From Combustion to Consumption — Researching the Atmospheric Mystery of Mercury
Mercury: We know that substantial amounts of this highly toxic element are released into the atmosphere through the burning of coal and petroleum for fuel and the incineration of our civilization’s garbage. We also know that mercury entering the atmosphere can eventually find its way into the soil and, especially, the world’s oceans, where it poses a threat to health by accumulating in many species of fish that we eat.
But the chemical transformation of mercury released by combustion that takes place in the atmosphere as a precursor to dangerous contamination of soil and water is not clearly understood. It’s a scientific mystery that Assistant Professor Alexei Khalizov, Department of Chemistry and Environmental Science, is working to solve with substantial support from the National Science Foundation (NSF).
To advance his investigation of the atmospheric mystery of mercury, the NSF recently awarded Khalizov a five-year CAREER grant totaling some $670,000. The NSF’s Faculty Early Career Development (CAREER) Program offers the foundation’s most prestigious awards in support of younger faculty who, in building their academic careers, have demonstrated outstanding potential as both educators and researchers. The work that Khalizov will pursue with this support promises to yield critical knowledge about the environmental impacts of mercury.
Khalizov’s path to NJIT was via the Russian Federation, where he earned his undergraduate and graduate degrees in chemistry. His first postdoctoral position brought him to Canada’s McGill University, to an opportunity that involved researching atmospheric chemistry. This included investigating the chemistry of rapid mercury-depletion events in the Arctic atmosphere that led to significant inputs of oxidized mercury into the soil and water over a very short time span. This is a particular health concern for the region’s indigenous people because of their dependence on fish as a staple food. “So in a sense, mercury ‘just happened’ with respect to becoming an important research interest for me,” Khalizov says.
It’s an interest that Khalizov pursued periodically during further research at Texas A&M University. Now at NJIT, which he joined as a faculty member in 2013, mercury again has become a major focus of his research. He also has been studying another pollutant, atmospheric soot, with substantial NSF funding. It is noteworthy that both soot and mercury pollution problems originate from humanity’s heavy reliance on fossil fuel combustion for energy generation and transportation.
“We can measure how much gaseous elemental mercury is released into the atmosphere as a result of combustion,” Khalizov explains. “However, we really don’t understand the chemistry by which this form of mercury is oxidized and then becomes bound to particles in the atmosphere. These are the stages before the mercury becomes dangerous in the food chain, before rain and other forms of precipitation cause the oxidized mercury to enter the ocean and other bodies of water. We know that this process appears to occur in the atmosphere over one or two years, but chemical details are missing.”
Three Major Components
Going forward, Khalizov further explains that this research will have three major components. One will be investigating the relevant chemical reactions in the laboratory, particularly how gaseous elemental mercury is oxidized by reacting with bromine atoms to form a short-lived radical and how that radical is converted into stable molecules. This will require characterizing reactions that take place on a time scale of milliseconds. A second major objective will be to clarify how the resulting gaseous products attach to particles in the atmosphere.
Gaining this knowledge will require innovative measurement techniques and appropriate instrumentation, including instrumentation to measure oxidized atmospheric mercury in the field with accuracy comparable to that which can be achieved under controlled laboratory conditions. This is the third major component of the research effort that Khlaizov is mapping, and he anticipates developing new instruments such as a chemical ionization mass spectrometer for detection of gaseous oxidized mercury and a desorption electrospray ionization mass spectrometer capable of chemical analysis of mercury in aerosol nanoparticles.
Khalizov, who says that he will also be collaborating internationally with colleagues in Canada and China, looks forward to very productive experimental investigation at NJIT. “Again, we know how much mercury is introduced into the atmosphere and what the sources are. But we don’t understand the oxidation process very well.
“I hope to contribute to finding out the details of what happens in a complex chain of chemical events. We have opened the door to a new, very large field for research. It’s research that can provide the concrete data we need to develop better models of how atmospheric mercury migrates to other parts of the environment, and how this migration might be affected by different strategies for mitigation.”