AN ESTIMATION OF INDUSTRIAL MERCURY STORED IN SEDIMENTS OF A CONFINEDAREA OF THE LAGOON OF AVEIRO (PORTUGAL)

In the period from 1950 to 1994, most of the mercury discharged to the Lagoon of Aveiro was retained in the sediments of a small area of aro und 1.7 km(2) (25.4 x 10(3) kg, about 77% of the total), which corresp onds to the Estarreja Channel plus a basin named Laranjo Basin located downstream. In 1994, the mercury concentration in surface sediments o f the area ranged from 2.3 to 343 mu g g(-1), with the highest values recorded near the industrial source of the metal. In places of the bas in where the sedimentation rate could be considered uniform, the highe st levels of Hg (35 mu g g(-1)) were recorded at depths around 40 cm, as result of reduction of the anthropogenic mercury input to the lagoo n. Assuming an uniform sedimentation rate and a continuously low indus trial input of mercury for the near future, the levels of Hg in the su rface sediments would be less than 1 mu g g(-1) in 20 years. This may be considered the expected restoration time. The feasibility and conse quences of several management options for this pollution problems is b riefly presented. (C) 1998 IAWQ. Published by Elsevier Science Ltd.