speciation of metals in natural waters物种形成的金属在自然水域.pdf

Speciation of metals in natural waters Frank Millero Rosenstiel School of Marine and Atmospheric Science, University of Miami, 2900 Rickenbacker Causeway, Miami, FL 33149, USA. E-mail: fmillero@rsmas.miami.edu Received 1st June 2001, Accepted 17th July 2001 Published on the Web 12th September 2001 First published as an Advanced Article on the Article web 25th August 2000 The form or speciation of a metal in natural waters can change its kinetic and thermodynamic properties. For example, Cu(II) in the free ionic form is toxic to phytoplankton, while copper complexed to organic ligands is not toxic. The form of a metal in solution can also change its solubility. For example, Fe(II) is soluble in aqueous solutions while Fe(III) is nearly insoluble. Natural organic ligands interactions with Fe(III) can increase the solubility by 20-fold in seawater. Ionic interaction models that can be used to determine the activity and speciation of divalent and trivalent metals in seawater and other natural elements will be discussed. The model is able to consider the interactions of metals with the major (Cl2, SO42 2, HCO32, CO32 2, Br2, F2) and minor (OH2, H PO 2, HPO 2 2, PO 32, HS2) anions as a function of temperature (0 to 50 uC), ionic strength [0 to 2 4 4 4 6 m (m ~mol kg21)] and pH (1 to 13). Recently, it has been shown that many divalent metals are complexed with organic ligands. Although the composition of these ligands is not known, a number of workers have used voltammetry to determine the concentration of the ligand [Ln] and the stability constant (KML) for the formation of the complex M2 z n n z2 n z2 2 z n zL ?ML KML ~½ML =½M ½L We have added the experimental values of KML for the formation of comple