Determination of Dissolved Monomethylmercury in Saline, Estuarine and Fresh Waters of Croatia

Measurements of dissolved monomethylmercury (MeHg) (which included both the dissolved part and the part leached from the particles by addition of 2 M HCl) were carried out in natural waters of various origin and composition (fresh, estuarine saline and brackish water, saline coastal water and groundwater). Following a proper water sampling procedure, MeHg was leached by hydrochloric acid, preconcentrated on a sulphydryl cotton fibre (SCF), eluated with hydrochloric acid, decomposed, and detected as Hg0 by a cold vapour atomic absorption spectrometry (CVAAS). The MeHg concentrations determined in the water samples of the Krka River Estuary, groundwaters (landfill »Jaku{evec«, in the vicinity of Zagreb), and the Ka{tela Bay were: 3.5 10–14 to 7.5 10–13 mol dm–3, 2.0 10–13 to 3.0 10–12 mol dm–3, and 1.0 10–12 to 2.0 10–11 mol dm–3, respectively. The concentration of MeHg in the water column of the Krka River Estuary is inversely related to reactive mercury. The MeHg maximum is just above a fresh/saline water interface (FSI), whereas maximums of the reactive and total mercury are below and/or inside the FSI. Winds and other meteorological conditions exert significant influence upon the distribution of MeHg concentrations in the water column. The performance of the modified analytical procedure was improved, yielding a high recovery efficiency of MeHg (85–96%), reproducibility better than 15% (CV) and the limit of detection of 3.5 10–14 mol dm–3, i.e. 0.007 ng L–1 (3 s of the blank) for water sample of 3 L.