Particulate and Gaseous Mercury Emissions from Chlor-Alkali Plants (Air Streams) – USEPA Method 101

USEPA Method 101 is used for the determination of Mercury (Hg) emissions, including both particulate and gaseous Hg, from chlor-alkali plants and other sources (as specified in the regulations) where the carrier-gas stream in the duct or stack is principally air.
 
Particulate and gaseous Hg emissions are withdrawn isokinetically from the source and collected in acidic iodine monochloride (ICl) solution.  The Hg collected (in the mercuric form) is reduced to elemental Hg, which is then aerated from the solution into an optical cell and measured by cold vapor atomic absorption spectrophotometry (CVAAS).
 
Potential interferences include sulfur dioxide (SO₂), which reduces ICl and causes premature depletion of the ICl solution and condensation of water vapor on the optical cell windows.  ICl concentrations greater than 10-4 molar inhibit the reduction of the Hg (II) ion in the aeration cell.