The fraction which includes free cyanide and labile complexes(e.g. those formed with copper, zinc or silver) is extremely toxic and bioavailable [6].
This fraction is called “weak acid dissociable”(WAD) [7] or, more properly, acid dissociable cyanide (ADC), and its determination is more relevant than total cyanide, because stable and inert cyano complexes (e.g. those formed from iron and cobalt)
are not considered.
ADC then indicates the potential risk of con-tamination by acidification or incidence of UV radiation under the water body [6].