Chemical leaching and specific surface area measurements of marine sediments in the evaluation of mercury contamination near cinnabar deposits

This paper investigates mercury contamination in recent marine sediment of the Tyrrhenian continental shelf near the mouths of three rivers draining an area with cinnabar deposits (M. Amiata, Italy). By means of chemical leaching, two fractions of the total mercury were distinguished: a ‘non-leachable’ fraction, consisting of mercury held in relatively stable forms and a ‘leachable’ fraction, composed of forms that are more weakly bound to the sediments. The two Hg fractions are correlated to the organic matter content, the distribution of which is strictly dependent on the sediment surface area. In order to eliminate the effects of grain size variations among the samples, the Hg concentrations were normalized to the unit of surface area (ng/m2). Following this procedure, the ‘non-leachable’ Hg was found to be concentrated mostly in a belt along the coast, while the ‘leachable’ Hg fraction was shown to accumulate largely in the zones with high depositional dynamics near the mouths of the rivers. Hypotheses to account for the discrepancy between the low concentrations of ‘leachable’ Hg in the sediment of the outer continental shelf and the high concentrations in the fauna of the same area, reported in previous papers, are presented.

[1]  R. Chester,et al.  Trace elements in sediments from the lower Severn Estuary and Bristol Channel , 1975 .

[2]  B. Rust,et al.  Mercury and Bed Sediment in the Ottawa River, Canada , 1976 .

[3]  D. Phillips.  The use of biological indicator organisms to monitor trace metal pollution in marine and estuarine environments—a review , 1977 .

[4]  M. Bothner,et al.  Geochemistries of arsenic, antimony, mercury, and related elements in sediments of Puget Sound , 1975 .

[5]  B. Olson,et al.  In situ methylation of mercury in estuarine sediment , 1974, Nature.

[6]  A. Chau,et al.  An improved digestion method for the extraction of mercury from environmental samples. , 1976, The Analyst.

[7]  K. Turekian,et al.  Distribution of mercury in the sediments of New Haven (Conn.) Harbor , 1972 .

[8]  R. Reimers.  SORPTION PHENOMENON IN THE ORGANICS OF BOTTOM SEDIMENTS , 1975 .

[9]  B. G. Oliver.  Heavy metal levels of Ottawa and Rideau River sediments , 1973 .

[10]  R. Gibbs.  Effect of combustion temperature and time, and of the oxidation agent used in organic carbon and nitrogen analyses of sediments and dissolved organic material , 1977 .

[11]  A. Renzoni,et al.  The distribution of mercury in the surficial sediments of the northern Tyrrhenian sea , 1979 .

[12]  A. Mills,et al.  Surface properties and pore structure of marine sediments , 1965 .

[13]  E. Jenne,et al.  Mercury Dispersal from Lode Sources in the Kuskokwim River Drainage, Alaska , 1977, Science.

[14]  R. Harriss,et al.  Mercury-organic matter associations in estuarine sediments and interstitial water , 1974 .

[15]  R. Thomas.  The Distribution of Mercury in the Sediments of Lake Ontario , 1972 .

[16]  M. B. Jordan,et al.  The distribution of organic material and trace metals in sediments from the River Liffey Estuary, Dublin , 1979 .

[17]  L. D'alessandro,et al.  Il trasporto litoraneo lungo la costa toscana tra la foce del Fiume Magra ed i Monti dell'Uccellina , 1975 .

[18]  R. Cranston,et al.  Mercury pathways in a river and estuary , 1972 .