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Conditions in which power stations contribute to high ground level SO2 concentrations in the U.K.
ow-698l/a7 13.00+0.00 Perpmonhrn~lr Ltd.
~tmtupheric ,%kommenr Vol. 21, No. 8. pp. IMP-1853.1987 Printed inGreatBritain.
CONDITIONS IN WHICH POWER STATIONS CONTRIBUTE TO HIGH GROUND LEVEL SO2 CONCENTRATIONSIN THE U.K. D. J. MOORE Central Electricity Research Laboratories. Kelvin Avenue. Leatherhead, Surrey, KT22 7SE, U.K, (Receivedfor publication 19 February 1987) Abstract-Weather and topographical situations where different types of emission sourcesgive their highest ground Level~n~ntratio~ have been tabulated during a CORECH study. To see what daily average concentrations actually occur in an area where tbereare a large number of power stations, low level and other industrial sourcas but no topographical complications, occasionswhen one or more of the 10 SO, recorders in the Draxmonitoringnetwork exceeded200 pgm -’ during the IO-year period preceding the termination of sampling were noted. There were 44 such occasions. On 17 of them. the principal contribution to the peak value appeared to come from low level sourcesassociated with smoke emissions and on nine it appeared to come from industrial sources in the Doncaster (including Doncaster and Thorpe Marsh power stations), Scunthorpe (including Keadby power station) or Humberside (no power station) arcas. The source areas containing tbe most modern 2000 MW power stations, South Yorkshire (13 times) and Trent Valley (five times), appeared to predominate on other occasions. In these latter cases, with only one exception, the weather situation was either a persistent slow moving anti-cyclone with the free stream wind speed falling to 2.5 m s- t or less or a day with a very steady free stream wind direction, associated with a cot in the surface pressure distribution. In both of these situations, upward vertical mixing was limited by a subsidenceand/or advection temperature inversion aloft.
Past experience and information European
electricity
received from other
suppliers on the meteorological
in which the highest short to medium period (l-h to I day) ground level concentrations (glcs) of SO, associated with power stations occur are summari~ in Moore et uf. (1986). This paper describes the U.K. contribution to the above study. Daily average concentrations in an area where 10 power stations were operating within a circle of 60 km diameter were investigated. The proposed EEC limit of 250 pgmV3 of SOs in association with smoke was exceeded on only 13 occasions at the 10 sites over an lo-year period, therefore the investigation was extended to cover occasions where daily averages exceeded 200 pg me3. This is reported below. situations
2. STUDY OF HIGH POLWTlON
DAYS IN THE DRAX
AREA 1970/1980
Ten sampling sites in the Drax area of Yorkshire ceased operating on 31 March 1980. During the preceding years daily average readings of SO2 and smoke were recorded (De~rtment of Industry, 19704980). For much of the period, continuous SO1 recorders were also operating in the area and meteorological data were being recorded at Eggborough power station and on the television tower with its top over 500 m above sea-level, 70 km to the SE at Belmont in Lin~lnshire. Locations of the power stations and sampling sites are given in Fig. I.
Occasions when any one of the 10 daily sites recorded > 200 pgm of SO, were investigated over the IO-year period from 1 April 1970 to 31 March 1980. Forty-four such occasions were found and are listed in Table 1. Table 1 also shows the mean and S.D. of the SO1 and smoke for all 10 sitesand the peak daily smoke con~entratjon. An estimate of the proportion of the SO, associated with smoke was found from the regression equation of smoke against SO2 for adjacent urban monitoring networks for each month of the year. This enabled an estimate to be made of the proportion of the highest and average daily SO2 concentration that could not be explained by sources associated with smoke emission. These estimates are also given in Table 1 which is divided into ranges of this estimate for the site giving the peak daily SO1 value. Smoke is mainly associated with low level domestic and traffic emissions and the SO1 which correlated with it is assumed to come from these or commercial and small industrial sources in the Same locations. The remaining SO1 probably comes from larger industrial sources including power stations. Table 1 shows that the incidence of the pollution ‘events’ during the period was very erratic, none occurring during the 3-year interval I March 1975-12 July 1978 but five occurred in the 6 days l-6 kmber 1971. In the seven events occurring in April-August, the sources associated with smoke played a minor role. All the occasions when these latter sources appeared to be responsible for most of the pollution occurred in the winter period 25 November-5 March. No ‘events’ occurred in May, September or October. There were 16 in January, 11 in December, six in February, four in
1849
D.
Cinnock
MOORE
HELHSLEY
TM611 YOrkShiM Ddrr
J.
