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TREATMENT OF HEAVY METALS IN STORMWATER RUNOFF USING RETENTION PONDS AND CONSTRUCTED WETLANDS
Citation:
MUTHUKRISHNAN, S. TREATMENT OF HEAVY METALS IN STORMWATER RUNOFF USING RETENTION PONDS AND CONSTRUCTED WETLANDS. Presented at Society of Environmental Toxicology and Chemistry (SETAC) North American 26th Annual Meeting, Baltimore, MD, November 13 - 17, 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 - 1 μm; 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. These sediments may be toxic to benthic invertebrates and aquatic microorganisms. Research is being conducted at U.S. EPA's Urban Watershed Research Facility in Edison, NJ to evaluate the effectiveness of retention pond and constructed wetland BMP mesocosms to remove particulate-bound heavy metals from roof and parking-lot runoff. The runoff draining from roofs and parking lots is being investigated and the following heavy metals were chosen based on an earlier screening procedure: Cu, Zn, Pb, Cr, Fe, Al, and Mn. The research objectives include: (1) characterizing the association of heavy metals with fine particulates (20 to 0.4 μm) in stormwater runoff; (2) evaluating the relative removal of particulate-bound as well as dissolved heavy metals in wet pond and cattail wetland mesocosms; and (3) 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 characterization of stormwater runoff showed that Fe and Al were primarily particulate-bound; Mn was mostly in the soluble fraction; and Cu and Zn were associated with fine particulates and in the dissolved fraction. Preliminary results from the first stormwater sampling event conducted in April 2005 showed retention pond and cattail wetland mesocosms to be effective in attenuating Cu, Zn, and Al.