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TREATMENT OF HEAVY METALS IN STORMWATER USING WET POND AND WETLAND MESOCOSMS
Citation:
MUTHUKRISHNAN, S. TREATMENT OF HEAVY METALS IN STORMWATER USING WET POND AND WETLAND MESOCOSMS. Presented at 21st Annual International Conference on Soils, Sediments and Water, University of Massachusetts, Amherst, MA, October 17 - 20, 2005.
Impact/Purpose:
To inform the public
Description:
Urban stormwater runoff is a significant source of suspended sediments and associated contaminants, including heavy metals, to receiving waterways. These metals are either dissolved or bound to particulates (coarse - >75 µm; fine particulates - <75 - 1µm; colloids - <1 µm). Information on the particulate association of heavy metals in stormwater is a critical requirement prior to using pond and wetland best management practices (BMPs) as stormwater treatment controls. Heavy metals in stormwater are primarily removed by sedimentation in structural BMPs, and these sediments may be toxic to benthic invertebrates and aquatic microorganisms. The proposed research will be conducted at U.S. EPA's Urban Watershed Research Facility (UWRF) in Edison, NJ to evaluate the effectiveness of pond and wetland BMP mesocosms to remove heavy metals from stormwater runoff. The runoff draining from roofs and parking lots of the adjacent county college will be investigated. Seven heavy metals (Cu, Zn, Pb, Cr, Fe, Al, and Mn) will be investigated based on results from an earlier screening procedure (August 2004) on stormwater runoff in the same location. The research objectives include: (i) characterizing the association of heavy metals with fine particulates (20 to 0.4 µm) in stormwater runoff; (ii) evaluating the relative removal of particulate-bound as well as dissolved heavy metals in wet pond and cattail wetland mesocosms; and (iii) investigating the solid-phase chemical associations of heavy metals in cattail wetland sediments by selective sequential extraction procedures and thereby assessing the potential for sediment toxicity and heavy metal bioavailability. The project will commence in March 2005, and two actual rain events per season (winter, spring, summer, and fall) will be sampled in order to determine any seasonal variability in stormwater heavy metal-particulate associations. Wetland sediments will be sampled twice; at the start and after the completion of the stormwater sampling events.