Dr. Dinesh Adhikari1,2, Dr. Nancy Hess3, Malak Tfaily3,4, Ravi Kukkadapu3, Qian Zhao3, Rosey Chu3, Trent Graham3, Dr Yu Yang1
1University Of Nevada, Reno, Reno, United States, 2Lawrence Livermore National Lab, Livermore, United States, 3Pacific Northwest National Laboratory, Richland, United States, 4University of Arizona, Tucson, United States
Association with minerals, especially poorly crystalline iron (Fe) minerals, plays an important role in the persistence of dissolved organic carbon (DOC). Chemical fraction can occur for DOC upon its association with Fe minerals, however, scant information is available for the fractionation of DOC during co-precipitation with Fe-minerals. Herein, applying Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS), we investigated the fractionation of DOC during co-precipitation with ferrihydrite (Fh) in systems with C/Fe molar ratio of 0.5 and 3. Our results showed that high-molecular-weight DOC was preferentially precipitated for system with C/Fe of 3. In addition, a higher fraction of condensed polycyclic aromatic hydrocarbons (98.12%) was co-precipiated compared to unsaturated phenolic (66.25%) and aliphatic (39.01%) DOC. Our findings demonstrated that high-molecular-weight aromatic compounds preferentially co-precipitate with Fh in systems with feed C/F ratio relevant to the natural systems. Results from this study provided valuable information regarding the importance of DOC composition in its association with Fe-minerals and stability in the natural environment.
Yang is an expert in Fe-oxide and OM dynamics and has applied extensive tool sets for molecular-scale analytical determination of soil and solution OM and Fe-oxide chemistry, including application of X-ray absorption spectroscopy, Mössbauer spectroscopy, and state-of-the-art mass spectroscopy (MS) such as Fourier-transform ion cyclotron resonance MS (FT-ICR-MS).