© 1993 Heron Publishing—Victoria, Canada
Sulfate concentrations in Norway spruce needles in relation to atmospheric SO2: a comparison of trees from various forests in Germany with trees fumigated with SO2 in growth chambers
Werner Kaiser, Andreas Dittrich and Ulrich Heber
Julius-von-Sachs-Institute of Biosciences, University of Würzburg, Mittlerer Dallenbergweg 64, D-8700 Würzburg, Germany / Received May 5, 1992
Summary
Concentrations of inorganic sulfur, organic sulfur and water-soluble cations and anions were determined in needles of young
Norway spruce trees (Picea abies L. (Karst.)) that had been fumigated in growth chambers for weeks or months with different concentrations of SO2, SO2 plus ozone, or SO2 plus NO2. Measurements were also made on needles from older trees growing in forests in various regions of Germany with different
mean annual atmospheric SO2 emissions. In the fumigated young trees, sulfate accumulation in the needles was a linear function of atmospheric SO2 concentration. Little or no sulfur was incorporated into the organic sulfur fraction. The mean accumulation rate of sulfate
in needles of fumigated trees was about 0.4 nmol gdw–1 (nl l–1)–1 h–1, which is very similar to the estimated rate of uptake of atmospheric SO2 calculated from mean stomatal conductances (15 mmol m–2 s–1) and the external SO2 concentration (the calculated rate of uptake was 0.37 nmol gdw–1 (nl l–1)–1 h–1). Concentrations of organic acids and other inorganic ions did not change much in response to SO2 fumigation.
In needles collected from trees in south and southeast Germany, large differences in sulfate concentrations were observed
that probably reflect SO2 emissions in the different regions. The highest foliar sulfate concentrations, and the highest annual increase in sulfate
concentration with needle age were observed in material collected from the heavily polluted Erzgebirge (up to 12 µmol gdw–1 year–1), followed by material from the Fichtelgebirge (up to 6 µmol gdw–1 year–1). If it is assumed that this annual increase is the result of uptake of SO2 from the atmosphere, mean annual atmospheric SO2 concentrations can be calculated. The calculated values were somewhat below the measured values in the
Fichtelgebirge and in the heavily polluted Erzgebirge.
Norway spruce trees can cope with high concentrations of atmospheric SO2, provided that they can neutralize the sulfuric acid formed from SO2. It appears that, in the field, the acid load is decreased by H+ translocation to the roots and subsequent H+/K+ exchange. However, this may be a very slow process, because it was not observed in the short-term fumigation experiments.
Keywords:
acid load, air pollution, forest decline, nitrogen dioxide, ozone, pH regulation, Picea abies, proton/potassium ion exchange, proton translocation, sulfate, sulfur dioxide.
