VOLAMOD

VOLAMOD – Field experiments in artificial streams to develop and evaluate a model approach for volatilization of hydrocarbons and other organic pollutants from natural rivers

In the past, hydrocarbon spills have occasionally been observed in rivers. The quality of drinking water taken directly from these rivers can be significantly affected, if hydrocarbons originating from spills upstream of the water supply station enter the drinking water facility. To enable establishment of appropriate countermeasures such as water treatment or stoppage of water extraction from the river, it is necessary to get information on actual concentrations of possible contaminants in the river. For this purpose, simulation models can be used that estimate temporally and spatially resolved concentrations based on emission data as well as environmental parameters and substance properties.

The fate of organic pollutants in natural streams and rivers is determined by loss processes such as photo-oxidation and microbial degradation as well as transfer to sediments and volatilization to the atmosphere. The latter loss process is dominant for volatile hydrocarbons such as MTBE or Ethylbenzene. Hydraulics (flow velocity, stream bed roughness, dispersion, transient water storage), chemical substance characteristics (Henry’s law constant, water solubility), and environmental parameters (air and water temperature, wind velocity) are possibly affecting volatilization from surface waters. To predict the actual mass flux from water bodies to the atmosphere, the quantitative influence of these parameters on volatilization is investigated in this project. Volamod aims to develop and evaluate a mathematical model describing volatilization from surface waters in dependence on the above-mentioned parameters. The model will rely on empirical and analytical model approaches for gas exchange of volatile pollutants between surface waters and the atmosphere, e.g. the two-film model and the surface renewal model.

Therefore, experiments with appropriate chemical tracers and reference compounds are conducted to measure volatilization in artificial channels and ponds at the artificial stream and pond system (FSA) of the German Federal Environment Agency (UBA) in Berlin-Marienfelde. The experimental design includes variations of single parameters with several replicates for each variation in order to determine the sensitivity of the parameters on the observed volatilization. Pond experiments with dissolved compounds allow for a separate evaluation of still water and wind effects.

Stoppage of tracer experiments at the UBA in Berlin-Marienfelde because of snow and ice (Foto by Stefan Heller, UBA)

VOLAMOD is funded by the Kompetenzzentrum Wasser Berlin and the VÉOLIA AG, and conducted in close cooperation with the German Federal Environment Agency (UBA) in Berlin.

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