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Department of Agronomy

Major Research Programs

 

     The Hettiarachchi Lab explores a range of topics related to soil and environmental chemistry. Please see below for brief descriptions of our research programs, titles to some of our more recent presentations from the ASA, CSSA, & SSSA International Annual Meetings and links to recent webinars.

Dr. Ganga Hettiarachchi:

     Dr. Hettiarachchi has been involved in a multitude of research projects within the field of soil chemistry. Primarily, her interests have focused on better understanding the mechanisms and interactions involved in soil chemical reactions enhancing soil quality to improve crop production and/or protection of human health. Main research areas include: the fate and transport of hazardous trace elements along with the steps that may be taken to remediate contaminated sites including urban brownfields and abandoned mines; determining reaction pathways of macro- and micronutrient fertilizer sources in soils to understand their relationship to potential availability and plant uptake; and the role soil mineralogy/chemistry play to enhance aggregation and soil C sequestration in agroecosystems. Together with her group, she employs a wide variety of methods to understand trace and nutrient element mobility including but not limited to wet chemical analysis and synchrotron-based investigations.

2014 - Growing Food Crops on Urban Soils

2014 - Minimizing Human Exposure to Contaminants in Urban Soils

2013 – Contaminant Transfer From Contaminated Urban Garden Soils To Plants – Do We Need To Worry?

2012 – Contaminants in Urban Gardens – Lessons Learned in the Past

Recent Webinars

Hettiarachchi, G.M. and S. Martin. 2014. Contaminant Uptake in Food Crops grown on Brownfield Sites. One-hour long webinar as part of the Redevelopment Institute’s Sustainability Series (an ongoing series of webinars focused on sustainable development). Sep. 26, 2014. 

Click here to view 


Hettiarachchi, G.M. 2014. Managing contaminants in urban vegetable gardens to minimize human exposure. Two-hour long Webinar as part of CLU-IN Webinar Series (an ongoing series of webinars organized by USEPA Technology Innovation and Field Service Division). Oct. 15, 2014. 

Click here to view

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Soil Carbon Sequestration:

Effect of long term agricultural management practices and changing climate 

     This facet of our research focuses on understanding process‐level physico- and biogeochemical mechanisms that control soil carbon (C) stabilization allowing for the development of climate change mitigation strategies.  We assess the intra- and interrelationships between the physical, chemical, mineralogical, and biological processes that take place in our environment with our overarching goal being increased soil C retention.

Research Objectives:

     1. Investigate the coupled physicochemical and biogeochemical processes responsible for C dynamics and stabilization.

     2. Better understand how management alters the physicochemical, and biogeochemical processes of soil C dynamics and stabilization.

     3. Determine the resilience of the stabilized C under various temperature regimes.

     Quantifying the relative contributions of the chemical, mineralogical and biological soil factors to carbon stabilization is needed to develop accurate and useful soil C models. The outcomes of our effort will help to develop/improve management options for climate change adaptation or mitigation.

     Pavithra’s and Dorothy’s research aims to gather information on how interactions between physical location, organic carbon chemistry, and mineralogy of soil aggregates contribute to soil organic carbon sequestration using an integrated approach. Currently, they are focusing on soil aggregates collected from two long-term field sites in temperate and tropical climates.  The soils of interest were managed differently (e.g. tillage, crop rotation, manure addition, and/or fertilization) and led to varying levels of aggregation, soil C concentration/speciation, and microbial communities. Pavithra uses both new generation and traditional analytical techniques including NEXAFS-STXM, bulk NEXAFS, 13C NMR, HPLC, FTIR, XRD, SEM and other laboratory based wet chemical methods. 

     In-situ process-level biogeochemical mechanisms of C sequestration in microaggregates are being studied using NEXAFS-STXM spectromicroscopy. This research provides information on distribution and chemistry of C compounds, organo-mineral interactions and possible physical protection mechanisms. To achieve an accurate understanding of underlying biogeochemical mechanisms, aggregate architecture at the submicron scale must be carefully preserved. In the future Pavithra hopes to involve electron microscopy techniques to strengthen findings from the NEXAFS-STXM study. Bulk NEXAFS studies are useful in identifying chemical characteristics of soil organic carbon without any alteration to the natural structure of the molecules.  Just as important as the structure, is the resilience of sequestered organic carbon to different temperature and moisture conditions. Planning for studies tackling this objective is taking place.

