Mercury distribution, speciation and flux in the Sepetiba Bay tributaries, SE Brazil

Abstract

Dissolved gaseous Hg, reactive Hg, total dissolved Hg and particulate Hg concentrations were measured in samples of majors tributaries of the Sepetiba Bay, SE Brazil (Itimirim, Itinguçu, Guarda, Guandu, São Francisco and Ita rivers), in dry and rainy seasons. The average Hg concentrations found varied from 0.02 to 0.18 ng L −1 for dissolved gaseous Hg, from 0.1 to 18.1 ng L −1 for reactive Hg, from 0.1 to 66.6 ng L −1 for total dissolved Hg and from 0.3 to 250 ng L −1 for particulate Hg. During the rainy season, a decrease in the dissolved Hg concentrations and an increase in the particulate Hg concentrations was observed. Positive correlations were found between the reactive Hg and the total dissolved Hg concentrations ( r=0.99), between the particulate Hg and TSS concentrations ( r=0.82) and between total Hg and particulate Hg concentrations ( r=0.95). The instantaneous Hg fluxes varied among rivers from 0.02 to 412 μg s −1 for total dissolved Hg and from 0.03 to 12,572 μg s −1 for particulate Hg. The log K d varied from 3.76 to 6.43 and showed a significant increase in rainy season following an increase in particulate Hg and a decrease in dissolved Hg concentrations. These results suggest that erosion and runoff are the major pathways of Hg transport to rivers and eventually to Sepetiba Bay.