Oecd Guideline for the Testing of Chemicals

INTRODUCTION 1. This Guideline is based on the proposal submitted by the European Commission in 1993 and takes into account the comments on that proposal submitted by the Member countries. Several activities undertaken in the European Union bore on the development of an adsorption test. These included an extensive investigation due to the The Workshop agreed on the main elements of the updated Test Guideline 106 for an adsorption/desorption test and, in particular, on the characterisation and selection of the soil types for use in the test. 2. Other guidelines concerning adsorption/desorption exist only at national level and are mainly focused on pesticides testing (5)(6)(7)(8)(9)(10)(11). These documents as well as an extensive relevant literature were considered when developing this Guideline. SIGNIFICANCE AND USE 3. Adsorption/desorption studies are useful for generating essential information on the mobility of chemicals and their distribution in the soil, water and air compartments of our biosphere They can be used in the prediction or estimation, for example, of the availability of a chemical for degradation (22)(23), transformation and uptake by organisms (24); leaching and runoff from land surfaces into natural waters (18)(31)(32). Adsorption data can also be used for comparative and modelling purposes (19)(33)(34)(35). 4. The distribution of a chemical between soil and aqueous phases is a complex process depending on and climatic factors such as rainfall, temperature, sunlight and wind. Thus, the numerous phenomena and mechanisms involved in the process of adsorption of a chemical by soil cannot be completely defined by a simplified laboratory model such as the present Guideline. However, even if this attempt cannot cover all the environmentally possible cases, it provides valuable information on the environmental relevance of the adsorption of a chemical. SCOPE 5. This Guideline is aimed at estimating the adsorption/desorption behaviour of a substance on soils. The goal is to obtain a sorption value which can be used to predict partitioning under a variety of environmental conditions; to this end, equilibrium adsorption coefficients for a chemical on various soils are determined as a function of soil characteristics (e.g. organic carbon content, clay content, soil texture, and 106 OECD/OCDE 2/45 pH). Different soil types have to be used in order to cover as widely as possible the interactions of a given substance with naturally occurring soils. 6. In this Guideline, adsorption represents the process of the binding of a chemical to surfaces of soils; it does not distinguish between …