E V O L U T I O N OF A I R P O L L U T I O N IN O P O R T O A R E A M. C. A L V I M F E R R A Z and M. C. F A R I A F E R R A Z
Centro de Engenharia Qufmica (INIC), Faculdade de Engenharia, Rua dos Bragas, 4099 Porto Codex, Portugal.
(Received October, 1987) Abstract. The analysis of pollution data was the support for the proposed remodelation of the network and allowed an estimation of the Air Quality evolution since 1968. The most important pollution sources in Oporto area are the motor traffic, one oil refinery and one petrochemical complex. Strong acidity levels are generally small, but black smoke concentrations are similar to that observed in several European cities. The interpretation of the temporal evolution of network yearly averages, is sometimes not reliable, in consequence of not being possible to get the mean validation of every sites for all years. The network should be increased installing stations in the oldest commercial areas where sulfur dioxide, black smoke, nitrogen oxides, hidrocarbons, carbon monoxide, lead and ozone should be measured. Sulfur dioxide and black smoke should be measured too, in six more areas of the metropolitan Oporto.
1. Introduction
The present paper was based on results collected by oil refinery Petrogal which were obtained from its measuring network, assembled in the Oporto area in 1968 with the purpose to evaluate the impact of refinery activity on Air Quality. The management of this network, where strong acidity and black smoke daily average are determined, is since March 1986 of the responsibility of the Commission for Air Quality Management of Oporto Area (CGA-AP). The main purpose of this Commission is to remodel the network and transform it into one with a more urban characteristic. The analysis of pollution data was the support to the proposed remodelation and also an estimation of Air Quality evolution since 1968. The study reported here should be inserted in studies of vaster ambit, which will allow a diagnosis of the situation and a proposal for 'curative' and 'prophylactic' measures. Thus, it is hoped, that in a short time, a detailed inventory of emissions will be available, which together with an analysis of meteorological conditions, will allow to make real that purpose. Oporto is the second largest city in Portugal and is situated in the north (latitude and longitude approximately: 41o10 ' North and 8040' East). Figure 1 shows geographical localization of the area that was studied by Petrogal, which includes Oporto, its suburbs and Matosinhos where Petrogal is situated. As a consequence of geographic and climatic factors, it was anticipated that pollution impact would make itself felt over Oporto. So the network was assembled for covering these two municipalities. The town center is rather old, with very narrow, dark streets, bordered by high Environmental Monitoring and Assessment 11 (1988) 43-58. 9 1988 by Kluwer Academic Publishers.
44
M, C. ALVIM FERRAZ
~IANA
AND M, C. FARIA FERRAZ
AST1ELO
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E v o l u t i o n o f a i r q u a l i t y ( 1 9 6 8 - 1 9 8 6 ) . Site 01 - s t r o n g a c i d i t y .
During the first years studied, black smoke values were higher than those for strong acidity at area 01. This situation has been changing, becoming clear a trend towards pollution levels decreasing since 1981/82. These facts are admitted to be related to the change in railway traffic that affects the area, which has gradually begun using electric traction since the end of the 70's. A new growing trend in pollution levels is predictable from 1985/86, but this fact will have to be confirmed with the analysis of more recent data. Site 09 was also observed similarly. On one hand, yearly averages of black smoke at this site, exceeded sometimes measured values at site 01; on the other hand, geographic situation of site 09, associated with wind direction and speed, make this site to be the one, where Petrogal emissions are mostly felt. As the refinery began working near the end of 1969, a different trend in strong acidity concentrations and mainly much higher values were expected to be noticed. Available data are shown in Figures 13 and 14. Low values observed for strong acidity may be justified by predictable negative interferences for strong acidity method; so it is proposed to analyse sulfur dioxide using a specific method. Sites 01 and 09 were compared to other sites of similar characteristics, localized in some European cities (Table II). For that, site 01 was classified as suburban-resi-
54
M. C, ALVIM FERRAZ AND M. C. FARIA FERRAZ
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dential and site 09 as suburban-industrial, chosen years being conditioned by available data in relation to other countries [10]. Comparison of network averages and black smoke-strong acidity ratios (which indicate the contribution from road traffic [11], was also made. It can be seen that the Oporto suburban-residential area has a comparative high value for strong acidity and the second highest value for black smoke. The suburban industrial area in Oporto, has one of the lowest values for strong acidity, while black smoke levels are high enough. It is admitted that, the relatively high strong acidity levels in suburban-residential areas, are associated with the existence in those areas, of several small enterprises spreaded in an unruly manner. The low level of strong acidity observed in Oporto suburban-industrial area, should be related with the negative interferences for strong acidity method in this area; it is important also for that, the relatively small number
mean
EVOLUTION OF AIR POLLUTION IN OPORTO AREA
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Fig. 13. Evolution of air quality (1968-1986). Site 09 - strong acidity. and size of industries and its localization, beneficiated by the climatic conditions, namely in what concerns to wind. Black smoke concentrations indicate a great contribution from road traffic in both areas. Comparison of network averages should take into consideration that for all cities except Oporto, the data in Table II were determined considering the influence of residential and commercial central areas, the Oporto values being therefore underestimated; even so, black smoke levels are just clearly surpassed in Madrid. In what concerns to black smoke-strong acidity ratios, Oporto has the second highest value, showing that in general to the area, the road traffic has a great hold on the influence of pollution levels [11]. As the traffic is less intense in Oporto than in most of the other cities, the high value of the ratio should be related with a transit processed in worse conditions. The temporal evolution of network yearly averages (Figure 15), shows that generally strong acidity levels are always below the black smoke levels, the trend being similar. The decrease in pollution concentrations, observed since 1982/83 to 1984/85, is related with a reducing of emissions in consequence of a lower industrial activity. Meanwhile, the decreased values observed in 1976/77 and 1977/78 are mainly related with the number and type of sites considered for mean determinations. Effectively, some of the sites that traditionally have the highest concentrations did not have enough data to validate averages in that period, being clear that when taken
56
M. C. ALVIM FERRAZ AND M. C, FARIA FERRAZ
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EVOLUTION OF AIR POLLUTION IN OPORTO AREA
57
into account, the network average increased. The interpretation of the temporal evolution of network yearly averages is therefore compromised, being important to note that the network average is only meaningful if the network is constituted by an equilibrated number of sites localized in characteristic places of the area. T A B L E II C o m p a r i s o n b e t w e e n p o l l u t i o n levels in O p o r t o a n d in o t h e r E u r o p e a n cities. Y e a r l y a r i t h m e t i c m e a n s o f s t r o n g a c i d i t y ( S . A . ) a n d b l a c k s m o k e (B.S.) ( g g m - 3); B l a c k s m o k e - s t r o n g a c i d i t y r a t i o s ( B . S . / S . A . ) Suburbanresidential
Suburbanindustrial
S.A.
