Archives of Environmental Contamination and Toxicology

, Volume 40, Issue 2, pp 161-172

Distribution of Inorganic Mercury in Sacramento River Water and Suspended Colloidal Sediment Material

  • D. A. RothAffiliated withU.S. Geological Survey, 3215 Marine St., Boulder, Colorado 80303, USA
  • , H. E. TaylorAffiliated withU.S. Geological Survey, 3215 Marine St., Boulder, Colorado 80303, USA
  • , J. DomagalskiAffiliated withU.S. Geological Survey, 6000 J. St., Placer Hall, Sacramento, California 95819-6129, USA
  • , P. DileanisAffiliated withU.S. Geological Survey, 6000 J. St., Placer Hall, Sacramento, California 95819-6129, USA
  • , D. B. PeartAffiliated withU.S. Geological Survey, 3215 Marine St., Boulder, Colorado 80303, USA
  • , R. C. AntweilerAffiliated withU.S. Geological Survey, 3215 Marine St., Boulder, Colorado 80303, USA
  • , C. N. AlpersAffiliated withU.S. Geological Survey, 6000 J. St., Placer Hall, Sacramento, California 95819-6129, USA

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Abstract

The concentration and distribution of inorganic Hg was measured using cold-vapor atomic fluorescence spectrometry in samples collected at selected sites on the Sacramento River from below Shasta Dam to Freeport, CA, at six separate times between 1996 and 1997. Dissolved (ultrafiltered, 0.005 μm equivalent pore size) Hg concentrations remained relatively constant throughout the system, ranging from the detection limit (< 0.4 ng/L) to 2.4 ng/L. Total Hg (dissolved plus colloidal suspended sediment) concentrations ranged from the detection limit at the site below Shasta Dam in September 1996 to 81 ng/L at the Colusa site in January 1997, demonstrating that colloidal sediment plays an important role in the downriver Hg transport. Sequential extractions of colloid concentrates indicate that the greatest amount of Hg associated with sediment was found in the “residual” (mineral) phase with a significant quantity also occurring in the “oxidizable” phase. Only a minor amount of Hg was observed in the “reducible” phase. Dissolved Hg loads remained constant or increased slightly in the downstream direction through the study area, whereas the total inorganic Hg load increased significantly downstream especially in the reach of the river between Bend Bridge and Colusa. Analysis of temporal variations showed that Hg loading was positively correlated to discharge.