Structural Characterization of Natural Nickel and Copper Binding Ligands along the US GEOTRACES Eastern Pacific Zonal Transect
Structural Characterization of Natural Nickel and Copper Binding Ligands along the US GEOTRACES Eastern Pacific Zonal Transect
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DOI：
10.3389/fmars.2016.00243
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发表时间：
2016-01-01
影响因子：
3.7
通讯作者：
Repeta, Daniel J.
中科院分区：
文献类型：
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作者：
Boiteau, Rene M.;Till, Claire P.;Repeta, Daniel J.
有机配体与海水中的多种微量元素形成强络合物。不同的金属可以竞争相同的配体螯合位置，结合金属的最终形态由相对结合亲和力、结合位置的浓度、未络合的金属浓度和缔合/解离动力学决定。不同的配体具有广泛的金属亲和力和特异性。然而，这些配体在海洋环境中的化学组成仍然没有得到很好的限制，这阻碍了海洋金属形态模拟的进展。在这项研究中，我们利用LC-ICPMS和高分辨率电喷雾电离质谱仪(ESIMS)检测和表征了东南太平洋东部与铜(Cu)和镍(Ni)结合的天然配体。溶解的铜、镍和配位体浓度在海岸附近最高。在海岸附近用固相萃取分离得到的配位体主要是色层未分解的极性化合物。近海，金属和配体浓度下降，但出现了几个新的配体。检测到一个主要的配体同时与Cu2+和Ni2+结合。根据准确的质量和裂解测量，该化合物的分子式为[C20H21N4O8S2+M](+)(M=金属同位素)，并含有几个唑类金属结合基团。额外的亲脂镍络合物也只存在于贫营养水域，质量分别为649、698和712 m/z(对应于Ni-58金属络合物)。测定了其中两个化合物的分子式[C32H54N3O6S2Ni](+)和[C33H56N3O6S2Ni](+)。向样品中添加铜和镍也表明存在可以结合镍和铜的额外化合物。虽然这些特定化合物只占总溶解的铜和镍库的一小部分，但它们突出了海洋镍和铜配体的组成多样性和空间异质性，以及同一环境中不同金属竞争配体结合的程度的差异性。
Organic ligands form strong complexes with many trace elements in seawater. Various metals can compete for the same ligand chelation sites, and the final speciation of bound metals is determined by relative binding affinities, concentrations of binding sites, uncomplexed metal concentrations, and association/dissociation kinetics. Different ligands have a wide range of metal affinities and specificities. However, the chemical composition of these ligands in the marine environment remains poorly constrained, which has hindered progress in modeling marine metal speciation. In this study, we detected and characterized natural ligands that bind copper (Cu) and nickel (Ni) in the eastern South Pacific Ocean with liquid chromatography tandem inductively coupled plasma mass spectrometry (LC-ICPMS), and high-resolution electrospray ionization mass spectrometry (ESIMS). Dissolved Cu, Ni, and ligand concentrations were highest near the coast. Chromatographically unresolved polar compounds dominated ligands isolated near the coast by solid phase extraction. Offshore, metal and ligand concentrations decreased, but several new ligands appeared. One major ligand was detected that bound both Cu2+ and Ni2+. Based on accurate mass and fragmentation measurements, this compound has a molecular formula of [C20H21N4O8S2+M](+)(M = metal isotope) and contains several azole-like metal binding groups. Additional lipophilic Ni complexes were also present only in oligotrophic waters, with masses of 649, 698, and 712 m/z (corresponding to the Ni-58 metal complex). Molecular formulae of [C32H54N3O6S2Ni](+) and [C33H56N3O6S2Ni](+) were determined for two of these compounds. Addition of Cu and Ni to the samples also revealed the presence of additional compounds that can bind both Ni and Cu. Although these specific compounds represent a small fraction of the total dissolved Cu and Ni pool, they highlight the compositional diversity and spatial heterogeneity of marine Ni and Cu ligands, as well as variability in the extent to which different metals in the same environment compete for ligand binding.