- Email: [email protected]
Meteorological effects on sulphur dioxide concentrations on the area of Turbigo
M e t e o r o l o g i c a l Effects on S u l p h u r D i o x i d e C o n c e n t r a t i o n s on t h e A r e a of T u r b i g o M. Alabiso and F. Parrini ENEL, Centto Ricerche Termiche e Nu¢leari - Via Rubattino, 54 - 20134 Milan, Italy
Abstract This paper presents the relationship between meteorological parameters and sulphur dioxide concentrations in the area of Turbigo. A large number of sulphur dioxide sources are located in this area: they are both urban and industrial emissions. Mean half hourly SO 2 measurements were recorded over a three year period at five monitoring stations. Meteorological data were taken by a meteorological station in this network and included mean halfhourly measurements of wind direction and speed, air temperature, atmospheric pressure, relative humidity and rainfall. The SO 2 data were classified by the meteorological parameters, singly and in combination. From the analysis of the effects of various meteorological parameters, wind direction was found to be the parameter best correlated with pollution concentration. Additional results regarding the seasonal cycles of pollution levels are also presented. The work is also based on a set of statistical and graphic techniques. Key words: sulphur dioxide concentrations, air pollution, effects of meteorological parameters.
i. INTRODUCTION The Po Valley (Northern Italy) is the more density populated region of Italy and air pollution management needs particular attention. Also, winds induced by the Alps and Appennlnes, are generally weak and with large shears. The air pollution problem in the area of Turblgo, located in the Po Valley about 35 Km West of Milan, has already been analyzed in a number of studies (Melli P. et al,, 1985; Anfossi D, et al., 1980; Brusasca et al., 19851 De Bortoli et al., 1980). However, the relationships between ground-level SO 2 concentration and meteorological conditions have received little attention. In the present study halfhourly means of SO 2 concentrations obtained from measurements at five monitoring stations have been related to halfhourly means of meteorological data obtained from measurements at meteorological station. This research was conducted over a three year period (from December 1977 to December 1980).
2.
STUDY AREA
The area of Turbigo is located in the Ticino Valley, in an area whose climate may be considered typical of the Po Valley (Fig. i). The Po Valley is a flat region having dimensions of about 400 km x i00 km, with an average slope less than one in'~" thousand, extending from the Western Alps to the Adriatic Sea and bound to the North by the Alps and to the South by the Appennines. The region is complicated by the presence of Valleys of smaller size surrounding the flat area and converging from the mountains towards the plain. Turbigo is situated at the bottom of the Ticino Valley. The region is almost flat with the mountains about 40 km to the North and 100 km to the South.
Paper accepted ~5 January 1988 Referee: Dr. P. Halpern
At Turbigo there is an ENEL Power Plant having 6 thermoelectric units with the following rated power and stack height: Unit East East East East West We~t
Stack height (m) 1 2 3 4 1 2
96 150 150 150 48 48
HW 300 400 400 400 i00 i00
The average annual temperature is about If°C, the extremes ranging, over the year, from 30°C to -8 ° C. Relative humidity is fairly high, rainfall moderate, and the winds are extremely light and blow mainly from a north-westerly and south-easterly direction, due to the presence of the Alps and, consequently, to the circulation of breezes during the summer months. This can be seen from the wind pattern for the summer of 1979 and the winter of 1979-1980 (shown in Figs. 2 and 3), which shows that the wind blows more often from the northwest in the winter, while, in summertime, the prevailing direction is south-easterly during the day and northwesterly during the night. We therefore see that breezes blowing down from the mountains into the valleys appear to be a more marked feature in the summertime. Another meteorological feature, that occurs with a certain frequency, especially during the winter and as spring approaches, is the fohn, a strong northerly katabatic wind, which is often accompanied by a rise in temperature and insolation, with a consequent drop in relative humidity (averaging between 30 and 50~). An outstanding feature, especially during the cold season, is the presence of fog, which occurs when there is no wind ( ~ ) C o m p u t a t i o n ~ Mechancis Publications
Envkonmental So,ware, 1988, Vol. 3, No. 1
17
Meteorological Effects on Sulphur Dioxide Concentrations: M.Alabiso aad F.Parriai or rain, day.
keeping temperature values constant during
the 4.1
3. DATA Data used for the present analysis are divide into two categories: meteorological data and ground level sulphur dioxide concentration data. SO 2 concentrations were supplied by a network of five monitoring stations positioned as shown in Fig. I. As it can be seen, they are aligned along one particular direction, that of the prevailing mountain and valley breeze [i]. Meteorological data used in this study were measured by instruments located inside the power plant area and exposed at 20 m for air temperature, at 20 m and 145 m above ground for wind speed and direction. Wind direction is recording according to the eight sectors of the compass. The instruments were exposed in such a way that the distance of obstacles was three times as much as their height and that there was not evident point sources in the immediate area. Both the concentration and the meteorological data are automatically transmitted to a Power Plant computer and memorized as halfhourly average values.
4.
