Mineral-organic associations (MOAs) are important mechanisms for the protection of soil organic matter (SOM) from decomposition. The contribution of MOAs to the persistence of organic matter depends on soil's mineralogy and chemical attributes. In this project we will take a Ca-rich embryonic Technosol with high soil organic carbon (SOC) content (SOC > 8%), developed from limestone waste (shales and siltstones) as a model for understanding the dynamics of soil organic matter focused on mineral-organic associations (MOAs) during the first years of soil formation. As the steady state for SOM, we will consider a Ca-rich natural mature soil (Rhodic Lixisol) adjacent to the Technosol, developed from the same parent material (shales and siltstones). We hypothesize that the high amount of Ca in the Technosol is responsible for forming organo-mineral complexes, favoring the accumulation of SOC. We also hypothesize that the effect of Ca on organic matter stability is more important in the early stage of pedogenesis (i.e., in an embryonic soil containing 2:1 phyllosilicates) than in the kaolinitic/oxidic mature soil, where Fe oxides should account for most of the SOC in the organo-mineral complex. For this purpose, we will use single and sequential chemical extractions combined with Rock-Eval thermal analysis to evaluate SOM stability in different MOAs, and 13C CPMAS NMR and FTIR spectrometry to characterize SOM. This work will help to elucidate the mechanisms behind SOC stabilization in both embryonic and mature Ca-rich soils. Also, we expect that our study will highlight the role of constructed Technosols as strategies for increasing carbon sequestration.
News published in Agência FAPESP Newsletter about the scholarship: