/rn3] 601
•
1
J
Tra.,c •
[
regional
background
]
Fig. 5. Schematic horizontal profile of the ambient PM10 concentration.
•
•
the urban background station Nansenstrasse in the inner city is taken as representative of the urban background level, and the rural stations Waldhof, 180 km from Berlin and Neuglobsow, 100 km from Berlin are representatives for regional background levels in 1990 and 1998, respectively, only marginally influenced by the city.
the differences of particulate matter and its chemical components between the traffic station and the urban background station can be attributed to the local influence of traffic on the adjacent street, the differences between the urban background station and the rural background station can be attributed to the sources of the agglomeration and the concentrations of particulate matter at the rural background station can be attributed to global sources with little contribution from the agglomeration.
We assume that there is a natural background of 5 . g g g m -3 due to primary and secondary emission of wind blown dust, pollen, volcanic eruptions, thunderstorms, oceans and other sources and apportion this as shown in Table 4a. In the third step, it is assumed that •
•
the relative influence of the German source groups can be taken as representative for all sources outside the agglomeration, the emissions of SO2, NOx and NH3 shown in Table 1 are the sources for the concentrations of SO3, NO3 and NH4 in Table 3, respectively, and
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the major source groups contribute to ambient concentrations of primary and secondary particles in proportions as their emissions displayed in Table 1 with the following modifications. In Table 1 besides the gaseous emissions there is only one category "particles PM10", that has to be combined with EC, OM and the unresolved portion of the measurements. For the partitioning of traffic, we used emission data from the "Handbook for emission factors of motor vehicles" (Keller et al., 1999), according to which 60% of the diesel emissions of passenger cars and LDV and 40% of the emissions of HDV consist of EC. The other part is counted as primary OM. Taking into account that 14% of all vehicles are diesel-engine cars, and 3.5% LDV and 3.4-5% HDV with diesel motors, this gives an average EC-partition of about 50%. The particle emissions of petrol cars are neglected in the handbook. We, therefore, included a small proportion of the volatile organic compounds as secondary material to the primary organic particulates. The difference between the traffic station and the urban background station consists solely of carbonaceous material (55%) and unresolved rests (45%). We assume that the carbonaceous material stems from the exhaust emissions of vehicles with 20% tyre abrasion (Rauterberg-Wulff, 1998, 2000) and the unresolved rest from resuspension of road dust, mainly soil. From the differences of the unresolved rests of PM10 and PM2.5 (Table 3) near the street it can be deduced that the resuspended particulates include a high proportion of about 70% coarse particles. These will be deposited within a range of some kilometres. Therefore, for the apportionment of the urban sources only 50% are taken into account and for the German sources 2O%. In the scale of the agglomeration there is a high dependency of ambient concentrations on the stack height of emissions. The Berlin plant subjected to licensing have stack heights of 50 150 m. To take this into account we assumed that they contribute only 20% of their emission to the urban background. The factor is derived from dispersion calculations of the Berlin Air Pollution Management Plan for the years 1994-2000 (SenStadt, 1995). For most relevant sources outside the agglomeration, which lie more than 50 km away, the emission heights are not taken into account. The coupling of the emissions of Table 1 with the ambient concentrations of Table 3 is shown in Table 4a which gives the results of our source apportionment of PM10 in as much detail as possible. The relative contributions of the main sources in the three spatial source groups are compared in Table 4b. Similar investigations have been conducted by e.g., Harrison et al. (1997), Chow et al. (1996) and Thurston and Spengler (1985). But in our paper we tried to get a full
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balance between the measured concentration of PM10 with its components and our knowledge about the emissions and to discriminate between the three spatial groups of sources. The comparison of secondary aerosols in the urban background and regional background by different laboratories shows that in the urban background there seems to be a surplus of NO3 that is as large as the regional background, the surplus of NH4 amounts to about 70% and SO4 to 60%. It is difficult to understand this and to identify the reasons. Therefore, we think that there is an urgent need for comparable measurements and chemical analyses in the regional background as well as in the urban agglomeration.
7. Results
In Berlin, the ambient concentration of PM10 near busy streets is about 40% higher than in the urban background. 55% of this additional pollution consists of carbonaceous material resulting from exhaust emissions and tyre abrasion. 45% of the additional PM10pollution can be attributed to resuspended soil material. From the PM2.5 measurements (Table 3) it can be calculated that one third (2.2ggm 3) of the resuspension is PM2.5 and two thirds coarser material. The difference of urban background and regional background data shows that about 50% of the urban background pollution is caused by emissions specific to the agglomeration. Half of this contribution is due to traffic emissions and 15% to domestic heating and households. If the regional background concentration is attributed to all sources outside the agglomeration, with negligible influence of the specific sources of the agglomeration, about 55% of the urban background pollution is caused by long range transport from outside the region and by natural sources such as pollen and wind-borne soil. The main contributors to this part of the ambient concentration are power plants and other industrial plant with about 35%, and traffic and nature with about 20% each. As Fig. lc shows, the average concentrations of SPM are much higher with south-easterly than with westerly winds. This is also valid for the PM 10 concentration in the regional background. Therefore, it has to be taken into account that sources lying south to south-east of Berlin have high impact on PM10-concentrations in the town. According to Table 4b, traffic is the most important group of sources (50%) causing high PM10 pollution in a busy street. About one quarter of the traffic influence is exhaust emissions and tyre abrasion in the individual street, a further quarter is resuspension of soil particles in the individual street and the remaining half is traffic
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influence on the city background--containing also the regional background. The second group of sources is combustion (24%)--from individual stove for heating apartments through to big power plants. About two thirds of it consists of secondary aerosols, mostly sulphate and nitrate, formed from Europe-wide SO2- and NO~emissions. One third is due to a source typical for eastern European cities: emission from lignite combustion in stoves to heat apartments. The third group consists of various natural sources (12%). These three groups are the sources of about 90% of PM10 pollution in a busy street. In the urban background the partition is similar but shifted to combustion (traffic 31%, combustion 33%, natural origin 14%). It should be noted that the results of the PM10 source apportionment presented here should be considered as a preliminary estimate based on a first set of data. Comparing these results with those from other cities would help to improve this analysis and gradually remove factors of uncertainty.
