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Trace Metal Accumulation in Sediments and Benthic Macroinvertebrates before and after Maintenance of a Constructed Wetland
Citation:
OCONNOR, T., S. Muthukrishnan, K. Barshatzky, AND W. Wallace. Trace Metal Accumulation in Sediments and Benthic Macroinvertebrates before and after Maintenance of a Constructed Wetland . WATER ENVIRONMENT RESEARCH. Water Environment Federation, Alexandria, VA, 84(4):370 - 381, (2012).
Impact/Purpose:
To inform the public.
Description:
Periodic maintenance of stormwater best management practices (BMP) includes the removal of accumulated sediment. The resulting impact on trace metal concentrations of copper (Cu), lead (Pb), and zinc (Zn) in a constructed stormwater wetland BMP on Staten Island, NY was investigated by analyzing sediment concentrations and tissue residues of select macroinvertebrates prior and subsequent to maintenance. Metal concentrations were assessed using standard serial extraction (for sediment) and acid digestion (for tissue burdens) techniques, followed by quantitative determination via graphite furnace atomic absorption spectrometry (GFAAS) and inductively coupled plasma optical emission spectrometry (ICP-OES), respectively. Data suggested that disturbance of sediment during maintenance of the BMP resulted in an increase in the mobile fraction of metals, especially those associated with finer grained sediments (< 63um), and as a consequence, measured metal concentrations in macroinvertebrates increased. Regressions of metal concentrations in the sediment and the dominant macroinvertebrate (Tubifex tubifex) were generally responsive to the maintenance and the changes in sediment metal loadings both in the BMP and a natural wetland to which the BMP discharged. A follow-up sampling event nine months after maintenance demonstrated that sediment metal loadings were returning to “pre-maintenance levels,” suggesting that elevated concentrations following maintenance were potentially a transient feature of the disturbance. The study suggested that in the long term, performing maintenance activities will help manage metal sediment metal concentrations in the BMP and the receiving water to which a BMP discharges.
