The Use of Constructed Wetlands for the Treatment of Heavy Metals in Urban Stormwater Runoff
Swarna Muthukrishnan, U.S. EPA, Edison, NJ

Electrokinetic Treatment of Marine Sediments Contaminated by Heavy Metals
Aldo Muntoni, University of Cagliari, Cagliari, Italy

Use of XRF to Characterize Mine Waste Sediment in a Marine Environment 

Wolfgang D. Calicchio, MACTEC, Inc., 511 Congress Street, Portland, ME 04101, Tel:  207-828-3466, Fax: 207-772-4762, Email: wdcalicchio@mactec.com
Peter Baker, MACTEC, Inc., 511 Congress Street, Portland, ME 04101, Tel: 207-828-3692, Fax: 207-772-4762, Email: psbaker@mactec.com
Tige Cunningham, NRCC EAC, MACTEC, Inc., 511 Congress Street, Portland, ME 04101, Tel: 207-828-3692, Fax: 207-772-4762, Email: tlcunningham@mactec.com
Christian Ricardi, NRCC EAC, MACTEC, Inc., 511 Congress Street, Portland, ME 04101, Tel: 207-828-3694, Fax: 207-772-4762, Email: csricardi@mactec.com

MACTEC utilized XRF for metals analysis of estuarine sediment samples collected to delineate lateral and vertical extent of contamination in support of a remedial investigation/feasibility study (RI/FS) to complete a record of decision (ROD) at a former copper, lead, and zinc sulfide ore mine site on a unique coastal location in Maine .  Five hundred and thirty seven samples were collected and analyzed by on-site XRF during a 15 day period.  Sufficient sediment volume was collected to fill soil jars.  Aliquot was prepped and analyzed in accordance with EPA Method 6200.  Remaining original sample was archived.  Thirty seven sediment samples (seven percent) were submitted to a contracted commercial laboratory for metals analysis by EPA Method 6010B (ICP)/6020 (ICP-MS).  Samples were analyzed for antimony, arsenic, barium, cadmium, chromium, cobalt, copper, lead, manganese, mercury, nickel, selenium, silver, thallium, and zinc.  Metal concentrations reported by commercial laboratory were compared to on-site XRF concentrations to determine precision, accuracy, and bias of XRF data.  Average relative percent differences (RPDs) between XRF and commercial laboratory results ranged from 24 to 68 for copper (24), lead (58), zinc (37), arsenic (68), and manganese (35) indicating good comparability.  Barium (192), cadmium (91), and chromium (196) had high average RPDs.  General trend of higher concentrations reported by XRF observed indicating possible high bias.  Of the 176 calculated RPDs, 70 exceeded 50 (EPA Region I guidelines comparing solid matrices field duplicates).   Statistical analysis of variance and comparison of RPDs to grain size analyses were reviewed to determine usability of data and effects on XRF quantitation of metals in sediment.  Overall agreement was observed using XRF analysis supported by commercial laboratory confirmation.  The XRF demonstrated to be an effective, cost-saving instrument to support contamination assessments of copper, lead and zinc in sediments at the coastal former mine site.

The Use of Constructed Wetlands for the Treatment of Heavy Metals in Urban Stormwater Runoff

Swarna Muthukrishnan, Ph. D., ORISE Postdoctoral Fellow, U.S. EPA, Office of Research and Development, National Risk Management Research Laboratory, Urban Watershed Management Branch, 2890, Woodbridge Avenue, Edison, NJ 08837, Tel: 732-321-4436, Fax: 732-321-6640, Email: Muthukrishnan.swarna@epa.gov
Ariamalar Selvakumar, Ph. D., Environmental Engineer, U.S. EPA, Office of Research and Development, National Risk Management Research Laboratory, Urban Watershed Management Branch, 2890, Woodbridge Avenue, Edison, NJ 08837, Tel: 732-906-6990, Fax: 732-321-6640
Thomas O’Connor, Environmental Engineer, U.S. EPA, Office of Research and Development, National Risk Management Research Laboratory, Urban Watershed Management Branch, 2890 Woodbridge Avenue, Edison, NJ 08837, Tel: 732-321-6723, Fax: 732-321-6640

