HR: 0800h
AN: B11B-0405    [Abstracts]
TI: Size Distribution and First Flush Effects of Mercury Containing Particles in Highway Runoff Water
AU: * Ferguson, K
EM: kjferguson@ucdavis.edu
AF: University of California, Davis, One Shields Ave., Davis, CA 95616,
AU: Green, P
EM: pggreen@ucdavis.edu
AF: University of California, Davis, One Shields Ave., Davis, CA 95616,
AB: Human and environmental health concerns have recently prompted many California water quality control boards to lower the Total Maximum Daily Loads (TMDL) of Mercury into their water systems. A size distribution study of mercury containing particles was conducted in order to begin to understand the possible sources of the contamination in highway storm water runoff. Four storms were studied from a monitoring site in the Los Angeles area near the crossing of highways 605 and 91. Storm water ran through an extended detention basin made of earthen material with a maximum water depth of 1.17m. Grab samples were collected manually starting at the beginning of the runoff, continuing at every fifteen minutes for the first hour, followed by a collection every hour after that for the duration of the storm. The particle sizes were separated into five size ranges (larger than 100um, 20-100um, 8-20um, 0.45-8um, and 0-0.45um) by sequential filtration. The samples were then acid digested for further analysis. Five standard Mercury solutions ranging from 5 to 100 parts per trillion were prepared in nitric acid immediately before analysis. Samples were analyzed for both the Hg-199 and the Hg-202 isotopes using an Agilent 7500i Inductively Coupled Plasma Mass Spectrometer. Substantial sub-micron concentrations of mercury were detected from all four storms, and in all five particle size ranges studied. The total amount of Mercury detected from each of the storms ranged from 8.5 to 35.5 pptr. Bursts of rain correlate well with increases of influent Hg concentration. Although a First Flush effect can be seen in the first storm, it is not as strong and/or not shown at all in the remaining three. The detention basin used at the site was shown to be an efficient BMP, reducing the amount of Hg in the effluent runoff as much as 30 pptr and down to as little as 2 pptr. The majority of Hg was found in either the 8-20um or the 0-0.45um particle size ranges. Mitigation of either portion will be challenging, but necessary to meet proposed 50 percent reductions.
DE: 0461 Metals
SC: Biogeosciences [B]
MN: 2007 Fall Meeting