- Surface reactivity and stability of nano-sized metal oxides
- Investigation of nano-bio processes in the environment
- Development and effective deployment of environmental remediation methods
- Application of analytical transmission electron microscopy (TEM) analyses on various environmental and biological samples
1) Surface reactivity and stability of nano-sized metal oxides
Manganese (Mn) oxides are ubiquitous in the environment, and are also among the most reactive mineral phases for adsorption and oxidation reactions, playing critical roles in controlling biogeochemical elemental cycles. While natural Mn oxides typically contain a variety of structural impurities, such as nickel and cobalt, and are also intimately associated with other minerals, numerous laboratory studies have used freshly-synthesized, impurity-free, individual Mn oxide. Thus, my research aims to quantify the effect of structural impurities or the presence of secondary minerals on the oxidizing capacity of Mn oxides toward arsenite (As(III)) or chromium (III), and hence further improve the prediction of environmental reactivity of Mn oxides, as well as the fate and behaviors of associated toxic elements.
2) Investigation of nano-bio processes in the environment
The transport and fate of manufactured and naturally-occurring nanoparticles in the environment is often regulated through interactions with living organisms, such as plants and microorganisms, which result in nanoparticle redistribution via uptake, bioaccumulation, or biotransformation. First, a study by Hayes* et al. (2020, Science of the Total Environment) focuses on plant interactions with alumina nanoparticles (Al2O3 NPs), one of the most commonly used metal oxides, and investigates whether Al2O3 NPs cause plant toxicity in a similar fashion as Al ions. Inhibitory effects of Al ions on root growth are well-known, and Al toxicity is often the primary limiting factor for crop production in acid soils. Yet, this is the first work published that provides differences and similarities in plant responses from seed germination to full maturity, with mechanisms of higher plant tolerance to the Al2O3 NPs observed in lettuce plants to Al ions. Secondly, microbial interactions of manufactured and naturally-occurring nanoparticles are also an interest of mine, specifically in two important receiving environments, namely anaerobic digesters in wastewater treatment plants and natural sediments in the San Francisco Bay-Delta estuary (California, USA), both of which present sulfide-rich conditions that are likely to induce the (trans)formation of manufactured and naturally-occurring nanoparticles.
3) Development and effective deployment of environmental remediation methods
Environmental remediation is costly and poses significant technical challenges. Thus, my research aims to develop and effectively deploy unique and inexpensive remediation technologies that can aid in accelerating the removal rate of environmental contaminants. For instance, polycyclic aromatic hydrocarbons (PAHs) are widespread persistent organic toxins, and pose serious risks for ecosystems and human health due to their carcinogenic and mutagenic effects. PAHs have very low water solubility and high octanol-water partition coefficient, and hence, they tend to strongly adsorb onto organic matter, which makes them less susceptible to biological and chemical degradation in the environment. With the use of nanoparticle supported lipid bilayer (NP-SLB), the desorption process of once-adsorbed PAHs is facilitated, making them more accessible for in situ biodegradation or removal in soil environments.
4) Application of analytical transmission electron microscopy (TEM) analyses on various environmental and biological samples
I have been particularly interested in using analytical TEM analyses to characterize nanoparticles present in environmental samples. I am strongly committed to educate future generation/workforce with electron microscopy techniques. For example, both undergraduate and graduate students of my research group have been trained and used electron microscopy techniques for their research projects (7 out of 8 original research papers have presentations of electron microscopy results and analyses). I have also incorporated them into lecture and laboratory components of my courses and support the use of electron microscopy techniques in studying environmental and biological samples.