Sulphur and seasalt deposition as reflected by troughfall and runoff chemistry in forested catchments

At forested catchments at lake Gårdsjön on the Swedish west coast the deposition and runoff chemistry has been followed during the period 1979-1990 by throughfall and runoff mesurements as well as by measurements of atmospheric concentrations. The 10 years means in throughfall and runoff is very similar for sulphur and the main seasalt ions sodium and chloride; for sulphur 26.1 and 27.6 kg/ha/yr, for sodium 49 and 52 kg/ha/yr and for chloride 96 kg/ha/yr and 93 kg/ha/yr respectively. The actual flows are 100-200 % higher than the wet deposition as collected in open bulk precipitation collectors indicating a very large input by dry deposition. One important question is to what extent the throughfall and runoff values can be used as measures of total deposition. From througfall and runoff studies at different experimental catchments we will present a number of results illustrating the possibilities of using throughfall and runoff data as measures of atmospheric deposition of sulphur and seeasalt