Pluriannual Watershed Discharges of Hg into a Tropical Semi-Arid Estuary of the Jaguaribe River, NE Brazil

Abstract

Mercury fluxes were measured during the dry and rainy seasons (2005 to 2009) at the Jaguaribe
\nRiver estuary, which discharges into the Equatorial Atlantic Ocean in NE Brazil. During rainy
\nperiods, the water masses exhibited a short residence time within the estuary (0.8 days). During
\ndry periods, seawater choked the fluvial discharge, resulting in longer residence times (3.1 days).
\nDissolved (< 0.7 µm) and particulate Hg concentrations and fluxes were greater from the river to
\nthe estuary than from the estuary to the sea, producing accumulated particulate Hg in the estuary.
\nParticulate Hg export (1.8 to 12.6 mg s-1) to the ocean occurred during extremely rainy periods,
\nwhile dissolved Hg export was practically nonexistent during rainy periods and increased up to
\n0.45 mg s-1 during dry periods. Because continental runoff in semi-arid regions is affected by land
\nuse and global climate changes, the increasing accumulation of particulate Hg in the estuaries and
\nincreasing export of dissolved Hg to the ocean are expected