8. Future development
1.
2.
3.
4.
The Directive on National Emission Ceilings proposed by the European Commission (CEC, 1999) with SO2, NOx and NH3 emissions in Europe decreasing by about 50% until 2010 will also result in a reduction of PM10 by about 15% within the last years before that date. As the impact of the traffic sector is not confined to exhaust emissions but also includes tyre abrasion and resuspended soil particles, even zero-emissionvehicles still cause about half the PM 10 pollution of "dirty" vehicles. Therefore, the reduction of the traffic impact will be much smaller than the reduction of exhaust emission. We, therefore, expect that the continuous replacement of old cars (e.g. with ages more than 10 years) by new ones with lower emissions will cause a reduction of exhaust emissions of about 8% per year (Keller et al., 1999) but a reduction of PM10 concentrations of only 1-2% per year. The introduction of cleaner fuels by 2005 according to EC Directive 98/70/EC (EC, 1998) will result in a decrease of PM10 pollution by about 1-2%. Therefore, Germany is promoting introduction of these fuels in 2001 by reducing the tax rate. In an important step in Berlin, the total public bus fleet of 1200 buses will be equipped with particle filters (CRT) by the end of 2000. This big step will reduce the PM10 pollution by about 2% (corresponds to a 10% reduction of the carcinogenic EC-
5.
6.
pollution). Particle filters also trap ultrafine particles quite effectively. The further substitution of lignite by gas, light heating oil or district heating is still a quite important development. A very important problem is the reduction of the resuspended soil particles by traffic. We still do not know how to reduce the significant influence of about 5% in the urban background and up to 15% near urban main streets.
In conclusion, there is a lack of effective measures to control PM10 emissions with the aim of attaining the limit values, in particular the short-term limit value of PM 10 for 2005 in the vicinity of traffic sources. As this is probably a widespread problem, it is necessary to intensify mutual exchange of experiences between European cities on investigations about the sources of PM10 pollution as well as on the development of effective control strategies. Apart from that, it is also necessary--as planned by the European Commission-to review and investigate, what part of the PM mixture actually affects human health. This ought to be followed by a definition of appropriate limit values, with the aim of avoiding costly and possibly ineffective or even regrettable abatement strategies.
References Abraham, H.-J., 1999. PM 10 und PM2.5-Staubmessungenund Inhaltsstoffanalysen in Berlin (Measurements of PM10 and PM2.5 particulates and their main chemical components in Berlin). 34th Messtechnisches Colloquium, 1999. Air Consult, 1997. Stichprobenmessprogramm Berlin 1995/96 (Random sampling measurements of air pollution Berlin 1995/96). Technical report, Department of Urban Development, Environmental Protection and Technology, Berlin. CEC, 1999. Proposal for a Directive of the European Parliament and of the Council on national emission ceilings for certain atmospheric pollutants. Communication 99/125 of the European Commission to the European Parliament and the Council. Official Journal of the European Communities, No C 56E, 29.2.2000, p 34, accessibleat http://europa.eu.int/ comm/environment/docum/99125sm.htm. Chow, J.C., Watson, J.G., Lowenthal, D.H., Countess, R.J., 1996. Sources and chemistry of PM10 aerosol in Santa Barbara County, CA. Atmospheric Environment 30, 14891499. EC, 1980. Council Directive 1980/779/EEC on air quality limit values for sulphur dioxide and suspended particulates. Official Journal of the European Communities. No. L229, 30.08.1980, p. 30, Brussels. EC, 1996. Council Directive 1996/62/EC of 27 Sept 1996 on ambient air quality assessment and management. Official Journal of the European Communities, No. L296, 21.11.1996, p 55, Brussels.
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EC, 1998. Directive 1998/70/EC of the European Parliament and of the Council of 13 October 1998 relating to the quality of petrol and diesel fuels and amending Council Directive 93/12/EEC. Official Journal of the European Communities, No. L350, 28.12.98, p 58. EC, 1999. Directive 1999/30/EC of the European Parliament and of the Council of 22 April 1999 relating to limit values for SO2, NO2 and NOx, particulate matter and lead in ambient air. Offficial Journal of the European Communities, No. L163, 29.6.1999, p 41, Brussels. Ehrlich, Ch., Noll,G., Kalkoff, W.D., 2000. Emissionsuntersuchungen von PMI0, PM2.5 und PM1.0 an Industrieanlagen und Hausbrandfeuerst/itten (Investigation of PM10, PM2.5 and PM1.0 emissions of industrial plants and domest{c heating systems) Zeitschrift fuer Immissionsschutz 4, 141-148. Harrison, R.M., Deacon, A.R., Jones, M.R., Aplleby, R.S., 1997. Sources and processes affecting concentrations of PM10 and PM2.5 particulate matter in Birmingham (UK). Atmospheric Environment 31, 41034117. Israel, G., Erdmann, A., Shen, J., Frenzel, W., 1992. Analyse der Herkunft und Zusammensetzung der Schwebstaubimmission (Analysis of the origin and composition of particulate matter pollution). Fortschritt Berichte, VDI Reihe 15, No. 92, 277pp., VDI Verlag, Dusseldorf. Keller, M., Heldstab, J., de Haan, P., Knoerr, W., 1999. Handbuch fuer Emissionsfaktoren des Kraftfahrzeugverkehrs Version 1.2 (Handbook for emission factors of road traffic). On behalf of Swiss Agency for the Environment, Forests and Landscape (BUWAL) and German Federal Environmental Agency, Berne/Berlin. Kirchner, M., Braeutigam, S., Roemmelt, H., Feicht, E., Kettrup, A., 2000. Ammoniakimmissionen aus dem Verkehrsbereich (Ammonia in ambient air from motor vehicle emissions). Gefahrstoffe~Reinhaltung der Luft 60 (10), 383-388. OECD, 1999. Advanced air quality indicators and reporting, ENV/EPOC/PPC(99)9/FINAL.
