Inter-annual variability in atmospheric input and partitioning of heavy metals in the lagoon of venice

摘要

Atmospheric bulk deposition of major and trace elements was measured at Venice from November 1995 to October 1997 Collection was carried out using polyethylene bulk passive sasmplers,samplex being collected bi-weekly In order to highlight the contribution of hte atmosphere to water chemsitry and particle budgets in the Lagoon of Venice the geochemical composition(Si,Al Ca,Mg k,Na Mn,Cr Zn Pb Cd,Cu As) of dissolved and insoluble bulk fractions was determined by AAS+ICP mass spectrometry Great sample variability was found with almost two orders of magnitude beteen mzximum and minimum values for several metals.All fluxes in 1995-96 were 30% lower than in 1996/97 ranging from -3% (Ca)to -57% (Li) except for Zn Cd and As On the contrary the solubility of all elements decrteased during 1996-97 Partitioning between soluble and indoluble phases shows that Al Cr Fe and Si are mainly in the insoluble form whereas for As Ca Cu Mg Na Ni k Pb and Zn the dissolved fraction repesents 50-90% of total input The amount of particle load affects partition ing between dissolved and particulate especially for Al and Pb.Seasonal variability was evident.The lowest Ph valuews (~5.2) were recorded in winter causing an increased of solubility for all metals except for As which showed the highest solubility in summer.