In this project, measurements of elemental mercury (Hg(0)), reactive gaseous mercury (RGM), and particulate mercury (HgP) will be made at Appledore Island, 10 km off the southern New Hampshire coastline, and sampling artifacts for RGM and HgP will be investigated. Three objectives will be addressed at this island sampling site: 1) determination of the phase partitioning of mercury (Hg(0), RGM, HgP, and TGM [total gaseous mercury; Hg(0) + RGM]) with high time resolution, quantification of its spatial and temporal variation in the marine environment, and comparison with nearby coastal and inland sites, 2) assessment of the relative importance of sources and sinks of atmospheric mercury in the marine boundary layer (MBL) and construction of a first-order budget, and 3) documentation and an improved understanding of the impact of Hg(0)-rich polluted continental outflow on maritime cycling of atmospheric mercury. This work will provide detailed information on mercury source and sink strengths in the MBL, which is critical for determining the lifetimes of Hg(0), RGM, and HgP, and ultimately regional and global budgets.
Two graduate students will be involved in the measurement and data analysis components of this research. Two undergraduates will help with the field site setup and ongoing maintenance activities at Appledore Island and participate in data analysis. An outreach program at the University of New Hampshire will be utilized to better inform the public about mercury (a ubiquitous toxic contaminant in the global atmosphere) in the Northeast through public displays and a quarterly publication. The results from this project will also be integrated into an NSF-sponsored teacher training program.
1) Continuous year-round measurements We moved the Tekran speciation unit to the air quality monitoring site on the rooftop of the ESF Chemistry Department building Jahn Lab in Syracuse, NY. The move was simply taken because of PI's relocation from University of New Hampshire to SUNY-ESF. Ambient mixing ratios of Hg° have been measured continuously using a Tekran model 2537A cold vapor atomic fluorescence spectrometer with 5-minute time resolution and a limit of detection of ~10 ppqv (1 ng m-3 = 112 ppqv). This dataset together with concurrent measurements of other trace gases and PM concentrations would be very useful to study mercury sources and sinks in an urban environment. 2) Numerical modeling and computation A gas phase chemical box model was developed that included O3, halogen, and mercury chemical mechanisms (Kim et al., 2010). Gas phase halogen, sulfur, VOC, and aerosol chemistry and aqueous chemistry were added into the previous model. We studied Hg° loss from the gas phase associated with gas-aqueous mass transfer during the nighttime in summer at the Thompson Farm (coastal), Appledore Island (marine), and Pac Monadnock (inland, rural, elevated) sites. Several different measurement data sets were utilized to set the initial conditions of gas phase chemical compounds. We conducted sensitivity runs with our newly computed rate constant rate of HgBr → Hg +Br for the midlatitudes marine boundary layer and examine the effect of different rate constants on rate of Hg° oxidation. We are in the process of computing more rate constants for reactions involving Hg° oxidation and reactive mercury transformation and quantify the effect of ranges of those rate constants on mercury cycling in the marine boundary layer. We are also working to improve the box model with more complete halogen and VOC chemistry as well as surface and aqueous chemistry. We are working to couple our box model with detailed mercury chemistry with CMAQ to better simulate regional distributions of speciated mercury. A Ph.D. student, Zhuyun (Julia) Ye, was funded on this grant during the year of 2013 working on these tasks and is preparing a manuscript on the results. 3) Data analysis We continued to analyse the dynamical, physical and chemical mechanisms that control the temporal and spatial variabilities of mercury in marine, coastal, and inland locations. Interesting results were found in the analysis and were presented at the 11th International Conference of Mercury as a Global Pollutant in July 2013 in Edinberguh, Scotland. A manscript on these results in in preparation. A graduate student, Casey Hall, was supported in summer 2013 to conduct analysis of mercury in a metropolis in East-central China. The student was funded on this grant to present his results at the 11th International Conference of Mercury as a Global Pollutant in July 2013 in Edinberguh, Scotland. The results were further published in Atmospehre in March 2014. (Hall et al., 2014). 5) Education and outreach In my undergraduate course "Introduction to Atmospheric Science" offered in Fall 2013, I used our field campaigns and findings from this project to illustrate applications of the fundamentals of the course in understanding atmospheric chemical composition and regional to global budgets of air pollutants. In my higher level graduate course "Regional Air Quality" offered in Spring 2014, I presented our latest measurement, modeling, and data analysis work to the class to demonstrate the most up-to-date Hg issues in the community, how we approached them, and what we got. During the ESF Chemistry Department Open Houses in Spring 2014, and during my invited talks at Tsinghua University and Zhejiang University in January 2013, at Hong Kong Polytechnic University in January 2014, I included work from this project to illustrate the importance of studying atmospheric mercury, the state of our understanding of mercury cycling. Zhuyun Ye, a Ph.D. student under my supervision, modified the mercury box model that was developed by a former Ph.D. student Su Youn Kim (Kim, 2010) by including most up-to-date mercury cycling chemistry and halogen chemistry. She used sensitivity simulations to find out key reactions that have significant effects on mercury cycling. She worked on coupling this box model with the EPA/NOAA regional air quality model CMAQ to improve simulated distributions of speciated mercury concentrations by improving the mercury chemistry in CMAQ. This is the first part of Zhuyun’s Ph.D. dissertation work. She presented her results at the Fall AGU meeting in San Francisco in December 2013. Casey Hall, a M.S. student under my supervision, analyzed a one-year TGM dataset from Nanjing, China, a metropolis in East-central China, and published the findings in Atmosphere. This is the first half of his M.S. thesis. He was supported on the grant to go to the 11th International Conference of Mercury as a Global Pollutant in Edinburgh, Scotland in July 203.
