Spatial variation of atmospheric deposition in Europe in 2015

Monitoring the atmospheric deposition to forests is a prerequisite for understanding forest ecosystem processes and an important contribution for evaluating the spatio-temporal trends of air pollution. In this report, we present the annual throughfall deposition of eutrophying, acidifying and buffering components on ICP Forests Level II plots in 2015. The nitrogen (N) compounds nitrate (NO₃^-) and ammonium (NH₄ ⁺) are the main drivers of eutrophication and also contribute to acidification. High deposition rates to forests (throughfall deposition > 8 kg N ha^-1 yr^-1) were measured at several plots in central Europe (Belgium, Germany) but also in the Czech Rupublic, Denmark and southern Sweden. Low depositions rates have been reported primarily in northern Europe. Sulfate (SO₄ ^2-) has been the most important driver of soil acidification. High deposition of SO₄ ^2- (throughfall deposition > 8 kg SO₄ ^2--S ha^-1 yr^-1) was still found in central Europe (e.g. Belgium, Germany) as well as in the Czech Republic. In addition, high sulfate deposition occurred in southern Europe (Italy, Greece) which is probably related to natural sources. Similarly, high calcium (Ca²⁺) deposition across southern Europe is likely related to contributions from Saharan Dust. The spatial pattern of magnesium (Mg²⁺) deposition is mainly dominated by marine sources. Both Ca²⁺and Mg²⁺ are macronutrients and act as buffers against acidification. The overall spatial patterns of deposition of eutrophying, acidifying and buffering substances in 2015 remained similar to results from the previous years.