Interaction between Hg(II) and natural dissolved organic matter: A fluorescence spectroscopy based study

Interaction between Hg(II) and dissolved organic matter (DOM) collected fro m surface water samples of the Florida Everglades was studied using differe nt fluorescence spectroscopic methods. Complexation between Hg(II) and DOM leached from mangrove leaves, sawgrass, and periphyton was investigated. Bo th fluorescence emission and synchronous fluorescence spectra showed that t hese dissolved organic materials, whether they are highly degraded or are f reshly leached, can "complex" Hg(II) since fluorescence intensity was quenc hed upon addition of Hg(II) to the DOM samples. Synchronous fluorescence sp ectra disclosed structural information on the DOM sample, regarding possibl e binding sites for Hg(II). Chemical parameters on the complexation of Hg(I I), including the conditional stability constants and the percentage of flu orophores participating in the complexation, were estimated by the modified Stern-Volmer equation. A detailed investigation under different experiment al conditions showed that the complexation of the DOM samples collected fro m the Everglades was influenced by pH, Cl-(aq)(-) anion, and cations such a s Ca2+ and Mg2+. Experimental results suggest that DOM-Hg(II) complexes run be removed from the water column through adsorption on biogenically precip itated CaCO3(s). (C) 2001 Elsevier Science Ltd. All rights reserved.