     Dorothy’s research focuses on understanding the role of microorganisms in carbon sequestration.  She is specifically trying to understand how microbial community structure changes in temperate and tropical agroecosystems under changing climate.

 

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Pavithra Pitumpe Arachchige:

2014 - Characterization of Organic Carbon in Soil Aggregates from Temperate Continuous Corn System with Contrasting Management Practices Using NEXAFS and 13C-NMR Spectroscopy

2013 – STXM-NEXAFS Spectromicroscopy Studies of Intact Soil Microaggregates from a Tropical Agroecosystem

2012 – Organic Carbon Chemistry and Mineralogy of Soil Aggregates in Soils from a Temperate Continuous Corn System – Effects of Different Management Practices

Dorothy Menefee:

2013 – Mechanisms of Soil Carbon Protection in a Tropical Agroecosystem Under Differing Management Practices

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Urban Brownfields Research

     As the global population continues to grow towards the projected nine billion by 2050 and a greater proportion of the Earth’s residents dwell in cities, the availability of fresh, nutritious produce in densely populated, low income areas has become cause for concern. “Food deserts,” as they often have been called, are appearing in urban areas of not only the United States but around the world; places where grocery stores, if present, lack the means to obtain and/or sell quality fruits and vegetables in an economically efficient manner. Those unable to travel out of these areas are left reliant upon fast food establishments and convenience stores to satisfy, at the very least, their daily caloric requirements. One solution to this unfolding social injustice that has received widespread public and governmental support as well as a fair amount of success is the implementation of urban community gardening programs. Not only have these programs helped to alleviate malnourishment in economically unstable areas, but they have served to improve social relations creating networks that further foster improved community development.

Click here to view the website

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     An issue hindering the rapid implementation of urban gardens in many areas is the concern of growing food in soil that may not be safe. Research is making information available to address these misgivings, however knowledge in reference to assessing the risks associated with urban gardening is still lacking in certain facets. Lead (Pb) contamination remains the primary culprit in a multitude of urban areas. The heavy metal, an artifact of anthropogenic activity, has descended upon the soil primarily as a result of the prolonged use of leaded gasoline in the internal combustion engine and leaded paint applied inside and out of many buildings from approximately the 1920’s until 1996 and 1978 in the United States, respectively. Human exposure has been linked to a variety of health maladies leading the Center for Disease Control (CDC) to recommend action at blood lead levels (BLL) exceeding 5 µg/dL. Children are especially susceptible to the toxic effects of Pb resulting in developmental impairment due to their high frequency of hand to mouth activity and increased intestinal absorption capabilities. Adults are not immune though. Arsenic (As) poses yet another cause for concern as various chemical forms have been utilized over the years in pressure treated lumber, agrochemicals, and poultry feed as well as a byproduct released to the atmosphere from ore smelting activity. Understanding the mechanisms facilitating exposure to these contaminants as well as others is essential to the implementation of safe urban gardening programs. 

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Chammi Attanayake:

     Chammi not only investigated the pathway of lead and arsenic uptake from soil to plants, but worked to understand the potential for dermal transfer of polycyclic aromatic hydrocarbons from the soil to human blood.

2013 – Transfer of Polycyclic Aromatic Hydrocarbons (PAHs) from Urban Soils to Humans via Dermal Absorption

2012 – Potential for Transfer of Lead, Arsenic, and Polycyclic Aromatic Hydrocarbons from Compost Added Urban Soils to Vegetables and Humans

2011 – A Field Evaluation of Lead Transfer from Urban Soils to Vegetables.

Phillip Defoe:

     Phillip invested a considerable amount of time in testing whether or not common garden plants take lead and arsenic up into their edible portions and what measures may be taken in the garden and the kitchen to mitigate the transfer of contaminants from the soil into the human bloodstream.

