The air has a strong salty-metallic taste to it, probably because of the aluminum and barium salts that they contain.
I've been watching the skies for 30 years and I know that contrails are very rare. You're very lucky to see one per month. Normally less. Contrails dissipate in 2 to 4 seconds and are rounded and faded at the trailing edge. They leave no residue at all and are faint at best.
These are clearly not contrails.
Chemtrails have been tested and shown to contain mercury, aluminum, barium, lead, arsenic, mycoplasma, and mold spores.