CHEMICAL SPECIATION AND REACTIVITY IN SOIL MICROSITES

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 0223867
• Project Start Date: Oct 1, 2010
• Project End Date: Sep 30, 2015
• Program Code: [(N/A)]- (N/A)

Recipient Organization
NORTH CAROLINA STATE UNIV
(N/A)
RALEIGH,NC 27695

Performing Department
Soil Science

Non Technical Summary
The agriculture and forestry sectors in the United States and worldwide face enormous challenges in meeting the food, fiber, and energy needs of a world population projected at 9 billion by 2050. Crucial roles of soils in this challenge include supporting increased agricultural productivity and providing environmental protection to the global environmental ecosystem. Soils regulate the flow of macronutrients (e.g.,nitrogen, phosphorus, and potassium), micronutrients (e.g., copper, zinc, molybdenum, and boron) carbon (organic matter and CO2), and environmental contaminants (As, Hg, Pb, Cd, personal care products, toxic organic micropollutants, etc.) from land surfaces to waterways or the atmosphere. In the face of continuous losses of farmland to urbanization, global change, and environmental degradation; it is of utmost importance that we increase the precision of managing soils on a site-by-site basis to optimize their performance for a variety of foreseeable conditions and purposes. Precise soil management is problematic because soils are one of the most complex biogeochemical systems on Earth. Soils comprise a highly-heterogeneous mixture of loosely-consolidated mineral, organic, and biological materials. Their chemical, physical and biological properties change over time at varying rates, and heterogeneous properties develop through an almost infinite number of biogeochemical reactions occurring within soils. This project aims to discover new principles of soil chemistry that will better address the great challenge of precisely regulating the flow of plant nutrients and environmentally harmful substances within soils, and between soils and the hydrosphere and atmosphere. The focus is on developing new concepts and approaches for dealing with the extreme complexity of soil matrices, e.g., by considering that complex assemblages of minerals and organic matter can potentially act as chemical units that control chemical reaction kinetics and mechanisms in soil micro- or nano-sites. Experimental methods will be developed for measuring chemical reaction kinetics and determining mechanisms directly in soil microsites, and theoretical bases for interpreting these results will be evaluated.

Animal Health Component

(N/A)

Research Effort Categories

Basic

100%

Applied

(N/A)

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
133	0110	2000	100%

Knowledge Area
133 - Pollution Prevention and Mitigation;

Subject Of Investigation
0110 - Soil;

Field Of Science
2000 - Chemistry;

Keywords

soil contamination

soil heterogeneity

soil microsite chemistry

micro-chemical reactors

synchrotron x-rays

microspectroscopy

spectromicroscopy

redox kinetics

reaction mechanisms

macroscale chemistry

Goals / Objectives
The goals of the proposed research are to determine whether soil complexity produces unique chemical behavior of strongly bound contaminants compared with model systems, and to develop explanatory models. The central paradigm of this research is that a soil can be viewed from a chemical perspective as a series of interconnected micro-chemical reactors, and the reaction mechanisms and kinetics of chemical reactions within these micro-reactors (micro-sites) depends in part on the combination of matrix components that compose the microsite. The objectives are as follows: 1. Develop an in-situ soil chemical reactor system that enables the kinetics of transformations of trace-element species within nanometer- to micron-sized regions ("microsites") to be measured in relation to matrix properties of the microsite. 2. Determine how variations in the matrix components within soil microsites (minerals, organic matter) affect the kinetics and mechanisms of in-situ reactions in relation to measurements from model (single-component) chemical systems. 3. Develop a framework theory for explaining micro-scale variations in chemical reactions of trace elements in soil and to relate microscale variations to the macroscale behavior of the contaminants. Outputs, if successful, will include a reactor design and methods for studying soil chemical reactions in-situ, an assessment of the heterogeneity of chemical kinetics of at least one type of soil redox reaction in relation to soil properties, and the development of a conceptual (model) framework for explaining soil complexity and reaction mechanisms.

