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 groun dwater). Following a proper water sampling procedure, MeHg was leached by h ydrochloric acid, preconcentrated on a sulphydryl cotton fibre (SCF), eluat ed with hydrochloric acid, decomposed, and detected as Hg-0 by a cold vapou r atomic absorption spectrometry (CVAAS). The MeHg concentrations determine d in the water samples of the Krka River Estuary, groundwaters (landfill >> Jakusevec<<, in the vicinity of Zagreb), and the Kastela Bay were: 3.5 x 10 (-14) to 7.5 x 10(-13) mol dm(-3) 2.0 x 10(-13) to 3.0 x 10(-12) mol dm(-3) , and 1.0 x 10(-12) to 2.0 x 10(-11) mol dm(-3), respectively. The concentr ation of;MeHg in the water column of the Krka River Estuary is inversely re lated to reactive mercury. The MeHg maximum is just above a fresh/saline wa ter interface (FSI), whereas maximums of the reactive and total mercury are below and/or inside the FSI. Winds and other meteorological conditions exe rt significant influence upon the distribution of MeHg concentrations in th e water column. The performance of the modified analytical procedure was im proved, yielding a high recovery efficiency of MeHg (85-96%), reproducibili ty better than 15% (CV) and the limit of detection of 3.5 x 10(-14) mol dm( -3), i.e. 0.007 ng L-1 (3 sigma of the blank) for water sample of 3 L.