Conceptual approach to estimating the effect of home-range size on the exposure of organisms to spatially variable soil contamination

Spatial variability of soil properties leads to uncertainties in the ecotoxicological risk assessment of polluted soil in situ. Mobility of organisms causes that they are not exposed chronically to pollutants in soil, which is in contrast with laboratory experiments. Moreover, only a fraction of the total amount of contaminants is available for organisms. Developing a conceptual model, we identify the information that is required for an ecotoxicologically based risk assessment. Field data of Cd-polluted soil are used in a Monte Carlo simulation for the illustration of the concept. The data are analysed geostatistically and predictions at unsampled locations are made using Ordinary Block Kriging. The accumulation of the pollutant in fictitious organisms is estimated with the one-compartment toxicokinetic model. Both the home-range size of the organism and the spatial pattern of cadmium content affect the extent of the area where exposure to the pollution leads to exceeding of a specific Cd concentration in the organisms. On average, larger home-range sizes lead to lower Cd concentrations in organisms. However, larger home-range sizes lead to an increase of the probability that a specific exposure level is exceeded. Research in uptake-and assimilation coefficients, excretion activities, and the behaviour of organisms in a polluted area is needed.