B.S.
S.A.
Averages of network
B.S.
S.A.
B.S.
B.S./S.A.
Belgium (Brussels)
1979 1980
74.7 68.7
19.7 17.0
84.4 64.4
16.9 14.6
85.0 69.8
21.3 16.9
0.25 0.24
Denmark (Copenhagen)
1979 1980
12.8 16.3
9.9 13.8
32.4 26.5
10.8 16.0
23.9 21.4
12.2 17.8
0.51 0.83
Spain (Madrid)
1979 1980
46.2 48.8
66.0 56.5
---
---
France (Gourdon)
1979 1980
---
45.4 44.0
France (Toulouse)
1979 1980
-.
Ireland (Dublin)
1979 1980
22.9 25.0
15.1 16.0
31.7 36.2
13.6 14.2
Yogoslavia (Zagreb)
1979 1980
32.7 46.2
---
40.5 33.2
Portugal (Porto
1979 /80
52.6
48.2
United Kingdom (Glasgow)
1979 1980
43.6 67.0
United Kingdom (London)
1979 1980
76.8 --
104 95.3
77.8 100
1.9 1.2
94.6 87.7
45.6 44.9
0.48 0.51
--
--
--
34.0 39.4
19.6 23.8
0.58 0.60
---
51.3 58.0
---
---
26.6
42.3
31.9
38.4
1.2
20.9 46.3
68.7 103
33.3 56.0
65.5 90.9
30.0 50.0
0.46 0.55
24.8 --
75.9 70.0
84.4 38.4
81.2 77.1
42.9 28.1
0.53 0.36
-.
40.9 39.5
148 116
-.
25.8 .
.
.
.
Therefore it is absolutely necessary to provide Oporto area with a more urban network, installing stations in the oldest commercial areas strongly influenced by traffic. Nitrogen oxides, carbon monoxide, hydrocarbons, lead and ozone should also be measured. As a consequence of industrial development of the Oporto metropolitan area, which includes eight administrative regions, it would be convenient to consider the
58
M.C. ALVIMFERRAZAND M. C. FAR|AFERRAZ
inclusion o f a site to m e a s u r e sulfur d io x i d e a n d black s m o k e in each o f the six regions where A i r Q u a l i t y has n o t yet been analysed.
Acknowledgements S u p p o r t fo r this w o r k was p r o v i d e d by C o m i s s ~ o de C o o r d e n a ~ o da Regi~o N o r t e , I N I C an d Direcg~o G e r a l da Q u a l i d a d e do A m b i e n t e .
References [1] Instituto Nacional de Estatistica - Recenseamentos Gerais da Populaqho. [2] G. Norcross, 'Abatement of Industrial Air Pollution in Three Areas of Portugal', Report on a visit to Portugal WHO 1985. [3] ISO/DIS- 4220.2, 1982. [4] AFNOR NFX43/005, 1977. [5] 'Selected Methods of Measuring Air Pollutants', WHO, Geneve, 1976. [6] G.E.M.S. 'Analysing and Interpreting Air Monitoring Data', WHO, Geneve 1980. [7] Comissariat a L'Energie Atomique, 'Statistique Appliqu6 h l'Exploitation des Mesures', Masson
1978. [8] Journal officiel des Communaut6s europ6ennes, Directive du Conseil 80/779/EEC, 15 juillet 1980. [9] M. C. Alvim Ferraz and M. C. Faria Ferraz, 'A Qualidade do Ar na/krea do Porto', Comissho de Coordenaq~.o da Regi~o Norte, Porto 1987. [10] G.E.M.S. 'Air Quality in Selected Urban Areas 1979-80', WHO, Geneve 1980. [11] P. Bandoin et al., 'Characteristics of Urban Air Pollution', Report No. 4/76, Concawe, The Hague
1976.