How to model...

How to choose the appropriate soil type?


When defining the appropriate soil profile in S-Risk, it is important that the soil layer types you add on the Soil tab have soil properties that are as close as possible to the ones of the soil profile at your site. As a first, pragmatic approach, you can choose the soil types that provide you the best match regarding organic matter and clay content (these properties are visible in Tier 1).

Why do RI (or ExCR) and CI results differ for volatile substances?


For volatile chemicals, there are a number of conditions which can result in a RI (or ExCR) which is more stringent than CIindoor air. Situations were CI is more stringent than RI (or ExCR) are explained in a separate FAQ.

Why do mercury, copper, nickel, zinc and lead simulations sometimes give counterintuitive results?


For mercury compounds, copper, nickel and zinc, S-Risk adopts non-standard model equations for most plant uptake factors (the so-called BCFs or bioconcentration factors). For mercury compounds, copper and nickel, these BCF models include a discontinuity (jump) at a soil concentration equalling four times the background concentration of the chemical (official background concentrations in 2007; values can be found in the substance data sheets). For zinc, the BCF models include two jumps, namely at a soil concentration of 60 and 360 mg/kg dm.

How to deal with a contamination that is only partially situated below a building?


Rule n°1: Always check the rules applicable to your region in order to see for which scenarios you can use this outlined approach, and for which not.

How to account for background exposure when using measured concentrations in air, food/feed or drinking water?

S-Risk FL/BRX takes into account background exposure in the risk characterization for threshold effects. For these effects, the risk is calculated using a TDI approach (see the Risk tab). Background exposures via food and drinking water are added to local oral exposure; background exposure via inhalation is added to local inhalation exposure. If you have measured concentrations, you should account for model background concentrations before entering values in S-Risk, in the following way:

How does switching land use affect the parameter values?


Within a simulation, it is possible to change the land use type of your scenario by selecting another land use on the Scenario tab.

When you do this, you have to keep in mind that the following parameter values will be reset to the corresponding land use defaults:

How does S-Risk deal with concentrations exceeding solubility?


S-Risk deals with concentrations exceeding solubility in different ways, depending whether it relates to a soil or groundwater contamination.

It should be noted that in case of very high concentrations, approaching solubility, attention should be paid to the presence of non-aqueous phase liquids. You should consult applicable guidance documents in your region on how to deal with non-aqueous phase liquids in site assessment.

Which parameters do I have to provide when adding a new chemical?


You can add a new chemical by selecting and adding "(Blank chemical)" from the drop-down menu on the Chemical tab. Afterwards, under Tier 2, you have to fill in various chemical related parameters on the following tabs:

Why can’t I customize the properties for copper, nickel, mercury, zinc or lead?


The metals copper, nickel, zinc, lead and the mercury compounds follow non-standard models for the calculation of Kd factors, pollutant uptake in plants and/or transfer to animal food products. These model exceptions were decided upon during the development of the Flemish soil remediation values, independent from the S-Risk development, and can be found in the substance data sheets (FL/BRX - WAL).

How to simulate the presence of a paved surface?


In case the soil on the site under study is paved, you can simulate the presence of a pavement (asphalt, concrete) by creating a top soil layer  on the Soil tab (the soil type of this layer does not matter), with a thickness corresponding to the real thickness of the pavement. The properties of that top layer should be modified as follows:


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