3 Forms of Mercury in Air
Gaseous Elemental Mercury (GEM) – also commonly known as elemental Hg vapor, Hg⁰, predominates and exhibits endurance with long range transport capability due to its volatility and low chemical reactivity.
This form of mercury can be originated from both anthropogenic (fossil fuel, municipal and medical waste combustions and more) emissions and natural sources such as volcano eurptions.
Reactive Gaseous Mercury (RGM) – RGM is highly water soluble, therefore, usually affects to local deposition. It is usually in the form of Hg2+ as a result of stack gas emissions from stationary combustion source such as coal-fired power plant.
Total Particulate Mercury (TPM) – consists of mercury bound or strongly adsorbed to atmospheric particulate matter, it could be either GEM or RGM adsorbed onto the particle surface and follow to deposits into water bodies and ecosystem.
GEM is relatively persistent compare to both RGM and TPM due to its endurance with the environment. Hence, both concentrations of RGM and TPM in ambient air are relatively low comparing to GEM. Thus, measurement of Total Gaseous Mercury in ambient air can be referred to measurement of total Gaseous Elemental Mercury (GEM).
Operating Principle at A Glance
Sampling (Gold Amalgamation)
Ambient air is drawn through a 47mm Teflon membrane pre-filter (0.2μm pore size) to protect the gold amalgamation tube from plugging by airborne particulate matter.
In-line with the Teflon pre-filter, a dryer cartridge (containing purified grade Soda-Lime) dries the sample gas before entering the instrument for gold amalgamation.
The amalgamated mercury is thermally desorbed onto an Argon carrier gas stream into the optics of the Atomic Fluorescence Spectroscopy detector for measurement.
The gold amalgamation tube is rapidly cooled by a fan and sweep clean with the carrier gas before repeating the Sampling cycle.