https://www.eea.europa.eu/data-and-maps/figures/development-of-mean-plot-concentration-in-open-field-measurements-of-sulphate-so4-285-plots-nitrate-no3-294-plots-and-ammonium-nh4-294-plots-1996-2001/development-of-mean-plot-concentration-in-open-field-measurements.eps/development-of-mean-plot-concentration.png/download