1. Scope

1.1

This Standard applies to the integrated measurement of the concentration of total mercury (particulate and vapour phase) in ambient air over a concentration range of 5 to 5000 ng?m-3. The sampling time and/or flow rate must be adjusted so that the amount of mercury collected is within the linear range of the detector.

1.2

The method consists of the following steps:

(a) low-volume filtration of airborne particulate matter;

(b) pyrolysis of mercury compounds (organic and inorganic) to elemental mercury vapour;

(c) amalgamation of elemental mercury vapour on metallic silver collectors and subsequent release by thermal desorption; and

(d) measurement of thermally desorbed elemental mercury vapour by cold vapour atomic absorption spectrophotometry.

Notes: (1) All concentrations referred to throughout this Standard are based on a temperature of 25?C and an atmospheric pressure of 101.3 kPa unless otherwise stated.

(2) This Standard is not directly applicable to in-stack or in- plume measurements. Under certain conditions, the method may be suitable for the above-mentioned applications provided that test conditions and interferences are well known and all operational aspects are compatible with procedures indicated in this Standard. When measuring low mercury concentrations (less than 100 ng?m-3), extreme precautions are required in all aspects of this method to avoid contamination.