LRTAP-3-74.pdf (3.930Mb)

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LR ^{TTtP- 3} /1-y

..

'

ADVANCED STATIONS.

RESULTS FROM 45-DAY PERIOD

OF EXTENDED CHEMICAL ANALYSIS PROGRAMME, FEBRUARY 15 - MARCH 31, 1974

A preliminary discussion

(Steering Committee, 26-27 September 1974)

Kjeller, 16th September 1974

NORWEGIAN INSTITUTE FOR AIR RESEARCH P.

0.

BOX 115, N-2007 KJELLER

NORWAY

(2)

ADVANCED STATIONS.

RESULTS FROM 45-DAY PE~IOD

OF EXTENDED CHEMICAL ANALYSIS PROGRAMME, FEBRUARY 15 - MARCH 31, 1974

A preliminary discussion

(~teering Committee, 26-27 September 1974)

INTRODUCTION

At the last meeting of the Steering Committee, it was decided that a total of 100 samples from one sampling site in each country should be analyzed for strong acid, nitrate, ammonium, and other species in addition to sulphate in airborne particulate matter. Precipitation samples from the same site should be analyzed for the same components.

The samples were to be taken within 2 periods, the first 45-day period of 24-hourly samples from February 15th, and a second period later in 1974, subject to decision by the Steering Comm ittee.

This is a preliminary report of the results from the first 45-day period. The discussion of the results is only meant to draw attention to conclusions which may be drawn at this stage.

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- ll -

.K.ESULTS

^,_j,;

6 countries have reported results from the first period (tne

Un i.t

ed Kingdom, France, Denmark, Norway, Sweden and Finland). Copies of the results are enclosed. Table I lists the data available.

In addition, similar data from 1973 are also available from Sweden, Denmark, Finl~nd and Norway in connection with

the NORDFORSK 100-days programme. These data will be re- ported separately.

Chemical composition

)

Figure 1 shows the mean values of watersoluble aerosol constituents for the 6 stations. For easy comparison the values have been given in nanoequivalents per cubic metre.

Because of errors and uncertainties in the chemical ana- lysis, .the sum of anionic and cationic charges is not

always zero. It should also be recalled that the number of components analysed is not complete. Chloride, phosphate, zinc, and lead has not been determined. Iron and aluminium will have an effect on the H+ titration results, depending on the titration procedure, and the filter medium will

absorb protons to some extent Cl)_. Nevertheless, the agree- ment is generally good, which indicates that the ionic

ballance of the watersoluble aerosols is mainly determined

by

the concentration of the components: sulphate, ammonium and nitrate.

The chemical composition of aerosol and precipitation is rather variable from one station to another. Particularly

interesting are the high concentrations of ammonium and

nitrate ions observed at Cottered and Keldsnor. Because

ammonium nitrate decomposes if the partial pressure of

ammonia falls below a critical level corresponding to a

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- iii -

few micrograms of ammonia per cubic metre, ammonium nitrate in the aerosol phase will not occur simultaneously with an acid aerosol containing sulphuric acid. In Norway at

Birkenes (N 01), and at RåB (S 02) in Sweden, the concentration of nitrate in the aerosol therefore is generally very low.

Nitrate in precipitation, however, is .not negligible. It is interesting to note that at N 01 nitrate and amm onium in precipitation are very well correlated, see Table II

(correlations between concentrations in precipitation), and that they also are present in nearly equimolar amounts.

This relationship has also been found in samples from the winier 1973-74 (2), but no explanation.for this behaviour has so far been found. ,

From this brief discussion one may conclude that the

emissions of nitrogen compounds and the chemical reactions of these compounds in the atmosphere.are very important for the understanding of the behaviour of the sulphur oxides, particularly the formation of acid aerosols.

Comparison of air and precipitation data

The low frequency of rainfalls only to some extent permits a statistical comparison of air and precipitation data.

In Figures 2 - 7 the units neq/m³

and µeq/i have been used to allow a visual comparison of the concentrations of

aerosols in the air and the concentrations of watersoluble constituents in precipitation.

