Aquatic Sciences Meeting, Albuquerque 2001

PC13 Phytoplankton: Trace Metals and Biochemistry

Date: Thursday, February 15, 2001

Location: Southwest Hall

Choe, K, Y, Texas A&M University, Galveston, USA, kchoe@tamug.tamu.edu

Gill, G, A, Texas A&M University, Galveston, USA, gillg@tamug.tamu.edu

Lehman, R, , Texas A&M University, Galveston, USA, lehmanr@tamug.tamu.edu

COLLOIDAL METHYL MERCURY DISTRIBUTION IN SAN FRANCISCO BAY ESTUARY

The scavenging processes of trace metals in the water column, combined with the adsorption onto colloids, coagulation into particulate phases and removal processes suggest the importance of colloids in the transport, distribution and fate of methyl mercury (MeHg) and mercury (Hg) in estuarine environments. The phase speciation of MeHg and Hg was investigated using a cross-flow ultrafiltration (CFUF) technique in San Francisco Bay estuary, California. Surface waters were collected across the salinity gradient from Sacramento-San Joaquin Delta to the Golden Gate Bridge. Samples were ultrafiltered with an 1 kDa nominal molecular weight cut-off membrane (Amicon spiral wound S1Y1) immediately after collection and fractionated into particulate (larger than 0.45 um), filter-passing (smaller than 0.45 um), colloidal (1 kDa – 0.45 um) and truly dissolved (smaller than 1 kDa) fractions. Methyl Hg, Hg, trace metals (Al, Fe, Mn and etc), dissolved organic carbon, were measured in each fraction. Preliminary results indicate that the colloidal MeHg fraction comprises over 50 % of the filter-passing concentration in low salinity regions, and that particle-water partition coefficients based on colloidal and truly dissolved MeHg are higher than those based on particulate and filter-passing, or particulate and truly dissolved MeHg. This observation suggests that colloids play an important role in the geochemistry of MeHg in estuarine environments.

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Aquatic Sciences Meeting, Albuquerque 2001

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