Tham khảo tài liệu 'passive sampling techniques episode 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | In situ monitoring and dynamic speciation measurements Concentrations of Cd Cu and Mn measured in situ by DGT in river-and lake-waters was first compared with the total dissolved concentrations measured in filtered samples in four Australian waters 25 . Over a 72 h deployment period the mass of Cd and Cu in two rivers increased linearly with time and matched the total dissolved concentrations. This indicated that biofouling was not a concern and that concentrations of strong complexing ligands were negligible in these waters. However in two other rivers the fraction of Cu and Cd measured by DGT was only 30 and 50 of the total dissolved concentration. DGT was used to obtain an in situ depth-profile of Mn in a stratified estuary which showed a pronounced concentration maximum associated with redox-associated reductive mobilization. Zhang and Davison 26 were able to obtain more quantitative speciation information. They made the simplifying assumption that natural waters can be regarded as having two classes of compounds that can be measured by DGT a labile inorganic species including the free ion of total concentration Ci with a mean diffusion coefficient Di and b labile organic species of total concentration Co with a mean diffusion coefficient Do. This assumption is reasonable in humic-rich fresh-waters where the metal speciation is dominated by complexes with fulvic acid. The mass of metal Mdgt accumulated by a DGT device is then the sum of the contributions from both labile inorganic Mi and organic complexes Mo . Mdgt Mi Mo According to Fick s first law of diffusion the inorganic and organic contributions to Mdgt are given by Eqs. and respectively. Mi DC A Dg M DCA Dg Combining Eqs. - gives Mdgt DiCi DCoW It can be rearranged to MDGTDg Ci Do Co DiAt Di 267 Chapter 12 Use of ceramic dosimeters in water monitoring Hansjorg Weifi Kristin Schirmer Stephanie Bopp and Peter Grathwohl INTRODUCTION Passive .