CONCFACTRATION LK'ELS AND THEEFFECTS OF THE DIFFERE[~rl "°
POLLUTANT SOURCES ON CONCENTRATION LEVELS The monthly trends in respect of sulphur dioxide concentrations for the 5 stations are shown in Fig. 4. As will be seen, the levels recorded by the 5 sensors show an extremely even trend (apart from the anomalous case of Sensor i during the period May-June '79). This undoubtedly suggest~ that the positions of the stations were well chosen. As regards seasonal trends, it is clear (see Table I) that ground concentrations during the summer period (MayOctober) are much lower (average level: 8.79 ppb) than those recorded during the winter (average level: 38.7 ppb). This situation is repeated, the characteristics being the same for all the years considered. B y w a y of comparison, Table I also gives the seasonal data for electric energy. As will be noted, the seasonal drop in the load is less pronounced (40Z) than that of the SO 2
(75X). This would seem to indicate that SO 2 pollution is associated mainly with domestic heating systems, although it should be remembered that, during the winter months, weather conditions generally aggravate pollution. Moreover, it may be pointed out that concentrations for the winter months tend to diminish over the years. This might be explained by the diversification that has taken place in recent years in the types of fuel used for domestic heating, the tendency being to convert more and more to methane. This seems to be borne out by Fig. 5, which compares total electric energy output figures with 502 ground concentrations during the three-year period. We note that, when the load is fairly constant, there has been a decrease in sulphur dioxide concentration over the years. The pages that follow present some considerations regarding links between pollution by SO 2 and the meteorological variables that most affect ground concentrations of sulphur dioxide.
18
Environmental Software, 1988, Vol. 3, No. 1
Effects of Wind Direction
By associating the SO 2 ground concentration level with wind direction it is, generally speaking, possible to obtain information on the spatial distribution of the sources of pollutant. Pollution roses have been drawn in Fig. 6-9 for each station in order to show the average seasonal SO 2 concentration values for eight wind direction sectors in summer '79 and Winter '79-'80 for the two different heights (20 m and 145 m). A statistical test was carried out to ascertain the significance of the average concentration levels obtained for each wind direction. The results show, with 95Z probability, that these average levels must be considered significant. We can thus use them to draw conclusions regarding the directions from which sulphur dioxide pollution originates. It is apparent that, in winter time, the highest concentrations are associated with northeasterly winds. This seems to confirm that, during the winter, the main source of pollution is urban heating. In this connection, it is relevant to note that an area of high urban and industrial concentration is located northeast of the sensors (see Fig. i 0 ) . Since the monitoring stations are arranged according to the N-NE/S-SW wind direction, were compared mean SO 2 concentrations for downwind stations in respect to the power plant when the wind blows from N-NE (stations I and 4 - 63.2 ppb) and from S-SW (stations 7 and 3 - 62.1 ppb), with mean SO 2 concentrations for upwind stations when the wind blows from N-NE (stations 2 and 3 - 69.8 ppb) and from S-SW (stations 1 and 4 - 52.9 ppb). Comparisons between upwind and downwind mean concentrations (62.6 and 61.4 ppb respectively) points out that the impact of the power plant seems to be not considerable. Pollution roses recorded for the summer show markedly lower values than those recorded during the winter months. Station No. 1 registered higher concentration levels than those of the other stations, with the highest values for southerly or south-easterly winds. The main directions originating pollution seem, moreover, to indicate that the presence of th~ power plant affects only the nearer stations. 4.2 Effects of Wind Speed As regards Stations 2 and 4, mean seasonal concentration values have been plotted versus wind speed for two wind direction categories: -
-
"Polluted winds", from the ENEL power plant "Clean winds", from other directions.
The graphs in Fig.s ii-14 show, for each of the two stations examined, the average SO 2 concentration levels for Summer '79 and Winter '79-'80, calculated by breaking wind speed down into 35 intervals of 0.2 m/s, starting with a minimum speed of 0.4 m/s. In wintertime, ground concentration diminishes as wind speed increases. As regards clean wind situations, we may note that trends are even and levels fairly high for the two stations and
Meteorological Effects
on
two years considered ('79 and '80). This indicates a very high degree of background pollution. In the c a s e of polluted wind, it may be noted that, apart from significant random fluctuations, the average trend is not too different from that in respect of clean winds. In the sua~er, concentrations do not depend on wind speed. In the case of clean winds, levels are definitely lower and the trend is uniform for all the years considered. In respect of polluted winds, on the other hand, we note higher average levels and peaks of concentration whose occurrence, as a function of wind speed, appears to be of a random nature. In both cases, it would seem that concentration levels diminish as wind speed increases.
Sulphur Dioxide Concentrations: M.Alabiso and F.Parrini ACKNOWLEDGEMENT The authors would like to thank dr. P. Bacci for both his help and interest in this work. Appreciation is also expressed to ing. M. Pagliari for his careful review of the final manuscript. REFERENCES i.
knfossi D, et al. Ricerche embientali nella valle del Ticino. Stato di avanzamento (giugno Relazione ENEL/DSR, n. 375, luglio 1980.
2.
Raynor G.S., Smith M.E. and Singer I . A . Meteorological effects on sulfur dioxide concentrations on suburban Long Island, New York. Atmospheric Environment, 1974,8, 1305-1320.
3.
Zannetti P., Helli P. and Runca E. Meteorological factors affecting SO 2 pollution levels in Venice. Atmospheric Environment, 1977, ii, 605-616.
4.
Alabiso M., Brusasca G. e Sidri R. Descrizione e procedure di utilizzo della banca dati della reti meteochimiche, installate presso le centrali termoelettriche di Turbigo e Ostiglia. Relazione ENEL/DSR/CRTN, G0/83/01, 1983.
5.
klabiso M . , Apadula F. e Carboni G. Inventario della sorgenti di emissione per un modello climatologico. Relazione ENEL/DSR/CRTN, E2[02/01, 1982.
