**2. Physico-chemical properties of triazines**

Chemically, triazine herbicides are comprised of asymmetrical triazines (triazinones, triazidinones) and symmetrical or 1,3,5-triazines (*s*-triazines): chlorotriazines, methoxytriazines, methylthiotriazines. Structures of the more important triazines and their transformation products (TPs) are shown in Fig. 1.

Physico-chemical properties of compounds relevant for their behaviour in the environment are their polarity (expressed as *n*-octanol-water partitioning coefficient *K*ow), linked to water solubility, moreover their acido-basic properties (expressed as dissociation constant *K*a) and volatility (usually expressed as vapour pressure). These are listed in Table 1 for the more environmentally important triazines.
