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Effect of Bioirrigation on Sediment−Water Exchange of Methylmercury in Boston Harbor, Massachusetts
Environmental Science and Technology (2009)
  • David H. Shull, Western Washington University
  • Janina M. Benoit
  • Rebecca M. Harvey
  • Sanuel A. Beal
Coastal marine sediments are important sites of methylmercury (MMHg) production, and dissolved efflux provides an important source of MMHg to near-shore, and possibly off-shore, water columns and food webs. We measured the flux of MMHg across the sediment−water interface at four stations in Boston Harbor that span a range of infaunal population densities and bioirrigation intensities. At each station we carried out total MMHg flux measurements using core incubations and collected near-surface pore waters to establish MMHg gradients for diffusive flux calculations. The flux cores were also imaged by CT scanning to determine the distribution of infaunal burrows, and pore−water sulfide and 222Rn profiles were measured. Total MMHg fluxes, measured using core incubations, ranged from −4 to 191 pmol m−2 d−1, and total MMHg fluxes were strongly correlated with burrow densities at the stations. Estimated diffusive fluxes, calculated based on MMHg concentration gradients below the sediment−water interface, were much lower than total fluxes at three of the stations, ranging from 2−19 pmol m−2 d−1. These results indicate that MMHg exchange may be significantly enhanced over molecular diffusion in bioturbated sediments. Furthermore, burrow density provides a strong predictor of total MMHg flux. Pore−water exchange of both dissolved MMHg and 222Rn, a naturally occurring pore-water tracer, increased across the range of observed burrow densities, suggesting that the presence of burrows enhances both MMHg production and flux.
  • Methylmercury,
  • Boston Harbor,
  • bioturbated sediments
Publication Date
Publisher Statement
Copyright © 2009 American Chemical Society DOI: 10.1021/es803552q
Citation Information
David H. Shull, Janina M. Benoit, Rebecca M. Harvey and Sanuel A. Beal. "Effect of Bioirrigation on Sediment−Water Exchange of Methylmercury in Boston Harbor, Massachusetts" Environmental Science and Technology Vol. 43 Iss. 10 (2009)
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