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NILU

TEKNISK NOTAT NR: 5/81 REFERANSE: 03075

DATO: APRIL 1981

AIRBORNE MEASUREMENTS OVER SKAGERRAK 29 JANUARY 1981

BY Y, GOTAAS

NORWEGIAN INSTITUTE FOR AIR RESEARCH P.O. BOX 130, N-2001 LILLESTRØM

NORWAY

- 2 -

LIST OF CONTENTS

Page:

1

2 3

BACKGROUND •...•••••..•..•.•.••.•••••••.••••.••

SAMPLING EQUIPMENT

SAMPLING PROCEDURE AND RESULTS - 29 JANUARY 1981 4 ESTIMATE OF SF6 RELEASE FROM PORSGRUNN

3 3 4

FACTORIES . . . . . . . . . . • • 4

5 CONCLUSION . 5

AIRBORNE MEASUREMENTS

OVER SKAGERRAK, 29 JANUARY 1981

1 BACKGROUND

To study the chemistry of power station plumes over the North Sea, a programme of aircraft measurements is conducted by the Central Electricity Research Laboratories (CERL). In order to locate the position of the plume, tracer material is released at a rate of 50 kg SF₆h-¹ for 20 h from the power station Eggborough

(53 42N,0107E).

The Norwegian Institute for Air Research (NILU) has agreed to undertake airborne measurements near Norwegian waters, if suit- able conditions exist. One such measurement flight took place over Skagerrak on 29 January 1981, when CERL experiments were conducted, and trajectory forecasts were favourable.

Some emission of SFs to the atmosphere near the southern

Norwegian coast is known to take place from a factory of Norsk Hydro A.S. near Porsgrunn. To estimate the release to the atmos- phere, low level sampling in the Hydro plume was conducted

the following day.

2 SAMPLING EQUIPMENT

Aerosol sulphate and sulphur dioxide were collected on plain and impregnated filters arranged in series. The sampling time was between 15 and 20 minutes, and the samples were analyzed by

ion chromatography. Concentrations of sulphur dioxide below 3 µg m-³ and of sulphate aerosols below 1.5 µg m-³ could not be estimated with any accuracy, due to slightly contaminated filters.

- 4 -

Air samples taken with syringes and in plastic bags were later analyzed in the laboratory on NILUs tracer gas chromatograph to determine SF₆ concentrations.

The detection limit for laboratory analyses is about 1 ppt SF_6•

Detection limit on the gas chromatograph used in the aircraft is around 10 ppt.

3 SAMPLING PROCEDURE AND RESULTS - 29 JANUARY 1981

Table 1 and Figure 1 give location of sampling tracks (midpoints).

It had been planned to continue the flight along the west coast of Denmark after refuelling at Kjevik. Unfortunately, the flight had to be abandoned due to low clouds and fog covering southern Scandinavia.

Only the traverse over the inner part of Skagerrak, midpoint E, gave a positive indication of SFs in the air. Positions of the syringe samplings are not shown, because no SF₆ was detected.

Locations of bag sampling are also shown.

Figure 2 shows the vertical temperature distribution and extent of the haze layer observed during an ascent/descent close to position E. Surface and 850 mb weather charts are shown in Figure 3. A cold front was encountered at position F.

4 ESTIMATE OF SFs RELEASE FROM PORSGRUNN FACTORIES

It is known that SF₆ is used as a flame quenching gas at Herøya.

An amount of 30 kg per 8-work shift has been quoted.

On the return flight to Oslo, 30th January, a low level inversion, marked by a smoke layer over the Porsgrunn area, prevented the vertical rise of the SF₆ containing plume. The sampling in the plume was performed at a distance of between 4 and 5 km from the plant, where plume width was about 1500 m and the vertical extent about 150 m. Twd bag samples showed SFs concentrations of 175 ppt.

Five syringe samples gave values from 8 ppt to 539 ppt SFs.

As 1 ppm equals 5.9 mg SF₆m-³, and the observed wind speed at the flight level (from a weather station near by) was 3.5 m s-¹, the rate of release was estimated at about 2.5 kg SF₆ h-¹• Considering all uncertainties involved, all that can be said is that the re- lease rate most probably is somewhere between 1 and 5 kg h-^1• The quoted use of 30 kg SF₆ per 8-shift (i.e., 3.8 kg h-¹) is of the same order. It thus seems that virtually all the SFG used at Herøya escapes into the atmosphere.

5 CONCLUSION

On 29 January, a positive observation of SF₆ over Skagerrak was made at one location only. It is not clear whether this concen-

tration was due to the experimental release in England or was the result of a continuous release of SF₆ from a factory at Herøya near the Norwegian coast.

Low level winds in the area indicate a NE-ly plume drift from Herøya, that is to the north of the actual sampling track.

It is therefore a possibility that the observed concentration was indeed due to long range transport.

Preliminary results from aircraft sampling made by CERL, over the North Sea along the Danish coast, indicate that SFG was concen- trated in and below the low level clouds. Concentrations were about 5 ppt. That may explain why our sampling over western parts of Skagerrak, made at higher levels, did not show any concen- trations.

Concentrations of sulphur dioxide and of sulphate particles were fairly low. The highest SO2 value, 13 µg m-³ over Oslofjord, most probably was due to local sources.

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Table 1: Aircraft scarrpling 29 January 1981.

Sulphur on filters. SFG: bag (a), syringe (b).