*
SCARSOROUGii
l
Chase LERESTER l
50 EASTJNGS, fOkm units Fig. l.(a) Location of the 80 km square
I k6
I 1s
50
52
EASTINGS. lOkm units
Fig. I.fb) Locations of power stations and SGI recorders on the 80 km square. Grid refenrws of Drax daily SO, sites. 1 888 323, 2 840 295, 3 750 286. 4 714 283. 5 672 3II. 6 745 350, 7 737 233. 8 698 212, 9 695 151, 10 622 383.
June, three in November and one in each of March, April, July and August. The seven summer events were ah of 1 day-duration. The 37 winter days were comprised ofthree 3-day, seven 2&y and 14 l-day periods. The last column ofTable 1shows the location ofthe nearest pressure centre on the midday synoptic weather map. In most cases this was a col, indicating a strengthening of the normal subsidence inversion by an advectively produced temperature and velocity d~~ontinujty. Table2 shows the daiiy mean vector free stream (900 mb or 900 m) wind speed (U, kt)and direction (D, degrees from N) and the r.m.s. vector cross wind standard deviation (cry,kt) measured at the two nearest Meteorological O&e upper wind stations at 6-h intervals. Maximum and minimum speeds are atso shown. Table 2 shows that ‘events’ appear to require either a minimum free stream wind < 6 ktf L) or a very steady wind with u, c U/3(S), at one or both of the upper wind stations. These criteria were not met in only one ‘event”, on 10 February i975. In that case a very steady SE wind shifted to a steady SW wind over the network during the day. 0, was determined for the five observations spanning each day. Table 3 shows the pattern ofpower generation in the area during 19?O-1981, The small stations. Ferrybridge ‘A’ and Doncaster reduced their output
Conditions in which power stations cont~bute to high ground kvel SO2 con~ntrations Table I. Peak,
mean and standard deviation of Drax National Survey daily smoke and SO2 concentrations in pgm-’
Peak
Date
1851
SO1
Smoke
on days with peak SO1 > 200 pgmA3
Site
All sites Mean SD.
All sites Mean SD.
No.
SO2
Smoke
% of so* not from
Met. L = Low
smoke Peak Mean
c = col H = high
Less than 25 % of peak SO, associated with smoke
50
11
41
38
69 46
63
146 138 103 201 78 106 245 71 173 56 8X
87 53 52 90 48 71 139 59 40 55 64
63 18 16 74 25 48 73 72 43 17 IS
25-49x of peak SO, associated with smoke 67 2 129 3.1.80 210 90 9 117 21.2.79 200 133 7 181 5.12.78 220 28.2.75 207 97 9 98 27.2.75 102 9 152 225 124 9 21.12.72 201 304 113 10 112 20.12.72 228 112 9 64 25.11.72 201 101 10 123 2.11.72 229 154 8 132 3.12.71 270 86 5 115 5.1.71 210
39 34 27 46 58 92 62 57 60 76 52
54 38 91 56 71 86 62 69 84 120 53
50-75 % of peak SO, associated with smoke 162 9 157 26.1.79 246 131 9 141 21.1.79 z. 190 9 61 17.2.73 130 9 65 26.11.72 201 118 8 65 6.1.72 200 184 9 107 22.12.71 211 173 9 183 2.12.71 263 326 9 147 1.12.71 33.5 169 ‘7 165 53.71 238
38 43 59 56 58 56 43 99 53
93 45 95 103 75 123 102 251 131
19.6.79 20.1.79
266 205
19.12.78
259
13.7.78 21.2.75 10.2.75 20.6.74 18.6.73 8.1.73~ 7.1.73 6.1.73 22.12.72 3.1.72 15.4.71 23.8.70 10.6.70
306 259 235 379 200 270 523 200 251 211 205
16 33 81 38
2 2 7 9
I55 95 170 99
85 19 11 106 3.5 48 107 55 42 13 38
10 5 3 10 10 10 9 10 7 2 9
Mote than 75% of peak SO, associated with smoke 92 197 9 116 40 27.1.79 202 133 221 9 81 65 5.1.79 225 21.1.72 180 112 206 52 120 20.1.72 231 274 122 53 190 6.12.71 254 387 9 106 59 202 5.12.71 314 9 91 2S5 65 180 13.1.71 242 7 216 134 43 143 4.1.71 351 5 146 230 62 329
3 12 19 9 12 16 5 2: 8 :; 49 5 14 II 20 20 21 :(: 32 :: 29 25 18 30 36 40 29 21 :: 96 51 44 56 :: 72 65 41 15
93
!Z 84 91 76 72 61 62 59 61
69 62 54 64 56 64 43 44 26 47 49 33 50 25 26
SSN 53N 53N 55N SON S9N 83 54N 79 38N 68 54N 72 56N 61 57N 77 48N 12 C 53N 76 C 53N 55 C 52N 77 C 53N
3E 1OW 6W 3W 9W 2E 1E OW 4W ow 1E 1OW 2W 5W IOW IW
63 72 54 51 59 67 57 9 44 8 59
7E 6W 1OE 9E 1lE 7W 1W 4W 1OW 1OW 5w
91 65 71 76 45 63
86 76 76 80 76 91 94 76 85 85
H
55N 52N 48N 53N 5fN 52N 47N 49N SON SON 58N
L 72 c -3s c -31 H 8 c 9 c 57 C -31 c 17 c 49
15 31 15 -43 7 24 -3 -35 -17 -46 6 -51 2 -33 -100
c C C C
C H H C
57N 3E 56N OE 60N 2E 49N 9W 5ON 2E 52N 2E 57N 1OW
6ON 6W 53N SW 53N 54N 50N 53N 53N 5ON 6ON 6ON
OE SW 11E OE SW 4E 30E SW
-vc vafucs - cstimatcd % of surviving smoke associated SOI deposited.
