Application of ultra clean sampling and analysis methods for the speciation of mercury in the Venice lagoon (Italy)

Abstract
The Venice lagoon is an estuarine environment stressed by pollution from urban, industrial and agriculture settings. In spite of the importance of Hg as a pollutant, many aspects of its biogeochemistry within this fragile ecosystem are still unknown. Since the Venice lagoon is shallow, is high in marine SO ₄ and nutrient loading from agriculture and urban origins, it may act as a vigorous microbiological incubator for Hg methylation. We report here initial results of a year-long survey of Hg and CH ₃Hg in water column, suspended material, sediment samples and biota collected using ultra-clean sampling techniques in different seasons of the year. The samples were obtained in zones of different anthropic influence, ranging from the more agriculture impacted northern area, through the urban area of Venice and up to the Marghera industrial zone. Samples from Adriatic sea collected just outside of the Lido port mouth provide a local "background" for comparison. Total Hg was determined by cold vapor atomic fluorescence spectroscopy, while CH ₃Hg detemiination was caiied out by the same technique after chromatograplc separation of the ethylated forms.