Molecular Signature of Organic Nitrogen in Septic-Impacted Groundwater

Abstract:

Dissolved organic nitrogen (DON) is altered by anthropogenic inputs and land use changes. The impacts of alterations of the DON pool would be more clearly constrained if specific sources were identified and if the molecular-level composition of DON were better understood. The pharmaceutical carbamazepine was used to identify septic-impacted groundwater in a coastal watershed. Using ultrahigh resolution mass spectrometry data, the nitrogen-containing features of the dissolved organic matter in septic-impacted and non-impacted samples were compared. A larger abundance of nitrogen-containing formulas were present in the septic-impacted groundwater sample. Impacted samples have additional DON features in the regions ascribed as ‘protein-like’ and ‘lipid-like’ in van Krevelen space and have more intense nitrogen-containing features in a specific region of a carbon versus mass plot. These features are potential indicators of dissolved organic nitrogen arising from septic effluents. Ultrahigh resolution mass spectrometry is a potentially valuable tool to identify and characterize sources of DON.