Abiotic reaction of nitrite with dissolved organic carbon? Testing the Ferrous Wheel Hypothesis

The Ferrous Wheel Hypothesis (Davidson et al. 2003) postulates the abiotic formation of dissolved organic N (DON) in forest floors, by the fast reaction of NO₂ ⁻ with dissolved organic C (DOC). We investigated the abiotic reaction of NO₂ ⁻ with dissolved organic matter extracted from six different forest floors under oxic conditions. Solutions differed in DOC concentrations (15-60 mg L⁻¹), NO₂ ⁻ concentrations (0, 2, 20 mg NO₂ ⁻-N L⁻¹) and DOC/DON ratio (13.4-25.4). Concentrations of added NO₂ ⁻ never decreased within 60 min, therefore, no DON formation from added NO₂ ⁻ took place in any of the samples. Our results suggest that the reaction of NO₂ ⁻ with natural DOC in forest floors is rather unlikely.