6.
Melli P., Bonino G., Bacci P. e Longhetto A. Studio della dispersione media stagionale d'inquinanti atmosfericl emessi da sorgenti industriali. ConveKno AEI, 1982.
7.
Melli P., Spirito A., Alabiso M., Bacci P., Carboni G., Bonino G. and Longhetto A. A climatological diffusion model for ground level and elevated emissions in a week-wind area. Ii Nuovo Cimento, vol. 8C, N. 3, 282-299, 1985.
8.
M. De Bortoli et al. Sulphur hexafluoride dispersion experiments at a power plant. CEE-EUR 6997 EN, 1980.
9.
Brusasca G., Finzi F. and Zannetti P. Modelli Statistici per la previsione a breve termine dei livelli di concentrazione di SO2 nell'area di Turbigo. Relazione ENEL/DSR/CRTN, G14/85/01, 1985.
4.3 Effects of Temperature Lastly, let us consider the link between seasonal average S0% levels and the air temperature. The graphs (in Figs. 15 and 16) show the seasonal SO 2 averages for 38 temperature classes in respect of the winter (from -6°C to 13°C, at 0.5°C intervals), and for 38 temperature classes in respect of the summer (from II°C to 31°C (at 0.5°C intervals) for the winters of '78-'79 and '79-'80 and the summers of '79 and '80. We may note that, in winter time, the concentrations diminish rapidly with increases in temperature, while the opposite trend is witnessed during the summer months. The winter trend would again appear to confirm the significant contribution made by domestic heating.
5. COMPUTE AVAILABILITY The statistical and graphic techniques have been developed to investigate the relationship between meteorological variables and sulphur dioxide concentrations. These procedures are written in Fortran VS language for a IBM3081-K computer but, with few modifications, could be adapted to run on other computer systems.
bassa '79).
6. CONCLUSIONS Sulphur dioxide concentrations measured over a three year period in the area of Turbigo were studied with respect to different meteorological conditions. The analysis carried out indicated substantially homogeneous performance on the part of the sensors. It was noteworthy that the picture presented of the relationship between the seasons and the degree of pollution was a coherent one, inasmuch as that SO 2 levels in wintertime were markedly higher than in summer. During the winter, higher concentrations are found with northeasterly winds than winds from other directions. Also during the winter, SO 2 concentrations average higher wi%~ light than with strong wind speeds and with low than with high temperatures. This show that a substantial fraction of winter pollution is due to the home heating. It would therefore seem to be essential to use, in the future, these data in conjunction with various pollution models to define the complex relationship existing in the Turbigo area between meteorological parameters and the contributions of the sources to the observed SO 2 values.
Table I Seasonal SOz c o n c e n t r a t i o n s and seasonal e l e c t r l c
E l e c t r i c energy
(Gk11)
energy
Mean SOz concentration (ppO)
Wlnter '79-'80 Summer '80
1895 3968 2312 3637 2236
7,91 43,27 10,43 34,15 8,04
Mean winter energy Mean summer energy
3802 2148
38,71 8,79
SuM,er '78 Winter '78-'79 summer ' 79
Environmental Software, 1988, Vol. 3, No. 1
19
Meteorological Effects on Sulphur Dioxide Concentrations: M.Alabiso and F.Parrini
.au sto ,4rsizio
~ l.on#e Pozzo/o
"IB~'n.aven:o
Cast,no Primo
I I ~ /#~'eru#o
,I I I/
dI.'~5~Came~-i
I I
7-1
I
"4f;~Ir ,f~ome#hne,
I 4k
o I
Figure 1.
20
2.5 I
Km
('er,~no
Rap of the Turbigo a~ea. Sulphur d i o x i d e data were used from the 5 s t a t i o n s indicated by open c i r c l e s .
Environmental Software, 1988, Vol. 3, No. 1
Meteorological Effects on Sulphur Dioxide Concentrations: M.Alabiso and F.Parrini
N
daytime N
Flgure
2,
night-time N
daytime N
Wlnd roses at 20 m: Summer 1979
Wind roses at 20 m: Wlnter '79-80
STATION f
n
)
Flgure 3,
1OO m D_
night - time
STATION 2 STATION 3 STATION 4 STATION 5
80
ft.
z
1
~
.... , .........
o_ 6O F-< r~
7" f
Z £9
/ ~
^
/ fi
L~,\,
/ ~
~-t..i
'
Z
0 L)
}1!, "~\
'~t
:A
,'.
20
0
0
I Jan ~
I
L ~ l ' ~ " t MWApr hSmddun~
"l" ~.~(~ct
1978
I
i
I
n
,
I
"n
i
I
I
I
~iovDec J ~ R~b Mot 0q~rPie/din hi ~ S . , p
I
~
I
I
!
