This project focused on atmospheric mercury, a toxic pollutant released to the air by various anthropogenic activities and transported globally. The deposition of mercury to land and oceans depends on its chemical speciation, and so does its subsequent bioaccumulation. The major research goal was to enable retrieving molecular speciation of oxidized mercury (Hg(II)) and establish detailed chemical mechanisms for atmospheric mercury oxidation and removal by environmental surfaces. The educational and outreach goals were to improve the recruitment and professional training of future workforce, with specific focus on increasing enrollment of high school students into STEM university programs and improving retention, training, and professional placement of the currently enrolled environmental science undergraduates.

Intellectual Merit

This project has led to a new instrumental approach, which is based on the chemical ionization mass spectrometry, for chemically resolved detection of gaseous Hg(II). Powered by this approach, we conducted laboratory experiments to show the importance of gas-surface interactions in controlling the concentration and speciation of atmospheric gaseous Hg(II). We measured the rates of uptake of gaseous Hg(II) by surfaces made of organic and inorganic chemicals, and established the associated reaction mechanisms. Using kinetic data, we have shown that the lifetime of gaseous Hg(II) with respect to its scavenging by atmospheric aerosol surfaces could be as short as 1 hour. Furthermore, processing on aerosols changes the chemical makeup of the originally generated gaseous Hg(II). Such processing would also occur on surfaces of the sampling equipment (tubing, filters, and adsorbing media) used for pre-concentration of the atmospheric gaseous Hg(II) during its analysis in the field, leading to speciation artifacts.

We show that one way to avoid such artifacts could be by employing direct detection of atmospheric gaseous Hg(II) by ambient pressure chemical ionization mass spectrometry and our project has laid out the foundation for such future work. We conducted preliminary studies of the intermediates and products of oxidation of gaseous elemental mercury by bromine atoms, setting up the foundation for future work to decipher its complete gas-phase oxidation mechanism in the presence of various radicals and molecules in the atmosphere. 

Broader Impacts

The mechanistic knowledge and kinetic data generated in this project will improve the accuracy of predictions of the mercury transport and deposition in atmospheric models, allowing for better estimates of mercury accumulation in biological food chains. The project provided professional and research training for high school, undergraduate and graduate students, including several female students and students from underrepresented minorities in STEM fields.

Over the course of the project, the PI has developed a departmental open house venue, helping the department to more than double its undergraduate enrollment (from 90 to 220 students) since 2016. A significant fraction of these students come from Newark and surrounding areas, which have a significant fraction of minority population. The open house was augmented with other recruitment efforts, including giving a series of public lectures on air pollution and climate change during earth day at environmental centers and enriching the summer research programs for high school students at the PI's institution. The latter activities included bringing several separate summer research programs (including the ACS SEED program for financially disadvantaged students) under one roof and developing workshops and seminars to provide the high school students with hard and soft skills related to scientific research.

Enrollment, retention, and professional placement of students pursuing the environmental science major have been improved by increasing the program's visibility, revamping the coursework, and connecting the students with recent alumni and employers. Enrollment to the Environmental Chemistry course taught by the PI has been increased by 50% since 2015 as a result of the introduction of outcome-oriented instructional materials for learning and testing and other efforts to enrich the course contents.

Last Modified: 09/20/2023
Modified by: Alexei Khalizov