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首页> 外文期刊>Environmental Science & Technology >Effect Of Humic Acid On Cd(Ⅱ), Cu(Ⅱ), And Pb(Ⅱ) Uptake By Freshwater Algae: Kinetic And Cellwall Speciation Considerations
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Effect Of Humic Acid On Cd(Ⅱ), Cu(Ⅱ), And Pb(Ⅱ) Uptake By Freshwater Algae: Kinetic And Cellwall Speciation Considerations

机译：腐殖酸对淡水藻类吸收Cd（Ⅱ），Cu（Ⅱ）和Pb（Ⅱ）的影响：动力学和细胞壁形态学考虑

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The present study examines the effect of humic acid on the uptake kinetics of Cd(Ⅱ), Cu(Ⅱ), and Pb(Ⅱ) by the freshwater alga Chlorella kesslerii. The results demonstrated that the relative proportion of Pb in the cell wall layer is greater than that of the internalized Pb, while internalized Cd and Cu were comparable or greater than the adsorbed metal concentration. In the presence of 10 mg L~(-1) humic acid (HA), Cd and Cu uptake kinetics were consistent with that predicted by measured free metal concentrations. For Pb, the uptake flux and amount of lead bound to internalization and adsorption sites were an order of magnitude higher than those found at the same free lead ion concentrations in the presence of citric acid. Chemodynamic modeling suggested that the enhancement of the Pb uptake flux in the presence of HA originates from an increasing amount of Pb bound to the internalization sites through a ternary complex formation between lead-humic acid complex and internalization sites. Cell wall speciation calculations indicated that the lead-humic acid complex is the predominant species in the cell wall layer, while for Cu(ll) and Cd(Ⅱ) metal bound to the internalization (Cu) and adsorption (Cd) sites significantly dominated over the M-HA complex. The findings of the work show the relevance of the cell wall layer concentration and speciation and its key role in defining the local equilibrium conditions between metal and internalizations sites. The results of the present kinetic study have important consequences for improvement of the mechanistic understanding of the role of dissolved organic matter in metal uptake in phytoplankton and biogeochemical cycling of metals in the surface waters.
机译：本研究探讨了腐殖酸对淡水藻类小球藻对Cd（Ⅱ），Cu（Ⅱ）和Pb（Ⅱ）的吸收动力学的影响。结果表明，胞壁层中Pb的相对比例大于内化Pb的相对比例，而内化Cd和Cu相当或大于吸附的金属浓度。在10 mg L〜（-1）腐殖酸（HA）存在下，Cd和Cu的吸收动力学与通过测量的游离金属浓度预测的一致。对于Pb，与内在和吸附位点结合的铅的吸收通量和铅量比在柠檬酸存在下相同的自由铅离子浓度下所发现的铅高。化学动力学模型表明，在HA存在下Pb吸收通量的增加是由于铅-腐植酸络合物与内在化位点之间形成三元络合物，从而增加了结合到内在化位点的Pb量。细胞壁形态计算表明，铅-腐植酸复合物是细胞壁层中的主要物质，而对于Cu（II）和Cd（Ⅱ），金属与内在化（Cu）和吸附（Cd）结合的位点明显占主导地位。 M-HA复合体。这项工作的发现表明，细胞壁层浓度和形态的相关性及其在定义金属和内在化位点之间的局部平衡条件中的关键作用。本动力学研究的结果对于改善对溶解性有机物在浮游植物吸收金属和地表水中金属的生物地球化学循环中作用的机理的理解方面具有重要意义。

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