Considering all available information, it is clear that in some soil phosphonate seems to degrade/dissipate very rapidly while in other soils the compound seems to be more persistent. Obviously there are two processes involved in the dissipation of phosphonate. In the GLP study it was seen that immediately after contact of phosphonate with soil, a chemical (abiotic) reaction takes place which led to low recoveries of 45-85% (contact time: one hour). As it was demonstrated that no degradation occurred during application and that the analytical method is valid, the study director concluded that this instantaneous decrease is probably due to physico-chemical interactions of the phosphonate with the soil components. Phosphonate has two pKa values (i.e. of 2.0 and 6.6) and two types of salts can be formed, i.e. M(I)H(HPO3) and (M2(I)(HPO3). Among these salts, there are many others insoluble salts. Furthermore, phosphoric acid has a high reduction potential and is easily transformed to phosphorus acid. In addition, a good correlation between the extractability at time 0 and the cation exchange capacity of the soils was seen in the GLP study indicating that the ionic properties of phosphonate lead to a strong and rapid reaction with the soil components. The second process involved in the dissipation of phosphonate is the biotic degradation of the available (mobile) portion of phosphonate. This process was found to be slow.