The presence of heavy metals in stormwater runoff is a major concern due to their toxicity, bioavailability, and persistence in the environment.  The sources of heavy metals are varied, and their geochemical partitioning in stormwater runoff is significantly influenced by the land-use pattern.  Stormwater runoff investigations increasingly focus on evaluating quality and the effectiveness of adopting best management practices (BMPs) to minimize heavy metal inputs to receiving waters.  Structural BMPs such as constructed wetlands primarily rely on sedimentation to reduce heavy metal loads associated with particulate matter and improve runoff quality.  The continued accumulation of heavy metals in these sediments can lead to their migration and increase the risk for ground and surface water quality deterioration downstream.  Additionally, they may also be toxic to benthic invertebrates and aquatic microorganisms downstream of the BMP.  These accumulated sediments have to be routinely removed to minimize the risk of contamination and maximize the operational efficiency of these BMPs.  However, the frequency of such maintenance practices and the handling of sediments require a full understanding of the quantity and quality of the deposits, especially with reference to their heavy metal content.  Chemical speciation studies help in understanding and controlling the behavior of heavy metals, and are recognized as a necessary requirement in designing an effective BMP maintenance protocol.  This research is being conducted at U.S. EPA’s Urban Watershed Research Facility in Edison , NJ , to evaluate the relative efficiencies of wetlands and retention ponds in attenuating heavy metal loads in urban stormwater runoff.  BMP removal efficiencies were assessed for both particulate and soluble heavy metals.  The geochemical associations of heavy metals in wetland sediments were investigated by sequential fractionation procedures in order to understand heavy metals behavior in BMP sediments.  Additionally, a stormwater wetland BMP in the Staten Island Blue Belt ( New York ) was monitored to investigate the effects of maintenance and clean up procedures on sediment heavy metal loads and their speciation.  Results from different stormwater sampling and sediment monitoring events will be discussed.    

Electrokinetic Treatment of Marine Sediments Contaminated by Heavy Metals

Giorgia De Gioannis, Aldo Muntoni, University of Cagliari, Department of Geoengineering and Environmental Technologies, Piazza d’Armi – 09123 Cagliari, Italy, Tel: +39 070 675 5546, Fax: +39 070 675 5523
Alessandra Polettini, Raffaella Pomi, Department of Hydraulics, Transportation and Roads, University of Rome ‘‘ La Sapienza ’’, Via Eudossiana, 18-00184 Rome, Italy, Tel. +39-06/44.585.037, Fax +39-06/44.585.037

Sediment contamination is a complex technical framework which requires the study of different treatment alternatives. Sediment contamination is problematic also for marine trade routes; in fact, although sediments can be left in place covered by a low permeability capping and innovative in situ treatment technologies are under development, around 500 millions m3 have to be dredged each year for navigational purposes and 1-4% of these requires dewatering and treatment prior to disposal. Despite decades of research, surprisingly little is known about successful treatment of contaminated sediments, which are usually landfilled after dredging. While in soils the contaminated fine fraction is typically less than 50% of the total solid matrix, in sediments usually the opposite occurs, 80-95% are generally very finely grained particles. In these cases many treatment technologies have proved to be ineffective in order to achieve a reduction of the contaminant concentration. Electrokinetics could represent a possible solution in order to achieve dewatering and removal of heavy metals and salts in a single stage. Electrokinetics is reported among the viable treatment alternatives for dredged marine sediments worth to be investigated. In this framework electrokinetics was applied on two types of marine sediments sampled from the Veneto and South-West Sardinian coasts ( Italy ) in order to achieve at the same time dewatering and removal of heavy metals and salts. The sediments were previously characterised for the contaminant content and the main chemical-physical properties which influence the treatment. Tests were performed either on samples pre-washed with soft water or on samples with the natural content of salts. The efficiency of the process was evaluated on the basis of the achieved cathodic flow and of the residual concentration values of salt and contaminants in the solid sample. The results of the tests proved that the different characteristics of the sediments mirror in the achieved heavy metal removal.

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