Rivers of North-Rhine Westphalia revisited: tracing changes in river chemistry.

An investigation was carried out into the hydrochemical properties of the Lippe, Ems and Ruhr rivers, including the stable isotopic composition of water and dissolved river compounds, in order to assess potential anthropogenic versus natural sources for river solutes and to quantify the changes in river chemistry over the past 15 years for the rivers Lippe and Ruhr. Decreasing concentrations were found for most river constituents commonly linked to anthropogenic activities. An observed increase in (SO4)2- for the river Lippe probably reflects varying discharges from the 4 mines whose effluent still introduces Cl- and (SO4)2- into the water. Variations in the isotopic composition of water show the effect of ocean water (river Ems) or of evaporation that occurred either in channels (river Ems), in reservoirs (river Ruhr) or due to the use of river water for cooling purposes (river Lippe). The isotopic composition of dissolved (SO4)2- shows that atmospheric deposition and sulphide oxidation are the major sources. The sulphate introduced from mining activities into the Lippe and the Ems does not alter the isotopic composition of (SO4)2-, despite the rather high discharges.
An investigation was carried out into the hydrochemical properties of the Lippe, Ems and Ruhr rivers, including the stable isotopic composition of water and dissolved river compounds, in order to assess potential anthropogenic versus natural sources for river solutes and to quantify the changes in river chemistry over the past 15 years for the rivers Lippe and Ruhr. Decreasing concentrations were found for most river constituents commonly linked to anthropogenic activities. An observed increase in (SO4)2- for the river Lippe probably reflects varying discharges from the 4 mines whose effluent still introduces Cl- and (SO4)2- into the water. Variations in the isotopic composition of water show the effect of ocean water (river Ems) or of evaporation that occurred either in channels (river Ems), in reservoirs (river Ruhr) or due to the use of river water for cooling purposes (river Lippe). The isotopic composition of dissolved (SO4)2- shows that atmospheric deposition and sulphide oxidation are the major sources. The sulphate introduced from mining activities into the Lippe and the Ems does not alter the isotopic composition of (SO4)2-, despite the rather high discharges.