Model experiments on nitrite and nitrate in simulated primeval conditions

Abstract

In experiments on the prebiotic formation of nitric oxides, anoxic mixtures of N₂ and water vapour were sparked in contact with phosphate buffer solutions at various pH values. Nitrite was found in the aqueous phase, and nitrate grew from it, presumably by reaction with H₂O₂. In acid solutions, these anions were reduced and destroyed by Fe²⁺, and the same was true of nitrite in solutions kept at a pH value similar to that of the contemporary ocean (8.2) with HEPES buffer. Nitrate was not destroyed in short-term experiments, but as in sparking nitrate is formed only via nitrite, neither anion could accumulate. In further sparking experiments with alkaline sulphide, both nitrite and nitrate were reduced entirely. It is concluded that it is unlikely that the primeval ocean contained appreciable concentrations of nitrite or nitrate either at the reducing or at the redox-neutral stage.