Aquatic Biogeochemistry and Ecotoxicology, Institute F.-A. Forel, Faculty of Sciences, University of Geneva , 10, route de Suisse, 1290 Versoix, Geneva, Switzerland.
Environ Sci Technol. 2011 Apr 15;45(8):3452-8. doi: 10.1021/es104288y. Epub 2011 Feb 25.
The present study provides results on the influence of humic substance (HS) photoalteration on lead availability to the freshwater microalga Chlorella kesslerii . The evolution of the free lead-ion concentrations measured by the ion exchange technique Pb and intracellular lead contents was explored in the presence of Suwannee River humic (SRHA) and fulvic (SRFA) acids, as well as Aldrich humic acid (AHA) exposed at increasing radiance doses under a solar simulator. Modifications of HS characteristics highly relevant to Pb complexation and accumulation of HS to algal surfaces, including Fourier transform infrared spectroscopy, were followed. It was demonstrated that simulated sunlight exposure of HS increased Pb in the medium for SRFA and SRHA, but had no effect for AHA. No clear relationship was observed between the changes in free lead-ion concentrations and intracellular content in alga for all studied HS, suggesting that HS photodegradation products also exhibit Pb complexation properties, and that direct interactions between HS and alga are affected. Indeed, photoalteration of humic substances reduced the adsorption of HS to the algal surface; the effect was more pronounced for SRFA and AHA and less significant for SRHA. The bioavailability results were consistent with the characterization of the phototransformation of humic substances: Pb speciation changes followed the modification of the relative abundance of the carboxylic groups and their molecular environment, while the reduced HS adsorption to the alga correlated with losses of the double bond abundance and aromaticity.
本研究提供了腐殖质（HS）光致变化对淡水微藻 Chlorella kesslerii 中铅生物可利用性影响的结果。通过离子交换技术 Pb 和细胞内铅含量来探索在存在苏万尼河腐殖酸（SRHA）和富里酸（SRFA），以及在太阳模拟器下辐照剂量增加时暴露的 Aldrich 腐殖酸（AHA）的情况下，游离铅离子浓度的演变。跟踪了与 Pb 络合和 HS 积累到藻体表面高度相关的 HS 特性的变化，包括傅里叶变换红外光谱。结果表明，HS 的模拟阳光暴露增加了介质中 SRFA 和 SRHA 的 Pb，但对 AHA 没有影响。对于所有研究的 HS，未观察到游离铅离子浓度和藻类细胞内含量变化之间的明显关系，这表明 HS 光降解产物也表现出 Pb 络合特性，并且 HS 和藻类之间的直接相互作用受到影响。事实上，腐殖质的光致变化降低了 HS 对藻类表面的吸附；对于 SRFA 和 AHA 的影响更为明显，而对于 SRHA 的影响则不那么显著。生物有效性结果与腐殖质光转化的特征一致：Pb 形态变化遵循羧酸基团相对丰度和其分子环境的变化，而 HS 对藻类的吸附减少与双键丰度和芳香度的减少相关。
