Optical-Trapping, Single-Particle Reactor for the Study of Surface and Heterogeneous Chemistry of Mercury
CHUJI WANG, Yukai Ai, Yong-Le Pan, Gorden Videen,
Mississippi State University Abstract Number: 78
Working Group: Aerosol Physical Chemistry and Microphysics
AbstractMercury is a neurotoxin that impacts human health and the health of ecosystems globally. Mercury exists in the atmosphere in three major forms: elemental mercury, gaseous oxidized mercury, and particulate mercury. Gas-phase mercury chemistry has been extensively studied through some key kinetic constants are being measured. However, the heterogeneous and surface chemistry of mercury has been much less studied due to its complexity and experimental difficulties in accurate measurements. Current studies of atmospheric mercury predominantly use flow-tubes or reaction vessels that inevitably suffer the wall-effect and surface interferences.
We create a single-particle reactor (SPR) using optical trapping to mimic single, particulate mercury particles freely suspended in the atmosphere. We investigate reactions and equilibrium processes on the surface of mercury compound-contained single-particles that are exposed to ozone, UV light in a range of relative humidity. In particular, we mixed HgX
2 (X
2=Cl
2, Br
2, or ClBr) with single-wall carbon nanotube particles and trapped a single mercury compound contained particle (a SPR) in an airtight chamber under controlled condition (concertation of ozone, relative humidity, UV light). We explored multiphase chemical reactions via measuring the time- and position-dependent Raman spectra of the particle. The Raman spectra revealed details of heterogeneity of the mercury compounds in the particle, time-evolution of the particle surface, reaction of the mercury compounds with ozone, and photochemistry effect. We present some preliminary results from this study.