Hydrology and Environmental Geology
Research in this area is focused on investigating surface water and groundwater quality. Currently, we have been working on the Upper Pearl River Watershed in Central Mississippi. Land Use Land Cover (LU/LC) has a close association with the quality of water, with many point sources (poultry industries, for example) contributing to pollution. Nutrients, such as nitrate, and metals, such as arsenic and lead, were found to be in excess.
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Sediments from different aquatic systems (rivers, coastal, lake/reservoir, wetland and agricultural ponds) were evaluated for the metal-related pollution levels. We reported that agricultural ponds are one of the hotspots for metal accumulation, a previously unknown source.
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Biochar, a pyrolysis product of plant material, has shown to be an excellent, cheap and affordable adsorbent for a variety of metals, nutrients and contaminants. Current studies done in our lab investigate the functionality of biochar in different geological media that could bear important implications for its environmental use. In addition, biochar can also influence the physical properties of soil. It's ability to reduce shrink-well capacity of the infamously notorious Yazoo clay is also being investigated for its engineering application.
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Other ongoing environmental-themed projects include, sequential extraction of sediments downstream of a coal factory, estimating nitrate risk in groundwater using machine learning algorithm, and determining carbon cycling in coastal water related to algal bloom.
Principal Component Analysis showing relationship of LU/LC with metals found in sediments
Land Use Land Cover (LU/LC) map of the State of Mississippi
Microbial mats from Tuticorin solar salterns
Microbial population and their corresponding isotopic signatures along the different layers of the mat
Different types of microbialites from Storr's Lake,
The Bahamas
Biogeochemistry
One of my core interest is in investigating microbe-mineral interactions that occur in microbial mats, sediments and water. I am particularly interested in hypersaline settings, extreme environments, where only microorganisms can survive. Study sites include Soap Lake, Washington, Storr's Lake, Bahamas, and Solar Salterns of Tuticorin, India. The microbial mats from these environments have been studied as proxies to Paleo-Earth and Martian conditions (Exobiology). Microbial sequencing in addition to isotopic (C, N, O and clumped) of the mats are collectively studied. Recently, my team has been working with algae to investigate its response to changing climate and its potential role in remediating metals in estuarine and marine settings.
Some interesting observations:
-One never before observed result was that the internal structure of the mats has its own salinity gradient, which influences the type and mechanism of microorganisms present
-Modern microbialites in the Bahamas, counterparts of oldest evidences for life on Earth, revealed unique response to turbidity and salinity. The whole microbial consortium, typically dominated by photosynthetic cyanobacteria, could likely be dormant or replaced by other groups, such as sulfate-reducing bacteria (SRB)
-SRB's carbonate biomineralization can be a potential pathway for carbon dioxide sequestration in the subsurface
-SRB and/or its sulfide by-products can potentially influence Mississippi Valley Type (MVT) deposits
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Soil Chemistry and Soil Health
Our lab team recently has been investigating the effects of elevated carbon dioxide on the soil chemistry, particularly soil inorganic carbon. An increase in atmospheric CO2 could theoretically increase soil acidification and weathering, and in turn is important for agricultural management.
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Soil health has been receiving plenty of recent attention and serves as an important assessment tool for quality of the soil and the plants. Our work has been focused on combining chemical, physical and biological indicators that are important to South East USA, normalizing and calculating weight, eventually to arrive at a soil score. This tool is game-changing and is projected to a staple tool for agronomic and agriculture-related environmental research projects.
Image by Tingting Chang
Scanning Electron Microscopic (SEM) images of hematite and remnant exopolymeric substances (EPS). Image by Sudeera Wickramarathna
Other Projects
Hematite and Mars: Scanning Electron Microscope (SEM) investigations of hematite (Fe2O3)-rich soil from Sri Lanka revealed unique association and layering of the minerals, suggesting the role of exopolymeric substances (EPS or biofilms) in biomineralization. This could have useful implications for identifying important clues for life on hematite-rich Mars. Samples proposed to be brought from the red planet most likely will have not live microorganisms or even the broken down organic components due to the heavy oxidation. Therefore, looking for more stable 'morphological and chemical' clues in these samples could provide invaluable glimpse into potential life-related processes
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Mollusc Shell Chemistry: The chemical composition of mollusc shells from different river systems in Eastern USA helped give a characteristic fingerprint of the system. This could be useful in archaeology for provenance studies.