while the large 20 NW stations’ output increased. There was no output from Drax during the first part of the study period when 25 of the pollution ‘events’ occurred. As far as the monitoring network is concerned, the power stations fall into the four main geographical locations South Yorkshire, Doncaster, Keadby and
Ttent Valley, indicated in Table 3 and Fig. la. Each 01 these is also associated with low level and other industrial sources. Jn addition, there is a source area to the E of the network, Humberside (H) centred round Kingston-upon-Hull, with no power stations. The principal industrial source location associated with each ‘event’ is indicated in the last column of Table 2.
1852
D. J. MOORE Table 2. Twenty-four hour mean vector winds for days listed in Table I
Date
Dir.
Aughton S.D. Max
Mean
Less than 25 % of peak SO2 associated with smoke 19.679 5.1 3.2 11 4 238 318 20.1.79 141 37.8 6.8 44 21 136 19.12.78 181 13.2 2.2 25 6 130 13.7.78 3.0 3.6 8 2 273 284 21.2.75 195 15.1 4.6 20 12 170 10.2.75 174 12.3 11.4 20 15 153 20.6.74 7.0 3.0 14 223 279 18.6.73 279 14.8 3.5 24 : 295 8.1.73 187 3.0 6.8 10 9 15 7.1.73 130 12.4 3.9 19 12 75 6.1.73 171 11.4 2.8 15 9 93
6.3 33.9 9.3 3.0 24.2 7.8 9.1 12.2 8.7 7.6 14.0
6.2 2.7 6.5 4.9 3.0 7.1 3.6 3.6 2.9 2.1 5.5
12 42 17 11 29 16 14 21 17 15 18
22.12.72 3.1.72 15.4.71 23.8.70 10.6.70
25-49 % of peak SO, 3.1.80 246 21.2.79 183 512.78 208 28.2.75 162 27.2.75 166 21.12.72 235 20.12.72 209 25.11.72 307 2.11.72 265 3.12.71 181 51.71 174
Min
Hemsby SD. Max
Dir.
133 103 85 71 95
Mean
22.12.71 2.12.71 1.12.71 5.3.71
b/s b/s S
95 104 157 76 71
1.2 9.9 6.5 6.8 13.8
0.0 1.8 3.2 6.4 2.4
6 16 12 10 19
associated with smoke 18.2 5.3 39 7 17.3 4.5 25 9 8.9 8.7 18 14.9 2.0 24 1; 17.2 5.1 21 14 6.0 4.7 14 3 12.3 2.5 18 6 9.0 8.8 27 19.9 3.2 26 1: 1.3 6.4 10 4 10.0 1.9 29 3
299 143 327 114 167 171 162 351 263 73 215
9.2 17.1 12.5 1.8 0.7 5.9 6.6 8.0 17.9 8.7 5.6 1.5 15.8 3.7 18.7 10.3 14.1 3.6 7.7 4.1 8.4 5.4
27 23 11 18 28 15 23 31 18 15 15
6 5 4 4 14 0 12 16 12 4 9
s L/S L L/S S L/S s L s L L/S
249 199 12
9.9 5.8 13.2
6.7 10.7 6.6
22 16 18
2 5
348 121 276 215 92 28
10.5 13.1 4.2 1.9 20.7 6.9 2.3 4.8 9.1 11.6 14.8 3.5
26 8 43 9 25 17
11 4 0 4 4 5 13
L L L L L L/S L
6.4 29.7 7.8 10.0 2.9 9.4 9.1 2.9
12 36 14 28 10 16 10 7
1: 4 0 2 7 8 0
3.5 2.5 2.0 2.1 2.5
8 16 7 17 7
139 327
2.0 6.0 12.1 11.3
13 38
2 6
101 270 155 260 35s
6.7 17.0 1.6 4.6 4.2
12 20 12 11 12
5 12 5 2 4
282 261 228 206 120 143
L/S L S x
0 7 4 0 4
0.8 11.7 5.2 6.6 4.8
4.8 3.4 6.3 5.7 7.6
More than 75% of peak SO2 associated with smoke 19 14 27.1.79 291 12.1 6.5 267 33 11 5.1.79 112 16.9 3.0
21.1.72 20.1.72 6.12.71 5.12.71 13.1.71 4.1.71
4 28 4 2 20 8 7 7 5 4
L = light S = stead
11 0 4 4 8 10
50-75x of peak SO2 associated with smoke 26.1.79 187 1.0 12.6 21 11 21.1.79 172 11.9 5.2 26 7 17.2.73 26.11.72 6.1.72
Min
18.6 18.9 6.5 16.9 4.9 3.4
8.4 3.3 4.5 3.0 3.6 1.6
33 30 10 25 15 6
16 11 1: 3 2
3: 280 179 312 236 7
3.9 6.8 0.9 4.1 1.5 4.1 3.0 2.2
T Y T Y Y Y Y Y K’
:,s k/S L/S
:: H H Y T D T DT Y Y Y H Y
k/s
D T H Y K D ? ? I-i
L S L/S L/S L s L L
D K Y D D Y D K
S.D. = vector S.D.normal to mean vector wind (Mean). Max and Min are maximum and minimum speeds, directions in degrees from N, speeds in kts.
