Personal Mercury Monitor for Exposure Measurements - Personal Mercury Monitor for Exposure Measurements
Project Summary/Abstract
Workers in the oil and natural gas industry are vulnerable to exposure to toxic mercury (Hg) vapor as a
result of routine inspection and maintenance of equipment such as compressors and other process equipment
that concentrate species of low volatility over time. Exposure of workers to mercury is of concern in many other
industries as well, including the chlor-alkali industry where mercury is used as an electrode, gold and silver mining
where these precious metals are extracted with mercury, manufacture of fluorescent and other lamps, dentistry,
etc. The mercury monitors currently on the market are large and difficult to transport and operate in many of the
settings where mercury exposure occurs. As a result, there is a great need for a personal mercury monitor to
protect the health of industrial workers. Mercury vapor concentrations are best measured by absorbance of the
253.7-nm emission line of a low pressure Hg lamp, the same method used for measurements of ambient ozone.
Compared to ozone, however, mercury detection is ~1,300 times more sensitive. In preliminary work, we
modified our recently developed Personal Ozone Monitor™ (POM™) for mercury concentration measurements.
This pocket-sized instrument weighs only 0.75 lb and consumes only 3 watts of power. In a proof-of-concept
application earlier this year, the modified POM displayed excellent precision for Hg of 0.1 µg/m3 in field testing by
a leading oil and gas company on their oil and gas production platforms in the North Sea during annual inspection
and maintenance. A problem discovered with this prototype instrument, however, is that the necessarily small
internal mercury scrubber (1 cm3 volume) has very limited capacity due to the limited number of adsorption sites
on the sorbent surface. In order to solve the problem of limited scrubber capacity for Hg, we propose to develop
a photochemical mercury scrubber that photo-oxidizes Hg in the gas phase to nanoparticles of HgO that pass
through the instrument. We have demonstrated and quantified this Hg-scrubbing principle in laboratory
experiments. Advantages of the photochemical mercury scrubber include 1) theoretically unlimited scrubbing
capacity, 2) endowment of the personal mercury monitor with high selectivity against other UV-absorbing species
such as ozone, NO2, and volatile aromatic compounds that may occur in industrial environments, and 3)
elimination of any interference due to sudden changes in humidity. With these advantages and our company’s
previous innovations in miniaturizing instruments for detecting airborne trace gases, a breakthrough in
technology for monitoring mercury exposure in the workplace is achievable. The deliverable for this project, if
funded, will be a pocket-sized personal mercury monitor with precision and accuracy comparable to much larger,
fixed-location monitors. Deployment of the Hermes Personal Mercury Monitor™ will improve the safety of
workers in all industries where exposure to mercury vapor is a potential hazard.