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Rauterberg-Wulff, A., 1998. Beitrag des Reifen- und Bremsenabriebs zur Russimmission an Strassen (The contribution of tyre and brake abrasion to the ambient concentration of soot near streets). Fortschritt Berichte, VDI Reihe 15, No. 202, 178pp., VD1 Verlag, Dusseldorf. Rauterberg-Wulff, A., 2000. Untersuchung fiber die Bedeutung der Staubaufwirbelung ffir die PMl0-Immission an einer Hauptverkehrsstrasse (Investigation of the influence of resuspension of dust on the ambient concentration of PM10 near a main street). Technical report, Department of Urban Development, Environmental Protection and Technology, Technical University, Berlin. SenStadt, 1995. Luftreinhalteplan Berlin 1994 bis 2000 (Air pollution management plan 1994-2000). Brochure No. 19 in the Air Quality Management Series. Technical report, Department of Urban Development, Environmental Protection and Technology, Berlin. SenStadt, 1998. Air quality management in Berlin 1997. Brochure No. 22 in the Air Quality Management Series. Department of Urban Development, Environmental Protection and Technology, Berlin. Thurston, G.D., Spengler, J.D., 1985. A quantitative assessment of source contributions to inhalable particulate matter pollution in Metropolitan Boston. Atmospheric Environment 19, 9-25. TUEV, 1989. Messungen der Luftqualit/it in Berlin (West) 1988 (Measurement of the air quality in Berlin (West) 1988). Technischer Ueberwachungs-Verein Berlin e.V. Report no. D-89/185, Technical report, Department of Urban Development, Environmental Protection and Technology, Berlin. Umweltbundesamt, 1997. Personal communication. VDI (Verein Deutscher Ingenieure), 1999. Measurement of soot (ambient air), thermographic determination of elemental carbon after thermal desorption of organic carbon. VDI Guideline 2465, Part 2.
Atmospheric Environment 35 Supplement No. 1 (2001) $23-$33 www.elsevier.com/locate/atmosenv
Some ideas about the sources of PM10 P. Lenschow, H.-J. Abraham, K. Kutzner, M. Lutz*, J.-D. PreuB, W. Reichenbficher Department of Urban Development, Berlin, Germany Received 3 May 2000; received in revised form 18 January 2001; accepted 24 January 2001
Abstract In Berlin, about 50% of the urban background PM10 concentration is due to long range transport--mainly secondary aerosols (ammonium nitrate and ammonium sulphate) and natural sources. At kerbside sites on main streets the PM10-concentration is up to 40% higher than the urban background. Half of this additional pollution is due to motor vehicle exhaust emission and tyre abrasion and the other half is due to resuspended soil particles. On the basis of comparison of the main chemical components at stations in the regional and urban background and a station at the kerbside of a busy street, we estimate the source apportionment for the main source groups. Possible reduction measures are discussed. © 2001 Elsevier Science Ltd. All rights reserved. Keywords. Source apportionment; Chemical composition; Secondary aerosols; Resuspension by traffic; Measures of reduction
1. Introduction Concentrations of airborne particles have been measured in Berlin over almost 30 years. Exposure to huge emissions of sulphur dioxide and particulate matter in the 1970s and 1980s, especially in the then East Berlin and in the surrounding industrial agglomerations of East Germany, created a strong need to measure these and other pollutants at up to 43 measuring sites (SenStadt, 1998). Recorded series of air pollution data showed strikingly high levels of total suspended particulates (TSP) and sulphur dioxide concentration until the early 1990s, which led to smog alarms and traffic bans in the western part of the then divided city of Berlin. So, public pressure on the need for abatement of air pollution became strong and so was the necessity for identifying the sources of air pollution where control measures would have to be taken. Hence, surveys on the emission from all sectors led to a rather detailed
*Corresponding author. Present address: Senatsverwaltung fuer Stadtentwicklung-IX D-, Brueckenstrasse 6, D-10173 Berlin, Germany. E-mail address: [email protected] (M. Lutz).
emission register of Berlin for all major pollutants which has been updated regularly (SenStadt, 1998). The reunification of the city in 1989 led to a total reconstruction of the heating systems in the east, to an abandonment of high-sulphur lignite as a fuel in this part of the city as it had already been since 1981 in the western part, a total restructuring of the industrial and electricity sector in east Germany and so to an accelerated reduction of emissions of particulate matter and sulphur dioxide from these sources. The situation thus looks a lot better than illustrated in OECD (1999), one of the rare comparisons of air pollution between a larger number of cities in the world. Since 1993 the levels of suspended particulates have again fallen by about one third and the concentration of sulphur dioxide has dropped far below the limit values of EC-Directive 99/30/EC (EC, 1999). However, as shown in this paper, it is still necessary to assess sources of air pollution-especially as regards the levels of fine particles smaller than 10pro (PM10). Among other things, the above mentioned Directive sets tough limits for PM10 for 2005 and a further preliminary set of even tougher limit values for 2010. As these new limit values were based on recent findings on health effects from exposure to fine particles they are by far more stringent than those in the previous legislation. Together with the Air Quality
1352-2310/01/$-see front matter © 2001 Elsevier Science Ltd. All rights reserved. PII: S 1 352-23 1 0(0 1)00 1 22-4
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o f 100 km 2. The city is situated in the N o r t h e r n G e r m a n Lowlands less than 100km west o f G e r m a n y ' s border with Poland and a r o u n d 200 km northwest o f the more industrialised so-called "Black Triangle" o f the borders o f G e r m a n y , Poland and the Czech Republic. It has a m o d e r a t e climate with 50% winds from Southwest to N o r t h w e s t (mainly maritime influence) and 30% winds f r o m Southeast to N o r t h e a s t (mainly continental influence), average wind speed o f 3 m s 1 ( 1 0 m above r o o f tops in the built up area) and yearly mean temperature o f 8.8°C ( - 0 . 5 ° C in January, 17.9°C in July). The n u m b e r o f passenger cars and light duty vehicles (LDV) totalled 1.1 million at the end o f 1999 which means 323 cars per 1000 inhabitants (73% with threeway catalytic converter, 15% diesel) and the n u m b e r o f heavy duty vehicles (HDV) is 100000. This is still a rather low vehicle density in c o m p a r i s o n with other cities o f similar size. There are 13 bigger c o m b i n e d power and heating plants with a capacity o f 2800 M W electrical power run with coal, oil and natural gas. They all meet the G e r m a n emission limits. The coal and oil p o w e r plant are equipped with flue gas desulphurisation, denitrification and filters. One domestic waste incineration plant exists with a capacity o f 376000 tonnes waste per a n n u m equipped with flue gas filters o f a very high technical standard. There is nearly no heavy industry. Fuel used for domestic heating consists o f 30% natural gas, 20%
F r a m e w o r k Directive 96/62/EC (EC, 1996) authorities in n o n - a t t a i n m e n t z o n e s are required to assess PM10 pollution, including investigation into the origins o f air pollution, its major sources, and pollution which might be i m p o r t e d from other regions. F o r Berlin, the following questions arise: Will the PM10-1imits be met in 2005 without additional action or are the current reduction regulations sufficient? If not: • •
•
W h a t are the major sources (industry, transport, domestic, agriculture etc.)? H o w do sources inside the agglomeration which are directly accessible to the local authorities contribute to the PM10 pollution? W h a t sort o f additional action should be taken at regional, national, EC or U N - E C E levels?
