Forschungszentrum Dresden-Rossendorf e. V., Institute of Radiochemistry, P.O. Box 510119, 01314 Dresden, Germany.
Sci Total Environ. 2010 Dec 15;409(2):384-95. doi: 10.1016/j.scitotenv.2010.10.011. Epub 2010 Nov 2.
Biosorption of uranium(VI) by the green alga Chlorella vulgaris was studied at varying uranium concentrations from 5 μM to 1mM, and in the environmentally relevant pH range of 4.4 to 7.0. Living cells bind in a 0.1mM uranium solution at pH 4.4 within 5 min 14.3 ± 5.5 mg U/g dry biomass and dead cells 28.3 ± 0.6 mg U/g dry biomass which corresponds to 45% and 90% of total uranium in solution, respectively. During 96 h of incubation with uranium initially living cells died off and with 26.6 ± 2.1 mg U/g dry biomass bound similar amounts of uranium compared to dead cells, binding 27.0 ± 0.7 mg U/g dry biomass. In both cases, these amounts correspond to around 85% of the initially applied uranium. Interestingly, at a lower and more environmentally relevant uranium concentration of 5 μM, living cells firstly bind with 1.3 ± 0.2 mg U/g dry biomass to 1.4 ± 0.1 mg U/g dry biomass almost all uranium within the first 5 min of incubation. But then algal cells again mobilize up to 80% of the bound uranium during ongoing incubation in the time from 48 h to 96 h. The release of metabolism related substances is suggested to cause this mobilization of uranium. As potential leachates for algal-bound uranium oxalate, citrate and ATP were tested and found to be able to mobilize more than 50% of the algal-bound uranium within 24h. Differences in complexation of uranium by active and inactive algae cells were investigated with a combination of time-resolved laser-induced fluorescence spectroscopy (TRLFS), extended X-ray absorption fine structure (EXAFS) spectroscopy and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. Obtained results demonstrated an involvement of carboxylic and organic/inorganic phosphate groups in the uranium complexation with varying contributions dependent on cell status, uranium concentration and pH.
用小球藻研究了铀（VI）在不同铀浓度（5 μM 至 1mM）和环境相关 pH 值（4.4 至 7.0）下的生物吸附。在 pH 4.4 的 0.1mM 铀溶液中，活细胞在 5 分钟内结合 14.3 ± 5.5mg U/g 干生物质，而死细胞结合 28.3 ± 0.6mg U/g 干生物质，分别对应于溶液中总铀的 45%和 90%。在最初与铀孵育的 96 小时内，活细胞死亡，与 26.6 ± 2.1mg U/g 干生物质结合的铀量与死细胞相同，结合 27.0 ± 0.7mg U/g 干生物质。在这两种情况下，这些量都相当于最初应用的铀的 85%左右。有趣的是，在较低的、更具环境相关性的铀浓度 5μM 下，活细胞最初以 1.3 ± 0.2mg U/g 干生物质的速度结合，在最初孵育的 5 分钟内几乎结合了所有铀（1.4 ± 0.1mg U/g 干生物质）。但随后，在 48 小时至 96 小时的孵育过程中，藻类细胞再次动员高达 80%的结合铀。据推测，代谢相关物质的释放是导致铀动员的原因。作为藻类结合铀的潜在浸出物，测试了草酸盐、柠檬酸和 ATP，并发现它们能够在 24 小时内动员超过 50%的藻类结合铀。通过时间分辨激光诱导荧光光谱（TRLFS）、扩展 X 射线吸收精细结构（EXAFS）光谱和衰减全反射傅里叶变换红外（ATR-FTIR）光谱相结合，研究了活细胞和失活细胞对铀的络合差异。结果表明，羧酸和有机/无机磷酸盐基团参与了铀的络合，其贡献取决于细胞状态、铀浓度和 pH 值。
