Experimental and computational identification of essential parameters governing biocide distribution in soil

Biocides conventionally contained in building materials can leach out and penetrate the environment. Simulating the concentration and persistence of substances in environmental habitats is an effective approach to risk assessment. While the modeling has been effectively applied for risk assessments of pesticide input into the soil environment, the release of biocides from facades notably differs from those in agricultural use. The aim of this study was to assess the applicability of adapted simulation approaches to approval procedures. Herein, a preliminary PELMO-generated simulation was compared against an experimental setup to identify the key parameters and optimization thereof of biocide soil distribution. The 5-day soil column experiment was performed to address the higher application dilutions of biocides. Based on the adapted parameters in the preliminary findings a 90-day experimental study was compared against the corresponding simulation. Experimentally, the presence of hydrophobic and slowly degradable biocides in soil layers up to 25 cm was observed, which was in contrast to maximum of 5 to 7.5 cm of soil layer depth identified via the PELMO simulation. Furthermore, weather events, such as dry periods or heavy rain events, were shown to influence the biocide distribution, which is a parameter excluded from the simulation. The main finding herein was that adjustment of the dispersion length standalone is not sufficient to approximate the biocide application scenario. The adjustment of the adsorption parameter should be adapted in the simulation, accompanied by the water-substance application. Finally, these adaptions should be evaluated against a field study since a laboratory set-up does not represent all aspects of natural weathering events.