Abstract
Continuous mercury monitors (CMMs) have the advantage of performing real-time or near real-time measurement, although they are often vulnerable to measurement interferences. For example, CMMs based on atomic absorption spectrometry (AAS) are subject to interferences by components of the sample gas, such as ozone, if they happen to have strong absorption bands or lines overlapping the Hg absorption line. Studies on a selected commercially available CMM showed that 120 ppb of ozone could exert an interference of approximately 63 ng/m3 on Hg measurement. This interference may consequently affect the risk assessment of human exposure to Hg. On a similar basis, it was found that Hg can also result in significant interferences on an ozone analyzer based on UV absorption. Results showed that Hg at a concentration of 300 ng/m3 can potentially cause a bias in ozone measurement of approximately 35 ppb, comparable to the average ambient ozone concentration. It should be noted that interferences discussed in this paper are applicable only to UV-absorption-based Hg and ozone analyzers. It is also possible that certain models of such analyzers are not compromised by the reported interferences, and thus, the findings in this work should be considered as analyzer-specific.
Highlights
The 1990 United States Clean Air Act Amendments (CAAA) listed 189 hazardous air pollutants (HAPs), and among them, mercury (Hg) is believed to have a significant impact on human health (Brown et al, 1999)
It was found that ozone in the range of 0 to 120 ppb can exert an interference of up to 63 ng/m3 on an atomic absorption spectrometry (AAS)-based Hg analyzer
A linear relationship was established between the ozone concentration and corresponding interference on Hg measurement
Summary
The 1990 United States Clean Air Act Amendments (CAAA) listed 189 hazardous air pollutants (HAPs), and among them, mercury (Hg) is believed to have a significant impact on human health (Brown et al, 1999). The U.S Environmental Protection Agency made a regulatory decision in 2000 that Hg should be controlled (USEPA, 2000), and issued the Clean Air Mercury Rule in 2005 to permanently cap and reduce Hg emissions from stationary sources (USEPA, 2005a). Hg emission control technologies have developed rapidly in recent years (Pavlish et al, 2003). Both Hg emission regulations and development of Hg control technologies require that reliable methods be used for accurate Hg measurement. Monitoring ground level of ozone, another significant air pollutant, is required by the U.S EPA. Deployment of accurate ozone measurement is of great importance to demonstrate compliance with the National Ambient Air Quality Standard (NAAQS) for ozone
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have