I
CDctNo~Doc J ~ F-.13~
1979
I
I
!
u "Y'~'I
I
¢~r I~O.u~dun . l i ~ O c t
I
l
,
~k~Do=
1980
MONTHS Flgure
~, -
Monthly average S0z concentrations measured at flve stations durlng the perlod from January i978 to December 1980,
Environmental Software, 1988, Vol. 3, No. 1
21
Meteorological Effects on Sulphur Dioxide Concentrations: M.Alabiso and F.Parrini
GWh
ppb
6000
30
--
4000
20
2000
10
0
1979
1978 [
I Electric Average
0
1980
energy
(GWh)
SO 2 c o n c e n t r a t i o n s
(ppb)
Figure 5 - Electric energy and average S0z concentrations,
) [--~ II
)~--1
I
~I ~P
l
~2
I
I
I I
l~-'~i
N
+
I
i
Figure 6 -
I
I
~l
I
I
I
N
0 I
,
1
Refiner 514m
[] Power Plant
~( ~-5
I
0
100 ppb i
l
I
Pollution roses: summer 1979 Station 20 m
i
22
I I
~~----~ i }i
I
F--(-
I
l
o w e r Plant
,
0
1 II
Environmental Software, 1988, Vol. 3, No. 1
l
+ l
Figure 7
/-"
Refinery 5Km
0
I
I
100ppb l
I
- Pollution roses: summer 1979 Station
lq5 m
Meteorological Effects on Sulphur Dioxide Concentrations: M.Alabiso and F.Parrini
I
I
I I I
I
--
Ptant
II
b
I
Refinery a
N
+
0
!
Figure 8 -
N .:-* .~
5Km
0!
' ~';~o
', ',
I I I
P tant
Power
I
lOOppb I
0
I
Pollution roses: winter 1979-80 Station 20 m
+ I
m
5Km I
Figure 9 -
0
I
I
lOOppb I
I
Pollution roses: winter 1979-80 Stotlon 145 m
IM £SlKm
2olKm
I
,y
i
W --4--
I
= 40"o0o people
5
Figure 10 Population d i s t r i b u t i o n in tile radius of 25 Km from the power p l a n t , i i
i
ih"
I
i
Environmental Software, 1988, Vol. 3, No. 1
i ii
i
23
Meteorological Effects on Sulphur Dioxide Concentrations: M.Alabiso and E.Parrini
S u m m e r '79
.-. 150 rn O. (3.
v
z
Station
n*4
Station
n* 2
---
< I,-z w
~z
50
12) 0
0
i"""
0
Figure
150
'~'~ "~''"
1 2 CLEAN
"I"'~
" " - - ..r •
~
I
I
9
Seasonal average S0z concentrations measured at two stations as a function of wind speed for clean winds
11 -
S u m m e r '79
m 13_ 13. v
z
o 100 I< rr F-Z I~J
__----
3 4=~5 6 7 8 WI N D S P E E D 1 4 5 m ( m / s )
Station
n*4 - - -
Station
n*2
50
z 0 IM
0 m
I
vV
\ ; t^
I
0
" I'~"
.
-V
~.-----,
~
"~
I
1 2 3 4 5 6 7 8 POLLUTED WIND SPEED 145m ( m l s ) Figure
24
12
-
S e a s o n a l a v e r a g e S0z c o n c e n t r a t i o n s m e a s u r e d a t two s t a t i o n s as a f u n c t i o n wlnd speed for polluted winds,
Environmental Software, 1988, Vol. 3, No. 1
i
9
of
Meteorolog{cal Effects on Sulphur Dioxide Concentrations: M.Alabiso and F.Parrini
Winter '79
150 nn (3_ D.
Station n° 4 - - -
z 100
Station n° 2
0 I-< nFz
uJ u
I 50
z 0 u 0
00
u~
I
I
I
I
I
I
1
2
3
4
5
6
I
I
? 8 CLEAN WIND ~PEED 145m (mls)
Figure 13 -
I
9
Seosonol overage S0z concentrotlons measured ot two stotlons os o function of wlnd speed f0F cleon winds,
Winter '79
150 nn (2. (3_
Station n° 4
Z
100
o
~
I-< ¢r I-z uJ
c~ 50 Z
A
//
O u
Station n°2
" V',' ',.,.^, ,,
(M
0
m
00
Figure
I I I 2 POLLUTED
14 -
I
I
~'~/
I~"
I
I
I
3
4
5
6
7
8
9
WIND
SPEED
145 m
(m/s)
Seasonel eve'roge S02 concentrations measured ot two s t a t i o n s as o f u n c t i o n of wind speed for
polluted
winds,
Environmental Software, 1988, Vol. 3, No. 1
25
Meteorological Effects on Sulphur Dioxide Concentrations: M.Alabiso and F.Parrini
WINTER
1978/'79
S U M M E R 1979
125 ,, S t a t i o n
n° 4
•
n° 2
Station
100 fZ3
..'~
n O. V
Z
O
/k •
75
/X
oeO
,¢ O: Z UJ L9 Z
/k
•
~•
/%~
•
50
O
o •
~9 O t/3
•
o~
25 ~
0
-I0
I
I
I
i
-5
O
5
10
15
TEMPERATURE Flgure 15 -
26
20
•
I
I
I
25
30
35
(°C)
Seasond~ average S0z c o n c e n t r a t i o n s measured at two s t a t i o n s as a f u n c t i o n of temperature f o r 1978 - 1979,
Environmental Software, 1988, Vol. 3, No. 1
Meteorological Effects oa Sulphur Dioxide Concentratioas: M.Alabiso aad F.Parriai ....
