| An assessment of tributyltin and metals in sediment cores from the St. Thomas East End Reserves - :16393 | National Ocean Service (NOS)
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An assessment of tributyltin and metals in sediment cores from the St. Thomas East End Reserves
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  • DOI:
    doi:10.7289/V5/TM-NOS-NCCOS-217
  • Description:
    This is the sixth report in a series from a project to assess land-based sources of pollution (LBSP) and their effects, and to characterize the biological community within the St. Thomas East End Reserves (STEER) in St. Thomas, USVI. Here we summarize the results of a study to assess the distribution and depositional history of tributyltin (TBT), heavy metals and other trace elements in the sediments in the Benner Bay sub-region of the STEER. Tributyltin and copper concentrations in Benner Bay on St. Thomas USVI were found to be elevated relative to other areas in the larger study of the STEER. At the request of the USVI Coastal Zone Management Program, sediment cores and surface sediment samples were collected to better define the extent and history of TBT deposition in the vicinity of Benner Bay. The sediment cores were sectioned into 2 cm intervals and dated using 210Pb and 137Cs. The core sections and the surface samples were analyzed for butyltins and 16 metals and trace elements. Sediment deposition rates varied from 0.7 -5.0 mm/yr, and were highest in the marina complex. Core ages ranged from 54 to 200 yrs. The inner reaches of northern Benner Bay are severely degraded by marina operations, shoreline development and watershed changes. Sediment dynamics and sediment quality are, and have been for decades, heavily impacted. The bottoms of the cores contained shell hash from a once thriving benthic community. That community has vanished and has been smothered by very fine sediment that accumulates at rates an order of magnitude above normal rates. The sediment is highly contaminated with butyltin paint residues, copper, and other toxic metals. Surface concentrations of TBT exceeded 2,000 ppb at two locations. At a depth of 8 cm TBT exceeded 8,800 ppb in the marina complex sediment. Based on the ratio of tributyltin to total butyltins, it appears the marina sediments are the source of contamination of the surrounding area. There is evidence that vessels from neighboring islands may also be a source of fresh TBT. Gradients of virtually all metals and trace elements extended away from the marina complex. NOAA sediment quality guidelines were exceeded for As, Pb, Cu, Zn and Hg. Pile driving and dredging new or deeper channels will spread these contaminants over a wide area. [doi:10.7289/V5/TM-NOS-NCCOS-217 (https://doi.org/10.7289/V5/TM-NOS-NCCOS-217)]

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