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Modeling soil aggregate size distribution and water-stability in eroded sediment
Abstract
Sediment has been pivotal in the establishment and sustainability of human civilization throughout history. Public road safety and the longevity of water management structures are affected by displaced sands. Public health and water quality are limited by turbidity and contamination from displaced silts and clays. Particle-size distributions of soils are critical determinants of the potential impact and management of sediment. Water-stable aggregates are similar in size to primary particles but differ from them in density, specific surface area, porosity, the presence of encapsulated nutrients or contaminants, and binding agents that may return to reactivity upon elutriation. The objective of this study was to quantify the relative contributions of primary particle-size distribution, organic binding agents, inorganic binding agents, and water-stable aggregates to the aggregate-size distribution of sediment. A mathematical model of aggregation in sediment was developed using empirical data from 36 cropland soils representative of the USA which were treated with a rainfall simulator for the Water Erosion Prediction Project (WEPP) in 1987 and 1988. Particle-size distribution in situ was compared to eroded aggregate size distribution. Eroded aggregates in this study were compared to chemical binding factors (organic carbon, iron oxides, and clay extensibility) and management properties (relative saturation, bulk density, and gravimetric water content). Four standardized canonical variates provide significant estimates of potential aggregation (PA) based on eroded aggregate size fractions: two for particle-size distribution (PAp), one for chemical binding (PAc), and one for indirect management indices (PAm). Potential aggregation is the sum of particle size, chemical binding, and management contributions of soil properties in situ and was derived using eroded aggregate sizes. The equation to calculate scores for potential aggregation is: PA = (PAp + PAc + PAm). The model provides quantitative estimates of potential aggregation that may affect soil erosion, sediment size and amount, and transport distances. Potential aggregation also provides some information on differences among soils in soil pore space, active surface area, water-stability, and related soil structural stability. Future applications are expected to aid in the design of management systems to maximize content of water-stable aggregates of non-erodible sizes for sustainable land use.
Subject Area
Soil sciences|Environmental science
Recommended Citation
Scheyer, Joyce Charlene Mack, "Modeling soil aggregate size distribution and water-stability in eroded sediment" (1998). ETD collection for University of Nebraska-Lincoln. AAI9917859.
https://digitalcommons.unl.edu/dissertations/AAI9917859