,
,
SUMMER 1980
WINTER 19791'80 200
Station •
175 m CL If.
n° 4
Station n°2
150 Q
v
Z
O I-.-
125 A
rr"
I-Z
IJ.l U Z 0 L)
100
A
75
~41 •
e~
0 u")
• ° ee
qDe
50
oAo ''L °" 'P'-
25
~'~
-I0
-5
0
~
5
,~"
10
15
20
25
30
35
TEMPERATURE (°C) Flgure 16
-
SeasQnal average $02 concentrations measured at two s t a t l o n s as a functton of temperature for 1979-1980
Environmental Software, 1988, Vol. 3, No. 1
27
Abstract This paper presents the relationship between meteorological parameters and sulphur dioxide concentrations in the area of Turbigo. A large number of sulphur dioxide sources are located in this area: they are both urban and industrial emissions. Mean half hourly SO 2 measurements were recorded over a three year period at five monitoring stations. Meteorological data were taken by a meteorological station in this network and included mean halfhourly measurements of wind direction and speed, air temperature, atmospheric pressure, relative humidity and rainfall. The SO 2 data were classified by the meteorological parameters, singly and in combination. From the analysis of the effects of various meteorological parameters, wind direction was found to be the parameter best correlated with pollution concentration. Additional results regarding the seasonal cycles of pollution levels are also presented. The work is also based on a set of statistical and graphic techniques. Key words: sulphur dioxide concentrations, air pollution, effects of meteorological parameters.
i. INTRODUCTION The Po Valley (Northern Italy) is the more density populated region of Italy and air pollution management needs particular attention. Also, winds induced by the Alps and Appennlnes, are generally weak and with large shears. The air pollution problem in the area of Turblgo, located in the Po Valley about 35 Km West of Milan, has already been analyzed in a number of studies (Melli P. et al,, 1985; Anfossi D, et al., 1980; Brusasca et al., 19851 De Bortoli et al., 1980). However, the relationships between ground-level SO 2 concentration and meteorological conditions have received little attention. In the present study halfhourly means of SO 2 concentrations obtained from measurements at five monitoring stations have been related to halfhourly means of meteorological data obtained from measurements at meteorological station. This research was conducted over a three year period (from December 1977 to December 1980).
2.
STUDY AREA
The area of Turbigo is located in the Ticino Valley, in an area whose climate may be considered typical of the Po Valley (Fig. i). The Po Valley is a flat region having dimensions of about 400 km x i00 km, with an average slope less than one in'~" thousand, extending from the Western Alps to the Adriatic Sea and bound to the North by the Alps and to the South by the Appennines. The region is complicated by the presence of Valleys of smaller size surrounding the flat area and converging from the mountains towards the plain. Turbigo is situated at the bottom of the Ticino Valley. The region is almost flat with the mountains about 40 km to the North and 100 km to the South.
Paper accepted ~5 January 1988 Referee: Dr. P. Halpern
At Turbigo there is an ENEL Power Plant having 6 thermoelectric units with the following rated power and stack height: Unit East East East East West We~t
Stack height (m) 1 2 3 4 1 2
96 150 150 150 48 48
HW 300 400 400 400 i00 i00
The average annual temperature is about If°C, the extremes ranging, over the year, from 30°C to -8 ° C. Relative humidity is fairly high, rainfall moderate, and the winds are extremely light and blow mainly from a north-westerly and south-easterly direction, due to the presence of the Alps and, consequently, to the circulation of breezes during the summer months. This can be seen from the wind pattern for the summer of 1979 and the winter of 1979-1980 (shown in Figs. 2 and 3), which shows that the wind blows more often from the northwest in the winter, while, in summertime, the prevailing direction is south-easterly during the day and northwesterly during the night. We therefore see that breezes blowing down from the mountains into the valleys appear to be a more marked feature in the summertime. Another meteorological feature, that occurs with a certain frequency, especially during the winter and as spring approaches, is the fohn, a strong northerly katabatic wind, which is often accompanied by a rise in temperature and insolation, with a consequent drop in relative humidity (averaging between 30 and 50~). An outstanding feature, especially during the cold season, is the presence of fog, which occurs when there is no wind ( ~ ) C o m p u t a t i o n ~ Mechancis Publications
Envkonmental So,ware, 1988, Vol. 3, No. 1
17
Meteorological Effects on Sulphur Dioxide Concentrations: M.Alabiso aad F.Parriai or rain, day.
keeping temperature values constant during
the 4.1
3. DATA Data used for the present analysis are divide into two categories: meteorological data and ground level sulphur dioxide concentration data. SO 2 concentrations were supplied by a network of five monitoring stations positioned as shown in Fig. I. As it can be seen, they are aligned along one particular direction, that of the prevailing mountain and valley breeze [i]. Meteorological data used in this study were measured by instruments located inside the power plant area and exposed at 20 m for air temperature, at 20 m and 145 m above ground for wind speed and direction. Wind direction is recording according to the eight sectors of the compass. The instruments were exposed in such a way that the distance of obstacles was three times as much as their height and that there was not evident point sources in the immediate area. Both the concentration and the meteorological data are automatically transmitted to a Power Plant computer and memorized as halfhourly average values.
4.
