title: Assessing bioavailability levels of metals in effluent-affected rivers: effect of Fe(III) and chelating agents on the distribution of metal speciation.
abstract: To assess the effects of Fe(III) and anthropogenic ligands on the bioavailability of Ni, Cu, Zn, and Pb, concentrations of bioavailable metals were measured by the DGT (diffusive gradients in thin ﬁlms) method in some urban rivers, and were compared with concentrations calculated by a chemical equilibrium model (WHAM 7.0). Assuming that dissolved Fe(III) (<0.45 μm membrane filtered) was in equilibrium with colloidal iron oxide, the WHAM 7.0 model estimated that bioavailable concentrations of Ni, Cu, and Zn were slightly higher than the corresponding values estimated assuming that dissolved Fe(III) was absent. In contrast, lower levels of free Pb were predicted by the WHAM 7.0 model when dissolved Fe(III) was included. Estimates showed that most of the dissolved Pb was present as colloidal iron-Pb complex. Ethylene-diamine-tetra-acetic acid (EDTA) concentrations at sampling sites were predicted from the relationship between EDTA and the calculated bioavailable concentration of Zn. When both colloidal iron and predicted EDTA concentrations were included in the WHAM 7.0 calculations, dissolved metals showed a strong tendency to form EDTA complexes, in the order Ni > Cu > Zn > Pb. With the inclusion of EDTA, bioavailable concentrations of Ni, Cu, and Zn predicted by WHAM 7.0 were different from those predicted considering only humic substances and colloidal iron.
authors.affiliation: Faculty of Environment and Information Sciences, Yokohama National University, 79-7, Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa 240-8501, Japan E-mail: han-shuping-cw@ynu.jp.
authors.forename: Shuping
authors.initials: S
authors.lastname: Han
authors.affiliation: Research Institute of Science for Safety and Sustainability (RISS), National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba, Ibaraki 305-8569, Japan.
authors.forename: Wataru
authors.initials: W
authors.lastname: Naito
authors.affiliation: Faculty of Environment and Information Sciences, Yokohama National University, 79-7, Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa 240-8501, Japan E-mail: han-shuping-cw@ynu.jp.
authors.forename: Shigeki
authors.initials: S
authors.lastname: Masunaga
mesh_terms: D001682:Biological Availability; D002614:Chelating Agents / Q000737:chemistry*; D004784:Environmental Monitoring / Q000379:methods; D005290:Ferric Compounds / Q000737:chemistry*; D006812:Humic Substances; D008670:Metals / Q000737:chemistry* / Q000145:classification; D008962:Models, Theoretical; D045483:Rivers / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D002614:Chelating Agents; D005290:Ferric Compounds; D006812:Humic Substances; D008670:Metals; D014874:Water Pollutants, Chemical