This paper aims to get first answers for those questions and to identify further areas o f investigation so as to gain a more reliable basis for a b a t e m e n t plans and programmes.
2. Some basic information about Berlin and its monitoring network With a surface area o f 8 9 0 k m 2 and 3.4 million inhabitants Berlin is G e r m a n y ' s largest single c o n u r b a tion. 1.12 million people live in the inner city in an area
Table 1 Annual emissions of various source sectors in Germany and Berlin (1998)a'b Particles PM10
Plants subjected to licensing Domestic heating Households Small industries Traffic (motorvehiclesonly) Resuspension by traffic Traffic (other) Use of soIvents Agriculture (cattle) Agriculture (fertilize0 Other sources (construction,etc) Sum of all sources
Sulphur dioxide
Oxides of nitrogen
Volatile organiccompounds
Ammonia
Gerlnany
Berlin
Germany
Berlin
Germany
Berlin
Germany
Berlin
Germany
kt
%
kt
kt
%
kt
%
kt
%
kt
%
kt
%
kt
%
kt
%
95
38.8
1.9 20.3 1119
86.6
7.9
71.3 564
31.7
7.5
24.8
140
8.2
2.2
3.8
8
1.3
29
11.8
0.5 5.3
102
7.9
2.5
22.6 103
5.8
3.0
9.9
1.0
1.7
5
2.0
0.1
37
2.9
0.0
0.4
38
2.1
1.0
3.3
3.3 0.3
10.0 10.0
17.2 17.2
43
17.6
2,4 25.6 30
2.3
0.5
4.5
856
48.1
17.0 56.3 409
24.0
28.0
48.3
43
17.6
2,4 25.6
20
8.2
0,2 2.6
0.4
0.1
1.3
220
12.4
1.7
3.1 58.7
2.8
4.8 525
84.0
70
l 1.2
22
3.5
11 245
4.5
%
1.5
5
0.0
1.8 19.2 9.4
1292
11.1
0.0
0.0 1780
30.2
5.6
0.0
56 5
53 I000
42 1705
2.5
4.0 58.0
6.9
625
~Remarks: (1) All emissions extrapolated from data of 1995, (2) natural emissions not included, (3) use of solvents in Berlin is included in households and light industry. bData sources: Berlin: Senatsverwaltung fuer Stadtentwicklung, Germany: according to Umweltbundesamt Berlin and minutes of expert hearing III 2.2 H 50231-18/11 and Ehrlich et al. (2000).
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light oil (sulphur content less than 0.2%) and 15% lignite (sulphur content less than 1%). 30% are supplied by district heating and 5% by electricity. The annual mean emissions are shown in Table 1 together with German total emission data. In 1999 the Berlin air pollution monitoring network (Berliner Luftguete Messnetz, BLUME) consisted of 21 stations. Particulate matter is currently measured at 18 stations (see Fig. 1). A majority of 12 automatic instruments (radiometric monitors Eberline FH62IN) still measure TSP as was required by the recently repealed Directive 80/779/EEC (EC, 1980). The automatic network has been fitted to gravimetric TSP-measurement in 1988 with a constant factor (1.34) after gravimetric reference measurements at nine collocated background stations with about 100 daily samples each and correlation coefficients of 0 . 9 4 < r < 0 . 9 8 (TUEV, 1989). Gravimetric reference measurements of PM10 were performed during a measuring campaign in 1996 at three urban background stations and three stations near streets with 72-100 daily samples (Air Consult, 1997). The gravimetric reference measurements are made using low volume samplers (Kleinfilterger/it GS050) and high volume samplers (Digitel DHA80). After the elimination of 8% of data with PM 10/TSP less than 0.5 or more than 1.2 comparison of PM10 and TSP series resulted in conversion factors of 0.76-0.79 at the investigated urban background sites and slightly higher values of 0.82-0.85 at the three traffic sites with correlation coefficients of 0.953 < r < 0.967. Taking into account the uncertainties of the measurement techniques, the low correlation and the microlocation of measuring instruments an overall factor of 0.8 is considered as an appropriate approximation when estimating PM10 concentrations on the basis of TSP measurements with the Berlin BLUME network. The same factor has been used by federal institutions in Germany to gain an overview of the PM10 pollution. There have been two campaigns to measure and chemically analyse PM10 and PM2.5. The first was from November 1989 to October 1990 at an urban background station (and three other stations) in Berlin and the rural EMEP station Waldhof, about 180 km west of the town (Israel et al., 1992). The second was in 1998 at one urban background and one traffic station in Berlin (Abraham, 1999). These measurements have been made with teflon filters on Dichotomous Samplers (PM10 and PM2.5) and quartz filters on Digital DHA80 (TSP) in 1989/1990 and with quartz filters on Kleinfiltergeraet GS050 (PM10 and PM2.5) in 1998. Before and after exposure the filters are stored for more than 24h at 40 50% relative humidity and temperatures of 20 _+ 2°C. The methods used for chemical analysis were ion chromatography after extraction with ethanol or acetone and water for the ions and three step thermography (350°C and 620°C with helium, 700°C with
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monitoring stations E~] urban background traffic
(a) " "
1999 a n n ~ M l O (PMIO~
concentrations ~'/,,, PMIO=O,8xTSP) ~ r o 2 "
2
(b) 1999 90.14-percentiio (equivalent to 36. highest daUy mean of PM10 concentration) . . . . . . . . . . .
