A calibration assembly generates elemental mercury and oxidized mercury for calibrating components of a mercury monitoring system, including making necessary adjustments to efficiencies of a mercury compound converter and an elemental mercury detector. The calibrator generates an elemental mercury sample having a known elemental mercury concentration, [Hg.sup.0].sub.1 and combines an oxidizing component with the elemental mercury sample, thereby producing a reduced concentration of elemental mercury [Hg.sup.0].sub.2 within the sample. The calibrator measures the concentration of elemental mercury [Hg.sup.0].sub.2 within the sample and calculates a difference between the known elemental mercury concentration, [Hg.sup.0].sub.1 and the reduced concentration [Hg.sup.0].sub.2. The difference between [Hg.sup.0].sub.1 and [Hg.sup.0].sub.2 is substantially equal to the concentration of oxidized mercury produced by the calibrator. The concentration of oxidized mercury can also be calculated as the difference between elemental mercury detected after passing a sample stream containing oxidized mercury through a channel which includes the converter and the reduced concentration [Hg.sup.0].sub.2 detected after passing the sample stream through a channel which bypasses the converter. By providing oxidized mercury at calculated concentrations, the calibrator allows a user to calibrate continuous emission monitoring systems for accurate response to both elemental mercury and oxidized mercury.

The invention relates to the use of used alumina to reduce the level of inorganic contaminants, such as mercury and arsenic, from waste fluid streams. The invention further provides a process for reducing the level of mercury or arsenic in fluid streams by contacting the fluid stream with used alumina, such as used Claus catalyst.