Karlsson Ulrika, Karlsson Stefan, Düker Anders
Man-Technology-Environment Research Centre, Department of Natural Sciences, Orebro University, 70182 Orebro, Sweden.
J Environ Monit. 2006 Jun;8(6):634-40. doi: 10.1039/b516445a. Epub 2006 Apr 24.
The distribution of aqueous Tl(I)/Tl(III) as a function of light exposure and solution properties was studied by quantifying the oxidation states after separation with ion chromatography and on-line detection with ICP-MS. Ultraviolet irradiation of aqueous solutions containing 1 microg l(-1) Tl(III) and in equilibrium with the atmosphere increases the reduction rate. In systems with photoreduction of Fe(III)(aq) a quantitative oxidation of Tl(I)(aq) was observed, notably at low pH. The process is reversible, as indicated by formation of Tl(I) when the irradiated systems were kept in the dark. In systems with colloidal silica-stabilised ferrihydrite, UV irradiation also leads to oxidation of Tl(I)(aq), but not quantitatively. It is suggested that adsorption of thallium to the ferrihydrite determines the rate of oxidation. Detectable, but not quantitative, oxidation of Tl(I)(aq) took place when natural water samples with 1 microg l(-1) Tl(I)(aq) were exposed to either sunlight or UV-light. For these samples, the reduction was not quantitative when they were kept in the dark for 24 h. The results suggest that the light dependent iron cycle in fresh water systems strongly influences the redox state of thallium.
通过离子色谱分离后用ICP-MS进行在线检测来定量氧化态，研究了水相中Tl(I)/Tl(III)的分布与光照及溶液性质的关系。对含有1 μg l⁻¹ Tl(III)且与大气处于平衡状态的水溶液进行紫外线照射，会提高还原速率。在Fe(III)(aq)发生光还原的体系中，观察到Tl(I)(aq)发生了定量氧化，尤其是在低pH值时。该过程是可逆的，如将照射后的体系置于黑暗中会形成Tl(I)所示。在含有胶体二氧化硅稳定的水铁矿的体系中，紫外线照射也会导致Tl(I)(aq)氧化，但不是定量的。有人认为铊吸附到水铁矿上决定了氧化速率。当含有1 μg l⁻¹ Tl(I)(aq)的天然水样暴露于阳光或紫外线下时，会发生可检测但非定量的Tl(I)(aq)氧化。对于这些样品，当它们在黑暗中放置24小时后，还原反应并非定量进行。结果表明，淡水系统中依赖光的铁循环强烈影响铊的氧化还原状态。
