Research Objectives | My research goal is to characterize the dominant atmospheric Hg species and sources entering and circulating within diverse environmental media, such as oceans, snowpack, and sediments. I also seek to assess how these Hg species and sources vary in response to anthropogenic and natural influences over time and space. Understanding Hg cycling is crucial for developing effective policies and interventions aimed at mitigating its impacts. My work aims to provide critical insights into how atmospheric Hg sources influence marine and coastal ecosystems, informing global efforts to reduce Hg pollution and protect ecological and human health.
Background | My research explores the complex pathways of atmospheric mercury (Hg), a neurotoxic and bioaccumulative pollutant that impacts both ecosystems and human health. Hg is emitted into the atmosphere from both natural and anthropogenic sources. Natural sources emit mercury primarily in its elemental form, Hg(0), while human activities, such as emissions from coal-fired power plants, release Hg(0) as well as two other forms: divalent mercury (Hg(II)) and particulate-bound mercury (Hg(P)). In its elemental form, Hg(0), Hg can persist in the atmosphere for approximately 0.5 to 1 year, allowing it to travel long distances and impact diverse environmental compartments on a global scale. Once atmospheric Hg enters the biosphere, it can either undergo long-term burial, providing historical records of environmental conditions, or cycle back through the atmosphere, snowpack, and ocean surfaces. This cycling can lead to bioaccumulation in the biosphere, resulting in ecosystem-level and human health issues on both regional and global scales.
Research Methods | To trace mercury’s sources and transformation pathways, I use Hg stable isotopes as a primary analytical tool. Hg isotopes undergo three types of fractionations during their biogeochemical cycling in the environment: mass-dependent fractionation (δ202Hg), mass-independent fractionation of odd mass number isotopes (Δ199Hg, Δ201Hg), and mass-independent fractionation of even mass number isotopes (Δ200Hg, Δ204Hg). Mass-dependent fractionation occurs through a variety of processes, including methylation, demethylation, and mineral sorption. Odd-mass-independent fractionation is predominantly associated with photochemical reactions, including aqueous photochemical reduction of Hg(II), photochemical demethylation of methylmercury, and photochemical reduction of Hg(II) in snow. Even-mass-independent fractionation is thought to be produced from photochemical oxidation of Hg(0) in the upper troposphere. By applying isotope mixing models and considering both Hg isotope fractionations and concentrations, I can quantify the contributions of different Hg sources and understand their impacts on marine ecosystems.
Mercury isotope analysis process
