5. Conclusions Monitoring data show

5. Conclusions
Monitoring data showed that concentrations of metals abundantly leached from ASSs (Al, Cd, Co, Cu,Mn, Ni and Zn) were mostly elevated in the water column. The concentrations of Al, Cd and Zn were at levels likely to have adverse effects on the estuary ecosystems in the ASS hotspot areas. Low pH values (b5.5) were also observed in the studied estuaries. Acidic and metal rich river waters clearly impaired water quality during flood period.
Metals that were elevated in the water column were also enriched in the surface sediments of the studied estuaries. Concentrations of Al, Cd, Co, Cu,Mn,Ni and Zn were several folds greater in the sediment samples than the background concentrations indicating that several Baltic Sea estuary ecosystems are under stress due to ASS effects. This was supported by the observed deteriorated benthic invertebrate community in the estuaries. Instead metals that are not generally abundantly leached from ASSs (As, Cr, Fe and Pb) were not typically enriched in the surface sediments.
Although this risk assessment included some uncertainties the WoE approach showed that the Baltic Sea estuaries under the influence of ASS catchments were likely to experience deterioration of ecosystems if no remedial actions are considered. This is especially important due to changing climate and forecasted increase in the precipitation in the Northern Europe. More information is needed especially concerning low salinity (1–2‰ S) estuaries where water temperature and pH are also low.