ORCID Profile
0000-0002-6378-7168
Current Organisation
University of Sydney
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Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-10919
Abstract: Soil water retention is important for the establishment and productivity of ecosystems through its role in governing the flux, depth distribution, and availability of soil moisture. With increasing application of global and regional hydrologic and climate models, there is a concomitant need to accurately predict and map soil hydraulic properties to parameterize these models and simulate soil water dynamics across spatiotemporal scales. Soil water retention functions created to fulfill this need typically assume a unimodal pore-size distribution, despite the common observation that soil pore-size distributions are multimodal due to soil structure and interpedal macropores. Existing dual porosity functions ide pores into two categories: larger pores, controlled by structure, and smaller pores, controlled by texture. Obtaining the parameters for the structural domain is difficult due to the poor characterization of large pores. Large pores cannot be characterized from water retention curves because measurement of water retention near saturation, and CT scans of soils rely on small soil s le volumes which limits the pore characterization to tens of millimeters in range, while pores may be much larger. In this study, we developed multiple PTFs to predict the van Genuchten parameters (& #593 and n) of the structural domain in dual porosity models, as well as the w coefficient, which reflects the relative abundance of these two types of pores in the dual porosity model. Our PTFs were developed from characterized pores 180 & #181 m from nine pedons across Kansas, USA, using recent advances of multistripe laser triangulation (MLT) scanning applications. MLT scanning pore characterization allowed us to characterize soil pores 10 cm and was conducted on 30-cm wide soil monoliths collected from excavation walls of each pedon that were either 20 or 40 cm tall depending on the thickness of the horizon. We used ImageJ to quantify pore-size distributions that were then used to estimate the water retention curve (WRC) and hydraulic conductivity of the structural domain. We fitted van Genuchten functions to characterize the WRCs in the structural domain, and ROSETTA 3.0 was used to characterize the WRCs in the matrix domain. These WRC fits were used to develop new PTFs that predict the parameters of the dual porosity model using mixed linear models with inputs including NRCS soil structure field descriptions along with standard physical and chemical properties (clay, sand, SOM, bulk density, coefficient of linear extensibility, cation exchange capacity, horizon midpoint depth, and quantified morphological descriptions of structural type, grade, solidity, roundness, and circularity). Using the predicted parameters, we estimated water retention for each horizon and achieved high levels of correlation and accuracy when compared with the water retention derived from the MLT scans. The approach for creating PTFs can be used to improve soil hydraulic property parameterization of soils with structure in regional hydrologic and climate models by providing a framework for integrating multiple recent advances such as the characterization of large pores using MLT and use of quantified soil structure from profile descriptions. Future studies will examine performance of these PTFs in numerical hydrologic models.
Publisher: Wiley
Date: 21-09-2023
DOI: 10.1002/SAJ2.20588
Abstract: The recognition that texture is a “master soil property” points towards the need for actual quantification of particle size in organic soil material. Using a multi‐wave particle size analyzer, fibric and sapric soil s les were circulated in deionized water through a closed aqueous loop at 9.6 L min −1 and the following methodological parameters were investigated: pre‐treatment, circulation time, and refractive index. Our results show that pre‐treatment for organic soil s les is dependent upon the degree of decomposition the intact and dispersed PSDs for fibrous s les were not different, whereas the PSDs for sapric s les showed a shift from 500 to 2000 (intact) μm to 5 to 100 (dispersed) μm. Circulation time was investigated using mean particle diameter and specific surface area. We demonstrated that as circulation time increased, the mean particle diameter decreased and the specific surface area increased out to 30 minutes as mechanical dispersion and/or the fragmentation of organic particles occurred. However, circulation time after 5 minutes is not significantly different in terms of mean particle diameter. To investigate refractive index, 12 optical models were created. When determined across all intact s les, uncertainty was low within in idual bins, with a maximum value of 0.07 ± 0.04% v/v. For dispersed s les, uncertainty increased within the silt sized region and had a maximum value of 0.17 ± 0.07% v/v. This study demonstrates that the particle diameter of organic soil material can be measured by LD with comparable certainty as mineral soil material using the methodological approach in this study. This article is protected by copyright. All rights reserved
Location: United States of America
No related grants have been discovered for Julio Pachon.