Pilot Programme on Integrated Monitoring: 1 Annual Synoptic Report 1990. Convention on Long-range Transboundary Air Pollution

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Convention on Long-range Transboundary Air Pollution

Pilot Programme on Integrated Monitoring

1 ANNUAL SYNOPTIC REPORT 1990

Environment Data Centre

National Board of Waters and the Environment

Helsinki 1990

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Convention on Long-range Transboundary Air Pollution

Pilot Programme on Integrated Monitoring

1 ANNUAL SYNOPTIC REPORT 1990

Environment Data Centre

National Board of Waters and the Environment Helsinki 1990

Annual Synopsis Report 1990

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Annual Synopsis Report 1990

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4.3.3 Anion/cation balance in precipitation

Ion balance calculations can be used for quality assurance purposes: sums of positive and negative ions in paq/I should be equal if all major ions in precipitation have been measured. The paired stacked bars in Fig. 4.4 a, b, c and d illustrate the anion and cation sums in bulk/wet-only precipitation samples in Czechoslovakia, Finland, Norwayand Sweden at two stations in each country. The comparison of the length of the bars is presented in Table 4. 3.

Table 4.3. Comparison of anion (A) and cation (C) sums in monthly bulk/wet-only precipitation at two stations in Czechoslovakia, Finland, Norway and Sweden (2 missing values) during one year. The sums are marked to be equal if the difference is less than about 10 peq/I.

Country A>C A<C A=C Czechoslovakia 5 1 18

Finland 0 1 23

Norway 0 19 5

Sweden 7 11 4

The small amount of anions might in summertime possibly be explained by the presence of organic anions in the sample, all major cations are included in the measurement programme. In Czechoslovakia the results for May at area CS04 seem to be erroneous. In Norwayall cation sums are higher than anion sums due to marine-corrected sulphate (edit.

comm.). At both Swedish stations the anion sum is higher from December to March-April and the cation sum is higher from May-June to October.

In order to check the quality of the measurements, calculation of ion balance should be done routinely in the laboratory and the sample reanalyzed, if necessary. From the beginning of 1988 the Finnish Meteorological Institute has used the classification of precipitation samples according to EMEP (Schaug, 1988). We have found it very useful. Three parallel samples are also collected, and the mean value used, excluding obviously contaminated samples.

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