2013 – Uptake of Lead and Arsenic by Vegetables Grown in a Contaminated Urban Soil Amended with Biosolids and an Iron(III) Oxyhydroxide.

2012 – Reducing Bioaccessibility of Lead and Arsenic in a Contaminated Urban Soil.

2011 – Gardening On Arsenic and Lead Contaminated Brownfields: Is It Safe?

Janelle Price:

     Janelle looked at the variability of lead and arsenic uptake from variety to variety within the same species of common garden plants grown on urban brownfield sites. She also more closely researched where in the plant the elements concentrated if they were transported into plant tissue.

2012 – Trace Metal Concentration and Partitioning Among Vegetable Varieties

Joseph Weeks Jr. (Jay):

     Jay’s master’s work has largely focused on repurposing urban brownfields sites for agricultural production. Besides working with some gardener’s to ensure the use of best practices, he is trying to quantify the dust inhalation exposure pathway created when cultivating soils contaminated by lead and arsenic. For his PhD, Jay will be looking more closely at the chemical mechanisms within the rhizosphere that impact the movement and availability of trace elements.

2014 - Assessment of Potential Human Inhalation Exposure to Soil Trace Elements Resulting from Agricultural Activity on Urban Brownfields Sites. 

2013 – Assessing Soil Preparation Techniques to Improve Portable XRF Precision and Recovery Efficiency of Lead in Urban Soils as Compared to the EPA 3051 Total Soil Digestion Method

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Wastewater Remediation Research

Constructed Wetland Treatment Systems

     We are part of a multi-disciplinary research group at Kansas State University conducting laboratory and pilot scale evaluations of flue-gas desulfurization (FGD) wastewater to understand transport and transformation of trace elements in constructed wetlands.

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     Flue-gas desulfurization technology is being implemented in high sulfur coal-burning electric power plants to comply with Clean Air Act standards by minimizing sulfur dioxide emission in the flue gas. Wastewater generated by FGD systems commonly fail to meet surface water quality standards because of, in general, elevated concentrations of trace metals such as selenium (Se), arsenic (As), and mercury (Hg) as well as many other constituents including sulfur. Constructed wetland treatment systems (CWTS) are being considered to economically treat this wastewater to remove Se and other trace metals. A series of laboratory based continuous up-flow soil column studies mimicking pilot-scale CWTS are being conducted to understand the transport and transformation characteristics of Se and other constituents in FGD wastewater.

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Buddhika Galkaduwa: 

     Buddhika’s main research focus is how different soil treatments and/or conditions influencing the performance of  CWTS.  The mobility and bioavailability of trace metals such as Se and As depend upon their speciation alter with soil conditions. In addition to the direct effect of redox dynamics, indirect effects due to changing Fe and S biogeochemistry influence Se and As. Therefore, it is important to elucidate the mechanisms of changes in Se, As, Fe and S chemistry in the CWTS.  Buddhika’s research is integrating pilot-scale field study observations together with laboratory-based macro-scale, and synchrotron-based X-ray absorption spectroscopy studies such as bulk-X-ray absorption near edge spectroscopy (XANES) and micro-scale x-ray fluorescence mapping in combination with micro-scale XANES, to achieve these objectives. 

2014 - Minimizing Arsenic Mobility Using Ferrihydrite in a Small-Scale Constructed Wetland Treatment System Designed for Removal of Selenium in FGD Wastewater

2013 – Sequestration of Selenium in Flue Gas Desulfurization Wastewater Using Constructed Wetlands: A Synchrotron Based Investigation

2012 – Understanding Transport and Transformations of Selenium in Flue-Gas Desulfurization Wastewater Using Continuous Flow Column Systems

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Nutrient Chemistry 

Reaction Pathways of Phosphorus in Agricultural and Natural Systems

     Phosphorus (P) is an essential element for all life forms. However, it is one of the most difficult nutrients for plants to obtain from the soil and therefore, often represents a limiting factor to agricultural production. While P is needed in adequate quantities for optimal crop production, it has also been associated with eutrophication of surface water bodies.  Knowledge of the dominant solid P species present in soil following application of P fertilizers and linking that to potential P availability would help understanding how to manage P efficiently in reduced tillage systems as well as in high P-fixing soils.

