Investigation of hydrogeologic processes in a dipping layer structure: 2. Transport and biodegradation of organics.

Numerical simulation tools have been used to study the dominating processes during transport of aromatic hydrocarbons in the unsaturated soil zone. Simulations were based on field observations at an experimental site located on a glacial delta plain with pronounced layered sedimentary structures. A numerical model for transport in the unsaturated zone, SWMS-3D, has been extended to incorporate coupled multispecies transport, microbial degradation following Monod kinetics and gas diffusive transport of oxygen and hydrocarbons.

Investigation of hydrogeologic processes in a dipping layer structure: 1. The flow barrier effect.

Numerical simulations of a field experiment were performed in order to study the processes contributing to lateral diversion of water flow in the unsaturated zone. The experimental site is a glacial delta with dipping layers of alternating finer and coarser sand. Model soil physical parameters for each of the stratigraphic layers were estimated from soil grain size distributions.

Transport and degradation of toluene and o-xylene in an unsaturated soil with dipping sedimentary layers.

A lysimeter trench was established at the Gardermoen delta (50 km north of Oslo, Norway) to study the flow of water and transport and degradation of aromatic jet fuel components (toluene and o-xylene) in the undisturbed unsaturated zone. Site investigations with ground-penetrating radar revealed the presence of dipping sedimentary layers within the foreset unit. This study has shown that the foreset bed of the Gardermoen delta structure provided a preferential flow path for the transport of the solute plumes, but did not have dramatic effects on the degradation potential under the current conditions.