Bestimmung von Redoxzonen in einem mineral?lbelasteten Grundwasserleiter

摘要

Goal and Scope The goal of this study is the investigation and the grafic presentation of the characteristic redox zonation in a mineral oil contaminated aquifer which will be formed in the plume downstream of the contamination source. Methanogenic conditions, sulfate-reduction, Fe(III)-reduction, Mn(IV)-reduction, nitrate-reduction, aerobic conditions. By that indications type and degree of microbial degradation which is the most important part in Natural Attenuation (NA) processes can be obtained easily. Methods Changes of the groundwater parameters Eh, O2, NO 3 ? , SO4 2?, Fe2+, Mn2+, HCO3 ?, Ca2+ will be measured upstream, downstream and also in the centre of the plume. The results will be presented in a sequence of special diagrams. Results and Conclusion When microbial degradation of hydrocarbons takes place, a microbial community will always use that electron acceptor from which it will gain a maximum of energy by the corresponding redox-reactions. This means as long as oxygen is available this will be used. After its depletion nitrate serves as electron acceptor leading via nitrite to the formation of nitrogen or ammonia. Manganese (IV) and Iron (III) species which are rather insoluble are mainly available from the soil-phase, can act as electron acceptor as next, leading to soluble Manganese (II) and Iron (II) compounds in groundwater. Finally before methanogenic conditions occur sulphate will become a suitable electron acceptor leading to the formation of hydrogen sulphide. All these processes of mineralization of the hydrocarbons will lead to the production of CO2 and as consequence to an increase of HCO3 ? in groundwater changing the calcareous/carbonic acid-equilibrium. By that more soluble Ca(HCO3)2 is formed from insoluble CaCO3, so the concentration from Ca2+ will also inerease. Thus, by the action of microorganisms, a typical redox-zonation and changes of other parameters will occur. Recommendations and Perspective To follow the changes in time and space of some characteristic groundwater parameters is a simple way to estimate the potential of microbial degradation in a contaminated aquifer considering Natural Attenuation (NA)-processes.