Mercury in the water column

In fluvial and marine environments, Hg results mainly associated to suspended particulate matter within the water column. In occasion of the high Isonzo River inflow, it was possible to monitor the river plume from Trieste Gulf to the Primero tidal inlet. It was discovered that, in spite of the end of the mining activity at Idrija (1996), Hg is still loaded in the Gulf during the year through the huge contribution of suspended particulate matter during the extreme flood events in comparison with the lower ones transported when the River discharge is low. A rough estimate of the amount of Hg which would remain entrapped within the lagoon shows a positive balance for the lagoon. The amount of Hg (1.4 kg) which would remain deposited within the lagoon, in a semicycle of tides, is equal to 50% of the Hg suspended particulate matter entered into Primero inlet following the flood tide. Towards east, the amount of particulate and dissolved Hg within the water of Aussa-Corno River system, tributary of Marano Lagoon, seems noticeably high in the innermost sector of the estuarine zone, specially within Banduzzi Channel (20 ยตg/g), proving the existence of Hg loads, presumably of industrial origin, still evident in spite of the source (Torviscosa industrial area) being inactive.