In 2009, ARCHE developed a user-friendly calculator to facilitate the practical application of bioavailability normalization for use in the field of different soil policies such as the European Soil Framework Directive (COM(2006) 232). This bioavailability tool is based on the corrections for leaching and ageing and for variation in physico-chemical soil properties and estimates of risks associated with the presence of Ni in a particular terrestrial environment, based on a limited set of routinely screened input parameters. It can be downloaded from http://www.arche-consulting.be/Metal-CSA-toolbox/soil-pnec-calculator.
The tool is an Excel-based tool consisting of three main pages, i.e., introductory, input, and output (results). The introductory page gives the user information on how to use the tool, on which input parameters are needed to run the bioavailability tool, and on which output (results) are generated by the model. The tool calculates PNEC values for: i) a generic scenario; ii) a standard soil type (eco-regions); or iii) site-specific properties, depending on the level of information available. The site specific information required to run the tool is listed below.
- eCEC, as cmolc/kgdw11
- organic matter (OM) content, as %
- clay content, as %
- total Ni concentration as mg/kgdw
- Ni background concentration as mg/kgdw13
An example of the application of the soil bioavailability tool for Ni is presented in Figures 8 and 9. In this example, the total Ni soil concentration is 45 mg/kgdw, the Ni background concentration 22.0 mg/kgdw, the pH 5.1, the OM 3.2, and the clay content 35%. The pH, %OM, and %clay are used to calculate the eCEC, i.e., 22.1 cmolc/kgdw (Figure 8).
Entering the required input parameters for the soil bioavailability tool resulted in the calculation of the PNECnormalized, aged, added value (as mg/kgdw), the PNECnormalized, aged, total value (as mg/kgdw), the PECadded value (as mg/kgdw), the PECtotal value (as mg/kgdw), and the RCR (risk characterization ratio) (Figure 9).
11. If no value for eCEC is inserted, it will be predicted from pH, %OM, and % clay.
12. Data for pH, organic matter content, and clay content are not strictly required for the calculation of a site-specific PNEC for Ni if data for the eCEC of the soil are available.
13. Only required for calculation of added risks. If no Ni background concentration is inserted, a default value will be predicted from the soil type information.