Nitrate (NO₃⁻; aliases: NO3−, NO₃⁻) appears in this corpus in two roles. At the sso well grid it is a component of contaminated groundwater. In proposed ENIGMA wet-lab experiments it is a named compound to be tested 1,2.
Contamination Plume at the SSO
The SSO sits downhill and southwest of a contamination source at Oak Ridge Reservation Area 3 (see oak-ridge-field-research-center). The report describes this source as delivering high-nitrate, low-pH water containing heavy metals: uranium, chromium and nickel. The report says the plume enters the grid near U3 (upper-east) and flows diagonally toward L7 (lower-west), forming the “Column 3 corridor” identified in NB02 1.
The report proposes the central well M5 as a mixing zone where plume nitrate meets background organic carbon. This proposal rests on a denitrification-associated peak of rhodanobacter at 7.7% in that well. The proposal is an inference from community composition and has not been validated geochemically. The report states it can be validated once SSO geochemistry data is loaded into CORAL 1.
The nitrate gradient is a testable prediction, not a measured result. According to the report, NO₃⁻ concentration, pH and metal levels should show a NE→SW gradient, with the highest contamination at U3/M6 and the lowest at M4/U1. This has not been confirmed, because SSO geochemistry was not yet loaded into CORAL 1.
Proposed Growth Experiments
Nitrate is one of the named compounds in the 50-experiment list proposed in NB10, which also includes fumaric acid and melibionic acid. These compounds are crossed with the genera prescottella and microbacterium. The list is the project’s deliverable. Wet-lab execution is described as an ENIGMA experimental decision rather than an analytical one, so no growth outcomes on nitrate are reported 2.
Open Directions
- Load SSO NO₃⁻, pH and metal measurements into CORAL to test the predicted NE→SW gradient, which is expected to be highest at U3/M6 and lowest at M4/U1. The same data could check whether M5 is a nitrate–organic-carbon mixing zone, as the Rhodanobacter peak of 7.7% suggests 1.
- Execute the nitrate arms of the 50-experiment Prescottella/Microbacterium list to obtain measured phenotypes for the proposed conditions 2.