On 18 of the 44 occasions power stations could have been responsible for over half the ground level SO, at the worst affected sites.
3. DlSCtJSSlON Tables I and 2 show that high daily average SO2 concentrations in the Drax area occur predominantly in conditions wheredeep vertical mixing is inhibited by
a subsidence or air mass discontinuity temperature inversion. They are also associated with a period of very light winds or when the wind direction remains very steady over a 24-h period. In addition, on occasions when the maximum daily avenge SOi concentration is predominantly due to high level sources in the light wind case, there must be either a strong vertical shear of wind velocity or strong anticyclonic subsidence must persist for more than 24 h. The latter conditions occur with an intensifying,
1853
Conditions in which power stations contribute to high ground level SO2 concentrations Table 3. Annual output of local power stations (GWh) during 1970/1981
Ferrybridge
Eggboro.
Date
A
B
C
70/-l 1 71172 72/73 73174 74175 75176 76177 71/78 78179 79180 80/8 1
423 310 314 198 151
1638 1719 1767 1299 1179 1326 1431 1596 1258 1136 1761
7274 7340 8335 7398 7507 1674 12,669 10,035 11,721 12,590 13,110
7233 7594 7955 7119 9724 10,743 10,152 11.860 9372 10,527 10.112
300
2000
2000
Max MW Group
stationary
pressure
170
Drax
2: 8627 8948 13,150 11.946 10,750
586 490 547 509 437 337 171 224 126 183 62
1413 1186 1376 1179 753 815 835 935 970 1029 503
5156 4246 4650 4052 3722 3793 3366 2940 3264 4240 3945
3294 4854 5926 5795 6830 6772 6575 7418 8589 11,119 10,931
6501 6316 8641 7321 7561 6876 10,507 8761 10,938 10,840 11.570
2000
1100
120
378
1000
2000
2000
and the former in a co1 type of
distribution.
4.
West Burton
2894 3660 2795 3157 3467 3604 3984 2895 3750 2549 4012
South Yorkshire (Y)
anticyclone
High Thorpe Mrsh Doncaster Keadby Marnam Cottam
CONCLUSlONS
The frequency of episodes in the area studied was so low that existing legislation was not violated. There would, therefore, have ken no need to implement intermittent control of emissions during the period investigated, had such a facility been available. The highest observed daily concentrations of SO2 occurred on the last day of two of the three, 3-day episodes. The weather conditions prevailing during the episodes indicate that should more stringent regulations need to be complied with in the future, successful application of an intermittent control strategy to meet them would
Doncaster, D
K
Trent Valley (T)
require the prediction or monitoring anticyclonic or col situations.
of subsidence in
Acknowledgemetus-Daily SO, and smoke data were provided by Dr P. Gaunt, CEGB NE Region SSD. Harrogate. This paper is published by permission of the Central Electricity Generating Board.
REFERENCES Department of Industry (1970-1980)The Investigation of Air
Pollution, National Survey of Smoke and Sulphur Dioxide, 10 Vols, Warren Spring Laboratory. Moore D. J., Bacci P., Esteban F.. Lejeunc P.. Saab A., Scrivcn R. A. and Steenkist R. (1986) Summary report of the CORECH (COGAR) Workshop on the evaluation of air pollution episodes and associated control measures. Atmospheric
Environment
20, 2047-2052.