Project Methods
Objective 1: Here we aim to develop a micro-scale chemical reactor system that allows chemical perturbations to be imposed on a soil sample, ideally in an aqueous system, while simultaneously following changes in the chemical speciation of relevant elements in a focused synchrotron x-ray beam. We intend to design a micro-chemical reactor system that performs the following functions: 1. Maintains soil particles in a fixed position during chemical treatments. 2. Allows chemical treatments to be imposed across microsites while the sample is being analyzed in a synchrotron x-ray beam. 3. Provides spatial reference points whereby the sample can be placed in different analytical instruments to characterize the same microsites as needed using different types of analyses. For objective 2, we would follow microscale chemical reactions and determine how any variability in reaction rates or mechanisms are related to the chemical and mineralogical composition of the micro-sites. Based on existing knowledge of the kinetics of redox transformations and mechanisms of trace elements in model systems, we will systematically identify one or more redox couples to characterize. Research under objective 3 aims to begin developing a theoretical underpinning for two aspect of this research project: 1. Explain any variations in redox kinetics between microsites based on microsite properties that could produce multiple reaction pathways (mineralogy, associated elements, organic matter concentration, etc.). 2. Develop a theoretical connection between the overall variation in kinetics observed across microsites to the macroscale redox transformations of the soil(s) evaluated.

Progress 10/01/12 to 09/30/13

Outputs
Target Audience:The target audience was research scientists, and practitioners working in remediation of contaminated soils and horticultural production. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?A service-learning publication was developed in collaboration with an M.S. graduate student, Sarah Smith (Smith et al., 2014 - see product list). This work addressed ways to get diverse urban youth interested in gardening and agriculture. I also assisted a Ph.D. student in Forestry on a review paper on phytoremediation of organic-substances contaminated soils using trees or grasses (Cook and Hesterberg, 2013 publication), as well as a Ph.D. student in Sweden on chemical speciation of iron in lakes and soils (Sjostedt et al., 2013 publication), and a Ph.D. student in environmental toxicology on chemical speciation and transformations of selenium in periphyton biofilms that are common in aquatic systems (Conley et al., 2013). These latter two studies involved synchrotron X-ray techniques that were evolved for complex systems under this project. I provided soil chemical support to a Ph.D. student in Horticultural Sciences to control the pH of soilless media in greenhouse production systems. How have the results been disseminated to communities of interest?Results have mainly been disseminated via peer-reviewed journal publications (see list of products). What do you plan to do during the next reporting period to accomplish the goals?I am developing proposals to obtain external funding to support this line of research. I am also involved in a steering committee to develop a new X-ray beamline (Submicron Resolution X-ray spectroscopy, SRX) at the new NSLS-II synchrotron, which is particularly suited for the types of research studies in this project.

Impacts
What was accomplished under these goals? Micro-X-ray fluorescence experiments on arsenic reactivity with natural iron/aluminum oxide coatings on a soil sand grain from the North Carolina Piedmont showed a spatially heterogeneous pattern of arsenic accumulation following treatment of the grain with a dilute arsenic(V) solution. Although the arsenic pattern was similar to that of iron, implying arsenate adsorption onto iron oxides, other soil matrix elements were co-localized. Working with spatial statisticians, our X-ray microprobe images of multiple elements and arsenic on the soil sand grain were analyzed as multivariate spatial lattice maps of elemental abundance. Spatial statistical model was developed to disentangle the complex multivariate relationships among the elements in the soil matrix. The abundance of most elements, including arsenic, correlates strongly with that of iron, but conditional on the amount of iron, some elements may mitigate or potentiate the accumulation of arsenic. This work defined conditional correlatiosn in spatial lattice models and give general conditions under which two components are conditionally uncorrelated given the other components imaged. A publication (Guinness et al., 2014) described how to enforce that two components are conditionally uncorrelated given a third in parametric models, which provides a basis for likelihood ratio tests of conditional correlation between arsenic and chromium given iron. The model was applied to our large spatial datasets to demonstrate an improvement in spatial statistical models describing cross covariance among multiple chemical elements affecting arsenic accumulation in a complex soil matrix. In another complex system, research on selenium speciation changes in complex periphyton biofilms showed that both selenate and selenite taken up into the algal/bacterial communities is converted to organo-selenium species. Experiments with complex periphyton assemblages and ecologically relevant primary consumers improved our understanding of selenium at the base of the food web. Our research insights gained from experiments on complex systems enabled us to provide soil chemistry support to a number of other projects as reported in products.

