Wikipedia is not the last word for accuracy, but here is a good write-up about activated carbon: http://en.wikipedia.org/wiki/Activated_carbon
Briefly, activated carbon can adsorb a wide variety of molecules, depending on how it is processed. But, it adsorbs big molecules much more readily than small ones. Big molecules means organic molecules. Our basic fertilizers, KNO3, KH2PO4, and K2SO4 are not organic molecules, and are very small molecules. So, it is extremely unlikely that they would be removed by AC. Trace mixes usually contain chelators, which are organic molecules, but not especially big ones, so adsorption of the chelators should be minimal. (One Chelator is EDTA, with the formula C10H16N2O8) Ammonia can be adsorbed by AC, but the AC has to have been processed to do so first.