The ratio of these units correspond to a cloud water concentration of 1 g/m

³•

This implies that if the preci- pitation is formed by coalescence of cloud droplets, and the cloud droplets take up all the aerosols in the form of

condensation nuclei, the concentrations of ammonium (or any

other ion) in µeq/i of precipitation will be the same as the

concentrations of particulate ammonium in the a~r expressed

as nanoequivalents/m

³^•

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- iv -

This of course represents a fuuch too simplified picture of rainout and washout processes. Nevertheless, comparison of the left (air) and right (precipitation) coloumns in Figure 2 - 7 indicates that much of the concentration in the precipitation can be explained by aerosol scavenging, and that the efficiency of this process is fairly high

(> ~

50%).

The ratio of ammonium to sulphate is generally higher in aerosols than in rainfall. This may be explained by assuming that part of the sulphate in precipitation originates from sulphur dioxide which has been taken up and oxidized in the cloud droplets.

As pointed out by Penkett (3), sufficient ozone is present in the atmosphere to give SO

₂

oxidation rates in cloud droplets which are high enough to contribute significantly to the sulphate formation in rain.

In addition to this, it may also be that the composition of the aerosols at ground level is different from the com- position at rainforming levels several hundred metres above the ground. In particular, the ammonia concentration shows a pronounced decay with height (4), more so than sulphur dioxide (5). This will be more pronounced near the sources and in continental regions with agricultural activity.

When the air masses have passed over the North Sea or

the Skagerak and subsequently been broken up by the

topography, these differences may not be so important.

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- V -

Average washout factors ari' given in Table III. The definition of this factor is the ratio of the average air concentration, given in µg per kg of air; to the average concentration in precipitation, given in µg per kg water.

Following the discussion above, complete rainout and a cloud water concentration of 1 g/m

³

corresponds to a washout ratio of 7.7 x 10

²•

When the washout ratio is significantly higher, as for nitrate at Råo and Birkenes, the concentration level of

this

component in precipitation must be partly due to other effects. In this case the cause probably is rain- out/washout of gaseous nitrogen components.

,

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- vi -

RELATIONSHIP BETWEEN M°EASUREMENTS AND METEOROLOGICAL CONDITIONS

Trajectories have been calculated for the stations Birkenes, Cottered, Jokioinen, Keldsnor, Råo and Vert-le-Petit during the period. Since ~o data are available for the emission of nitrogen _compounds, or for atmospheric conditions of importance for transformation processes etc. the use of the

trajectories is limited to finding the trajectories for air samples of particular interest.

Trajectories for the 10 aerosol samples of highest sulphate air concentrations, and for the 10 samples of highest acid aerosol concentrations are shown in figures 8 to 23.

These figures give trajectories every 6 hour. For comparison the figures 24 to 35 give trajectories every 24 hour for the whole period. The trajectories are computed for 850 mb and are presented with 12 hours timestep.

The numbers in the figures indicate the starting point 48 hours before arrival and the positions of the stations

1.

Birkenes 2 . Råo

3.

Jokioinen

4 .

Keldsnor

5.

Cottered

6.

Vert-le-Petit

La Crouz.ille' s position is indicated by the number 7.

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J

- vii -

CONCLUSION

Continued measurements are needed in order to obtain a better data basis. It will be important that more

countries find it ~ossible to participate in this part of the programme.

The preliminary results given indicate that nitrogen

compounds are of particular importance for the formation

of acid precipitation. In continued measurements these

should therefore be given priority and it should be

considered to measure also nitrogen dioxide in the

gaseous phase.

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REFERENCES

( 1)

Askne, C.,

Brosset, C., Ferm, M.

( 2)

Nord¢, J.

( 3 )

Penkett, S.A.

(4)

( 5 )

Georgii,· H.W., Muller, W.J.

Jost, D.

Determination of the proton- donating property of air- borne particles.

IVL Publication B 157.

Swedish Water and Air Pollu- tion Research Laboratory, Gothenburg - Aug. 1973.

Sulphur pollution arising from distant emission sources.

Lecture presented at the ELMIA A/B Conference, Jonkoping, Sweden.

September 2nd., 1974.

Nature, 240, pp 105-106, 1972.

Tellus, 26, pp 180-185, 1974.

Tellus, 26, pp 206-211,

1974.

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- 5 -

FIGURES

1

Air samples, February 15 - March 31, 1974.

Mean values in neq/m³'..

2 - 7 Short periods, mean concentrations in air and precipitation samples.

