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AGU: Journal of Geophysical Research, Biogeosciences

 

Keywords

  • mercury
  • methylmercury
  • methylation
  • sediment
  • hurricanes
  • Gulf of Mexico

Index Terms

  • Biogeosciences: Biogeochemical cycles, processes, and modeling
  • Biogeosciences: Trace element cycling
  • Biogeosciences: Marine systems
  • Biogeosciences: Natural hazards
Abstract
Cited By (0)
 

Abstract

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 114, G00C07, 12 PP., 2009
doi:10.1029/2008JG000752

Disturbance impacts on mercury dynamics in northern Gulf of Mexico sediments

B. Liu

Harvard School of Public Health, Harvard University, Boston, Massachusetts, USA

L. A. Schaider

Harvard School of Public Health, Harvard University, Boston, Massachusetts, USA

R. P. Mason

Department of Marine Sciences, University of Connecticut, Groton, Connecticut, USA

M. S. Bank

Harvard School of Public Health, Harvard University, Boston, Massachusetts, USA

N. N. Rabalais

Louisiana Universities Marine Consortium, Chauvin, Louisiana, USA

P. W. Swarzenski

U.S. Geological Survey, Santa Cruz, California, USA

J. P. Shine

Harvard School of Public Health, Harvard University, Boston, Massachusetts, USA

T. Hollweg

Department of Marine Sciences, University of Connecticut, Groton, Connecticut, USA

D. B. Senn

Harvard School of Public Health, Harvard University, Boston, Massachusetts, USA

We evaluated the impacts of physical disturbance on sediment Hg biogeochemistry in the northern Gulf of Mexico by exploring changes in Hg abundance and speciation in cores collected between July 2005 and July 2006, a time period that included the passages of Hurricanes Katrina and Rita in this region. Comparisons across space and time reveal large changes in sediment characteristics, both with respect to Hg biogeochemistry and other measures of sediment composition, that indicate substantial disturbance. While the degree of disturbance varied between stations, at sites that clearly received new surface deposits considerable increases in OC and total Hg were observed, along with shifts in major element composition. At the station closest to Hurricane Katrina's track (station A′2), 210Pb levels are consistent with the episodic deposition of >10 cm of sediments. These surface sediments (0–10 cm) at A′2 had the highest %MeHg of all stations and all dates, suggesting that the disturbance resulted initially in increased net methylation. While the observed disturbances elsewhere could not in all cases be definitively linked to hurricane activities, the substantial thickness of deposits (>10 cm) at multiple sites is consistent with a major event, and the similarity in the deposits' chemical fingerprint across all impacted sites suggests similar sources or processes. We estimate that the two hurricanes redistributed approximately 5 times the annual Hg input from the Mississippi-Atchafalaya River system and atmospheric deposition. These observations highlight the need to consider the effects of major disturbances on the biogeochemical cycling of Hg in coastal systems.

Received 8 April 2008; accepted 4 February 2009; published 9 May 2009.

Citation: Liu, B., L. A. Schaider, R. P. Mason, M. S. Bank, N. N. Rabalais, P. W. Swarzenski, J. P. Shine, T. Hollweg, and D. B. Senn (2009), Disturbance impacts on mercury dynamics in northern Gulf of Mexico sediments, J. Geophys. Res., 114, G00C07, doi:10.1029/2008JG000752.

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