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 (Hg0) 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 Hg0 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, Hg0 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 Hg0 emission rate in the roof vent of 0.36 g min−1. Also, as determined from the tracer gas measurements, potential Hg0 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 Hg0 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.