Synthesis of Galactic deuterium in hot accretion disks

The abundance of D is calculated using a model for the chemical evolution of the Galaxy. The equations for calculating the mass of the gas and the abundance of the element are presented. The time dependences of the relative D abundance and the mass of gas in the Galaxy are analyzed. It is noted that if the sources of D were shut off at an epoch of 5 x 10 to the 9th years, as heavy elements proceed to enrich the interstellar medium diminishing the proportion of massive stars, then there should be no drop in the D isotope abundance; however, a drop in the D isotope abundance is detected.