~tmtupheric ,%kommenr Vol. 21, No. 8. pp. IMP-1853.1987 Printed inGreatBritain.
CONDITIONS IN WHICH POWER STATIONS CONTRIBUTE TO HIGH GROUND LEVEL SO2 CONCENTRATIONSIN THE U.K. D. J. MOORE Central Electricity Research Laboratories. Kelvin Avenue. Leatherhead, Surrey, KT22 7SE, U.K, (Receivedfor publication 19 February 1987) Abstract-Weather and topographical situations where different types of emission sourcesgive their highest ground Level~n~ntratio~ have been tabulated during a CORECH study. To see what daily average concentrations actually occur in an area where tbereare a large number of power stations, low level and other industrial sourcas but no topographical complications, occasionswhen one or more of the 10 SO, recorders in the Draxmonitoringnetwork exceeded200 pgm -’ during the IO-year period preceding the termination of sampling were noted. There were 44 such occasions. On 17 of them. the principal contribution to the peak value appeared to come from low level sourcesassociated with smoke emissions and on nine it appeared to come from industrial sources in the Doncaster (including Doncaster and Thorpe Marsh power stations), Scunthorpe (including Keadby power station) or Humberside (no power station) arcas. The source areas containing tbe most modern 2000 MW power stations, South Yorkshire (13 times) and Trent Valley (five times), appeared to predominate on other occasions. In these latter cases, with only one exception, the weather situation was either a persistent slow moving anti-cyclone with the free stream wind speed falling to 2.5 m s- t or less or a day with a very steady free stream wind direction, associated with a cot in the surface pressure distribution. In both of these situations, upward vertical mixing was limited by a subsidenceand/or advection temperature inversion aloft.
Past experience and information European
electricity
received from other
suppliers on the meteorological
in which the highest short to medium period (l-h to I day) ground level concentrations (glcs) of SO, associated with power stations occur are summari~ in Moore et uf. (1986). This paper describes the U.K. contribution to the above study. Daily average concentrations in an area where 10 power stations were operating within a circle of 60 km diameter were investigated. The proposed EEC limit of 250 pgmV3 of SOs in association with smoke was exceeded on only 13 occasions at the 10 sites over an lo-year period, therefore the investigation was extended to cover occasions where daily averages exceeded 200 pg me3. This is reported below. situations
2. STUDY OF HIGH POLWTlON
DAYS IN THE DRAX
AREA 1970/1980
Ten sampling sites in the Drax area of Yorkshire ceased operating on 31 March 1980. During the preceding years daily average readings of SO2 and smoke were recorded (De~rtment of Industry, 19704980). For much of the period, continuous SO1 recorders were also operating in the area and meteorological data were being recorded at Eggborough power station and on the television tower with its top over 500 m above sea-level, 70 km to the SE at Belmont in Lin~lnshire. Locations of the power stations and sampling sites are given in Fig. I.
Occasions when any one of the 10 daily sites recorded > 200 pgm of SO, were investigated over the IO-year period from 1 April 1970 to 31 March 1980. Forty-four such occasions were found and are listed in Table 1. Table 1 also shows the mean and S.D. of the SO1 and smoke for all 10 sitesand the peak daily smoke con~entratjon. An estimate of the proportion of the SO, associated with smoke was found from the regression equation of smoke against SO2 for adjacent urban monitoring networks for each month of the year. This enabled an estimate to be made of the proportion of the highest and average daily SO2 concentration that could not be explained by sources associated with smoke emission. These estimates are also given in Table 1 which is divided into ranges of this estimate for the site giving the peak daily SO1 value. Smoke is mainly associated with low level domestic and traffic emissions and the SO1 which correlated with it is assumed to come from these or commercial and small industrial sources in the Same locations. The remaining SO1 probably comes from larger industrial sources including power stations. Table 1 shows that the incidence of the pollution ‘events’ during the period was very erratic, none occurring during the 3-year interval I March 1975-12 July 1978 but five occurred in the 6 days l-6 kmber 1971. In the seven events occurring in April-August, the sources associated with smoke played a minor role. All the occasions when these latter sources appeared to be responsible for most of the pollution occurred in the winter period 25 November-5 March. No ‘events’ occurred in May, September or October. There were 16 in January, 11 in December, six in February, four in
1849
D.
Cinnock
MOORE
HELHSLEY
TM611 YOrkShiM Ddrr
J.