Publications

• Type: Journal Articles Status: Published Year Published: 2013 Citation: Sj�stedt, C., I. Persson, D. Hesterberg, D. Berggren Kleja, H. Borg, and J. P. Gustafsson. 2013. Iron speciation in soft-water lakes and soils as determined by EXAFS spectroscopy and geochemical modeling. Geochimica et Cosmochimica Acta. 105:172-186.
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Cook, R. L. and D. Hesterberg. 2013. Comparison of trees and grasses for rhizoremediation of petroleum hydrocarbons. International Journal of Phytoremediation. 15:844-860.
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Conley, J., D. Funk, D. Hesterberg, L.-C. Hsu, J. Kan, Y.-T. Liu, and D. Buchwalter. 2013. Bioconcentration and biotransformation of selenite versus selenate exposed periphyton and subsequent toxicity to the mayfly Centroptilum triangulifer. Environmental Science and Technology 47:7965-7973.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Barnes, J., P. Nelson, B.E. Whipker, D.A. Dickey, D. Hesterberg, and W. Shi. 2014. Statistical model for describing macronutrient impacts on container substrate pH over time. HortScience 49:207-214.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Guinness, J., M. Fuentes, D. Hesterberg, and Polizzotto, M. 2014. Multivariate spatial modeling of conditional dependence in microscale soil elemental composition data. Spatial Statistics. 9:93-108.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Smith, S., S. Prohn, L. Driscoll, D. Hesterberg, L. Bradley, and J. Grossman. 2014. Preparing students for a diverse future: Using service-learning to train students for careers in agricultural community outreach, North American Colleges & Teachers of Agriculture (NACTA) J. 58:293-301.

