In the development of organic matter (OM) source tracking tools, it is critical to validate if (1) the tracers are conservative with source mixing, and (2) they can be conservative under diagenetic processes (e.g., microbial degradation). In this study, these two critical points were rigorously tested for three commonly-used source tracking tools (i.e., absorbance and fluorescence proxies, stable carbon isotopes and lipid biomarkers) via a controlled experiment at laboratory scale. To this end, two end-members (e.g., soil and algae), which represent the most common and contrasted sources of OM to sediments in an aquatic environment, were mixed in different ratios and then incubated under different oxygen conditions (oxic versus anoxic) in the dark at 25 °C for 60 days. The initial and final signals of the source tracking tools were analyzed and compared for each mixing ratio. Based on three evaluation criteria concerning the linearity of the relationships, discrimination sensitivity, and conservative mixing behavior, we evaluated the applicability of the tools to trace the sediment organic matter in the aquatic environment. Although most of the source tracking proxies evaluated in this study showed a conservative nature after incubation, there are only a few that demonstrated both conservative behaviors with the sources mixing and under early diagenetic processes. The fluorescence proxies such as the relative distribution of a humic-like component associated with refractory source material (Ex/Em: 220/430 nm), modified fluorescence index (YFI), humification index (HIX), and carbon stable isotope ratios were identified to be the most reliable tracers for tracking sedimentary OM sources under early diagenetic processes. This study provides strong insights into the validation of common OM source tracking tools for sediment and a reasonable guideline to select the optimum indices for source discrimination via end-member mixing analysis.

中文翻译：

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早期的成岩过程会影响常用的有机物源追踪工具的适用性吗？通过受控降解末端成员混合实验进行评估。

在有机物（OM）源跟踪工具的开发中，至关重要的是要验证（1）示踪剂与源混合是否保守，以及（2）在成岩过程（例如微生物降解）下是否可以保守。在这项研究中，通过实验室规模的对照实验，对这三个关键点进行了严格测试，以测试三种常用的源跟踪工具（即吸光度和荧光代理，稳定的碳同位素和脂质生物标志物）。为此，将代表水生环境中沉积物中最常见和相反的有机质来源的两个末端成员（例如，土壤和藻类）以不同的比例混合，然后在不同的氧气条件下（有氧与无氧）孵育在黑暗中于25°C下放置60天。针对每种混合比率，分析并比较了源跟踪工具的初始和最终信号。基于有关关系的线性，辨别灵敏度和保守混合行为的三个评估标准，我们评估了该工具在水生环境中追踪沉积物有机物的适用性。尽管在这项研究中评估的大​​多数来源跟踪代理在孵化后都显示出保守的性质，但是只有少数几个证据表明在混合来源和早期成岩过程中都表现出保守的行为。荧光近似值，例如与耐火材料（Ex / Em：220/430 nm）相关的腐殖质样成分的相对分布，改良的荧光指数（YFI），增湿指数（HIX），碳稳定同位素比被确定为追踪早期成岩过程中沉积物OM源的最可靠示踪剂。这项研究为常见的沉积物OM源跟踪工具的验证提供了深刻的见解，并为通过末端成员混合分析选择最佳的源判别指标提供了合理的指导。