In the present day Earth, there is only one mechanism of supplying NEW components to the atmosphere and that is volcanic degassing . Over time, we expect H 2 to escape into the atmosphere leaving H 2 O as the dominant H compound. A gas also released by degassing that we have not explicitly discussed is HCl. During volcanic degassing, most Cl partition into the volatile phase as HCl.
Earliest organisms are prokaryotes that heterotrophically survived by fermenting early biomolecules.
At some point the consumption of abiotically produced organic and the changes in the environment will favor the autotrophs which can produce their own food. It is the predominance of the latter that eventually produced a more oxygenating atmosphere. Oldest one known are 3.5 by old in Warroona, Australia. Middle and late proterozoic carbonaceous compressions of probable algal affinity. The basic idea is that in contrast to podsols or laterites, etc., the Fe profile shows depletion of Fe throughout the entire soil horizon.