"
~ |f
(PM10 measurementin bold/italics, otherval~JesPMlO=O,SxTSP) ~
(c)
;
o
4
6 km
~" T 2 4 o km
Windroses of suspended particulates
Fig. I. Spatial distribution of suspended particulates in Berlin (1999). helium plus 20% oxygen) for elemental carbon (EC) and organic carbon (OC). The organic material (OM) is derived by multiplying OC with a factor 1.2 (Israel et al., 1992; VDI, 1999). In this paper all ions are displayed without their charges. Since no chemical analyses were available in the regional background in 1998 these values are estimated from 1996 data (Umweltbundesamt, 1997) and lowest
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concentrations of carbonaceous material measured at other stations in the region. There are differences between the results of the continuous automatic measurements and the results of the measuring campaigns that are mainly due to small sample size of the campaigns. Therefore, we avoid cross comparisons that could be affected by these differences.
sources like traffic, tram and sandy pavements have high influence at these points. The 90th percentiles (Fig. lb) show nearly the same spatial distribution as the annual means with lowest values at the borderline and highest values in the inner city near streets. As Fig. lc shows, the PM concentration is higher when the wind blows from the east (continental influence) than from the west (maritime influence). In the inner city, the background concentration for the east wind sectors (80-170 °) is higher than the west sectors (250-340 °) by a factor of 1.5-2.0 depending on the year. The measurements show that in 1999 the PM10 limit value of 4 0 g g m -3 as annual average was exceeded at one traffic site (Fig. la). The second PM10 limit value of 50 gg m -3 as 24 h mean not to be exceeded more than 35 times per year is equivalent to a limit for the 90th percentile of 50 ggm -3. As shown in Fig. lb, this limit value is exceeded more frequently throughout the city by up to 35% at stations with high influence of traffic. The situation looks even worse with regard to the indicative limit values for 2010 laid down in ECDirective 99/30/EC (EC, 1999) of 20ggm -3 as annual mean, with not more than seven peaks above 50 ggm 3. This short term limit is equivalent to a limit of the 98th percentile of 501agm 3. In 1999 the measured 98th percentiles go up to 100 lagm -3. It should be noted that in 1998 and 1999 westerly winds were more frequent than normal (and easterly
3. Present situation of P M I O
Fig. 1 shows the annual mean concentrations and relevant percentiles of PM10 as well as windroses of suspended particulate matter (SPM) at 18 automatic stations in Berlin. Six of them (one suburban, two urban background and three kerbside stations) measure PM 10. To give full information about the distribution in the city, the concentrations of the 12 TSP-stations are scaled down to PM10 by the above-mentioned factor of 0.8. As seen in Fig. la, in 1999 the annual mean values of PM10 in Berlin lay between 18 and 2 5 g g m -3 near the border line, 27-33ggm -3 in the inner city and 39-41ggm 3 at the two kerbside stations near main roads ( > 50 000 vehicles per day) in street canyons and 37ggm -3 near the inner city highway ring (180000 vehicles per day). Two stations in the eastern part of the town with 38 and 39ggm -3 do not fit into the concentration field of the background stations. Local
160
160 F
140
120 1-
.-..
!
I|
100 E 60
* TSP
/ .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
' .
.
.
.
.
.
.
.
.
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.
. . . .
,.
.
.
.
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.
.
.
.
,.
.
.
.
.
.
.
.
.
L
.
.
.
.
.
.
.
.
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--4--S02
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120
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E
bl
.
.
.
.
.
.
t ' -
.
.
.
.
.
.
,...
80
8 I.-
60
60 " i ' " 40 . . . . .
40
20
20
ol
1988
t989
1990
1991
1992
1993
1994
1998
1996
1997
Fig. 2. Monthly averages of TSP and S02 in the urban background.
1998
II 0 1999
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winds less frequent). With the usual distribution of winds the concentrations would have been higher than recorded. In order to meet the short-term limit values for 2005 also in hot spots with intense traffic the PM10pollution must drop by at least 27% by 2005. In order to develop an efficient abatement strategy more information is needed about the future trend and the sources of PM10.
4. Long-term changes in the characteristics of suspended particulate matter
Time series of monthly mean values of TSP and SO2 at three urban background stations in the inner city of Berlin show a distinct downward trend (Fig. 2). In summer there was always much more TSP than SO2. However, in winter in the period before 1991 peak levels of both substances were quite similar, while since 1991 much less SO2 than TSP has been found all over the year. A special feature of TSP is that the downward trend seems to remain on a high level with winter peaks sometimes nearly vanishing, whereas SO2 still shows clear winter peaks. The annual averages and the 98th percentiles of TSP concentrations measured in the urban background are
90
:
',
....... 7o
.......
This behaviour may be due to better particle filters in plants, less emission of smoke from domestic heating (the use of lignite in domestic heating has been reduced b y a b o u t 90% since 1990), and much better car engines. The lower reduction of EC can be attributed to the relative growth of influence of traffic, the influence of
:
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a strong reduction by about 50% of unresolved particles (mainly soil particles) and of OM, • a medium reduction of about 20% of SO4 and EC, and • a much smaller reduction of NO3 and NH4. •
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subject to nearly the same trend (Fig. 3). This is understandable if the main sources are subject to the same trends, or if the main sources react similar to the changes of climate influences. From this we infer that relative changes of annual averages may be taken in the first approximation as representative for the changes of higher percentiles. Table 2 depicts the decrease of TSP, PM10 and PM2.5 between 1990 and 1998 on the basis of annual mean concentrations measured at the urban background stations Fasanenstrasse in 1990 and Nansenstrasse in 1998. The last column of the table shows that the decrease of PM2.5 is less pronounced than of PM 10 and even less than TSP. As shown in Fig. 4, the development of the Berlin urban background since 1990 shows
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Fig. 3. Annual averages and 98-percentilesof daily mean concentration in the urban background.
