Research Overview
Microplastics as Vectors for Inorganic Contaminants
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Plastics are among the most widespread and persistent pollutants globally, necessitating a detailed process-level understanding of their behavior in the environment. Of these plastics, microplastics (MPs) (100 nm - 5 mm) are of particular concern due to their small size increasing their potential to be ingested by organisms, and their high surface area to volume ratio greatly increasing their sorption capacities for contaminants, resulting in biomagnification of pollutants.
As plastics enter into the environment, they are exposed to a wide variety of environmental systems conditions (e.g. exposure to sunlight, terrestrial vs aqueous conditions, growth of biofilms). As plastics chemically degrade, their surface chemistry changes significantly, influencing their ability to adsorb and accumulate inorganic contaminants such as toxic metals. This project seeks to understand the changes in plastic surface chemistry that occur upon degradation and how environmental systems conditions influence these degradation pathways with the overall goal of understanding the capacity of microplastics to serve as vectors for inorganic contaminants as they weather.
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Design of Sustainable, Multifunctional, and Selective Water Treatment Technologies
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This research project focuses on development of novel water treatment technologies using
nano-enabled biomaterials such as shrimp shells (chitosan), that are inherently more efficient, cost effective, and sustainable than traditional treatment technologies.
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We utilize chitosan, a natural waste product of the shellfish industry, repurposed
to now remove inorganic pollutants such as arsenic from water in a more sustainable way than traditional treatment techniques. By cross-linking chitosan with transition metals we design adsorbents that are multifunctional, combining what is traditionally multiple steps in a treatment process into a single step, thereby reducing costs and time associated with treatment.
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The adsorbents are also selective for arsenic over competing background ions such as phosphate and sulfate. By making the adsorbents selective, removal effectiveness of the target contaminant is increased, the need for a costly separation process at end of life is removed, and the recyclability of the removed contaminants as fresh feedstock is improved.
Evaluating the Influence of Soil Age and Regional Climate
on Clay Mineralogy and Cation Exchange Capacity
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The traditional conception of a tropical soil is one with high amounts of kaolinite, low pH,
and low cation exchange capacity (CEC). However, approximately 60% of soils in
moist-to-humid tropical environments do not fit this description.
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In this systematic study, the influence of regional climate (mean annual precipitation (MAP))
and soil age on soil clay mineralogy and cation exchange capacity was evaluated.
The findings have implications for nutrient cycling in humid tropical clay soils as well as
for accurate determination of CEC in clay-rich soils.
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Through detailed analyses the smectite to kaolinite/halloysite mineral weathering reactions
were correlated with the decrease in CEC (~70 cmolc/kg to < 10 cmolc/kg).
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Mean annual precipitation was found to be a major control on the rate of CEC decline, with CEC of soils in MAP of 4250 mm/yr declining at five to ten times the rate of soils in MAP of 2700 mm/yr.