Time Posn. Height Temp. Flight SO2 SO4

I

GMT FT oc Cond. µg m-3 µg m-3ppt

1157 A

5930N 1200 12.0 On top 13 <1.5

-

1040E 8/8-2/8 St

1233 B

5850N 1000 2/8 Sc 2

1020E ^(b)

1241 C

5830N 1000 12.0 On top < 3 <1.5

-

1020E 1/8-8/8

1303 D

5800N 1300 10.6 On top "' 3 <1.5

-

0945E 8/8 Sc

1328 E

5750N 10500 Top of haze

-

0830E

1340 F

5745N 10000 -2.1 Between ^~ 5 <1.5

-

0750E layers -

near front

1345 G

5745N 9750 0

0730E (a)

1405 H

5745N 6500 0

0800E (a)

1407 I

5750N 6500 3.2 Between ^~ 5 ~2.0

-

0820E layers -

thick haze

1426 J

5745N 3500 10.1 On top 6 <1.5 0

0820E 8/8 Sc

1445 K

5900N 1500 ^~ 2 <1.5 0

0800E (a)

0...,.6 0'-'7 0.,...8 0~9::.- __ 1~----'111E

PORSGRUNN

SS> N +---~---+---1---~~t='.:cc..-=--11

. B

~c

...,

58

-~

'# I

,--

...,._

LM,

...

...

"'~

57 v-<"

"'""

~

Figure 1: Aircraft flight 29 January 1981.

Letters refer to positions given in Table 1.

ÆET j.

'10000]/

I

5000

HAZE

1

' ' _' ' ' _'

~' '

AOIABAT ',

29.1.81 1311-1328 GMT 5750N

0830 E

~ -4 -2

o

a

Figure 2: Vertical temperature distribution.

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12 GMT 12 GMT

/ -l• ^If~ 1005 /. ! ' \ H>~Y/ \\

10io -- --

. . . , 1-,-89.,-09\

. -28 078 · .. \ .,,_ ;·~ /. ,-, 1 · Cb.. r. \

. -_1s __ .,e9<60(·· / ·· 1... -11so1~

.jf)-- .\ • - ~ 0 '\ . . .

I .

- . · - . -11'1t100 . I · · ::.,~

. 29 ;

,<· , -

0 1'0 \

/ I,-..

='~71-·

/ ·. 3.,-102 . -- -155_4 ,' 8!,. -

, . 80 ~/ -18 • · 0· · ..

/ -.:,, 7,W _{. "} • "-- - dl09 / - --,-- ' _ i·· ' --~ 67 ^{I, 2 -}

1 lr.E'5 , 89 q2 - • )- c6 I

82 ~ 03 ..A . .

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06 I 108 ~

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10 160 • ,,... l Jt) • ~ 229 '. -I

5 05 0-6· ·- 0⁷

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~ 96-,,-"' 9 .oS:.e&,~ff(Z;ij'JS '2- -

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71

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ø. .;;;~ ,~./. ~ j ~{~--- ~"' ~

60 · ~..,. -q/}4~8.,.../ ~2-ff" -l~6ir .__ ~-...-- -' ~ -I .'.389 -4 406 16

I ⁹ 1"';74 ~a!/2Y IO l3 c6 I~ oo 3 51 ;;,,V 35 7 =rr '\

=~

10 06 o~..,5 02 · --3'· · --- -56-6

;I\ 1J (:>- l".,,.-? ,/ '\ 2~594 -8 06 4 . ~2.

29

1981

-J~~

30

1981

-6,3 _(.;60 ¹L..60 -10 3 <.... 5~

4 7 -3 -•

r ⁶¹ ₂ ^L..58

-7 p9

850 mb. 00 GMT 850 rnb. 00 -GMT

Figure 3.

TLF. (02) 71 41 70 ELVEGT. 52.

RAPPORTTYPE RAPPORTNR. ISBN--82-7 24 7- 241-4 Teknisk notat TN 5/81

DATO ANSV.SIGN. ANT.SIDER

APRIL 1981 B. Ottar 8

TITTEL PROSJEKTLEDER

V r!rir r1 r1 s

Airborne measurements over Skagerak, NILU PROSJEKT NR 21 January 1981

03075

FORFATTER-(E) TILGJENGELIGHET

**

A Yngvar Gotaas

OPPDRAGSGIVERS REF.

OPPDRAGSGIVER ^•·

NILU

3 STIKKORD (a rnaks.20 anslag)

Flymåling

I

Sorn ledd i en undersøkelse av kjemiske endringer i plurner ble sporstoff (SF6) sluppet ut fra et varmekraftverk i England.

Samtidig med at et eriqeLs k fly påviste stoff (SF6) utenfor Danmarks vestkyst, foretok NILU flyginger over Skagerak.

Kun en måling, over ytre Oslofjord, var positiv. Det er

imidlertid mulig at dette skyldes et kontinuerlig utslipp av SF6 fra Herøya, et utslipp påvist ved flymålingene neste dag.

TITLE Airborne measurements over Skagerak, 21 January 1981 ABSTRACT (max. 300 characters, 5-10 lines)

To study the chemistry of power station plumes, tracer material is released from a station in England. An English aircraft observed measurable concentrations along the west coast of Denmark. NILU undertook aircraft sampling over

Skagerak and one positive observation was made. This, however, was possibly due to a continuous release of _SF6 from a

factory near the Norwegian coast (Herøya) , a release con- firmed by aircraft sampling the following day.

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Må bestilles gjennom oppdragsgiver B

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