Progress 10/01/11 to 09/30/12

Outputs
OUTPUTS: Outputs from this research included scientific publications, invited presentations, and collection and analysis of new data at a National User Facility (Brookhaven National Laboratory). Invited presentations included the following: 1. Hesterberg, D. "Hitting the Complexity Wall in the Quest for Reaction Mechanisms in Geochemical Systems". Kansas State University, ADVANCE Distinguished Lecture Series, Dept. of Agronomy. March 7, 2012. 2. Hesterberg, D. "Chemical Speciation of Phosphorus in Relation to System Complexity". Kansas State University, Dept. of Agronomy. March 7, 2012. 3. Hesterberg, D. "Successes and Challenges in Applying Chemical Principles in Molecular Environmental Soil Science". Davidson College, Dept. of Chemistry. March 30, 2012. 4. Hesterberg, D. Overview of Soil Chemistry Research Program. CALS Research Overview, Stewards of the Future: Research for Human Health and global sustainability. McKimmon Center, April 17, 2012. (video presentation). 5. Hesterberg, D., M. Fuentes, and M. Polizzotto. Chemical Reactivity in Soil Microsites: The Need for Rapid, High-Resolution, Multi-Element Synchrotron X-ray Capabilities. Rock & Cell-Early Science Workshop, NSLS-II, Brookhaven National Laboratory. Sept. 17-18, 2012. 6. Hesterberg, D., M. Fuentes, and M. Polizzotto. Chemistry in Soil Microsites: A Pathway for Predicting Environmental Impacts of Trace Elements. National Taiwan University (NTU), Taipei, Taiwan. Nov. 9, 2012. 7. Hesterberg, D. The Power and Limitations of Synchrotron X-rays in Agro-Environmental Research. KSEA-KBRC (Korean Society of Environmental Agriculture - Korean Biochar Research Center) International Symposium: Heavy Metal Remediation in Agricultural Systems. Kangwon National University (KNU), Chuncheon, Korea. Nov. 15, 2012. (Keynote) 8. Hesterberg, D. X-ray Absorption Spectroscopy: Principles and Applications to Soils. Kangwon National University (KNU), Chuncheon, Korea. Nov. 16, 2012. 9. Hesterberg, D., M. Fuentes, and M. Polizzotto. SAE: Predicting Environmental Impacts of Toxic Metals from Geochemical Reactions. Presentation (presented by Montserrate Fuentes) for NCSU Internal Competition for a Limited Submission Proposal to the W.M. Keck Foundation. July 17, 2012. As part of our efforts at the National Synchrotron Light Source at Brookhaven National Laboratory, we developed a sample holder for soil particles that allows us to apply chemical treatments to the sample and follow transformations using microscale synchrotron x-ray absorption spectroscopy. PARTICIPANTS: Dr. Dean Hesterberg (William Neal Reynolds Distinguished Professor - Soil Chemistry) is the principal investigator. Other participants from NC State University included Dr. Matthew Polizzotto (Assistant Professor of Soil Hydrogeochemistry), and Dr. Montserrat Fuentes (Professor and Department Head of Statistics). Dr. Hesterberg contributes soil microsite analyses, Dr. Polizzotto contributes knowledge of arsenic reactivity in soils, and Dr. Fuentes builds spatial statistical models for microsite complexity and reactivity. Drs. Owen Duckworth (Assistant Professor of Soil Biogeochemistry) and David Buchwalter (Molecular and Environmental Toxicology) are involved with Dr. Hesterberg in a related funded project studying chemical speciation, reactivity, and biological uptake of trace elements from coal fly ash. A postdoc on the project (Dr. Nelson Rivera) and a former postdoc (Dr. Navdeep Khaur) contributed aqueous chemistry and solid-phase chemical speciation analyses. TARGET AUDIENCES: This project focuses on a new paradigm of looking at soil chemical reactions within reactive soil microsites. This basis research is presently most useful for soil and environmental chemists who are studying fundamental mechanisms of soil reaction chemistry. The coal fly ash research is directly applicable to determining and controlling the long-term impacts of trace elements in fly ash in river sediments associated with the 2008 fly ash spill at the TVA Kingston Fossil Plant. The results will potentially impact regulations of coal fly ash. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Our research aims to develop a new strategy for predicting environmental impacts of soil trace elements by combining knowledge of trace-element reactions from model systems with statistical analysis of soil complexity. The research goals are to measure and model chemical transformations of trace elements within complex micron- to nanometer-sized soil volumes (microsites), and to develop an approach for scaling up this information. Our work to date provided the first evidence of arsenic(III) oxidation to arsenic(V) within soil microsites. Several iterations of system design and synchrotron analyses were made to develop a sample holder that is suitable for following such transformations. An invited presentation of this work at the "Rock & Cell-Early Science Workshop" contributed ideas for early science to be performed when the state-of-the-art Sub-Micron Resolution X-ray Spectroscopy (SRX) Beamline goes into operation in 2014 at the new NSLS-II facility at Brookhaven National Laboratory.

Publications

• Kim, H., D. M. Amatya, S.W. Broome, D. Hesterberg, and M. Choi. 2012. Sensitivity analysis of the DRAINWAT model applied to an agricultural watershed in the lower coastal plain, North Carolina, USA. Water and Environment Journal 26:130-145.
• Morris, A. J. and D. Hesterberg. 2012. Iron(III) coordination and phosphate sorption in peat reacted with ferric or ferrous iron. Soil Science Society of America Journal 76:101-109.
• Conley, J., D. Funk, D. Hesterberg, L.-C. Hsu, J. Kan, and D. Buchwalter. 2012. Dissolved selenium speciation (selenite versus selenate) affects uptake and biotransformation in freshwater periphyton. 6th SETAC World Congress, Berlin, May 20-24, 2012.
• Kaur, N., D.L. Hesterberg, O.W. Duckworth, C.R. Ward, and D. Buchwalter. 2012. Solubilization of trace elements from coal fly ash in relation to chemical speciation. 2012 Goldschmidt Conference, Montreal, June 24-29, 2012.
• Nowak, B., D. Hesterberg, O.W. Duckworth, and D. Buchwalter. 2012. Dissolution of Trace Elements from Coal Fly Ash as Affected by Citrate. Abstract 323-8 for ASA-CSSA-SSSA International Annual Meetings, Cincinnati, OH, Oct. 21-24, 2012.
• Liesch, A.M., A. Amoozegar, D. Hesterberg, and J.L. Heitman. 2012. Comparison of specific surface area measurement approaches for soils with a range of properties. Abstract 266-3 for ASA-CSSA-SSSA International Annual Meetings, Cincinnati, OH, Oct. 21-24, 2012.

