Influence of ocean acidification on the complexation of iron and copper by organic ligands in estuarine waters
Influence of ocean acidification on the complexation of iron and copper by organic ligands in estuarine waters
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DOI：
10.1016/j.marchem.2015.03.016
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发表时间：
2015-12-20
期刊：
影响因子：
3
通讯作者：
Rijkenberg, Micha J. A.
中科院分区：
文献类型：
--
作者：
Gledhill, Martha;Achterberg, Eric P.;Rijkenberg, Micha J. A.
海洋吸收人类活动产生的大气CO2导致碳酸盐化学系统发生变化，包括pH值降低;这一过程被称为海洋酸化。我们对海洋酸化对微量金属化学形态的具体影响，特别是对有机金属相互作用的了解有限。在这项研究中，我们已经通过实验确定了改变pH值从83到6.8（在NBS规模）的铁和铜的形态在河口沃茨的影响。我们的实验结果表明，铁和铜的络合将减少和无机铁和铜的浓度增加，随着pH值的降低，虽然它是不可能的，自信地量化在较低的pH值的形态变化，由于分析技术的限制。除了我们的实验方法，我们使用了一个非理想的竞争吸附（NICA）-唐南模型来确定铁和铜的化学形态作为pH值的函数。NICA-Donnan模型进行了优化，以产生类似的金属结合特性，在我们的研究中检查的pH值范围内，在我们的样品中观察到的。该模型允许同时建模的溶解度和有机络合。模型结果表明，在较低的pH值下，有机物结合铁和铜的减少，加上溶解度增加（铁），导致无机铁浓度增加3倍，无机铜浓度增加6倍，pH值为7.41相比，pH值为8.18（总规模表示）。与此相比，当溶解的有机碳（DOC）浓度减半时，在pH 8.18下获得的无机铁浓度增加10倍，无机铜浓度增加5倍。因此，DOC的变异性可能会对海水中的金属形态产生更大的影响，而不是由于大气CO2增加而导致的pH值的预计变异性。因此，我们的研究表明，在河口沃茨中，由于pCO（2）的增加，生物可利用的无机铁和铜的浓度可能会增加，但这种变化的幅度是中等的。(C)2015 Elsevier B. V.版权所有。
The uptake of anthropogenic atmospheric CO2 by the oceans causes a shift in the carbonate chemistry system which includes a lowering of pH; this process has been termed ocean acidification. Our understanding of the specific effects of ocean acidification on chemical speciation of trace metals, in particular on organic-metal interactions, is limited. In this study we have experimentally determined the effects of changing pH from 83 to 6.8 (on the NBS scale) on the speciation of iron and copper in estuarine waters. Our experimental results indicated that complexation of iron and copper would decrease and inorganic iron and copper concentrations increase, as pH decreased, although it was not possible to confidently quantify changes in speciation at lower pH due to constraints of the analytical technique. In addition to our experimental approach, we used a non-ideal competitive adsorption (NICA)-Donnan model to determine the chemical speciation of iron and copper as a function of pH. The NICA-Donnan model was optimised in order to produce similar metal binding characteristics to those observed in our sample across the pH range examined in our study. The model allowed for simultaneous modelling of solubility and organic complexation. Model results indicated that a decrease in iron and copper binding by organic matter at lower pH, coupled with increased solubility (for iron), resulted in a 3 fold increase in inorganic iron concentration and a 6 fold increase in inorganic copper concentration at pH of 7.41 compared to a pH of 8.18 (expressed on the total scale). This compared to a 10 fold increase in inorganic iron concentration, and a 5 fold increase in inorganic copper concentration, obtained at pH 8.18, when the dissolved organic carbon (DOC) concentration was halved. Variability in DOC might thus be expected to have a greater impact on metal speciation in seawater, than projected variability in pH resulting from increases in atmospheric CO2. Our study therefore suggests that increases in the concentrations of the more bioavailable inorganic iron and copper species in estuarine waters resulting from increased pCO(2) are likely to occur, but that such changes will be moderate in magnitude. (C) 2015 Elsevier B.V. All rights reserved.