Comparison of procedures for measurements of dissolved gaseous mercury in seawater performed on a Mediterranean cruise.

A comparison of manual procedures for measurements of dissolved gaseous mercury (DGM) in seawater was accomplished. The experiments were performed on board the Italian research vessel Urania during July 2000 as a subtask in the CNR "Med-Oceanor Project 2000". Water samples for DGM were collected by Go-Flo bottles and subsequently analysed for DGM on board the ship. Determinations of DGM were made in parallel by two groups using different analytical routines. The two sets of data obtained compare favourably. Based on the fieldwork and an additional laboratory study, analytical procedures are discussed and an optimised method to determine DGM is presented. In addition, a method for automated in situ measurements of DGM positioned in the water body was tested. This method has the potential to simplify studies of DGM dynamics, that is variation in concentration as a function of water temperature and solar radiation etc.