Total ammonium concentrations in rivers between 1992 and 2010 draining to different sea regions of Europe

The sea region data series are calculated as the average of annual mean data from river monitoring stations in each sea region. The data thus represents rivers or river basins draining into that particular sea. Only complete series after inter/extrapolation are included (see indicator specification). The number of river monitoring stations included per sea region is given in parentheses.