Mercury pollution near a chlor-alakali plant: distribution and availability of the metal

Eighty samples of sediments were collected from the continental shelf of the Northern Tyrrhenian Sea. High concentrations of Hg were found in sea-bottom sediments off the chlor-alkali plant of Rosignano Solvay (maximum 4.06 μg g-1 dry wt) and in two zones to the south. Because of the large differences in carbonate content and in grain size, Hg was determined in the finest particles of the sediments (15-2 μm), which were obtained by a sedimentation cylinder; concentrations of Hg were higher in the fine fraction and the enrichment factor (EF) was correlated with carbonate content. A sequential leaching method was applied to eight samples collected off the chloralkali plant in order to determine the availability of Hg bound to the inorganic or organic fractions of the sediment. The results show that this element is not easily available and that the sediment is a good sink. Hg availability is discussed. © 1984.