CONCFACTRATION LK'ELS AND THEEFFECTS OF THE DIFFERE[~rl "°
POLLUTANT SOURCES ON CONCENTRATION LEVELS The monthly trends in respect of sulphur dioxide concentrations for the 5 stations are shown in Fig. 4. As will be seen, the levels recorded by the 5 sensors show an extremely even trend (apart from the anomalous case of Sensor i during the period May-June '79). This undoubtedly suggest~ that the positions of the stations were well chosen. As regards seasonal trends, it is clear (see Table I) that ground concentrations during the summer period (MayOctober) are much lower (average level: 8.79 ppb) than those recorded during the winter (average level: 38.7 ppb). This situation is repeated, the characteristics being the same for all the years considered. B y w a y of comparison, Table I also gives the seasonal data for electric energy. As will be noted, the seasonal drop in the load is less pronounced (40Z) than that of the SO 2
(75X). This would seem to indicate that SO 2 pollution is associated mainly with domestic heating systems, although it should be remembered that, during the winter months, weather conditions generally aggravate pollution. Moreover, it may be pointed out that concentrations for the winter months tend to diminish over the years. This might be explained by the diversification that has taken place in recent years in the types of fuel used for domestic heating, the tendency being to convert more and more to methane. This seems to be borne out by Fig. 5, which compares total electric energy output figures with 502 ground concentrations during the three-year period. We note that, when the load is fairly constant, there has been a decrease in sulphur dioxide concentration over the years. The pages that follow present some considerations regarding links between pollution by SO 2 and the meteorological variables that most affect ground concentrations of sulphur dioxide.
18
Environmental Software, 1988, Vol. 3, No. 1
Effects of Wind Direction
By associating the SO 2 ground concentration level with wind direction it is, generally speaking, possible to obtain information on the spatial distribution of the sources of pollutant. Pollution roses have been drawn in Fig. 6-9 for each station in order to show the average seasonal SO 2 concentration values for eight wind direction sectors in summer '79 and Winter '79-'80 for the two different heights (20 m and 145 m). A statistical test was carried out to ascertain the significance of the average concentration levels obtained for each wind direction. The results show, with 95Z probability, that these average levels must be considered significant. We can thus use them to draw conclusions regarding the directions from which sulphur dioxide pollution originates. It is apparent that, in winter time, the highest concentrations are associated with northeasterly winds. This seems to confirm that, during the winter, the main source of pollution is urban heating. In this connection, it is relevant to note that an area of high urban and industrial concentration is located northeast of the sensors (see Fig. i 0 ) . Since the monitoring stations are arranged according to the N-NE/S-SW wind direction, were compared mean SO 2 concentrations for downwind stations in respect to the power plant when the wind blows from N-NE (stations I and 4 - 63.2 ppb) and from S-SW (stations 7 and 3 - 62.1 ppb), with mean SO 2 concentrations for upwind stations when the wind blows from N-NE (stations 2 and 3 - 69.8 ppb) and from S-SW (stations 1 and 4 - 52.9 ppb). Comparisons between upwind and downwind mean concentrations (62.6 and 61.4 ppb respectively) points out that the impact of the power plant seems to be not considerable. Pollution roses recorded for the summer show markedly lower values than those recorded during the winter months. Station No. 1 registered higher concentration levels than those of the other stations, with the highest values for southerly or south-easterly winds. The main directions originating pollution seem, moreover, to indicate that the presence of th~ power plant affects only the nearer stations. 4.2 Effects of Wind Speed As regards Stations 2 and 4, mean seasonal concentration values have been plotted versus wind speed for two wind direction categories: -
-
"Polluted winds", from the ENEL power plant "Clean winds", from other directions.
The graphs in Fig.s ii-14 show, for each of the two stations examined, the average SO 2 concentration levels for Summer '79 and Winter '79-'80, calculated by breaking wind speed down into 35 intervals of 0.2 m/s, starting with a minimum speed of 0.4 m/s. In wintertime, ground concentration diminishes as wind speed increases. As regards clean wind situations, we may note that trends are even and levels fairly high for the two stations and
Meteorological Effects
on
two years considered ('79 and '80). This indicates a very high degree of background pollution. In the c a s e of polluted wind, it may be noted that, apart from significant random fluctuations, the average trend is not too different from that in respect of clean winds. In the sua~er, concentrations do not depend on wind speed. In the case of clean winds, levels are definitely lower and the trend is uniform for all the years considered. In respect of polluted winds, on the other hand, we note higher average levels and peaks of concentration whose occurrence, as a function of wind speed, appears to be of a random nature. In both cases, it would seem that concentration levels diminish as wind speed increases.
Sulphur Dioxide Concentrations: M.Alabiso and F.Parrini ACKNOWLEDGEMENT The authors would like to thank dr. P. Bacci for both his help and interest in this work. Appreciation is also expressed to ing. M. Pagliari for his careful review of the final manuscript. REFERENCES i.
knfossi D, et al. Ricerche embientali nella valle del Ticino. Stato di avanzamento (giugno Relazione ENEL/DSR, n. 375, luglio 1980.
2.
Raynor G.S., Smith M.E. and Singer I . A . Meteorological effects on sulfur dioxide concentrations on suburban Long Island, New York. Atmospheric Environment, 1974,8, 1305-1320.
3.
Zannetti P., Helli P. and Runca E. Meteorological factors affecting SO 2 pollution levels in Venice. Atmospheric Environment, 1977, ii, 605-616.
4.
Alabiso M., Brusasca G. e Sidri R. Descrizione e procedure di utilizzo della banca dati della reti meteochimiche, installate presso le centrali termoelettriche di Turbigo e Ostiglia. Relazione ENEL/DSR/CRTN, G0/83/01, 1983.
5.
klabiso M . , Apadula F. e Carboni G. Inventario della sorgenti di emissione per un modello climatologico. Relazione ENEL/DSR/CRTN, E2[02/01, 1982.
6.
Melli P., Bonino G., Bacci P. e Longhetto A. Studio della dispersione media stagionale d'inquinanti atmosfericl emessi da sorgenti industriali. ConveKno AEI, 1982.