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Joy Pierzynski:

     Joy is involved with two separate studies meant to understand the movement of phosphorus in soil. The first investigates P cycling within the organic fraction of native prairie soil, while the second attempts to understand phosphorus fertilizer reaction products, fate and transport.

2014 - Soil Phosphorus Cycling in a Non-Agriculture Grassland Ecosystem: Influence of Fertilization

2013 – Effect of Phosphorus Fertilizer Source on Fate and Transformations of Phosphorus in High P Fixing Soils

2012 – Mobility, Availability, and Reaction Products of MAP, DAP, and APP Fertilizers.

Raju Khatiwada:

Raju’s research focused on understanding the influence of placement (broadcast- vs. deep band-P), fertilizer source (granular- versus liquid-P) and time on reaction products of P in reduced-till systems.

2011 – Mobility, Availability and Reaction Products of MAP, DAP, and APP Fertilizers in Acid and Calcareous Soils.

2010 – XANES Speciation of Phosphorus in Reduced-till System: Placement and Source Effect.

Rodrigo Silva:

2012 – Diffusion, Fate, and Reaction Products of Phosphate Fertilizers with Varying Solubility Applied to a Tropical Soil

Explaining the interactions and potential availabilities of different zinc fertilizers in soils using wet chemical, speciation and visual techniques

     Millions of hectares of arable land worldwide, particularly in arid and semi-arid regions, are deficient in plant available Zn. Thus, various organic and inorganic Zn fertilizers have been used to correct their deficiencies. Inclusion of Zn in commercial macronutrient fertilizers is a common practice throughout the world and has been driven mainly by product physical characteristics than by considerations of fertilizer efficiency. 

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 Buddhika Galkaduwa:

     The overall focus of Buddhika's research is to investigate how different sources of Zn in P fertilizers diffuse and react with soil and P using wet chemical, speciation and visualization techniques.

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Soil Remediation Research

Stabilization of mine waste materials

     Lead and Zn were mined extensively in the Tri-State Mining Region for over 100 years culminating in a multitude of environmental issues.  Large areas are void of vegetative cover, communities have been impacted by smelter emissions, and vast quantities of mine wastes and soils enriched with Pb, Zn, and Cd remain.  Phytostabilization, in situ stabilization via soil amendments, and sub-aqueous disposal of mine wastes are being studied as remediation approaches 

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Ranju Karna:

     Ranju devised a series of column experiments in order to better understand the chemical transformations that take place in the soil upon sub-aqueous disposal of mine wastes. By amending the mine waste materials with carbon and sulfur, she was able to elicit microbial responses that impact metal speciation.

2012 – Understanding Subsurface Transformations and Dynamics of Trace Elements in Multi-Metal Contaminated Mine Waste Materials in Southeast Kansas

Vindhya Gudichuttu:

     The overall focus of Vindhya's research was to monitor long-term effects of compost or lime additions at two different rates on soil properties, plants, and soil biota. She utilized the earthworm avoidance test as a screening tool for assessing effects of soil amendments on ecotoxicity

2010 – Long Term Monitoring of Vegetative Response and Microbial Activity Upon the Addition of Amendments to a Metal Contaminated Mine Waste.

Phytostabilization of contaminated sites

     There is a great need to develop in-field monitoring studies to assess the possibility of growing a biofuel crops successfully in contaminated soils as a part of remediation of contaminated sites using phytostabilization technique.  

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Phyto1Zafer Alasmary: 

     Zafer's research focus is safely using contaminated sites for biofuel crop production. He is studying how the contaminant uptake by crops and chemistry and quality of contaminated soils change with nutrient rich in situ soil treatments. This is a part of collaborative research effort began in 2016 between Eastern Europe and the United States, funded by North Atlantic Treaty Organization (NATO). 

     For more information and current progress of this new project please visit

http://military-site-cleaning.cz/