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Berlin Environmental Atlas

02.04 Quality of Near-surface Groundwater (Edition 2006)

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Oxidizability

Permanganate consumption (measured as CSV manganese, converted to the oxidation equivalent related to O2 in mg/l) is used as a measure of inorganic and organic compounds dissolved in the groundwater. In non-polluted groundwater, the origin of most organic substances is the ground zone inhabited by various forms of life. Dissolved organic substances are sources of energy and carbon for microorganisms living in the groundwater and are therefore relatively quickly decomposed in the presence of dissolved oxygen. However, in many cases dissolved organic substances contained in the groundwater are caused by anthropogenic pollution (for instance by wastewater or synthetic organic compounds). In addition, large amounts of iron or manganese compounds are dissolved in fine-grained sandy-silty aquifers that in the form of reduced inorganic compounds also result in high CSV manganese values.

The geogenic background value in Brandenburg - just like the limiting value stipulated in the TrinkwV and the range that Schleyer & Kerndorff (1992) considered to be the beginning of anthropogenic interference - is about 5 mg/l. In low-lying areas with boggy layers it may be slightly higher.

The Figure shows a clear regional correlation with the hydrogeological boundary conditions of the city zone: in the area of the plateaus, the values are within the normal range of concentrations, whereas in the glacial spillway they are generally increased. Values above 5 mg/l were measured mainly along the Spree River in city-centre areas (Wuhlheide), the upper reaches of the Havel River and in Spandau. In those areas there exist both boggy sediments and anthropogenic interferences from industrial estates (Haselhorst, Siemensstadt).

Orthophosphate

Phosphorus is mobile only under anaerobic conditions and is bound in the soil mainly to clay minerals and metal hydroxide. In unconsolidated rock, values up to 0.2 or 0.3mg/l orthophosphate (LUA 1996) are regarded as natural background contents. Higher phosphate contents in the groundwater are indicative of anthropogenic interferences and are, above all, problematic for the surface waters in the Berlin/Brandenburg region, since these are fed by groundwater to a large extent.

The figure shows the results of calculations done for the probability of exceeding the chosen threshold value of 0.3 mg/l, based on the indicator kriging technique (as for ammonium, the presentation of the calculation of the area based on the original data was dispensed with): As in the case of ammonium and oxidizability, the hydrogeological relationship is clearly discernible. The phosphate contents in the confined aquifers are always low (in most cases below 0.05 mg/l). Higher concentrations and thus a greater probability of exceeding the threshold value of 0.3 mg/l are discernible in the uncovered deposition beds in the glacial spillway and in particular in places where depositions of peat and muds from the Holocene period exist along water bodies. By drawing on the values furnished by the basic measuring network, this pattern was identified also in Brandenburg (LUA 2002). Organically-bonded or complexed phosphorus is easily transported by water that seeps into the ground, since organic anions block the sorption of phosphate.

In the Berlin region, this phenomenon appears mainly along the upper reaches of the Havel River (Henningsdorf, Heiligensee and Spandau) up to the area where the Spree River flows into the Havel River and in the area of the Spandau forest. Huge mud and peaty deposits are found everywhere in these areas. A surprising finding is that very high phosphate contents were measured in some places of the outlying area of Tegelort (on the eastern bank of Havel or of Tegel lake), for which no organogenic sediments were recorded in the General Geological Map 1 : 100,000(LGRB & SenStadt 1995).

High phosphate contents were identified also in the catchment area of the Johannisthal waterworks; here again, thick Holozenic deposits exist. The high phosphate contents measured in the area north of Müggelsee lake, in contrast, are attributable to pollution caused by the Münchehofe sewage treatment plant. Increased phosphate concentrations were also measured in the entire Berlin catchment area of the Dahme River.

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