Source: Norwegian Institute for Water Research.Yearly changes in surface water sulphate and alkalinity in the 1980s and 1990s in different regions of North America and Europe. Negative values reflect a decrease in sulphate or alkalinity, while positive values indicate an increase. The length of the bar reflects the magnitude of the change (positive or negative).The top chart shows that there is a ‘negative’ change in sulphate in all regions in the 1980s and 1990s and that the change is larger in the 1990s than in the 1980s.
The bottom chart shows an improvement in terms of acidification and water quality in the 1990s compared to the 1980s, with one exception (Midwestern North America).