scope:

Introduction

Mercury (Hg) in ambient air exists both in elemental form and as inorganic and organic mercury. The background mass concentrations of mercury in areas without mercury sources, averaged over many years, are less than 2 ng/m³ [1 to 4]. In urban air and the surroundings of mercury emitters, significantly higher mass concentrations are possible.

Because elemental mercury has a long residence time in the atmosphere, this is the predominant form (> 90 %) of total atmospheric mercury in air remote from industrial sites. However, in areas directly subject to the action of emitters, the conditions may be different.

Mercury exists in the atmosphere in the particulate and gaseous form. In clean marine and continental air, the mass concentration of particulate mercury is two orders of magnitude lower than the mass concentration of total mercury [1; 2]. The particulate share in urban air is usually significantly less than 10 %, whereas, at contaminated locations, higher particulate contents have also been found [3; 5; 6]. The majority of the gaseous fraction consists of elemental mercury [1; 3; 7]; in addition, smaller amounts of methyl mercury chloride (MMC), dimethyl mercury (DMM) and mercury(II) chloride (MC) may also be present as volatile mercury compounds [1; 8].

Guideline VDI 2267 describes methods for determining ambient air concentration of metals and semimetals that pass into ambient air from fired plants and also during their production and processing. This also ausincludes the metal mercury covered in this guideline. Because of chemical reactions, deposition or condensation, the predominant fraction of the metals and semimetals covered in further parts of guideline VDI 2267, as inorganic compound, is converted to the particulate form or deposited onto dust particles, which gives the guideline its title "Determination of suspended particles in ambient air". Although this is not similarly applicable to mercury, which has a particulate content of only a few percent (see above and Annex B), nevertheless, for systematic reasons, this part is published as a part of guideline VDI 2267.

This guideline describes a method for determining the mass concentration of total gaseous mercury (TGM) in ambient air. The method does not distinguish between elemental, inorganic or organic mercury. Because of the low mass concentrations of airborne mercury, an enrichment sampling method is used. Analytical determination is performed after thermal desorption using atomic fluorescence spectrometry (AFS).

Part 8 of guideline VDI 2267 also describes a method for determining total gaseous mercury (TGM) in ambient air using an enrichment sampling method. Analysis following thermal desorption is by atomic absorption spectrometry (AAS).