PNNL

Abstract

Soil microbes are responsible for contributing to the main components of the soil organic matter (SOM). Their micro- and nano-scale organo-mineral associations with soil minerals are the sites where complex processes including aggregate formation, microbial mineral weathering, and soil organic matter stabilization all occur in a narrow zone of biogeochemical gradients. This study aimed at identifying the mechanisms underlying soil organic matter stabilization in clay minerals, by characterizing organic matter (OM) association with mineral surfaces with high resolution multiscale visualization by chemical imaging and EDS mapping, to understand the mechanisms of OM formation and stabilization. Multiscale and high resolution TEM imaging and chemical imaging by high resolution EDS revealed very low concentrations of dissolved cations and a variety of newly formed nanominerals specifically associated with microbial surfaces and microbial EPS. It provided a new perspective on newly formed minerals as a physico- chemical way of SOM stabilization in clay minerals. This contributed to our understanding of the role of microbes in soil organic matter persistence in ecosystems, and it supported hypotheses in literature that were lacking the direct imaging of these processes.