Ambient mercury sources in Rochester, NY: results from Principle Components Analysis (PCA) of Mercury Monitoring Network Data.

Continuous atmospheric measurements of speciated mercury (Hg) (elemental mercury (Hg⁰), reactive gaseous mercury (RGM), and particulate mercury (Hgp)) were made in Rochester, NY from Dec 2007 to May 2009. Continuous measurements of ozone (O₃), sulfur dioxide (SO₂), carbonmonoxide (CO), particulate matter (PM₂.₅), and meteorological data were also available. A principle components analysis (PCA) of 3886 observations of 13 variables for the period identified six major factors. Melting snow was observed to be a source of Hg⁰in winters. Positive correlations between RGM and O₃ in the spring and summer may be indicative of Hg⁰ oxidation. RGM concentrations increased simultaneously with SO₂ suggesting the influence of coal fired power plants (CFPP). The fifth factor (F5) containing O₃ (high negative loading), CO (positive loading), Hg⁰ and Hg(p) (positive), and/or RGM (negative) was identified as a mobile source which was usually observed during morning rush hours (6:00-9:00 a.m.). The concentrations of the three mercury species from the direction of the CFPP were significantly reduced following the shutdown of this source.