7.
Melli P., Spirito A., Alabiso M., Bacci P., Carboni G., Bonino G. and Longhetto A. A climatological diffusion model for ground level and elevated emissions in a week-wind area. Ii Nuovo Cimento, vol. 8C, N. 3, 282-299, 1985.
8.
M. De Bortoli et al. Sulphur hexafluoride dispersion experiments at a power plant. CEE-EUR 6997 EN, 1980.
9.
Brusasca G., Finzi F. and Zannetti P. Modelli Statistici per la previsione a breve termine dei livelli di concentrazione di SO2 nell'area di Turbigo. Relazione ENEL/DSR/CRTN, G14/85/01, 1985.
4.3 Effects of Temperature Lastly, let us consider the link between seasonal average S0% levels and the air temperature. The graphs (in Figs. 15 and 16) show the seasonal SO 2 averages for 38 temperature classes in respect of the winter (from -6°C to 13°C, at 0.5°C intervals), and for 38 temperature classes in respect of the summer (from II°C to 31°C (at 0.5°C intervals) for the winters of '78-'79 and '79-'80 and the summers of '79 and '80. We may note that, in winter time, the concentrations diminish rapidly with increases in temperature, while the opposite trend is witnessed during the summer months. The winter trend would again appear to confirm the significant contribution made by domestic heating.
5. COMPUTE AVAILABILITY The statistical and graphic techniques have been developed to investigate the relationship between meteorological variables and sulphur dioxide concentrations. These procedures are written in Fortran VS language for a IBM3081-K computer but, with few modifications, could be adapted to run on other computer systems.
bassa '79).
6. CONCLUSIONS Sulphur dioxide concentrations measured over a three year period in the area of Turbigo were studied with respect to different meteorological conditions. The analysis carried out indicated substantially homogeneous performance on the part of the sensors. It was noteworthy that the picture presented of the relationship between the seasons and the degree of pollution was a coherent one, inasmuch as that SO 2 levels in wintertime were markedly higher than in summer. During the winter, higher concentrations are found with northeasterly winds than winds from other directions. Also during the winter, SO 2 concentrations average higher wi%~ light than with strong wind speeds and with low than with high temperatures. This show that a substantial fraction of winter pollution is due to the home heating. It would therefore seem to be essential to use, in the future, these data in conjunction with various pollution models to define the complex relationship existing in the Turbigo area between meteorological parameters and the contributions of the sources to the observed SO 2 values.
Table I Seasonal SOz c o n c e n t r a t i o n s and seasonal e l e c t r l c
E l e c t r i c energy
(Gk11)
energy
Mean SOz concentration (ppO)
Wlnter '79-'80 Summer '80
1895 3968 2312 3637 2236
7,91 43,27 10,43 34,15 8,04
Mean winter energy Mean summer energy
3802 2148
38,71 8,79
SuM,er '78 Winter '78-'79 summer ' 79
Environmental Software, 1988, Vol. 3, No. 1
19
Meteorological Effects on Sulphur Dioxide Concentrations: M.Alabiso and F.Parrini
.au sto ,4rsizio
~ l.on#e Pozzo/o
"IB~'n.aven:o
Cast,no Primo
I I ~ /#~'eru#o
,I I I/
dI.'~5~Came~-i
I I
7-1
I
"4f;~Ir ,f~ome#hne,
I 4k
o I
Figure 1.
20
2.5 I
Km
('er,~no
Rap of the Turbigo a~ea. Sulphur d i o x i d e data were used from the 5 s t a t i o n s indicated by open c i r c l e s .
Environmental Software, 1988, Vol. 3, No. 1
Meteorological Effects on Sulphur Dioxide Concentrations: M.Alabiso and F.Parrini
N
daytime N
Flgure
2,
night-time N
daytime N
Wlnd roses at 20 m: Summer 1979
Wind roses at 20 m: Wlnter '79-80
STATION f
n
)
Flgure 3,
1OO m D_
night - time
STATION 2 STATION 3 STATION 4 STATION 5
80
ft.
z
1
~
.... , .........
o_ 6O F-< r~
7" f
Z £9
/ ~
^
/ fi
L~,\,
/ ~
~-t..i
'
Z
0 L)
}1!, "~\
'~t
:A
,'.
20
0
0
I Jan ~
I
L ~ l ' ~ " t MWApr hSmddun~
"l" ~.~(~ct
1978
I
i
I
n
,
I
"n
i
I
I
I
~iovDec J ~ R~b Mot 0q~rPie/din hi ~ S . , p
I
~
I
I
!
I
CDctNo~Doc J ~ F-.13~
1979
I
I
!
u "Y'~'I
I
¢~r I~O.u~dun . l i ~ O c t
I
l
,
~k~Do=
1980
MONTHS Flgure
~, -
Monthly average S0z concentrations measured at flve stations durlng the perlod from January i978 to December 1980,
Environmental Software, 1988, Vol. 3, No. 1
21
Meteorological Effects on Sulphur Dioxide Concentrations: M.Alabiso and F.Parrini
GWh
ppb
6000
30
--
4000
20
2000
10
0
1979
1978 [
I Electric Average
0
1980
energy
(GWh)
SO 2 c o n c e n t r a t i o n s
(ppb)
Figure 5 - Electric energy and average S0z concentrations,
) [--~ II
)~--1
I
~I ~P
l
~2
I
I
I I
l~-'~i
N
+
I
i
Figure 6 -
I
I
~l
I
I
I
N
0 I
,
1
Refiner 514m
[] Power Plant
~( ~-5
I
0
100 ppb i
l
I
Pollution roses: summer 1979 Station 20 m
i
22
I I
~~----~ i }i
I
F--(-
I
l
o w e r Plant
,
0
1 II
Environmental Software, 1988, Vol. 3, No. 1
l
+ l
Figure 7
/-"
Refinery 5Km
0
I
I
100ppb l
I
- Pollution roses: summer 1979 Station
lq5 m
Meteorological Effects on Sulphur Dioxide Concentrations: M.Alabiso and F.Parrini
I
I
I I I
I
--
Ptant
II
b
I
Refinery a
N
+
0
!
