Methods for measuring mercury in rainfall and aerosols in Florida

The sampling and analytical methods used for the Florida Atmospheric Mercury Study (FAMS) have been carefully tested for reliability, accuracy and precision. A simple, 48 h low-wattage UV oxidation utilizing ultrapure dilute aqua regia was developed to solubilize Hg prior to analysis by reductive purge and trap stripping and dual amalgamation CVAFS. We found no significant differences for total Hg in rainfall samples among Teflon FEP (117 and 2500 cm2), polymethylpentane (716 cm2) or polycarbonate (49, 80, 117, 181 cm2) funnels. For samples deployed for as long as one month, we found no significant differences for total Hg concentrations between samples with no added HCl vs samples with 7.5 ml 6M Q-HCl added per liter prior to bottle deployment. However, we observed significant adsorption of dissolved Hg to the bottle walls, even for acidified samples. The adsorbed Hg was successfully resolubilized using the aqua regia/UV oxidation treatment. We found no significant differences for total Hg in rainfall samples deployed for integration periods ranging from 12 to 36 days compared to the volume-weighted average concentrations for 24 h integrated samples at the same sites. No significant differences were found between aerosol Hg samples collected at 40–60 ℓ per minute on 47 mm, 0.45 μm polypropylene filters for integration periods of 24 h vs 6 days.