| Project objectives:
The overall aim of the GRACOS-project was to deliver groundwater risk assessment guidelines for soil-contaminations with organic and inorganic compounds.
The procedures to be developed take the form of a scenario approach, as it is intended to be generally applicable to different situations in terms of classes/combination
of pollutants and site-specific conditions, such as climatic conditions, permeability and distance between contamination and groundwater table. Such
a scenario approach will allow the determination a priori whether, under given site conditions (subsurface permeability, distance to groundwater table,
type of material) and contaminant properties (volatile / non-volatile / water soluble etc.), a minor, medium or high risk of groundwater pollution exists.
The validation of these new risk assessment procedures were done 1) in a well controlled field experiment which comprises an emplaced source of a hydrocarbon
mixture consisting of volatile to semi-volatile, (partly) biodegradable compounds, 2) laboratory and field investigations for the quantification of contaminant
transfer rates across the capillary fringe for specific scenarios and 3) column leaching tests for the quantification of the mobile contaminant fraction
in various contaminated soils and waste materials (e.g. slag, bottom ash, construction/recycling materials). To cover as many different site-specific-scenarios
as possible, the project involves numerical modeling for vapor phase contaminant transport in the unsaturated zone and long-term leaching of contaminants
from specific materials.
Contaminated land in Europe poses a serious problem with respect to soil quality and the risk of spreading of pollutants into other compartments of the environment.
The major concern at most contaminated sites is the risk of groundwater pollution by organic and inorganic compounds. Since, the remediation of all the contaminated
sites in Europe is economically not feasible, groundwater risk assessment procedures are needed for the the ranking of sites, decision making on further use
and remedial actions. In contrast to existing procedures this proposal concentrates on the development of methodologies for the assessment of the mobile
contaminant fraction in contaminated soil and waste material (i.e. the contaminant fraction which would reach the acquifer). It will allow the determination
of the long-term contaminant release rates and the overall emission of pollutants into the groundwater at contaminated sites.
| Achieved Objectives:
Column leaching tests for the quantification of the mobile contaminant fraction in various contaminated soils and waste materials (e.g. slag, bottom ash,
construction/recycling materials) were performed.
A field experiment was conducted in Denmark to monitor all processes, which are relevant for groundwater risk assessment of volatile hydrocarbons such
as vaporisation, transport, diffusion, sorption/desorption, and biodegradation.
The biodegradation of volatile organic compounds and the microbial communities in the unsaturated zone during natural attenuation of petroleum hydrocarbon
vapors were assessed.
In terms of modelling of both, vadose and saturated zone, relevant model systems were selected and successfully applied to the complex processes of transport
of contaminants at different scales in the capillary fringe and in the water saturated zone.
| Product Descriptions:
A major risk at most contaminated sites is that of groundwater pollution by organic and inorganic compounds. Since complete restoration of all these contaminated
sites is economically and often technically not feasible, advanced procedures of groundwater risk assessment are needed as innovative tool for the ranking
of sites, decision making on further use, and remediation standards.
- A Guideline for Groundwater Risk Assessment at Contaminated Sites is available (Generic).
- A Newsletter with results of the 1st International Workshop on Groundwater Risk Assessment at Contaminated Sites is existent.
- Modelling results of the performed field experiment at the Værløse field site are available on the website.