8 - 16 Trajectories and concentrations on days with high sulphate concentration in air.

17 - 23 Trajectories and concentrations on days with high strong acid concentration in air.

24 - 35 Trajectories arriving at 12 GMT, February 15 - March 31, 1974.

TABLES

I

Data a~ailable February 15 - March 31, 1974.

II Correlations between concentrations in

precipitation, N 01, period March 25 - June 27, 1973.

III Washout ratios based on mean values for the period, February 15 - March 31, 1974.

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- 6 -

Air samples

Strong

Country acid NOrN NH4-N S04 Ca K Fe Mg Na Cl TPM

UK

-

^X ^X ^X ^X ^- ^- ^X ^- ^- ^-

France X X

-

^X ^X ^X ^X ^X ^X ^- ^X

Sweden X X X X X X X

-

^X ^- ^X

Denmark X X X X X

-

^X ^- ^X ^- ^X

Finland X X X X X - X - X - -

Norway X X X X X X X X X X -

Precipitation samples.

Country Strong

N03-N NH4-N S04 Ca K Fe Mg Na Cl N .S.

acid

UK - ^X ^X ^X ^X - - X - - 14

France X X - X X X

-

^X ^X ^- ¹²

Sweden X X X X X - -

-

^X ^- ⁶

Denmark X X X X X - - ^- X - 12

Finland X X X X X - ^X ^X ^X - ₂₉

Norway X X X X X X

-

^X ^- ^- 2.l

Table I: 45-days period February 15 - March 31, 1974 Data available.

Sampling period:

United Kingdom

A

22/2 - ^31/3

^p

^15/2

^-

^31/3

France

A

15/2 - ^23/3

^p

^15/2 - ^31/3

Sweden

A

15/2 - ^1/4

^p

^15/2 - ^31/3

Denmark

A

15/2

-

31/3

^p

15/2 - ^31/3

Finland

A

15/2

-

28/2; 16/3 - ^24/4

^p

^15/1 - ^31/5

Norway

A

15/2

-

31/3

^p

1/2 - ^31/3

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7

'D Q)

.µ CJ Q)

H H 0 CJ 0 I 0 N.s

0 ri ^(/) i::

0

I ·ri

0 N N.s f..J

0 co 0 _(/) fU f..J

ri ·ri

0..

0 ri ^(Y) "' ·ri ⁰

0 L() (Y) 0 _Q)

z

_H

ri 0..

+ i::

0 ill 0 N -'T •ri

0 co ^L() .:t ::r::

z _Cf)

ri

i:: Q(Y)

0 (Y) co .:t .:t + ^·ri^r---

0 .:t ^(Y) ^L() N ro ^f..J⁰⁾

z ^fU^ri

ri H

f..J "

+ ^{i:: r---}

0 ...--l lD co ...--l N N Q) N

0 (J) 0 0 (Y) 0 co 0

::,;:: i:: Q)

ri 0 i::

0 ~ I-:,

0 co ri co ^L() ri co + ^i::

0 lD co _ri N .:t 0 ~ ^Q) I

ri" ^Q)

~Lf)

f..J N

+ ^Q)

0 L() r--- ri ^L() ^L() ^(J) ri ^N ..0 ,.c:

0 L() (Y) N L() .:t ...--l 0 ₀ro 0

Cll H

ri i:: fU

0 ::s

0 co lD N 0 (J) (Y) co r--- + ·d f..J Cf)

0 (Y) ri 0 (Y) L() co ^(Y) N ::r:: _fU Q)

ri ri i::

Q) Q)

CJ H~

0 ri r--- r--- ^L() co co ^N ^(Y) r--- ^Q) _{H H}

0 N N (Y) ri N .0 ...--l ...--l 0 H _0.. O·ri

Ur:Q ri

ri s

'O H

I •

Q) H

.µ

CJ Q)

i Q) ri

I

I-'.-< ..0

I_ H

t

CJ 0 ru

(I) CJ E-l

I-'.-<

0.. + _N + _N + ^I ^I

+ ^-'T "' ^N.s ^N.s

ri + ro + eo ro ::r:: ⁰ 0 0

s ::r:: ⁰ ~ ^::,;:: z z z ^.^(/) ^(/)

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- 8 -

~

UK 1 F 03 DK 5 SF 2 S 02 N 01 t

H+ _108. _2.9 _45.

