The molecular composition of humic acids, as reflected by FTICR-MS, varies systematically in terms of the total C storage of the corresponding soils

Long-term stabilization of soil organic matter (SOM) as recalcitrant forms plays an important role in the Earth's carbon cycle. Hence, understanding biogeochemical mechanisms of soil C sequestration is crucial to control its emission to atmosphere. In this research the composition of humic acid (HA) is analyzed by Electrospray Ionization (ESI) Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FTICR-MS). Using Partial Least Squares (PLS) regression, a forecasting model for total soil C is obtained from the common compounds and its importance in the prediction is plotted in the space defined by their atomic ratios.