MERCURY SPECIATION AND DISSOLVED ORGANIC CARBON CHARACTERIZATION IN THE SURFACE WATERS OF SEPETIBA BAY, SE BRAZIL

Abstract

Mercury speciation and dissolved organic carbon (DOC) were measured during a flood tide event in surface waters of Sepetiba Bay, SE Brazil. Average concentrations were 0.08 ± 0.01 ng L-1 for elemental Hg, 1.0 ± 0.2 ng L-1 for reactive Hg, 2.3 ± 1.2 ng L-1 for total Hg, 5.9 ± 5.5 ng L-1 for particulate Hg and 1.2 ± 1.0 ng L-1 for organic Hg. Hg species concentrations showed no significant correlations between them, but total Hg concentrations were negatively correlated with the percent of reactive Hg relative to the total Hg concentrations (r = -0.92). Molecular fluorescence spectroscopy of DOC showed excitation/emission matrices, Ia/Ic and EM450/EM500 ratios typical of relatively young marine DOC rich in microbially derived fulvic acids, which may explain the observed relative increase of reactive Hg concentrations with increasing tidal height and favor Hg transport through the bay.