92. 70.

sot-

5.4 17. 12. 9.6 7.1 16.

NH4+ _4.0 _6.2 _5.4 _17.

N03- _7.9 _9.6 _33. _149.

Ca²+ _9.9 _39. _10. _27. _35.

Mg2+ 12. 40. 34.

Na+ _12. _5.3.

K+ _33.

Table III: Washout ratio in units 10

²

kg air

kg

rain

Period February 15 - March 31

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-9-

neq/m

400---,r---,

LA CROUZILLE

200-+---;

KELDSNOR

neq/m

400---.---,

BIRKENES COTTERED

300-t---

200-+---f-',--

100-+---

neq/m

400---

JOKIOINEN RÅØ

300-+---+---i

200-+---,...---1

100-+--

Figure 1: Air samples, February 15 - March 31, 1974.

Mean values in neq/rn³• ·

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-10-

neqlm

400

µeqll

300

200

100

0

neq/m

400

300

200

100

-

~-

- _D -1- ^B ^!~~~~

-

0 M

n

⁰ ^;l'/4

-

^•:•:•

-

^M ¹¹¹¹ ^M ⁰ ^~^···

0

neqlm

400

300

200

100

0

.·,

~

f.

,' (~

0 ^M

0

^'/,/

^:::::

⁰ ^M

n

¹¹¹¹ ^M ⁰ ^~ ^M

µeq/1

µeq/1

-

I

n

^~j

0 M

n

~ ^-,- :•:•:

.. ...

= M 1111 ^M 0 M

+ ⁺ ²⁺ ²⁺ ⁺ ^K+ ²- - ^♦ ⁺ ²⁺ ²⁺ ⁺ ⁺ ²- -

H NH, Ca Mg Na SO, NOJ H NH, Ca Mg Na K SO, NOJ

PERIOD 9/3

PERIOD 11-12/3

PERIOD 14/3

Figure 2: Station F 03. Short periods, mean concentrations in air and precipita·tion samples.

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+ l l "

neq/m

400---,~---,

µeqfl

neq/m µeq/l

400--..;__ ...,.... .,

PERIOD 21-22/2

PERIOD 16/3

neq/m

400---. ^µeq/l

463

200-+---

+ + 2 + 2+ + + 2 - -

H NH, Ca Mg No K SO, N0₃

- I

- -

+ + 2• 2+ +

H NH, Co Mg No K 50, N0⁺ ^{2 -} ^-₃

Figure 3: Station DK 5. Short per-Lod s , mean concentrations in air and precipitation samples.

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-12 - ^·-u---

neq/m

400

µeqfl

300

200

100

0

- -

^,-

- -

I ^- ^- ^-

,.

-

?')

-

^.,

- lif

~

-

~~

- -

^~

,~ -

^~

-I>

- -

^~

.. ^)'> ₀ ::::: -

^I~

ⁿ

¹¹¹¹ ^M

..

⁾

-

¹¹¹¹

-

^)I

^-

PERIOD 15-16/2

neq/m µeq/l

400

PERIOD

300 2-4/3

200 ¹⁰⁰

i ^--:jf ⁱ

::::::

...

0 ¹¹¹ ^M :::::·

neq/m JJeq/1

400

300-+---+---i

200---;

100-+---=---t---

+ + 2+ 2+ +

H 1'1-l, Ca Mg Na

- -

.. ...

-

···

-

^M ^1,1

• ^2- ^-

.

• ^2• ^2• ⁺

.

^2- ^-

K SO, N0₃ H NH, Ca Mg Na K 50, N0₃

PERIOD 17/3

Figure 4: Station N 01. Short periods, mean concentrations in air and precipitation samples.

(18)

-13- neq/m

400---"T""'---, µeq/l

300

i-li---'----•

^PERJOD^28/2

200-+---

100

neq/m µeq/l

400---,.---,

300-1---1---;

200...---~~---t---,

100

- I

I

M M M M

B :::::

0 ⁿ

neqfm µeq/1

400 ⁸²¹ ⁴⁹⁵

... - -

⁴⁵⁰

300

i _I i-~ _-

^23/3^PERIOD

_] ... - -

200

_~r~

^•····

- ^.. - - - ^...

