Role of the River Soča in transfering mercury compounds into the gulf of Trieste

Abstract

In presented work different mercury forms in inflow of River Soča at mixing zone between fresh and sea water have been investigated. Regarding to River Soča water regime three sampling periods have been proposed at nine sampling locations. Total Hg concentrations were between 4.5 and 174 ng/l with average value of 25.9 ng/ 1. Most Hg (72%) was bounded to suspended matter. The highest values in water column were measured in May when the average total Hg concentration was 33.6 ng/l. Methylmercury (MeHg) concentrations were in wide range between 12.0 and 1350 pg/l (average 175 pg/l). Most MeHg was in dissolved form (85%). Dissolved Hg (DGM) concentration in water was between 0.03 to 2.6 ng/l. More than ten years after closure of the mercury mine in Idrija concentrations of different Hg species in River Soča remains very high.