Striebel, T.: Investigations on the aquatic chemistry of the Blautopf Spring, Blaubeuren, Swabian Alb, Germany

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Summary
 
Some water samples from the Blautopf Spring were analysed on macro ions and heavy metals. Based on the data measured, calculations on solubilities of carbonate and heavy metals were performed.
 
The ions which dominate in the samples are Ca2+ and HCO3-. The concentrations of these ions are almost constant, differences are depending on the delivery of the spring, not on the season. Chloride and nitrate show distinct maxima in winter times caused by salting of roads and leaching of soils.
 
In the most cases the saturation index of calcite is near zero, meaning saturation. Only in a flood elevation a lower pH was measured, which causes undersaturation of calcite. The saturation index of dolomite is clear below zero, meaning distinct undersaturation. Dissolved carbon dioxide is oversaturated regarding its concentration in the atmosphere; this is common at karst springs.
 
The heavy metal concentrations measured are of low environmental significance. With the exception of Fe3+ regarding amorphous FeOOH the heavy metals are undersaturated regarding different important solid phases. The (apparent) oversaturation of Fe3+ is common at many different types of water and indicates the presence of colloidal forms of iron or organic iron complexes, both species which are passing the membrane filter. Inorganic complexation is mentionable for iron, copper, nickel and aluminium.
 
The calculations on the amount of removal of limestone in the drainage area of the Blautopf show that a limestone layer of 63 cm could be removed in a time of 10,000 years. The quantity of limestone removed in one year would be enough to create a cave with a length of 50 km and a diameter of 49 cm. After 10,000 years this cave would have a diameter of 49 m.