Abstract Dissolved organic matter (DOM) is omnipresent in natural waters and is commonly incorporated into carbonates. Records of DOM from speleothems (secondary carbonates found in caves) have often been interpreted to reflect groundwater DOM concentrations. However, the fidelity of these records is largely untested. An understanding of the relationship between dripwater and speleothem DOM is thus required to allow speleothems to be reliably used as archives of DOM concentration. We precipitated calcite (CaCO3) crystals from weak solutions of (NH4)2CO3, CaCl2 and NH4Cl. These solutions also contained peat DOM (from 0 to 15 mgC/L). Fluorescence 3D excitation-emission matrix (3D EEM) analysis showed a strong, positive correlation between [DOM] in the parent-solution, and [DOM] in the calcite. Calcite precipitation was reduced at high DOM concentrations, potentially indicating inhibition of crystallisation. Partition coefficient values showed that DOMaq was subtly preferentially incorporated into calcite. Scanning electron microscope images indicated that the crystal structures were heavily influenced by DOM adsorption with finer, smooth-faced, rhombohedral crystals forming in growth solutions with low aqueous [DOM] (0–5 mgC/L), and prismatic, ‘impure’ crystals produced at high aqueous [DOM] (10 and 15 mgC/L). Overall, our results indicate that authigenic carbonates are likely to faithfully record variations in aqueous [DOM] within the natural range of DOM concentrations in representative freshwater systems (caves, soil water), and that crystal habits are altered by aqueous [DOM] within their growth solutions. We also applied our findings to three flowstones collected from three New Zealand caves which vary in climatic, vegetation and hydrological regimes. We conclude that differences in initial aqueous [DOM] do indeed control incorporation of DOM into calcite, and thus 3D EEM fluorescence can be used to reconstruct original aqueous [DOM] from authigenic carbonates.

中文翻译：

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在溶解的有机物存在下形成方解石：分配、织物和荧光

摘要 溶解有机物 (DOM) 普遍存在于天然水域中，并且通常会结合到碳酸盐中。洞穴中的 DOM 记录（洞穴中发现的次生碳酸盐）经常被解释为反映地下水 DOM 浓度。然而，这些记录的保真度在很大程度上未经测试。因此，需要了解滴水和洞穴 DOM 之间的关系，才能可靠地将洞穴作为 DOM 浓度的档案。我们从 (NH4)2CO3、CaCl2 和 NH4Cl 的弱溶液中沉淀出方解石 (CaCO3) 晶体。这些溶液还含有泥炭 DOM（从 0 到 15 mgC/L）。荧光 3D 激发-发射矩阵 (3D EEM) 分析显示母体溶液中的 [DOM] 与方解石中的 [DOM] 之间存在很强的正相关。在高 DOM 浓度下方解石沉淀减少，可能表明结晶受到抑制。分配系数值表明 DOMaq 巧妙地优先并入方解石中。扫描电子显微镜图像表明，晶体结构受到 DOM 吸附的严重影响，在低含水 [DOM] (0–5 mgC/L) 的生长溶液中形成更细的、光滑面的菱形晶体和棱柱形、“不纯”晶体在高含水 [DOM]（10 和 15 mgC/L）下产生。总的来说，我们的结果表明，自生碳酸盐可能会如实地记录代表性淡水系统（洞穴、土壤水）中 DOM 浓度自然范围内含水 [DOM] 的变化，并且晶体习性被其内的含水 [DOM] 改变。增长解决方案。我们还将我们的发现应用于从三个新西兰洞穴中收集的三块流石，这些洞穴在气候、植被和水文状况方面各不相同。我们得出结论，初始含水 [DOM] 的差异确实控制了 DOM 掺入方解石中，因此 3D EEM 荧光可用于从自生碳酸盐重建原始含水 [DOM]。