Evaluation of the risk for soil organisms under real conditions

Abstract

In assessing the effects of plant protection products (PPP) on organisms in soil it is crucial to predict accurately the environmental concentration (PECsoil) which organisms are exposed to. The PECsoil is depending on the spatial and temporal distribution of the PPP, arising from characteristics of the chemical (e.g. Kow, water solubility, degradability) and from soil parameters (e.g. pH value, TOC, texture). The potential effects of PPP on soil organisms depend -besides the concentration of the chemical in the soil matrix- on the spatial and temporal distribution of the animals, i.e., their exposure as well as their specific sensitivity to the chemical. A new approach for deriving environmental concentrations in soil is currently under discussion, taking the preferred soil depth of the organisms into account. We conducted two different outdoor studies in Terrestrial Model Ecosystems (TMEs) to monitor (1) the movement of pesticides in soil over time and (2) the exposure and effects on soil organisms during the same time. Additionally, an indoor TME study was conducted to measure the fate of the radiolabelled pesticides and the formation of non-extractable resi-dues in soil. In study [1] (outdoor) and [2] (indoor) Lindane (log Kow > 3) and Imidacloprid (log Kow < 1) were applied, two pesticides with different physico-chemical properties. In study [3] (outdoor), we investigated the effects of Carbendazim, a pesticide which is known as to be toxic for earthworms at certain concentrations. The effect analysis was conducted by means of different multivariate and univariate statistical methods. The synergistic conclusions based on the project results are proposed as recommendations for risk assessment concerning exposure and risk of soil organisms exposed to PPP under realistic conditions. Quelle: Forschungsbericht

Plant protection products (PPP) can only be authorized if they have no unacceptable effects on the environment. Aim of the project was to investigate whether the ecology and behavior of soil organisms should be considered in PPP risk assessment. The possible spatial and temporal relationship between the preferred soil layer, the distribution of PPP and the ecotoxicological effects were studied in Terrestrial Model Ecosystems (TME). The results indicate that also soil organism living deeper in soils are affected by the concentrations detected in the uppermost soil centimeters. The implications for the development of terrestrial risk assessment guidance are discussed in the report.