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One can clearly recognise from Fig. 4 and Table 3 that in the busy street the PM10-pollution is up to 40% higher than in the surrounding urban background. Near the street there is a higher share of EC, OM and soil. It should be mentioned here that the method used to measure carbonaceous material does not perfectly separate EC from OM. Tests with extraction of OM with a mixture of 1 part of toluene and 3 parts of N , N dimethylformamide before thermographic analysis have revealed that about 30M0% of PM10 EC and 50-60% of PM2.5 EC may really be OM. Near streets where high concentrations of EC and OM are measured, the differences are not as distinct as in the background. For the source apportionment we could not take this finding into account.
tyre abrasion and the less restrictive emission limits for HDV in comparison with passenger cars. The lower reduction of SO4, NO3 and NH4 may be due to former limitations in the small scale conversion of SO2 and N O , in the atmosphere and perhaps emissions of NH3 from the growing number of cars with catalytic converters (Kirchner et al., 2000).
5. Main chemical composition of PMI0 The main chemical components of PMI0 in 1990 and 1998 are shown in Table 3 and Fig. 4. About one third of the mass of PM10 in the urban background is attributable to inorganic secondary aerosols originating from Europe-wide gaseous emissions. Another third is carbonaceous material, mainly emitted by motor vehicles and by lignite and coal combustion in stoves, but also secondary aerosol of organic matter from anthropogenic and natural sources. The remaining third consists of soil and ash particles, sea spray and water.
6. Source apportionment For the first approximation of the source apportionment presented in this paper, assumptions are made in three steps. The field structure of PM10-concentrations in the Berlin region (Fig. 1) suggests that concentrations measured at only one carefully sited station per type can be taken as representative for other stations of the three types "traffic", "urban background" and "regional background" as shown schematically in Fig. 5. So in the first step it is assumed that
Table 2 Average concentrations of TSP, PM10 and PM2.5 in the urban background Fasanenstrasse in 1990 (Israel et al., 1992), Nansenstrasse in 1998 (Abraham, 1999)
TSP PM10 PM2.5
1990 ggm -3
1998 pgm 3
Reduction %
77 58 39
43 38 30
44 34 23
Urban background Nansenstr
•
the kerbside station Frankfurter Allee at a busy main street with a traffic flow of about 60 000 vehicles per day with a HDV-share of 3.4% and a LDV-share of 7.1% is representative of the influence of traffic on air pollution near streets,
Traffic site Frankfurter Allee I
I
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II Eso4 III E]NH4 IV Florganie matter(OM) V Belemental carbon (EC) Vt D soil+water
Fig. 4. Chemical composition of PM10 in the city of Berlin (ggm 3).
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Table 3 Average concentation of PM10 and PM2.5 and main chemical components in the city of Berlin and the regional background ~ Type
UB Berlinb Fasanenstr.
RB Waldhofb
TR Berlin ° Frankfurter All.
UB Berlinc Nansenstr.
RB Neuglobsowd
PM10 (i.tgm-3) OM (gg m -3) EC (~tgm 3) SO4 (ggm -3) N O 3 (ggm 3) NH4(lag m -3) C1 (ggm -3) Unresolved (ggm 3) PM2.5 (ggm 3) OM (I,tgm -3) EC (ggm 3) S O 4 (,t.tgm-3) NO3 (I.tgm 3) NH4 (ggm -3) C1 (ggm 3) Unresolved (gg m -3) Start (MM.JJ) End (MM.JJ) No. of cases Sample (h)
57.6 15.0 6.3 9.3 4.3 3.7 0.7 19.0 39.2 10.1 5.3 7.8 3.3 3.9 0.4 8.8 10,89 10,90 254 12
26.9 5.8 2.1 4.9 3.0 2.4 0.7 8.7 18.6 4.0 1.7 4.2 2.2 2.2 0.2 4.3 10.89 10.90 313 12
51.5 11.0 9.0 5.7 4.6 3.3 0.8 17.9 38.6 9.4 7.7 5.6 4.3 3.8 0.7 7.8 02.98 12.98 33 24
37.7 7.5 5.1 6.1 4.4 3.4 0.7 11.2 30.2 7.0 4.7 5.5 3,7 3.7 0.5 5.6 02.98 12.98 33 24
18.6 3.0 1.8 3.9 2.4 2.0 5.5
01.98 12.98 24
aUB: urban background, RB: regional background, TR: Traffic, Unresolved: mainly metal oxides (soil) and water (Israel et al., 1992). bIsrael et al (1992). ~Abraham (1999). a Guessed after Umweltbundesamt (1997).
In the second step, it is assumed that
1, near traffic station (Frankforter Allee) 2. urban backgroond stations (N ansenstrasse; Fasanenstrage) 3. regional background stations (Waldhof; Neuglobsow)
•
PM [pg/rn3] 601
•
1
J
Tra.,c •
[
regional
background
]
Fig. 5. Schematic horizontal profile of the ambient PM10 concentration.
•
•
the urban background station Nansenstrasse in the inner city is taken as representative of the urban background level, and the rural stations Waldhof, 180 km from Berlin and Neuglobsow, 100 km from Berlin are representatives for regional background levels in 1990 and 1998, respectively, only marginally influenced by the city.
the differences of particulate matter and its chemical components between the traffic station and the urban background station can be attributed to the local influence of traffic on the adjacent street, the differences between the urban background station and the rural background station can be attributed to the sources of the agglomeration and the concentrations of particulate matter at the rural background station can be attributed to global sources with little contribution from the agglomeration.