Figure 8 -
N .:-* .~
5Km
0!
' ~';~o
', ',
I I I
P tant
Power
I
lOOppb I
0
I
Pollution roses: winter 1979-80 Station 20 m
+ I
m
5Km I
Figure 9 -
0
I
I
lOOppb I
I
Pollution roses: winter 1979-80 Stotlon 145 m
IM £SlKm
2olKm
I
,y
i
W --4--
I
= 40"o0o people
5
Figure 10 Population d i s t r i b u t i o n in tile radius of 25 Km from the power p l a n t , i i
i
ih"
I
i
Environmental Software, 1988, Vol. 3, No. 1
i ii
i
23
Meteorological Effects on Sulphur Dioxide Concentrations: M.Alabiso and E.Parrini
S u m m e r '79
.-. 150 rn O. (3.
v
z
Station
n*4
Station
n* 2
---
< I,-z w
~z
50
12) 0
0
i"""
0
Figure
150
'~'~ "~''"
1 2 CLEAN
"I"'~
" " - - ..r •
~
I
I
9
Seasonal average S0z concentrations measured at two stations as a function of wind speed for clean winds
11 -
S u m m e r '79
m 13_ 13. v
z
o 100 I< rr F-Z I~J
__----
3 4=~5 6 7 8 WI N D S P E E D 1 4 5 m ( m / s )
Station
n*4 - - -
Station
n*2
50
z 0 IM
0 m
I
vV
\ ; t^
I
0
" I'~"
.
-V
~.-----,
~
"~
I
1 2 3 4 5 6 7 8 POLLUTED WIND SPEED 145m ( m l s ) Figure
24
12
-
S e a s o n a l a v e r a g e S0z c o n c e n t r a t i o n s m e a s u r e d a t two s t a t i o n s as a f u n c t i o n wlnd speed for polluted winds,
Environmental Software, 1988, Vol. 3, No. 1
i
9
of
Meteorolog{cal Effects on Sulphur Dioxide Concentrations: M.Alabiso and F.Parrini
Winter '79
150 nn (3_ D.
Station n° 4 - - -
z 100
Station n° 2
0 I-< nFz
uJ u
I 50
z 0 u 0
00
u~
I
I
I
I
I
I
1
2
3
4
5
6
I
I
? 8 CLEAN WIND ~PEED 145m (mls)
Figure 13 -
I
9
Seosonol overage S0z concentrotlons measured ot two stotlons os o function of wlnd speed f0F cleon winds,
Winter '79
150 nn (2. (3_
Station n° 4
Z
100
o
~
I-< ¢r I-z uJ
c~ 50 Z
A
//
O u
Station n°2
" V',' ',.,.^, ,,
(M
0
m
00
Figure
I I I 2 POLLUTED
14 -
I
I
~'~/
I~"
I
I
I
3
4
5
6
7
8
9
WIND
SPEED
145 m
(m/s)
Seasonel eve'roge S02 concentrations measured ot two s t a t i o n s as o f u n c t i o n of wind speed for
polluted
winds,
Environmental Software, 1988, Vol. 3, No. 1
25
Meteorological Effects on Sulphur Dioxide Concentrations: M.Alabiso and F.Parrini
WINTER
1978/'79
S U M M E R 1979
125 ,, S t a t i o n
n° 4
•
n° 2
Station
100 fZ3
..'~
n O. V
Z
O
/k •
75
/X
oeO
,¢ O: Z UJ L9 Z
/k
•
~•
/%~
•
50
O
o •
~9 O t/3
•
o~
25 ~
0
-I0
I
I
I
i
-5
O
5
10
15
TEMPERATURE Flgure 15 -
26
20
•
I
I
I
25
30
35
(°C)
Seasond~ average S0z c o n c e n t r a t i o n s measured at two s t a t i o n s as a f u n c t i o n of temperature f o r 1978 - 1979,
Environmental Software, 1988, Vol. 3, No. 1
Meteorological Effects oa Sulphur Dioxide Concentratioas: M.Alabiso aad F.Parriai ....
,
,
SUMMER 1980
WINTER 19791'80 200
Station •
175 m CL If.
n° 4
Station n°2
150 Q
v
Z
O I-.-
125 A
rr"
I-Z
IJ.l U Z 0 L)
100
A
75
~41 •
e~
0 u")
• ° ee
qDe
50
oAo ''L °" 'P'-
25
~'~
-I0
-5
0
~
5
,~"
10
15
20
25
30
35
TEMPERATURE (°C) Flgure 16
-
SeasQnal average $02 concentrations measured at two s t a t l o n s as a functton of temperature for 1979-1980
Environmental Software, 1988, Vol. 3, No. 1
27