REACTIVITY, AGGREGATION AND TRANSPORT OF NANOCRYSTALLINE SESQUIOXIDES IN THE SOIL SYSTEM
Project Information
Funding Information
| Country | USA |
| Anticipated Total Funding | $123,471.00 |
| Annual Funding | $61,735.50 |
| Funding Source | USDA |
| Funding Mechanism | |
| Funding Sector | |
| Start Year | 2007 |
| Anticipated End Year | 2009 |
Abstract/Summary
NON-TECHNICAL SUMMARY: Sesquioxides are common products of chemical weathering and important constituents of most soils. Soil organic matter and sesquioxides affect each other’s dynamics, reactivity and transport. Currently we don’t fully understand how the size and concentration of oxides and the composition of soil organic matter affect destabilization of carbon from the oxide surfaces and how the oxides are distributed in the soil system. This project will establish treshold oxide concentrations beyond which OM-oxide associations become irreversible; establish the influence of changing soil moisture conditions (due to global climate change scenarios) on carbon stabilization and tranport of nano-sized oxides; and develop a relationship between reactivity, aggregation and transport of nanoparticles in the soil system. OBJECTIVES: Nano-sized sesquioxides are ubiquitous minerals in the environment. Reactivity, aggregation and transport of oxides strongly control sorption of anions, variable charge, soil physical characteristics, and mobility of nutrients and pollutants in the environment. These soil properties are critical for availability of nutrients, vitality of various organisms, and plant productivity in the soil system. But, we know very little about how concentration and size of different oxides affects desorption kinetics of organic matter (OM), and how different sizes and species of oxides aggregate and move through the soil system. This is particularly important and timely issue because anticipated future climatic changes in places like California could disrupt the current OM-sesquioxide association through their effect on quantity, quality and mobility of OM and weathering. The objective of this postdoctoral research is to make targeted contributions to address three critical questions concerning reactivity and distribution of sesquioxide in soils with different mineralogy. The study will specifically address the following questions: (1) how are size of oxide particles and their concentration related to quantity and quality of desorbed OM? (2) how does concentration an composition of dissolved OM (DOM) control aggregation of nanocrystalline sesquioxides? (3) how is transport of oxide particles through a soil column related to OM-oxide associations and aggregation? The project is a novel effort, combining methods and insights from the pedological, ecological, and geologic sciences. This proposed postdoctoral research project will characterize mechanisms and controlling variables of oxide reactivity, aggregation and transport in soils with different mineralogy in order to determine if there exist (1) thresholds oxide concentration beyond which OM-oxide associations become irreversible; (2) OM type and concentration that results in aggregation of fine oxide particles beyond the nano-range; (3) a relationship between reactivity, aggregation with transport of nanoparticles in the soil system; and (4) establish the influence of changing soil moisture conditions (due to anticipated global change scenarios) on C stabilization and transport of nano-sized oxides. The long-term goals of this project are to advance our understanding on the fate of oxides in the environment and their contribution to carbon sequestration.The proposed work will have broad impacts in several areas related to soil chemistry, physics and microbiology, and agricultural productivity and sustainability.APPROACH: For the first part of the project (to address how the size of oxide particles and their concentration are related to quantity and quality of desorbed organic matter): (a) the amount of dissolved organic matter (DOM) that can be sorbed and desorbed from soils with different oxide concentrations will be determined by equilibrating soils with different DOM concentrations; (b) the chemical composition of the DOM before the sorption experiments will be compared with the composition after each batch of sorption and desorption experiment using liquid state 13C-NMR (nuclear magnetic resonance), in order to determine if type and concentration of the varying oxides affects the quality, as well as quantity of DOM in a soil system; and (c) the modified Langmuir adsorption isotherm will be tested to interpret the reactivity of the DOM with soils having different sesquioxides, at varying degrees of availability. For the second part of the project (to address how the concentration and composition of DOM control aggregation of nanocrystalline sesquioxides, and how transport of oxide particles through a soil column is related to OM-oxide associations and aggregation): (a) a series of column experiments with different DOM and oxide concentrations, at various fluid flow rates will be conducted to determine if the changes in DOM concentration and water flow rates observed in the climate change experiment at Angelo reserve will result in significant change particle size (aggregation) of the oxides; (b) the rates and concentration (of the total and different forms of iron and aluminum (Fe and Al)) that are transported through the soil column will be used to determine the types of Fe and Al oxides that are associated with formation of different sized aggregates and significant rates of oxide transport; and (c) I will determine if the chemical composition of the leaching solution changes after the column experiments using total organic carbon analysis and liquid state 13C-NMR.
