Integrating Bioavailability in Risk Assessment of Contaminated Soils: opportunities and feasibilities
1-10-2011 – 30-9-2014


Parties involved:


It is well established that total concentrations of soil contaminants are useful to indicate pollution, however they do not necessarily indicate risk. Alternative measures are used to denote the availability and risk, the so-called bioavailability of soil contaminants. A myriad of soil testing methods have been developed to predict uptake, toxicity and degradation potential of soil contaminants. Some generic soil limits already account for bioavailability of metals, for example by making limits dependent on soil properties (pH, CEC: limits in Flanders). However, despite many years of intensive research, there is no generally accepted methodology to incorporate contaminant bioavailability in risk assessment models, likely because too little attention has been given to the practical aspects, i.e. sufficient calibration and validation, and sufficiently accounting the cost-benefit analysis. This project addresses these issues, with focus on soil remediation as well as wide area management of soils affected by proximal atmospheric deposition.

The overall aim of IBRACS is to provide policymakers, other authorities and service providers with guidelines on how bioavailability tests and results of bioavailability-based risk assessment models can be used for risk-based management decisions on contaminated land.

Experimental calibration/validation exercises will be on soil-plant transfer and ecotoxicity of contaminants. Focus will be on selected contaminants for which either soil-plant transfer (Cd, PAH-H) or ecotoxicity (Cu, Zn, Pb, PAH-L) normally are decisive for their over-all risk assessment. The soil-plant transfer is the first critical step in the soil-plant-human exposure pathway.

The specific objectives are:
1)     To review existing risk assessment models for soils with focus on bioavailablity, including proposed test methods (Cd, Cu, Zn, Pb and PAHs).
2)     To evaluate the ability of so-called passive samplers and established soil extracts to predict toxic responses of plants to exposures of metals (Cu, Pb, Zn) and organic contaminants like PAH. This evaluation will be based on field contaminated soils sampled across the three countries involved. Recommendations will be reported in a handbook.
3)     To propose appropriate plant uptake models and soil tests for Cd and PAH and to incorporate them into risk assessment models.
4)     To make a cost-benefit analysis of including bioavailability tests in site specific risk assessment. This analysis will be based on 5-7 contaminated sites in Sweden, Belgium and France and involve both stakeholders and end-users (Cd, Cu, Zn, Pb and PAHs).
5)     To develop a guidance paper on how to use the results of the tests applied in the project in risk assessments (Cd, Cu, Zn, Pb and PAHs).

The proposed project fits well within the SNOWMAN Call 3 research topic “Contamination”, where integration of pollutant bioavailability in risk assessment models is being stressed and a comparison of European risk assessment models and their validation is addressed. If bioavailability is accounted for, in a proper way, the accuracy of the risk assessments will be improved, promoting right decisions about amounts of contaminated masses to be treated and priority-order of contaminated sites to be remediated. Not taking bioavailability into account may result in excessive remediation actions and, in worst case, a net negative impact on the environment. The project also addresses the question of area-wide approach for soils affected by diffuse soil contamination in the so-called proximity atmospheric pollution zones. In these soils, that can not be removed, bioavailability based risk assessment models have the potential to provide decision makers with appropriate data for making sustainable decisions about the risk-based land management of these zones.

Research coordinator IBRACS: Professor Dan Berggren Kleja, SGI, Sweden

 Project Deliverables