A comparative study of mercury contamination in the Tagus estuary (Portugal) and major French estuaries (Gironde, Loire, Rhône)

Concentrations of mercury were determined for the waters, suspended matter and sediments of the Tagus and of major French estuaries. The Tagus estuary is one of the most contaminated by mercury derived from the outfalls of a chloralkali plant and from other industrial sources. In deposited sediments the median level, 1·0 μg Hg g−1, is twenty times higher than the natural background and Hg contents depend on the sediment grain-size, age and the distance from waste-outfalls. Suspended matter is more regularly and highly contaminated (median value: 4·5 μg Hg g−1). In the French estuaries Hg levels in the suspended material decrease with salinity due to dilution and/or remobilization processes. In June 1982, in the Loire estuary, high values of Hg are observed in the middle estuary and attributed to urban and industrial sources. In the Tagus estuary, the general distribution of total dissolved Hg confirms the contamination: it increases seaward from 10 ng 1−1 in the river to 80 ng 1−1 in the estuary outlet. The dissolved Hg is almost totally organic in the river, inorganic in the middle estuary due to inorganic Hg effluents and again organic in the lower estuary. This variation is related to the dissolved organic carbon values. The dissolved Hg levels in the Loire Estuary (5–300 ng 1−1) are much higher than in the Gironde estuary (3–6 ng 1−1) and of the same order as those observed in the Tagus estuary.

[1]  C. Nelson,et al.  Mercury distribution in ancient and modern sediment of northeastern Bering Sea , 1975 .

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

[3]  G. Millward,et al.  The distribution of mercury in the sediments of the plym estuary , 1981 .

[4]  H. Windom,et al.  The flux of mercury in the South Atlantic Bight , 1979 .

[5]  R. Cranston,et al.  Total mercury in sea water in the northwest Atlantic Ocean , 1974 .

[6]  L. Cros,et al.  Contenido en mercurio de los sedimentos marinos cercanos a la desembocadura del río Besós y de un colector de aguas residuales de Barcelona , 1980 .

[7]  R. Kretz.  Variation in the composition of muscovite and albite in a pegmatite dike near Yellowknife , 1970 .

[8]  F. Slemr,et al.  Latitudinal distribution of Mercury over the Atlantic Ocean , 1981 .

[9]  W. Lyons,et al.  Organic Mercury Compounds in Coastal Waters , 1973, Nature.

[10]  D. Loring.  Mercury in the Sediments of the Gulf of St. Lawrence , 1975 .

[11]  R. Jahnke,et al.  Rate of mercury loss from contaminated estuarine sediments , 1980 .

[12]  K. Iwashima,et al.  Estimation of organic and total mercury in seawater around the Japanese archipelago. , 1981, Environmental science & technology.

[13]  B. N. Desai,et al.  Mercury in Thana Creek, Bombay Harbour , 1981 .

[14]  P. J. Moore,et al.  Mercury in sediments from the thames estuary , 1973 .

[15]  R. Huggett,et al.  Mercury in sediments from three Virginia estuaries , 1971 .

[16]  P. Craig,et al.  Mercury in Mersey estuary sediments, and the analytical procedure for total mercury , 1976, Nature.

[17]  J. D. Burton,et al.  Mercury in a Coastal Marine Environment , 1971, Nature.

[18]  M. Kumagai,et al.  Mercury distribution in seawater in Minamata Bay and the origin of particulate mercury , 1978 .

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

[20]  F. Elbaz-Poulichet,et al.  Lead cycling in estuaries, illustrated by the Gironde estuary, France , 1984, Nature.

[21]  J. N. Smith,et al.  Geochronology for mercury pollution in the sediments of the Saguenay Fjord, Quebec. , 1981, Environmental Science and Technology.

[22]  H. Windom,et al.  Possible influence of atmospheric transport on the total mercury content of southeastern Atlantic Continental Shelf surface waters , 1975 .

[23]  G. Cauwet.  Optimisation d'une technique de dosage du carbone organique des sédiments , 1975 .

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