Quantification of cumulative bioactivity in soil via replacement of oxygen in labelled phosphate

Presuming that a steadfast amount of exchangeable phosphate (PO4), in a given volume of soil, is interspersed with a known amount of dually labelled PO4 [32P]P[18O]O4) and that the ensuming PO4 mixture is allowed time to equilibrate with the PO4 ions in the soil biosphere, we express subsequent cellular replacement of oxygen ([18O]O) in labelled PO4 by natural oxygen as a function, Q In Db, of the steady quantity, Q, of PO4-oxygen and the bioactively incurred dilution factor, Db, pertaining to the 18O enrichment of soil PO4.