Identifying the Molecular Signatures of Organic Matter Leached from Land-Applied Biosolids via 21 T FT-ICR Mass Spectrometry

Intensification of wastewater treatment residual (i.e., biosolid) applications to watersheds can alter the amount and composition of organic matter (OM) mobilized into waterways. To identify novel tracers of biosolids, characterization of biosolids and their impacts on OM composition in recipient ecosystems is required. Here, water-soluble OM was leached from surface soils from Florida pastures with differing levels of biosolid amendment and an adjacent control site. The biosolid endmember was further constrained by extracting water-soluble OM from biosolids sourced from four Florida wastewater treatment facilities. Nontargeted analysis of organic molecules by negative-ion electrospray ionization 21 T Fourier transform ion cyclotron resonance mass spectrometry examined the molecular composition of soil and biosolid leachates and identified molecular formulas unique to these biosolids and biosolid amended soils. Overall, biosolids leachates were enriched in aliphatic (+16.3% relative abundance) and heteroatomic (+42.5% RA) formulas and depleted in aromatic formulas (−33.5% RA) compared to soil leachates. A subset of 297 molecular formulas were present only in biosolids and amended soil leachates (i.e., not present in control soil leachates), the vast majority of which contained nitrogen (66%) or sulfur (27%). The identification of these molecular formulas is a key step in identifying novel tracers of biosolids movement through impacted watersheds.