Metal speciation dynamics in freshwaters
- 出版日期：2004.
- 页数：1 v. :
- 第一责任说明：Nouri Mohamed Hassan.
- 分类号：a484 ; a272
- ISBN：0612942007(ebk.) :
MARC全文
02h0029744 20120627172302.0 cr un||||||||| 120627s2004 xx ||||f|||d||||||||eng | NQ94200 0612942007(ebk.) : CNY371.35 NGL NGL NGL a484 ; a272 Hassan, Nouri Mohamed. Metal speciation dynamics in freshwaters [electronic resource] : a kinetic exploration / Nouri Mohamed Hassan. 2004. 1 v. : digital, PDF file. Adviser: Chakrabarti, C. L. Thesis (Ph.D.)--Carleton University (Canada), 2004. In chemical and toxicological studies of metals in the freshwater environment, Cd, Cu, Ni, Pb and Zn have been found to be toxicants at the concentration levels they are in polluted freshwaters, whereas some of these metals are nutrients at lower levels of concentration. Metal speciation dynamics was investigated using several metal-speciation methods: Competing Ligand Exchange Method/Graphite Furnace Atomic Absorption Spectrometry (CLEM/GFAAS)； Competing Ligand Exchange Method/Adsorptive Cathodic Stripping Voltammetry (CLEM/AdCSV)； Anodic Stripping Voltammetry (ASV) with a Rotating Disk Electrode (RDE). CLEM/GFAAS and CLEM/AdCSV were used to determine dissociation rate coefficients of metal complexes in freshwaters. ASV was used to determine stability constants, dissociation rate coefficients and diffusion coefficients, of Cd, Cu, Pb, and Zn complexes in freshwaters, soil solutions (pore waters) and through-fall precipitation samples collected from the Rouyn-Noranda, (Abitibi, Quebec) and Sudbury (Ontario) areas. In the above samples of soil solutions (pore waters), the order of the lability of the metal complexes, Ni(II) ＞ Cu(II) <； Zn(II), followed the reverse order of the Ligand Field Stabilization Energy (LFSE) with the exception of Cu(II)； the position of Cu(II) was compounded of the USE and the Jahn-Teller effect. The slow coordination equilibrium of 3d-transition elements, especially of Ni(II) and Cu(II), in freshwaters suggests that the usual equilibrium assumption for freshwaters may not be valid. This study has demonstrated a direct relationship between the kinetic lability and the metal-to-Dissolved Organic Carbon (DOC) mole ratio. The lability increased with decreasing size fraction, resulting in the labile fraction being small metal species e.g., aqua-complex or small inorganic metal complexes. It was found that in freshwaters, release of humic-substance-bound Ni(II) as Ni-aqua complex was dependent on the competition by AI(III) and Fe(III) with Ni(II) for binding sites of humic substances. Exposure of DOC in freshwaters to UV-B radiation (280--320 nm) resulted in photodegredation of the DOC, releasing the DOC-bound metals. The above results show that the freshwater systems are dynamic and often far removed from equilibrium. These kinetic speciation techniques therefore represent an important advance in our experimental ability to investigate lability of metal complexes in freshwaters, and soil solutions (pore waters) Metals ; Water ; Metals Speciation. ; Pollution. ; Environmental aspects. Electronic dissertations. aeBook. aCN bNGL http://pqdt.bjzhongke.com.cn/Detail.aspx?pid=jF5db30bY2g%3d NGL Bs1616 rCNY371.35 ; h1 bs1204