Environmental concerns piqued the interest of civil and environmental engineering PhD candidate Xiaojing “Ruby” Fu from a very early age. Growing up in Changsha, China, which she describes as an epicenter for environmental challenges, Fu spent the majority of her childhood witnessing visible changes to her surroundings, beset by a variety of natural and human influences.
“When I was a child, the sky was blue,” Fu says. “As the years go by, memories of blue sky became quite rare. It’s shocking to experience that, particularly as I did — growing up, watching a montage of environmental changes.”
Working with Department of Civil and Environmental Engineering (CEE, a.k.a. Course 1) Professor Ruben Juanes, Fu now studies multiphase flow in porous media and creates computer-simulated, mathematical models on environment-related fluidic processes. Her current work is focused on modeling the fate of methane bubbles rising in the ocean and studying the impact of these bubbles on the global methane budget.
As a Course 1 graduate student, Fu’s exposure to a myriad of resources, experts, and research has deeply influenced her decision to pursue a faculty position after MIT — a goal she has prepared for since joining the department. “Simulations, modeling, laboratory, and fieldwork — Course 1 has given me a taste of everything,” she says. “This sort of exposure pushes students to round out their skills, and experience research areas and opportunities they would not have otherwise.”
Fu received her BS in applied mathematics from Clarkson University in 2011. She spoke with the department recently to describe her work and experiences.
Q: What are the real-world implications of your research?
A: I am passionate about environmental problems with a mathematical twist — an interest that brought me to MIT’s Course 1 program. Professor Juanes turned out to be the perfect fit as an advisor, with his expertise in numerical simulation and modeling of multiphase flow in the natural environment. Currently, with sponsorship from the U.S. Department of Energy, we are developing a mathematical model to study methane bubble plumes that are escaping from the seafloor. These bubbly gas plumes are most likely fueled by melting methane hydrates buried within the ocean sediments.
I think the first thing to ask is: Why do scientists care about the methane plumes? The key issue here is climate change. Methane is a more potent greenhouse gas than carbon dioxide; therefore, understanding the “ins and outs” of methane gas to the atmosphere has significant implications in the study of climate change. How much methane is being released into the ocean? What happens to these bubbles once they enter the water? Do they make it into the atmosphere? If they do, how much methane ends up in the atmosphere? These are the kinds of big-picture questions we are encouraged to answer in Course 1.
Through a combination of model simulations, current field data, and laboratory experiments, we can better understand the fate of these bubbles and estimate the amount of methane released into the atmosphere. This research will help develop a more accurate atmospheric methane budget and predict climate change trends.
Q: What opportunities have you had to delve deeper into your research?
A: In April, I was invited to join a 10-day research cruise organized by U.S. Geological Survey (USGS) geophysicist and MIT research affiliate Carolyn Ruppel to explore my theoretical work in a real-world context. We traveled on Research Vessel Endeavor to visit a cluster of methane seeps, locations on the seafloor that release methane bubbles, [which were] discovered in the past few years off the east coast of the U.S.
I never doubted the existence of these methane plumes, but it was still overwhelming and exciting to experience something that I’d only read about in papers and simulated with my computer!
On the cruise, we used USGS instruments to image several hundred meters below the seafloor. These seismic images allowed USGS scientists to identify the location of gas pockets beneath the seeps, determine where gas might be frozen in the sediments in the form of gas hydrate, and find chimneys that may feed the seafloor seeps.
We also measured the sea-air flux of methane over the methane plumes using state-of-the-art instruments. We continuously pumped shallow seawater aboard the ship and measured the concentration of methane and carbon dioxide, in addition to determining the carbon isotopic characteristics, which can enlighten us on the origin of the methane. Combining these data with other information allows the USGS researchers to calculate the sea-air flux of methane over the seep areas.
After two days of sailing, we reached a previously recorded seep field where I watched, for the first time, a methane plume appear as acoustic signals on the computer monitor. Right there beneath our ship, an energetic methane plume was shooting out of the seafloor and reaching for the surface. For someone who does mostly theoretical modeling, this was the most exciting experience on my trip. In that moment, the importance of my work in CEE and its impact was clear.
Theoretical work can sometimes feel far away from the reality and nature of the investigation. This cruise connected the science conducted in the field with my theoretical work in Course 1.
Q: What’s the next step for you in your work?
A: The next step in my research is to use our current model, and consider the effect of gas hydrate coating on the fate of methane bubbles. Gas hydrate is a frozen product of methane and water that forms at certain pressure and temperature conditions. In field studies and laboratory experiments, gas hydrate forms around rising methane bubbles under the right water column conditions (temperature, methane saturation, salinity, etc.) Despite the fact that this process could play an important role in the fate of rising bubbles, study of this phenomenon is scarce.
For a hydrate-free bubble, the gas is directly exposed to the water column and will quickly dissolve. These ice-like hydrate shells that solidify on rising methane bubbles may shield the methane and allow it to be carried to shallower depths in the water column.
In addition to this, I am developing a series of bench-scale laboratory experiments to study the dynamics of rising and dissolving bubbles. This will help calibrate the model. Ultimately, we are looking to develop an up-scaled model to quantify methane flux into the water and the atmosphere from these plumes.
Following graduation, I hope to secure a faculty position. I would love to spend my life teaching to undergraduates the concepts I’ve explored in Course 1 and get people excited about science. Additionally, I aim to develop a deeper expertise in environmental science and establish collaborations with Chinese scientists to tackle the environmental problems back home.
In CEE, particularly as a graduate student, you are provided an incredible amount of access to worldwide visiting scientists, interactive seminars and peers from other fields. I’m surrounded by everything I need to pursue a career in academia, in addition to continuing to explore my personal research.
