Determination of the nitrate retention capacity of sediments in laboratory experiments using cores from the Lower Rhine Bight

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Determination of the nitrate retention capacity of sediments in laboratory experiments using cores from the Lower Rhine Bight

Project term: 2015 to 2020

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Project members: Thomas R. Rüde, David Hellmann

Nitrogen is an important chemical element in agriculture. In order to maintain the fertility of the soil, nutrients must be added regularly by the use of fertilizers. These fertilizers contain different chemical compounds like nitrate. The amount of nitrate, which is not absorbed by the crop plants, can be transported into groundwater by seepage water. In the aquifer reductive processes take place, so called denitrification, that are able to reduce the nitrate concentration.

The test series “nitrate retention” deals with the capability for chemolithotrophic denitrification of drill cores from the Lower Rhine Basin. In Summer 2016, drill cores where taken in the periphery of the well installation Amern operated by NEW NiederrheinWasser GmbH. In several depths iron sulphides where found, that can work as an electron donor in the denitrification process. These iron sulphides, namely pyrite, can protect underlying aquifers from nitrate contamination. These Reaction takes place under participation of anaerobic microbes. Thus, an anoxic test setting for the experiment was developed.

During the test series different drill cores from the borehole near Amern are perfused by an artificial groundwater in order to examine the interaction of groundwater and the drill core. Water samples are taken automatically and physico-chemical parameter are monitored continuously. The objective is to estimate the protection of the pyrite bearing rocks for the underlying aquifer and the water extraction for the waterworks Schwalmtal-Amern.