*
SCARSOROUGii
l
Chase LERESTER l
50 EASTJNGS, fOkm units Fig. l.(a) Location of the 80 km square
I k6
I 1s
50
52
EASTINGS. lOkm units
Fig. I.fb) Locations of power stations and SGI recorders on the 80 km square. Grid refenrws of Drax daily SO, sites. 1 888 323, 2 840 295, 3 750 286. 4 714 283. 5 672 3II. 6 745 350, 7 737 233. 8 698 212, 9 695 151, 10 622 383.
June, three in November and one in each of March, April, July and August. The seven summer events were ah of 1 day-duration. The 37 winter days were comprised ofthree 3-day, seven 2&y and 14 l-day periods. The last column ofTable 1shows the location ofthe nearest pressure centre on the midday synoptic weather map. In most cases this was a col, indicating a strengthening of the normal subsidence inversion by an advectively produced temperature and velocity d~~ontinujty. Table2 shows the daiiy mean vector free stream (900 mb or 900 m) wind speed (U, kt)and direction (D, degrees from N) and the r.m.s. vector cross wind standard deviation (cry,kt) measured at the two nearest Meteorological O&e upper wind stations at 6-h intervals. Maximum and minimum speeds are atso shown. Table 2 shows that ‘events’ appear to require either a minimum free stream wind < 6 ktf L) or a very steady wind with u, c U/3(S), at one or both of the upper wind stations. These criteria were not met in only one ‘event”, on 10 February i975. In that case a very steady SE wind shifted to a steady SW wind over the network during the day. 0, was determined for the five observations spanning each day. Table 3 shows the pattern ofpower generation in the area during 19?O-1981, The small stations. Ferrybridge ‘A’ and Doncaster reduced their output
Conditions in which power stations cont~bute to high ground kvel SO2 con~ntrations Table I. Peak,
mean and standard deviation of Drax National Survey daily smoke and SO2 concentrations in pgm-’
Peak
Date
1851
SO1
Smoke
on days with peak SO1 > 200 pgmA3
Site
All sites Mean SD.
All sites Mean SD.
No.
SO2
Smoke
% of so* not from
Met. L = Low
smoke Peak Mean
c = col H = high
Less than 25 % of peak SO, associated with smoke
50
11
41
38
69 46
63
146 138 103 201 78 106 245 71 173 56 8X
87 53 52 90 48 71 139 59 40 55 64
63 18 16 74 25 48 73 72 43 17 IS
25-49x of peak SO, associated with smoke 67 2 129 3.1.80 210 90 9 117 21.2.79 200 133 7 181 5.12.78 220 28.2.75 207 97 9 98 27.2.75 102 9 152 225 124 9 21.12.72 201 304 113 10 112 20.12.72 228 112 9 64 25.11.72 201 101 10 123 2.11.72 229 154 8 132 3.12.71 270 86 5 115 5.1.71 210
39 34 27 46 58 92 62 57 60 76 52
54 38 91 56 71 86 62 69 84 120 53
50-75 % of peak SO, associated with smoke 162 9 157 26.1.79 246 131 9 141 21.1.79 z. 190 9 61 17.2.73 130 9 65 26.11.72 201 118 8 65 6.1.72 200 184 9 107 22.12.71 211 173 9 183 2.12.71 263 326 9 147 1.12.71 33.5 169 ‘7 165 53.71 238
38 43 59 56 58 56 43 99 53
93 45 95 103 75 123 102 251 131
19.6.79 20.1.79
266 205
19.12.78
259
13.7.78 21.2.75 10.2.75 20.6.74 18.6.73 8.1.73~ 7.1.73 6.1.73 22.12.72 3.1.72 15.4.71 23.8.70 10.6.70
306 259 235 379 200 270 523 200 251 211 205
16 33 81 38
2 2 7 9
I55 95 170 99
85 19 11 106 3.5 48 107 55 42 13 38
10 5 3 10 10 10 9 10 7 2 9
Mote than 75% of peak SO, associated with smoke 92 197 9 116 40 27.1.79 202 133 221 9 81 65 5.1.79 225 21.1.72 180 112 206 52 120 20.1.72 231 274 122 53 190 6.12.71 254 387 9 106 59 202 5.12.71 314 9 91 2S5 65 180 13.1.71 242 7 216 134 43 143 4.1.71 351 5 146 230 62 329
3 12 19 9 12 16 5 2: 8 :; 49 5 14 II 20 20 21 :(: 32 :: 29 25 18 30 36 40 29 21 :: 96 51 44 56 :: 72 65 41 15
93
!Z 84 91 76 72 61 62 59 61
69 62 54 64 56 64 43 44 26 47 49 33 50 25 26
SSN 53N 53N 55N SON S9N 83 54N 79 38N 68 54N 72 56N 61 57N 77 48N 12 C 53N 76 C 53N 55 C 52N 77 C 53N
3E 1OW 6W 3W 9W 2E 1E OW 4W ow 1E 1OW 2W 5W IOW IW
63 72 54 51 59 67 57 9 44 8 59
7E 6W 1OE 9E 1lE 7W 1W 4W 1OW 1OW 5w
91 65 71 76 45 63
86 76 76 80 76 91 94 76 85 85
H
55N 52N 48N 53N 5fN 52N 47N 49N SON SON 58N
L 72 c -3s c -31 H 8 c 9 c 57 C -31 c 17 c 49
15 31 15 -43 7 24 -3 -35 -17 -46 6 -51 2 -33 -100
c C C C
C H H C
57N 3E 56N OE 60N 2E 49N 9W 5ON 2E 52N 2E 57N 1OW
6ON 6W 53N SW 53N 54N 50N 53N 53N 5ON 6ON 6ON
OE SW 11E OE SW 4E 30E SW
-vc vafucs - cstimatcd % of surviving smoke associated SOI deposited.
