AQS SELECTED METHOD DESCRIPTIONS

Mercury Sorbent Tube Method (40CFR75, Appendix K)

The Appendix K Sorbent Tube Method was developed with the critical support of ERPI, and is designed for the sampling of mercury emissions in combustion flue gas streams using dry sorbent traps, followed by analysis of each trap by EPA Method 1631, Revision E, using Cold Vapor Atomic Fluorescence Spectrometry (CVAFS). Known volumes of flue gas are extracted from a duct through a specially designed, low mercury blank, sorbent trap with a nominal flow rate of 0.2 to 0.6 L/min. The analyte measured by this method is total vapor-phase mercury, which represents the sum of elemental and oxidized forms of mercury. Mercury concentrations are determined on a mass basis (ug/m3) and then combined with flue gas flow data (m3/min) to calculate the continuous mass emission rate of total vapor phase mercury.

Fluegas Absorbent Mercury Speciation (FAMS) Method

The FAMS method relies on sequential selective capture to separate and quantify three mercury species, particulate Hg (Hgp), gaseous oxidized (Hg2+), and gaseous elemental (Hg0). A known, precise volume (±0.1 liter) of gas is pulled through the FAMS sorbent train using standard sampling equipment including a quartz probe liner, heated probe, silica-gel water trap, mass flow meter and pump. The temperature of the FAMS sorbent train is kept at 95 ± 5 °C during sampling to avoid water condensation in the trap. The sorbed Hg0 on the chemically impregnated carbon and the PHg on the glass wool plug is leached of collected Hg in the clean lab using hot-refluxing HNO3/H2SO4, then further oxidation in BrCl solution. The sorbed Hg(II) on the KCl trap is dissolved in (v/v) BrCl solution. Aliquots of all three Hg species digests are analyzed using EPA Method 1631.