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.
Reducing Bioavailability of Lead in Urban Residential Neighborhood Soil in Kansas City, Missouri
Young children in Kansas City’s urban core, where some lead poisoning rates exceed 9 times the national average. Nearly 50% of parcels tested exceed EPA’s play area lead threshold (400ppm), likely causing intransigent elevated blood lead levels (BLL), according to the health department. Research is lacking in the quantification of bioaccessibility and health risk reductions, especially for urban soils. This project will produce verifiable risk reduction data critical to developing affordable strategies to mitigate lead in urban soils, and correlate child BLL data with treated areas to identify potential health protection benefits.
Our Approach
In situ stabilization using soil amendments (e.g., phosphorus, iron minerals, and exceptional quality biosolids) is proven to reduce soil health risk by inducing biogeochemical reactions converting lead to forms with low bioaccessibility. This targeted community health study is designed to measure the effectiveness of in situ stabilization treatments at reducing lead bioaccessibility in urban soils. Study objectives include: 1) identify improved, cost-effective protocols to manage commonly elevated urban soil lead; 2) build community capacity to target these protocols where they are most needed to prevent child lead poisoning; and, 3) determine efficacy of mitigation. 
Funding Sources
U.S. Department of Housing and Urban Development
Collaborators: Department of City Planning & Development, City of Kansas City, Missouri; Health Department, City of Kansas City, Missouri, U.S. Environmental Protection Agency; and Children’s Mercy Hospital
Manipulating Nutrient Reaction Pathways to Optimize Nutrient Availability in Soils
The problem:
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.
Similarly, 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. The 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.
Approaches:
Researchers:
Buddhika Galkaduwa:(Micronutrients and Phosphorus)
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.
Joseph (Jay) Weeks: (Phosphorus)
Mohammad Almutari: (Zinc biofortification)
Mohammad mainly focuses on micronutrient biofortification, transformations of trace elements and Treatment options for marginal waters.
Joy Pierzynski:
Joy focused on 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.
Dissertation title: The effects of P fertilizer addition on P transformations on high-P fixing and grassland soils
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.
Thesis title: Speciation of phosphorus in reduced tillage systems: placement and source effect
Rodrigo Silva:
2012 – Diffusion, Fate, and Reaction Products of Phosphate Fertilizers with Varying Solubility Applied to a Tropical Soil
Resource recovery from wastewater for sustainable agricultural production systems
We hypothesize that innovative wastewater treatment technologies can produce the right water from different sources (such as swine wastewater) while recovering nutrients and producing soil amendments for crop production and protecting the environment. Anaerobic membrane bioreactors and Microbial Reverse Electrodialysis Cells are new technologies that can operate sequentially and remove harmful substances from wastewater to produce clean water for reuse. These processes also produce nutrient-rich co-products, allowing balanced/tailored nitrogen and phosphorus applications. The inclusion of new resource/reuse technologies will make agricultural production more sustainable, economical, and environmentally-friendly by reducing food and water quality deterioration from land application of livestock wastewaters and increasing water availability. This transformation will have a global impact as confined animal production wastewaters are increasingly used in water scarce areas in both developed and developing countries to meet food production and other demands.
Collaborators:
Prathap Parameshwaran, Department of Civil Engineering, KSU
Stacy Hutchinson, Department of Biological and Agricultural Engineering, KSU
Soil contaminants exposure reduction pathways
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.
Zafer 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
Reducing Children’s Blood Lead Levels by Mitigating Household Lead Paint in Central El Paso, Texas
Funding source: US Department of Housing and Urban Development
Collaborations : With University of El Paso, Texas, Drs. Christina Sobin, Carla Campbell and William Hargrove
https://www.utep.edu/leadresearchteam/index.html
The reduction of higher levels of child lead exposure in the United States is a public health success story. Given the growing evidence and broad acceptance that no level of lead exposure is “safe” for children, attention must now turn to developing strategies for lowering child blood lead levels that continue to impact millions of children nationwide to undetectable levels. El Paso, Texas is one of over 3000 cities nationwide with un-renovated pre-1978 housing and continuing high risk of child lead exposure from un-remediated lead paint. Current state and local intervention strategies were conceptualized for isolated cases of higher level lead exposure. New cost-effective child-relevant mitigation strategies are needed that can provide intervention for clusters of children in high-risk neighborhoods. Over the past ten years, our studies of early lead exposure among the children of our region have contributed substantially to the literature on this problem, and our interdisciplinary team is now uniquely positioned to test a novel community-engaged mitigation strategy for private homeowners living in high-risk neighborhoods. We propose a strategy that uses a holistic approach that integrates neighborhood-level community-engagement and education on child lead exposure hazards and solutions, with household level lead hazard detection and mitigation. The approach maximizes scarce resources by: 1) spatially mapping real time child BLLs determined by ICPMS in neighborhoods for identification of hotspots of child lead exposure; 2) using a late-generation x-ray fluorescence analyzer for efficient identification of possible home lead sources and bioaccessibility assays to narrow the focus of mitigation on likeliest child-relevant lead hazards; and 3) assisting home owners with low-cost mitigation of home lead exposure sources. In this study, we plan to test and refine these methods, and demonstrate their efficacy with post-mitigation tests of child BLLs and home dust samples.
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.
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.
Dissertation title: Mechanistic understanding of biogeochemical transformation of trace elements in contaminated minewaste materials under reduced condition
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.
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:
- Investigate the coupled physicochemical and biogeochemical processes responsible for C dynamics and stabilization.
- Better understand how management alters the physicochemical, and biogeochemical processes of soil C dynamics and stabilization.
- 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 aimed 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 focused 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.
Pavithra Pitumpe Arachchige:
Dissertation title: Understanding of coupled physicochemical and mineralogical mechanisms controlling soil carbon storage and preservation
Dorothy Menefee:
Thesis title: Anthropogenic influences on soil microbial properties
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.
View the Gardening on Brownfields website
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.
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.
Dissertation title: Bioavailability of contaminants in urban soils
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.
Dissertation title: Urban brownfields to gardens : minimizing human exposure to lead and arsenic
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 research work also focused on repurposing urban brownfields sites for agricultural production. Besides working with some gardener’s to ensure the use of best practices, he itried to quantify the dust inhalation exposure pathway created when cultivating soils contaminated by lead and arsenic.
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.
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.
Buddhika Galkaduwa:
Buddhika’s PhD research mainly focused on 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.