We assume that there is a natural background of 5 . g g g m -3 due to primary and secondary emission of wind blown dust, pollen, volcanic eruptions, thunderstorms, oceans and other sources and apportion this as shown in Table 4a. In the third step, it is assumed that •
•
the relative influence of the German source groups can be taken as representative for all sources outside the agglomeration, the emissions of SO2, NOx and NH3 shown in Table 1 are the sources for the concentrations of SO3, NO3 and NH4 in Table 3, respectively, and
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the major source groups contribute to ambient concentrations of primary and secondary particles in proportions as their emissions displayed in Table 1 with the following modifications. In Table 1 besides the gaseous emissions there is only one category "particles PM10", that has to be combined with EC, OM and the unresolved portion of the measurements. For the partitioning of traffic, we used emission data from the "Handbook for emission factors of motor vehicles" (Keller et al., 1999), according to which 60% of the diesel emissions of passenger cars and LDV and 40% of the emissions of HDV consist of EC. The other part is counted as primary OM. Taking into account that 14% of all vehicles are diesel-engine cars, and 3.5% LDV and 3.4-5% HDV with diesel motors, this gives an average EC-partition of about 50%. The particle emissions of petrol cars are neglected in the handbook. We, therefore, included a small proportion of the volatile organic compounds as secondary material to the primary organic particulates. The difference between the traffic station and the urban background station consists solely of carbonaceous material (55%) and unresolved rests (45%). We assume that the carbonaceous material stems from the exhaust emissions of vehicles with 20% tyre abrasion (Rauterberg-Wulff, 1998, 2000) and the unresolved rest from resuspension of road dust, mainly soil. From the differences of the unresolved rests of PM10 and PM2.5 (Table 3) near the street it can be deduced that the resuspended particulates include a high proportion of about 70% coarse particles. These will be deposited within a range of some kilometres. Therefore, for the apportionment of the urban sources only 50% are taken into account and for the German sources 2O%. In the scale of the agglomeration there is a high dependency of ambient concentrations on the stack height of emissions. The Berlin plant subjected to licensing have stack heights of 50 150 m. To take this into account we assumed that they contribute only 20% of their emission to the urban background. The factor is derived from dispersion calculations of the Berlin Air Pollution Management Plan for the years 1994-2000 (SenStadt, 1995). For most relevant sources outside the agglomeration, which lie more than 50 km away, the emission heights are not taken into account. The coupling of the emissions of Table 1 with the ambient concentrations of Table 3 is shown in Table 4a which gives the results of our source apportionment of PM10 in as much detail as possible. The relative contributions of the main sources in the three spatial source groups are compared in Table 4b. Similar investigations have been conducted by e.g., Harrison et al. (1997), Chow et al. (1996) and Thurston and Spengler (1985). But in our paper we tried to get a full
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balance between the measured concentration of PM10 with its components and our knowledge about the emissions and to discriminate between the three spatial groups of sources. The comparison of secondary aerosols in the urban background and regional background by different laboratories shows that in the urban background there seems to be a surplus of NO3 that is as large as the regional background, the surplus of NH4 amounts to about 70% and SO4 to 60%. It is difficult to understand this and to identify the reasons. Therefore, we think that there is an urgent need for comparable measurements and chemical analyses in the regional background as well as in the urban agglomeration.
7. Results
In Berlin, the ambient concentration of PM10 near busy streets is about 40% higher than in the urban background. 55% of this additional pollution consists of carbonaceous material resulting from exhaust emissions and tyre abrasion. 45% of the additional PM10pollution can be attributed to resuspended soil material. From the PM2.5 measurements (Table 3) it can be calculated that one third (2.2ggm 3) of the resuspension is PM2.5 and two thirds coarser material. The difference of urban background and regional background data shows that about 50% of the urban background pollution is caused by emissions specific to the agglomeration. Half of this contribution is due to traffic emissions and 15% to domestic heating and households. If the regional background concentration is attributed to all sources outside the agglomeration, with negligible influence of the specific sources of the agglomeration, about 55% of the urban background pollution is caused by long range transport from outside the region and by natural sources such as pollen and wind-borne soil. The main contributors to this part of the ambient concentration are power plants and other industrial plant with about 35%, and traffic and nature with about 20% each. As Fig. lc shows, the average concentrations of SPM are much higher with south-easterly than with westerly winds. This is also valid for the PM 10 concentration in the regional background. Therefore, it has to be taken into account that sources lying south to south-east of Berlin have high impact on PM10-concentrations in the town. According to Table 4b, traffic is the most important group of sources (50%) causing high PM10 pollution in a busy street. About one quarter of the traffic influence is exhaust emissions and tyre abrasion in the individual street, a further quarter is resuspension of soil particles in the individual street and the remaining half is traffic
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influence on the city background--containing also the regional background. The second group of sources is combustion (24%)--from individual stove for heating apartments through to big power plants. About two thirds of it consists of secondary aerosols, mostly sulphate and nitrate, formed from Europe-wide SO2- and NO~emissions. One third is due to a source typical for eastern European cities: emission from lignite combustion in stoves to heat apartments. The third group consists of various natural sources (12%). These three groups are the sources of about 90% of PM10 pollution in a busy street. In the urban background the partition is similar but shifted to combustion (traffic 31%, combustion 33%, natural origin 14%). It should be noted that the results of the PM10 source apportionment presented here should be considered as a preliminary estimate based on a first set of data. Comparing these results with those from other cities would help to improve this analysis and gradually remove factors of uncertainty.
8. Future development
1.
2.
3.
4.
The Directive on National Emission Ceilings proposed by the European Commission (CEC, 1999) with SO2, NOx and NH3 emissions in Europe decreasing by about 50% until 2010 will also result in a reduction of PM10 by about 15% within the last years before that date. As the impact of the traffic sector is not confined to exhaust emissions but also includes tyre abrasion and resuspended soil particles, even zero-emissionvehicles still cause about half the PM 10 pollution of "dirty" vehicles. Therefore, the reduction of the traffic impact will be much smaller than the reduction of exhaust emission. We, therefore, expect that the continuous replacement of old cars (e.g. with ages more than 10 years) by new ones with lower emissions will cause a reduction of exhaust emissions of about 8% per year (Keller et al., 1999) but a reduction of PM10 concentrations of only 1-2% per year. The introduction of cleaner fuels by 2005 according to EC Directive 98/70/EC (EC, 1998) will result in a decrease of PM10 pollution by about 1-2%. Therefore, Germany is promoting introduction of these fuels in 2001 by reducing the tax rate. In an important step in Berlin, the total public bus fleet of 1200 buses will be equipped with particle filters (CRT) by the end of 2000. This big step will reduce the PM10 pollution by about 2% (corresponds to a 10% reduction of the carcinogenic EC-
5.
6.
pollution). Particle filters also trap ultrafine particles quite effectively. The further substitution of lignite by gas, light heating oil or district heating is still a quite important development. A very important problem is the reduction of the resuspended soil particles by traffic. We still do not know how to reduce the significant influence of about 5% in the urban background and up to 15% near urban main streets.