_(i - _- -

100 _M _M

_r;~

:♦:-: ^···

_:::;: - ^... - - _- - - ^... _..

0 _H

.

_NH,_•_Ca²⁺_Mg^2• _Na_• _K

.

_so,^2-_NO

- ^. .

^2• ^2• ^M

. .

^M ^2-M ^-

3 H NH, Ca Mg Na K SO, NO₃

PERIOD 15/3

Figure 5: Station UK 1. Short periods, mean concentrations in air and precipitation samples.

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-14-

neq/m 400

µeqfl

300

200

100

0

neq/m µeq/1

400-,---

300--i---1---1

___ l---1

200

100

neq/rn 400

.. -

- - - - - -

- -

-

M M

-

^M ^M

,ueq /I

300

200

100

0

.. ·

(

·ir' ;-I

).,?

- _m

)-,i>

-

^~

0 ~ 0 M 7/ M '

... ..

r, ₀ 7/ M •:❖

~

-

~

t ...

n

~

n ...

..

^M ^I'/. ^M

_-~- _- _-

n 1/} M

=~=

♦ ♦ ²⁺ ²+ - - ⁺ ⁺

H NH, Ca Mg K⁺ 50, N0² 3 H Mg ²⁺Na ⁺

PERIOD 23/2 0820-1050

PERIOD 17/3 1650-2000

PERIOD 21/ 3 0950-1020

+ 2- -

K 50, N0₃

Figure 6: Station SF 2. Short periods, mean concentrations in air and precipitation samples.

-i

(20)

-15 -

neg/m 400

µeqll

300

200

100

') ~ ~

>,

-

~

))

" - _-

^~

)

