Characterization of fugitive mercury emissions from the cell building at a US chlor-alkali plant

In February 2000, an extensive measurement campaign was conducted of the fugitive (non-ducted) airborne elemental mercury (Hg 0) emissions from the cell building of a chlor-alkali plant located in the southeastern United States. The objectives of this study were to determine the total Hg 0 mass flux from the cell building under a range of typical wintertime meteorological conditions as well as to perform an air flow balance for the building and compare various Hg monitoring methods under a variety of sampling conditions. To meet these objectives, Hg 0 concentration and air velocity were monitored in the cell building roof vent over a 9-day period. In addition, tracer gas concentration and air velocity were also monitored during selected time periods in building side openings. The results of the study found an average Hg 0 emission rate in the roof vent of 0.36 g min −1. Also, as determined from the tracer gas measurements, potential Hg 0 transport from openings other than the roof vent was identified during one 24-h sampling period. Finally, the air flow balance performed for the building “closed” within 79–100% depending on which of three different calculation procedures was used, and the concentration of Hg 0 determined with the long-path ultraviolet differential optical absorption spectrometer (UV-DOAS) compared favorably with similar measurements conducted using a hand-held electrical resistance analyzer.