TIDAL EXPORT OF PARTICULATE MERCURY FROM THE MOST CONTAMINATED AREA OF AVEIROS LAGOON, PORTUGAL

Mercury pollution is a regional problem in the Aveiro's Lagoon. During 4 decades, a remote branch (Estarreja Channel) has received a dischar ge of mercury from a chlor-alkali plant, that is spread in the Laranjo Basin. Of special interest is the dispersion of mercury from these ar eas to the Lagoon. This work is a first attempt to quantify the net fl ux of particulate mercury from the most contaminated basin (Laranjo). Measurements of current intensity, suspended particulate matter and pa rticulate mercury were carried out at two sampling stations over a spr ing tidal cycle, in April 1994. Based on a mass balance calculation at two stations, at the end of Estarreja Channel (F-1) and near the outl et of Laranjo Basin (F-2), the net tidal fluxes of particulate anthrop ogenic mercury were estimated: 0.4 g of mercury enter the Laranjo Basi n and 94.5 g of particulate mercury escape the Basin. These results in dicate that mercury from the most contaminated area continues to be di spersed, predominantly through the particulate fraction, to the rest o f the Lagoon. (C) 1998 Elsevier Science B.V.