- ~-

,.,___.; ^.^.;^.;_; ~--- _~

- - _- _-

_~ _~

~

-

~ ~

~ ⁾

~~~~I - _- _- _n

_M

-

^I)

^,....,

^M ^1:111 ^'ll. ^M

^..

0

neq/m µeq/l

400-.---,---,

300-f---+---1

200--+--.X.---

neq/rn

400

300

200

100

0

µeq/1

•-~~ ~-

-

~ ~

···•··

-

::::::

-

_~

_if

~

...

···

-

_~

~ r, M ~ :::::: ^.,.

....

_~

rT M M :-:•:

-

^- ^-

^...

⁺ ^-^.·.··

PERIOD 20/2

PERIOD 15-17/3

PERIOD 18-21/3

+ + 2 + 2+ + + 2 - +

H NH, Ca Mg Na K SO, N0₃ H Mg Na ²⁺ ^♦ K ^•SO, N0² ₃

Figure 7: Station S 02. Short periods, mean concentrations in air and precipitation samples.

(21)

-16 -

Trajectories arriving at 740325, 0 GMT.

3

6

FIGURE 8

Day with high sulphate concentration.

Observed sulphate 9oncentration:

N 01 1.7 S 02 3.8 SF 2 3.1 DK 5 3.9 UK l 49.9 F 01

(22)

-17-

FIGURE 9

Observed sulphate concentration:

N 01 6.5 S 02 8.0 SF 2

DK 5 13.5 UK l 29.5 F 03 1.8

(23)

- 18-

T:..⁰ajectories arriving at 740316, 6 GMT.

Trajectories arriving åt 740316, 12 GMT.

FIGURE 10 Day with high sulphate concentration.

N 01 S 02 SF 2

25.0 12.5 4.2

DK 5 6.4

UK l

F 03 0.9

(24)

-19-

6

---''---..L...---.ll,5 Trajectories arriving at

740323, 6 GMT.

FIGURE 11

N 01 S 02 SF 2 DK 5

UK l

F 03

4.1 4.1 l. 7 3.7 23.9 2.2

(25)

-20-

N

oi

S 02 SF 2

4.0 1.0 5.4 DK 5 15.1 UK 1 22.3 F 03 18.2

(26)

-21-

N 01 S 02 SF 2

DK 5 4.5 8.8 2.1

UK l

F 03 22.3

(27)

-22-

N 01 S 02

3.1 2.7 SF 2 3.3

DK 5 1.4

UK l 18.7 F 03

(28)

-23-

i

... \,,_·,.

\

\ \ _;, _.

.

. ---✓3

FIGURE 15

N 01

S 02 SF 2

DK 5 17.6 9.4 8.5

UK l

F 03 4.9

(29)

-24-

2 4

.... ., ...

/

-- ->·_,/\

_,,..,,

,.-.-:·(,/<

_l

l

^_,Y

· ... z,

'·

Trajectories arriving at 740318, 6 GMT .

N 01 2.3

s

⁰² ^8.7

SF 2 17.0 DK 5

UK l

F 03 1.5

(30)

-25-

2 1

• 4

.. -·- . ..:"_,, ... \'('./ ... "_j'.·

6f ^L(~

-;:--·- , ...

·' I

\.\ ..

(

'·

·-.

' i '

;-" ~, . .,.1.:'

. / \

,·,/ ·' ^\

.,· I ⁰l

.l ... .i ,1..

"· i s ,.,-'\ '

\j ..

{-z_-/

'> _

^_.,i

. ._/_/ ,.,.-<

.J~,,, .... \ _1·\·."-:·'' _r' i

! r·

! ;.,

... ---,,

'·,. __

FIGURE 17 Day with high strong acid concentration.

Observed strong acid concentrations:

. N 01 S 02

84 3 SF 2

DK 5

22

UK l

F 03 0

(31)

- 26 -

Trajectories arriving at 7 4 0 21 7 , 0 GMT .

N 01

S 02 SF 2 DK 5

UK l F 03 0

54 42 48 27

(32)

-27-

Trajectories arriving at 740320; 0 GMT.

,--

--..--.,---~---,-. ---

.-·,...

',

\

I

\ ,,

N 01

S 02 SF 2

3

12 40

DK 5 53

UK l

F 03

(33)

- 28-

... · ... ,

/ \

-., ·,.

,·

N 01 S 02

27

7 SF 2 52 DK 5 9

UK l F 03 0

(34)

-29-

FIGURE 21

Day with high strong acid concentration. · N 01 7 Observed strong acid concentrations: S 02 15

SF 2 DK 5 52

UK 1 50 F 03 0

(35)

-30-

V i_

0 \

·,

I

4

N 01 S 02

45 3 SF 2 DK 5 26

UK 1

F 03 0

(36)

-31-

·-...v.-•'\

... \

I \

\

....

,.,

<'

'· _\

... · ... ,

'.--...;~---.

'·

FIGURE 23 Day with high stronc acid concentration;

N 01 44 S 02 9

SF 2 5 DK 5 l UK l 0 F 03

(37)

-32-

·11\\

0~

~

5 6

Trajectories arriving at 71+0215, ₁₂GMT.

FIGURE 24

(38)

- 33-

Trajectories arriving at 7Lf0219, 12 GMT.

. ... ,

_I ·,. _ . ·, ·,

.i ,·

.,., >.,...(<

,·,/ .' \

_,· I ·1

,. I

_/.,.i>-·-(·

/'.' .' \

I ·1

,

4 2

FIGURE 25

(39)

-34-

FIGURE

26

(40)

-35-

FIGURE 27

(41)

-36-

FIGURE 28

(42)

-37-

2 1

• 4

L-(

'

FIGURE 29

(43)

-38-

' \

~

'-.../ 1

r\

\ .... .-:.). / ,,,<

... - _'.-:t:,,'\,,,l<'..r·'-'

! J··

... s L,(:

·,

FIGURE 30

-f

(44)

-39-

'

\

'-·,

{ '\ · .... ,

~\ 3}·

2,i.-~

_{,_} _✓-

'i. 'i. .... ·~--•-.,. .... ·

I / ... -"

,•.,,i : \,

I '1

2

4

FIGURE 31

(45)

-40-

1

6

-:;--- , ... '·

(

·,\

·, I

Trajectories arriving at 74-0322, 12 GMT.

FIGURE 32

(46)

Trajectories arriving åt 740323, 12 GMT.

•J

3

FIGURE 33

(47)

-42-

0 \

FIGURE 34

(48)

-43 --

FIGURE 35

LRTAP-3-74.pdf (3.930Mb)

LR TTtP- 3 /1-y

..

ADVANCED STATIONS.

RESULTS FROM 45-DAY PERIOD

OF EXTENDED CHEMICAL ANALYSIS PROGRAMME, FEBRUARY 15 - MARCH 31, 1974

A preliminary discussion

(Steering Committee, 26-27 September 1974)

Kjeller, 16th September 1974

NORWEGIAN INSTITUTE FOR AIR RESEARCH P.

BOX 115, N-2007 KJELLER

NORWAY

.K.ESULTS

6 countries have reported results from the first period (tne

ed Kingdom, France, Denmark, Norway, Sweden and Finland). Copies of the results are enclosed. Table I lists the data available.

