Soil porous microstructure control over soil organic matter mobility: A multimethod workflow for understanding chemistry-dependent organic matter binding in soil

Authors: VARGA, TAMAS - Pacific Northwest National Laboratory; WIETSMA, THOMAS - Pacific Northwest National Laboratory; DIDONATO, NICOLE - Pacific Northwest National Laboratory; DUCKWORTH, SUMMER - Pacific Northwest National Laboratory; ZHAO, QIAN - Pacific Northwest National Laboratory; SCONZO, NICK - Pacific Northwest National Laboratory; BATTU, ANIL - Pacific Northwest National Laboratory; ZHENG, JIANQIU - Pacific Northwest National Laboratory; HE, XIAOLIANG - National Biological Control Reference Center; Rippner, Devin; QAFOKU, ODETA - Pacific Northwest National Laboratory; ROCKHOLD, MARK - Pacific Northwest National Laboratory; QAFOKU, NIKOLLA - Pacific Northwest National Laboratory

Submitted to: Environmental Technology & Innovation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2025
Publication Date: 11/3/2025
Citation: Varga, T., Wietsma, T.W., Didonato, N., Duckworth, S.C., Zhao, Q., Sconzo, N.A., Battu, A.K., Zheng, J., He, X., Rippner, D.A., Qafoku, O., Rockhold, M.L., Qafoku, N.P. 2025. Soil porous microstructure control over soil organic matter mobility: A multimethod workflow for understanding chemistry-dependent organic matter binding in soil. Environmental Technology & Innovation. 40. Article 104609. https://doi.org/10.1016/j.eti.2025.104609.
DOI: https://doi.org/10.1016/j.eti.2025.104609

Interpretive Summary: Soil organic matter is of interest to growers and policy makers alike because it can improve water and nutrient supplies while providing storage for atmospheric carbon, which is a triple win for agriculture. Most studies on soil organic matter are from wet climates. In this study, we used advanced instruments to study relationships between land use, soil particle arrangement, and soil organic matter accumulation in soils from dry climates. We found that soils from dry climates can capture large amounts of soil organic carbon when irrigated due to increased plant production. Such findings highlight the importance of irrigation for building soil organic matter for improved soil function and soil carbon storage in dry climates.

Technical Abstract: Soil organic matter (SOM) has attracted a great deal of interest and has been the focus of many recent studies because of the potential for soils to store organic matter and mitigate human derived CO2 emissions. Although recent studies have addressed different aspects of SOM behavior in soils, transport properties of different soil organic matter compounds, which may be directly and/or indirectly related to their stability, are poorly understood, and insufficiently documented. The objectives of the study were to 1) Investigate the advective and diffusive mass transport and desorption behavior of the soil organic matter compounds (compare mass transport of different compounds); 2) Measure the extent and rates of the desorption reactions using experimental data from stop-and continuous-flow experiments; 3) Conduct high-resolution imaging inspections and pre-and post-experimental extractions to provide additional insights on soil microporosity control on SOM compound-specific mobility. A series of stop- and continuous-flow column experiments were performed with small diameter intact cores (which allowed for high-resolution imaging) of two representative soil samples collected in a cultivated and an undisturbed/uncultivated area. X-ray computed tomography (XCT) imaging was used to characterize soil porosity and pore network connectivity in the intact cores and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) based analyses were carried out for SOM characterization. Our results revealed that the Cultivated soil had a greater total carbon and nitrogen content than the Natural soil due to irrigation and fertilization, indicative of the relatively high carbon capture potential of this arid soil. We found that soil pore network connectivity and the heterogeneity of the pore structure strongly influenced the state of soil carbon: the Natural soil with higher porosity and greater pore network connectivity contained more oxidized carbon. Pore network geometry-based calculations showed longer diffusion lengths in the Cultivated soil, which was compacted by farming machinery.