while the large 20 NW stations’ output increased. There was no output from Drax during the first part of the study period when 25 of the pollution ‘events’ occurred. As far as the monitoring network is concerned, the power stations fall into the four main geographical locations South Yorkshire, Doncaster, Keadby and
Ttent Valley, indicated in Table 3 and Fig. la. Each 01 these is also associated with low level and other industrial sources. Jn addition, there is a source area to the E of the network, Humberside (H) centred round Kingston-upon-Hull, with no power stations. The principal industrial source location associated with each ‘event’ is indicated in the last column of Table 2.
1852
D. J. MOORE Table 2. Twenty-four hour mean vector winds for days listed in Table I
Date
Dir.
Aughton S.D. Max
Mean
Less than 25 % of peak SO2 associated with smoke 19.679 5.1 3.2 11 4 238 318 20.1.79 141 37.8 6.8 44 21 136 19.12.78 181 13.2 2.2 25 6 130 13.7.78 3.0 3.6 8 2 273 284 21.2.75 195 15.1 4.6 20 12 170 10.2.75 174 12.3 11.4 20 15 153 20.6.74 7.0 3.0 14 223 279 18.6.73 279 14.8 3.5 24 : 295 8.1.73 187 3.0 6.8 10 9 15 7.1.73 130 12.4 3.9 19 12 75 6.1.73 171 11.4 2.8 15 9 93
6.3 33.9 9.3 3.0 24.2 7.8 9.1 12.2 8.7 7.6 14.0
6.2 2.7 6.5 4.9 3.0 7.1 3.6 3.6 2.9 2.1 5.5
12 42 17 11 29 16 14 21 17 15 18
22.12.72 3.1.72 15.4.71 23.8.70 10.6.70
25-49 % of peak SO, 3.1.80 246 21.2.79 183 512.78 208 28.2.75 162 27.2.75 166 21.12.72 235 20.12.72 209 25.11.72 307 2.11.72 265 3.12.71 181 51.71 174
Min
Hemsby SD. Max
Dir.
133 103 85 71 95
Mean
22.12.71 2.12.71 1.12.71 5.3.71
b/s b/s S
95 104 157 76 71
1.2 9.9 6.5 6.8 13.8
0.0 1.8 3.2 6.4 2.4
6 16 12 10 19
associated with smoke 18.2 5.3 39 7 17.3 4.5 25 9 8.9 8.7 18 14.9 2.0 24 1; 17.2 5.1 21 14 6.0 4.7 14 3 12.3 2.5 18 6 9.0 8.8 27 19.9 3.2 26 1: 1.3 6.4 10 4 10.0 1.9 29 3
299 143 327 114 167 171 162 351 263 73 215
9.2 17.1 12.5 1.8 0.7 5.9 6.6 8.0 17.9 8.7 5.6 1.5 15.8 3.7 18.7 10.3 14.1 3.6 7.7 4.1 8.4 5.4
27 23 11 18 28 15 23 31 18 15 15
6 5 4 4 14 0 12 16 12 4 9
s L/S L L/S S L/S s L s L L/S
249 199 12
9.9 5.8 13.2
6.7 10.7 6.6
22 16 18
2 5
348 121 276 215 92 28
10.5 13.1 4.2 1.9 20.7 6.9 2.3 4.8 9.1 11.6 14.8 3.5
26 8 43 9 25 17
11 4 0 4 4 5 13
L L L L L L/S L
6.4 29.7 7.8 10.0 2.9 9.4 9.1 2.9
12 36 14 28 10 16 10 7
1: 4 0 2 7 8 0
3.5 2.5 2.0 2.1 2.5
8 16 7 17 7
139 327
2.0 6.0 12.1 11.3
13 38
2 6
101 270 155 260 35s
6.7 17.0 1.6 4.6 4.2
12 20 12 11 12
5 12 5 2 4
282 261 228 206 120 143
L/S L S x
0 7 4 0 4
0.8 11.7 5.2 6.6 4.8
4.8 3.4 6.3 5.7 7.6
More than 75% of peak SO2 associated with smoke 19 14 27.1.79 291 12.1 6.5 267 33 11 5.1.79 112 16.9 3.0
21.1.72 20.1.72 6.12.71 5.12.71 13.1.71 4.1.71
4 28 4 2 20 8 7 7 5 4
L = light S = stead
11 0 4 4 8 10
50-75x of peak SO2 associated with smoke 26.1.79 187 1.0 12.6 21 11 21.1.79 172 11.9 5.2 26 7 17.2.73 26.11.72 6.1.72
Min
18.6 18.9 6.5 16.9 4.9 3.4
8.4 3.3 4.5 3.0 3.6 1.6
33 30 10 25 15 6
16 11 1: 3 2
3: 280 179 312 236 7
3.9 6.8 0.9 4.1 1.5 4.1 3.0 2.2
T Y T Y Y Y Y Y K’
:,s k/S L/S
:: H H Y T D T DT Y Y Y H Y
k/s
D T H Y K D ? ? I-i
L S L/S L/S L s L L
D K Y D D Y D K
S.D. = vector S.D.normal to mean vector wind (Mean). Max and Min are maximum and minimum speeds, directions in degrees from N, speeds in kts.