In addition, similar data from 1973 are also available from Sweden, Denmark, Finl~nd and Norway in connection with

the NORDFORSK 100-days programme. These data will be re- ported separately.

Chemical composition

Figure 1 shows the mean values of watersoluble aerosol constituents for the 6 stations. For easy comparison the values have been given in nanoequivalents per cubic metre.

Because of errors and uncertainties in the chemical ana- lysis, .the sum of anionic and cationic charges is not

always zero. It should also be recalled that the number of components analysed is not complete. Chloride, phosphate, zinc, and lead has not been determined. Iron and aluminium will have an effect on the H+ titration results, depending on the titration procedure, and the filter medium will

absorb protons to some extent Cl)_. Nevertheless, the agree- ment is generally good, which indicates that the ionic

ballance of the watersoluble aerosols is mainly determined

the concentration of the components: sulphate, ammonium and nitrate.

The chemical composition of aerosol and precipitation is rather variable from one station to another. Particularly

interesting are the high concentrations of ammonium and

nitrate ions observed at Cottered and Keldsnor. Because

ammonium nitrate decomposes if the partial pressure of

ammonia falls below a critical level corresponding to a

and µeq/i have been used to allow a visual comparison of the concentrations of

aerosols in the air and the concentrations of watersoluble constituents in precipitation.

The ratio of these units correspond to a cloud water concentration of 1 g/m

This implies that if the preci- pitation is formed by coalescence of cloud droplets, and the cloud droplets take up all the aerosols in the form of

condensation nuclei, the concentrations of ammonium (or any

other ion) in µeq/i of precipitation will be the same as the

concentrations of particulate ammonium in the a~r expressed

as nanoequivalents/m

50%).

The ratio of ammonium to sulphate is generally higher in aerosols than in rainfall. This may be explained by assuming that part of the sulphate in precipitation originates from sulphur dioxide which has been taken up and oxidized in the cloud droplets.

As pointed out by Penkett (3), sufficient ozone is present in the atmosphere to give SO

oxidation rates in cloud droplets which are high enough to contribute significantly to the sulphate formation in rain.

When the air masses have passed over the North Sea or

the Skagerak and subsequently been broken up by the

topography, these differences may not be so important.

Average washout factors ari' given in Table III. The definition of this factor is the ratio of the average air concentration, given in µg per kg of air; to the average concentration in precipitation, given in µg per kg water.

Following the discussion above, complete rainout and a cloud water concentration of 1 g/m

corresponds to a washout ratio of 7.7 x 10

When the washout ratio is significantly higher, as for nitrate at Råo and Birkenes, the concentration level of

component in precipitation must be partly due to other effects. In this case the cause probably is rain- out/washout of gaseous nitrogen components.

Birkenes 2 . Råo

Jokioinen

Keldsnor

Cottered

Vert-le-Petit

La Crouz.ille' s position is indicated by the number 7.

- vii -

CONCLUSION

Continued measurements are needed in order to obtain a better data basis. It will be important that more

countries find it ~ossible to participate in this part of the programme.

The preliminary results given indicate that nitrogen

compounds are of particular importance for the formation

of acid precipitation. In continued measurements these

should therefore be given priority and it should be

considered to measure also nitrogen dioxide in the

gaseous phase.

REFERENCES

Askne, C.,

Brosset, C., Ferm, M.

Nord¢, J.

Penkett, S.A.

(4)

Georgii,· H.W., Muller, W.J.

Jost, D.

Determination of the proton- donating property of air- borne particles.

IVL Publication B 157.

Swedish Water and Air Pollu- tion Research Laboratory, Gothenburg - Aug. 1973.

Sulphur pollution arising from distant emission sources.

Lecture presented at the ELMIA A/B Conference, Jonkoping, Sweden.

September 2nd., 1974.

Nature, 240, pp 105-106, 1972.

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