Progress 10/01/10 to 09/30/11

Outputs
OUTPUTS: The goal of this research is to integrate chemical speciation analysis with measurements of soil complexity to develop improved models for predicting the behavior of nutrients and contaminants in soils. Two of our publications in 2011 have outlined the general concept of complexity as a barrier to molecular-scale characterization of chemical species in soils, and data were presented along with a new concept of geochemical microreactors as fundamental reactive units in soils. This concept and the underlying difficulties of dealing with complex chemical matrices within the framework of established chemical principles such as thermodynamics was presented as part of an ADVANCE Distinguished Lecture at Kansas State University (March 7, 2012). As experimental research on this problem is undertaken, we have involved scientific experts with a variety of skills to help work out the challenging technical problems: three synchrotron x-ray scientists at Brookhaven National Laboratory with backgrounds in geosciences and x-ray physics, a spatial statistician at NC State, and an electron microprobe specialist at NC State. A research proposal has been submitted to the National Science Foundation to support the basic component of this research. PARTICIPANTS: Several individuals with varied expertise have recently become involved in this project: Dr. Matthew Polizzotto, a Hydrogeochemist at NC State whose interest lies in translating molecular scale mechanisms into field-scale soil management; Dr. Montserrat Fuentes, a spatial statistician at NC State with expertise in analyzing spatially heterogenous systems and developing ensembles as an approach to scaling; Dr. Dieter P. Griffis, the Director of the NC State Analytical Instrumentation Facility in the Engineering Research Center, who develops approaches for nanoscale analysis of surfaces; Drs. Paul N. Northrup and Ryan Tappero, geoscientists who build, develop, and operate synchrotron x-ray facilitiies at Brookhaven National Laboratory; and Dr. Juergen Thieme, an x-ray physicist at Brookhaven National Laboratory with expertise in x-ray microscopy. A visiting Ph.D. student from National Chung Hsing University in Taichung, Taiwan is developing expertise in this area by assisting with x-ray microscopy analyses of soil samples. TARGET AUDIENCES: The main target audience for this research is soil chemists and geochemists who seek to relate molecular-scale chemical speciation of soil chemicals to their impacts in agricultural and environmental ecosystems. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
The main outcome of the project is that we, along with scientists at Brookhaven National Laboratory, have begun developing and testing new analytical tools and approaches for measuring in-situ chemical transformations directly in soil samples. Our initial findings of heterogeneous oxidation of chromium(III) in samples of a serpentinic soil from Taiwan revealed the potential for microscale heterogeneities in soil matrices affecting chemical transformations of trace elements. The general approach to the research has implications for a wide range of strongly bound elements, including critical agricultural nutrients like phosphorus and potentially toxic trace elements like copper, zinc, chromium, and arsenic.

Publications

• Morris, A. J. and D. Hesterberg. 2011. Speciation of Fe(III) bound to organic matter by direct addition or oxidation of Fe(II). Soil Science Society of America Journal 76:101-109.
• Liu, Y. T. and D. Hesterberg. 2011. Phosphate bonding on non-crystalline Al/Fe-hydroxide co-precipitates. Environmental Science and Technology 45:6283-6289.
• Kang, J. H., A. Amoozegar, D. Hesterberg, and D.L. Osmond. 2011. Phosphorus leaching in a sandy soil as affected by fertilizer source. Geoderma. 161:194-201.
• Hesterberg, D., M. Duff, J. B. Dixon, and M. J. Vepraskas. 2011. X-ray microspectroscopy and chemical reactions in soil microsites. Journal of Environmental Quality 40:667-678.
• Kizewski, F., A. Morris, Y.-T. Liu, and D. Hesterberg. 2011. Spectroscopic approaches for phosphorus speciation in soils and other environmental systems. Journal of Environmental Quality 40:751-766.