Grad Research Experience: Yuan Li, Water Resources

Yuan Li, a graduate student advised by Judy Yang, is studying water resources. She received the Frank Y. and Julie C. Tsai Travel Award.

"Minnesota’s numerous lakes can host smelly and dangerous algal blooms each summer. My research focuses on using clay to remove these harmful algal cells from water bodies. We discovered that a synthetic clay called laponite is very efficient at removing harmful algae like Microcystis aeruginosa, as it requires much smaller amounts be added compared to traditional natural clays like bentonite and kaolinite. Laponite is biodegradable, more cost-effective, and environmentally friendly. By using laponite, we can better protect aquatic ecosystems and reduce the health risks associated with algal toxins."

I was born and raised in Dongying, Shandong, China; a large part of the city’s economy revolves around petroleum and the nearby Shengli Oil Field. I received my BS and MS degrees in petroleum engineering at China University of Petroleum (East China). Witnessing the pollution caused by oil extraction led me to reconsider my professional trajectory and shift toward addressing ecological challenges. I joined Judy Yang’s group in 2021. Currently, I am working on an environmental issue, harmful algal blooms (HABs). In Yang’s lab, we study the flocculation process between clay particles and algal cells using image processing technology on both the macro- and micro- scales. Once we understand the interaction between algal cells and clay particles, we can propose a comprehensive method to guide the use of clay to mitigate cyanobacterial blooms.

Clay-algae flocculation is a promising method to remove HABs in aquatic ecosystems. Many HAB-generating species, such as M. aeruginosa, produce toxins and harm the environment, human health, and the economy. Natural clays, such as bentonite and kaolinite, have been applied to mitigate HABs. By forming large aggregates in the water column, the flocculation of algal cells and clay particles can remove toxins and cells. In Judy Yang’s lab, we are investigating the effect of laponite, a synthetic, biodegradable, and commercially available smectite clay, on removing HAB cells. We compare its cell removal efficiencies with bentonite and kaolinite through clay-algae flocculation experiments. Our results show that laponite is more efficient in removing M. aeruginosa cells compared with bentonite and kaolinite. Specifically, we have shown that to remove 80% of M. aeruginosa cells from the water column, 0.1 g/L of laponite (clay mass to the total volume) is needed, which is much smaller than the required 2 g/L of kaolinite and 4 g/L of bentonite. We demonstrated that the superior performance of laponite clay occurs because its particle size is smaller compared to bentonite and kaolinite, which leads to a higher encounter rate between cells and clay particles. We also examined the influence of cell density on cell removal efficiency. We used this research to demonstrate that laponite can efficiently remove harmful algal cells from Powderhorn Lake.