On 18 of the 44 occasions power stations could have been responsible for over half the ground level SO, at the worst affected sites.
3. DlSCtJSSlON Tables I and 2 show that high daily average SO2 concentrations in the Drax area occur predominantly in conditions wheredeep vertical mixing is inhibited by
a subsidence or air mass discontinuity temperature inversion. They are also associated with a period of very light winds or when the wind direction remains very steady over a 24-h period. In addition, on occasions when the maximum daily avenge SOi concentration is predominantly due to high level sources in the light wind case, there must be either a strong vertical shear of wind velocity or strong anticyclonic subsidence must persist for more than 24 h. The latter conditions occur with an intensifying,
1853
Conditions in which power stations contribute to high ground level SO2 concentrations Table 3. Annual output of local power stations (GWh) during 1970/1981
Ferrybridge
Eggboro.
Date
A
B
C
70/-l 1 71172 72/73 73174 74175 75176 76177 71/78 78179 79180 80/8 1
423 310 314 198 151
1638 1719 1767 1299 1179 1326 1431 1596 1258 1136 1761
7274 7340 8335 7398 7507 1674 12,669 10,035 11,721 12,590 13,110
7233 7594 7955 7119 9724 10,743 10,152 11.860 9372 10,527 10.112
300
2000
2000
Max MW Group
stationary
pressure
170
Drax
2: 8627 8948 13,150 11.946 10,750
586 490 547 509 437 337 171 224 126 183 62
1413 1186 1376 1179 753 815 835 935 970 1029 503
5156 4246 4650 4052 3722 3793 3366 2940 3264 4240 3945
3294 4854 5926 5795 6830 6772 6575 7418 8589 11,119 10,931
6501 6316 8641 7321 7561 6876 10,507 8761 10,938 10,840 11.570
2000
1100
120
378
1000
2000
2000
and the former in a co1 type of
distribution.
4.
West Burton
2894 3660 2795 3157 3467 3604 3984 2895 3750 2549 4012
South Yorkshire (Y)
anticyclone
High Thorpe Mrsh Doncaster Keadby Marnam Cottam
CONCLUSlONS
The frequency of episodes in the area studied was so low that existing legislation was not violated. There would, therefore, have ken no need to implement intermittent control of emissions during the period investigated, had such a facility been available. The highest observed daily concentrations of SO2 occurred on the last day of two of the three, 3-day episodes. The weather conditions prevailing during the episodes indicate that should more stringent regulations need to be complied with in the future, successful application of an intermittent control strategy to meet them would
Doncaster, D
K
Trent Valley (T)
require the prediction or monitoring anticyclonic or col situations.
of subsidence in
Acknowledgemetus-Daily SO, and smoke data were provided by Dr P. Gaunt, CEGB NE Region SSD. Harrogate. This paper is published by permission of the Central Electricity Generating Board.
REFERENCES Department of Industry (1970-1980)The Investigation of Air
Pollution, National Survey of Smoke and Sulphur Dioxide, 10 Vols, Warren Spring Laboratory. Moore D. J., Bacci P., Esteban F.. Lejeunc P.. Saab A., Scrivcn R. A. and Steenkist R. (1986) Summary report of the CORECH (COGAR) Workshop on the evaluation of air pollution episodes and associated control measures. Atmospheric
Environment
20, 2047-2052.