Okochi Hiroshi, Brimblecombe Peter
School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UK.
ScientificWorldJournal. 2002 Mar 21;2:767-86. doi: 10.1100/tsw.2002.132.
It is possible that metal-organic complexation enhances the uptake of gaseous organic compounds and the solubility of metals in aerosols and atmospheric water. We investigated potential atmospheric organic ligands and the enhanced uptake of hydroxy-, oxo-, and dicarboxylic acids as well as dicarbonyls into atmospheric aqueous aerosol. We examined complexation with transition metals (iron, manganese, nickel, copper, zinc) and lead on the basis of available references and our experimental data. Humic-like substances are most likely ligands in the atmosphere, although this is a poorly characterized material. A number of polycarboxylic acids and hydroxy forms (e.g., citric and tartronic acids) effectively complex metals such as copper in atmospheric aerosols. The simple equilibrium model calculations show that the effect of the complexation on the gas-aqueous phase partition of gaseous atmospheric ligands is quite small for the ligands with the high physical Henry's law constants, e.g., dicarboxylic acids represented by oxalic acid, even if they have high affinity with metal ions. The lower Henry's law constants of the alpha-dicarbonyls, such as glyoxal and methylglyoxal, mean that the complexation could lead to profound increases in their partition into the aqueous phase. Despite quantum mechanical arguments for copper-glyoxal complexes, experiments showed no evidence of complexation between either hydrated or unhydrated alpha-dicarbonyls and the cupric ion. By contrast the beta-dicarbonyl, malondialdehyde, has properties that would allow it to partition into atmospheric water via the complexation with metal ions under some conditions.
金属-有机络合作用有可能增强气态有机化合物的摄取以及金属在气溶胶和大气水中的溶解度。我们研究了潜在的大气有机配体以及羟基酸、氧代酸、二羧酸和二羰基化合物在大气水气溶胶中的增强摄取情况。我们根据现有参考文献和实验数据，研究了它们与过渡金属（铁、锰、镍、铜、锌）和铅的络合作用。类腐殖质很可能是大气中的配体，尽管这是一种特性尚不明确的物质。一些多元羧酸和羟基形式（如柠檬酸和酒石酸）能有效地络合大气气溶胶中的金属，如铜。简单的平衡模型计算表明，对于具有高物理亨利定律常数的配体，如以草酸为代表的二羧酸，络合作用对气态大气配体气-水相分配的影响相当小，即使它们与金属离子具有高亲和力。α-二羰基化合物（如乙二醛和甲基乙二醛）较低的亨利定律常数意味着络合作用可能导致它们在水相中的分配大幅增加。尽管有关于铜-乙二醛络合物的量子力学观点，但实验表明无论是水合还是未水合的α-二羰基化合物与铜离子之间都没有络合的证据。相比之下，β-二羰基化合物丙二醛具有在某些条件下通过与金属离子络合而分配到大气水中的特性。
