Sediment accumulation and mixing in the Penobscot River and estuary, Maine

K. M. Yeager, K. A. Schwehr, K. J. Schindler, P. H. Santschi

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

Mercury (Hg) was discharged in the late 1960s into the Penobscot River by the Holtra-Chem chlor-alkali production facility, which was in operation from 1967 to 2000. To assess the transport and distribution of total Hg, and recovery of the river and estuary system from Hg pollution, physical and radiochemical data were assembled from sediment cores collected from 58 of 72 coring stations sampled in 2009. These stations were located throughout the lower Penobscot River, and included four principal study regions, the Penobscot River (PBR), Mendall Marsh (MM), the Orland River (OR), and the Penobscot estuary (ES). To provide the geochronology required to evaluate sedimentary total Hg profiles, 58 of 72 sediment cores were dated using the atmospheric radionuclide tracers 137Cs, 210Pb, and 239,240Pu. Sediment cores were assessed for depths of mixing, and for the determination of sediment accumulation rates using both geochemical (total Hg) and radiochemical data. At most stations, evidence for significant vertical mixing, derived from profiles of 7Be (where possible) and porosity, was restricted to the upper ~1–3 cm. Thus, historic profiles of both total Hg and radionuclides were only minimally distorted, allowing a reconstruction of their depositional history. The pulse input tracers 137Cs and 239,240Pu used to assess sediment accumulation rates agreed well, while the steady state tracer 210Pb exhibited weaker agreement, likely due to irregular lateral sediment inputs.

Original languageEnglish
Pages (from-to)228-239
Number of pages12
JournalScience of the Total Environment
Volume635
DOIs
StatePublished - Sep 1 2018

Bibliographical note

Publisher Copyright:
© 2018

Keywords

  • Geochronology
  • Penobscot River
  • River-estuarine system
  • Sediment transport
  • Sedimentation rates

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution

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