48-year-old Mr Buchan was driving a white Ford Transit tipper van at the time of the collision.
The 26-year-old male driver of a white Mercedes Vito panel van also involved suffered serious injuries.
He is in a stable condition and is being treated at Aberdeen Royal Infirmary.
Sergeant Colin Matheson said: “Our thoughts are with Mr Buchan’s family and friends at this very sad time.
“I am appealing once again to anyone who may have seen either of the vehicles prior to the collision, or who saw the incident itself and who has not yet come forward, to do so as soon as possible.
You can contact Police on 101.”