In conclusion, there is a lack of effective measures to control PM10 emissions with the aim of attaining the limit values, in particular the short-term limit value of PM 10 for 2005 in the vicinity of traffic sources. As this is probably a widespread problem, it is necessary to intensify mutual exchange of experiences between European cities on investigations about the sources of PM10 pollution as well as on the development of effective control strategies. Apart from that, it is also necessary--as planned by the European Commission-to review and investigate, what part of the PM mixture actually affects human health. This ought to be followed by a definition of appropriate limit values, with the aim of avoiding costly and possibly ineffective or even regrettable abatement strategies.
References Abraham, H.-J., 1999. PM 10 und PM2.5-Staubmessungenund Inhaltsstoffanalysen in Berlin (Measurements of PM10 and PM2.5 particulates and their main chemical components in Berlin). 34th Messtechnisches Colloquium, 1999. Air Consult, 1997. Stichprobenmessprogramm Berlin 1995/96 (Random sampling measurements of air pollution Berlin 1995/96). Technical report, Department of Urban Development, Environmental Protection and Technology, Berlin. CEC, 1999. Proposal for a Directive of the European Parliament and of the Council on national emission ceilings for certain atmospheric pollutants. Communication 99/125 of the European Commission to the European Parliament and the Council. Official Journal of the European Communities, No C 56E, 29.2.2000, p 34, accessibleat http://europa.eu.int/ comm/environment/docum/99125sm.htm. Chow, J.C., Watson, J.G., Lowenthal, D.H., Countess, R.J., 1996. Sources and chemistry of PM10 aerosol in Santa Barbara County, CA. Atmospheric Environment 30, 14891499. EC, 1980. Council Directive 1980/779/EEC on air quality limit values for sulphur dioxide and suspended particulates. Official Journal of the European Communities. No. L229, 30.08.1980, p. 30, Brussels. EC, 1996. Council Directive 1996/62/EC of 27 Sept 1996 on ambient air quality assessment and management. Official Journal of the European Communities, No. L296, 21.11.1996, p 55, Brussels.
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EC, 1998. Directive 1998/70/EC of the European Parliament and of the Council of 13 October 1998 relating to the quality of petrol and diesel fuels and amending Council Directive 93/12/EEC. Official Journal of the European Communities, No. L350, 28.12.98, p 58. EC, 1999. Directive 1999/30/EC of the European Parliament and of the Council of 22 April 1999 relating to limit values for SO2, NO2 and NOx, particulate matter and lead in ambient air. Offficial Journal of the European Communities, No. L163, 29.6.1999, p 41, Brussels. Ehrlich, Ch., Noll,G., Kalkoff, W.D., 2000. Emissionsuntersuchungen von PMI0, PM2.5 und PM1.0 an Industrieanlagen und Hausbrandfeuerst/itten (Investigation of PM10, PM2.5 and PM1.0 emissions of industrial plants and domest{c heating systems) Zeitschrift fuer Immissionsschutz 4, 141-148. Harrison, R.M., Deacon, A.R., Jones, M.R., Aplleby, R.S., 1997. Sources and processes affecting concentrations of PM10 and PM2.5 particulate matter in Birmingham (UK). Atmospheric Environment 31, 41034117. Israel, G., Erdmann, A., Shen, J., Frenzel, W., 1992. Analyse der Herkunft und Zusammensetzung der Schwebstaubimmission (Analysis of the origin and composition of particulate matter pollution). Fortschritt Berichte, VDI Reihe 15, No. 92, 277pp., VDI Verlag, Dusseldorf. Keller, M., Heldstab, J., de Haan, P., Knoerr, W., 1999. Handbuch fuer Emissionsfaktoren des Kraftfahrzeugverkehrs Version 1.2 (Handbook for emission factors of road traffic). On behalf of Swiss Agency for the Environment, Forests and Landscape (BUWAL) and German Federal Environmental Agency, Berne/Berlin. Kirchner, M., Braeutigam, S., Roemmelt, H., Feicht, E., Kettrup, A., 2000. Ammoniakimmissionen aus dem Verkehrsbereich (Ammonia in ambient air from motor vehicle emissions). Gefahrstoffe~Reinhaltung der Luft 60 (10), 383-388. OECD, 1999. Advanced air quality indicators and reporting, ENV/EPOC/PPC(99)9/FINAL.
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Rauterberg-Wulff, A., 1998. Beitrag des Reifen- und Bremsenabriebs zur Russimmission an Strassen (The contribution of tyre and brake abrasion to the ambient concentration of soot near streets). Fortschritt Berichte, VDI Reihe 15, No. 202, 178pp., VD1 Verlag, Dusseldorf. Rauterberg-Wulff, A., 2000. Untersuchung fiber die Bedeutung der Staubaufwirbelung ffir die PMl0-Immission an einer Hauptverkehrsstrasse (Investigation of the influence of resuspension of dust on the ambient concentration of PM10 near a main street). Technical report, Department of Urban Development, Environmental Protection and Technology, Technical University, Berlin. SenStadt, 1995. Luftreinhalteplan Berlin 1994 bis 2000 (Air pollution management plan 1994-2000). Brochure No. 19 in the Air Quality Management Series. Technical report, Department of Urban Development, Environmental Protection and Technology, Berlin. SenStadt, 1998. Air quality management in Berlin 1997. Brochure No. 22 in the Air Quality Management Series. Department of Urban Development, Environmental Protection and Technology, Berlin. Thurston, G.D., Spengler, J.D., 1985. A quantitative assessment of source contributions to inhalable particulate matter pollution in Metropolitan Boston. Atmospheric Environment 19, 9-25. TUEV, 1989. Messungen der Luftqualit/it in Berlin (West) 1988 (Measurement of the air quality in Berlin (West) 1988). Technischer Ueberwachungs-Verein Berlin e.V. Report no. D-89/185, Technical report, Department of Urban Development, Environmental Protection and Technology, Berlin. Umweltbundesamt, 1997. Personal communication. VDI (Verein Deutscher Ingenieure), 1999. Measurement of soot (ambient air), thermographic determination of elemental carbon after thermal desorption of organic carbon. VDI Guideline 2465, Part 2.