NBN ISO 21741:2021

This document describes a method for the sampling and measurement of mercury of both vapour and
solid phases on stationary source flue gas streams. Mercury generally exists as elemental (Hg0
) and
oxidized (Hg2+
) forms, both in the vapour and solid phases in flue gases. The vapour-phase (gaseous)
mercury is captured either isokinetically or non-isokinetically with a gold amalgamation trap after
removing solid-phase (particulate) mercury with a filter. Because gold amalgamation trap captures
only gaseous elemental mercury, the oxidized mercury (Hg2+
) in the vapour phase is converted to
elemental mercury (Hg0
) prior to the gold amalgamation trap. The concentration of gaseous mercury
is determined using atomic absorption spectrometry (AAS) or atomic fluorescence spectrometry (AFS)
after releasing mercury by heating the gold amalgamation trap. Separately, particulate mercury is
collected isokinetically on a filter and the concentration is determined using cold vapour AAS or cold
vapour AFS after dissolving the particulate mercury into solution.
The total concentration of mercury in flue gas is expressed as the sum of both gaseous and particulate
mercury concentrations.
The gold amalgamation method is intended for short-term (periodic) measurements of gaseous mercury
ranging from 0,01 µg/m3
to 100 µg/m3
with sampling volumes from 0,005 m3
to 0,1 m3
and sample gas
flow rate between 0,2 l/min to 1 l/min. The measurement range of particulate mercury is typically
from 0,01 µg/m3
to 100 µg/m3
with sampling volume from 0,05 m3
to 1 m3
.