Mercury phase speciation in the surface waters of three Texas estuaries: Importance of colloidal forms

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Abstract
Surface‐water samples were collected from Galveston Bay, Corpus Christi Bay, Sabine Lake, and Laguna Madre and analyzed for Hg in the µm, 0.45‐µm‐1‐kDa, and µm) ranged from 0.12 to 13.6 pM, with the highest values in Corpus Christi Bay. Within Galveston and Corpus Christi Bays, filter‐passing Hg exhibited nonconservative estuarine mixing behavior. The colloidal Hg fraction ranged from 12 to 93% of the filter‐passing pool and averaged 57 ± 20%, indicating that a major portion of the operationally defined “dissolved” Hg is associated with submicron particles and macromolecules > 1 kDa. Colloidal Hg covaries with colloidal organic C concentrations in Galveston Bay waters, suggesting that most of the filter‐passing Hg pool is associated with large organic macromolecules. The log of the particle‐water partition coefficient (Kd) ranged from 4.6 to 5.2, and covaried with suspended particulate matter concentrations, likely due to the presence of colloidal Hg.

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