|Abstract Title:||Improvements to the RMAS Used to Measure and Identify Concentrations and Chemistry of Reactive Mercury|
|Presenter Name:||Natalie Allen|
|Company/Institution:||Department of Natural Resources and Environmental Science, University of Nevada, Reno, Nevada, USA|
|Session:||Special Session - New developments in understanding reactive mercury concentrations and chemistry|
|Co-Authors:||Natalie Allen,Livia Lown,Sarrah Dunham-Cheatham,Mae Gustin|
Abstract Information :
At first, the Reactive Mercury Active System (RMAS) was developed to measure atmospheric reactive mercury (RM) to test whether the only commercially available instrument was making accurate measurements of RM. The RMAS system has been further improved allowing for measurement of gaseous oxidized mercury (GOM), and particulate-bound mercury (PBM). Additional tests with the RMAS are ongoing at the University of Nevada, Reno to improve the resolution and collection efficiency of compounds. In order to improve RMAS sampling resolution, tests have been done to compare the standard 1 Lpm flow rate with data collected at 2 Lpm. This will allow for reducing sampling durations that at most locations is biweekly. Currently, membrane surfaces have been identified to quantify GOM and PBM (cation exchange and PTFE membranes) and qualitatively identify GOM species (nylon membranes). Cation exchange and PTFE membranes are digested and analyzed to determine mercury concentrations, while nylon membranes are thermally desorbed to determine the RM or GOM chemistry. New surfaces are needed for determining the chemistry of RM compounds, because the nylon membrane does not collect all RM compounds with equal efficiency. Testing has been done with Sterlitech nylon and polyethersulfone (PES) membranes, a membrane material used by other researchers, to test their ability to accurately capture GOM compared with the traditionally used cation exchange and nylon membranes. These alternate membranes showed no statistical difference in their ability to collect RM compared to the traditional membranes. Laboratory experiments are focusing on the development of collection surfaces for GOM sorption that can be thermally desorbed into a GC-MS. The nylon membrane thermal desorption peaks are too broad for unequivocal identification of Hg species. Collection surfaces being tested will be discussed.