The Mackenzie River Basin (MRB) delivers large quantities of organic carbon (OC) into the Arctic Ocean, with significant implications for the global C budgets and ocean biogeochemistry. The amount and properties of OC in the Mackenzie River's delta have been well monitored in the last decade, but the spatial variability in OC sources transported by its different tributaries is still unclear. Here we present new data on the radiocarbon (¹⁴C) content of dissolved and particulate OC (Δ¹⁴C‐DOC and Δ¹⁴C‐POC) across the mainstem and major tributaries of the MRB, comprising 19 different locations, to identify factors controlling spatial patterns in riverine OC sources. The Δ¹⁴C‐DOC and Δ¹⁴C‐POC varied across a large range, from −179.9‰ to 62.9‰, and −728.8‰ to −9.0‰, respectively. Our data reveal a positive spatial coupling between the Δ¹⁴C of DOC and POC across the MRB, whereby the most ¹⁴C‐depleted waters were issued from the mountainous west bank of the MRB. This ¹⁴C‐depleted DOC and POC likely originates from a combination of petrogenic sources, connected with the presence of kerogens in the bedrock, and biogenic sources, mobilized by thawing permafrost. Our analysis also reveals intriguing relationships between Δ¹⁴C of DOC and POC with turbidity, water stable isotope ratio and catchment elevation, indicating that hydrology and geomorphology are key to understanding riverine OC sources in this landscape. A closer examination of the specific mechanisms giving rise to these relationships is recommended. For now, this study provides a road map of the key OC sources in this rapidly changing river basin.

中文翻译：

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加拿大麦肯齐河流域中动员的溶解性和颗粒状有机碳14C含量的控制

麦肯齐河流域（MRB）向北冰洋输送了大量有机碳（OC），这对全球C预算和海洋生物地球化学具有重要意义。在过去十年中，对麦肯齐河三角洲中的OC数量和性质进行了很好的监测，但由其不同支流输送的OC源的空间变异性仍不清楚。在这里，我们对放射性碳（本新数据¹⁴ C）溶解和颗粒OC（Δ的含量¹⁴ C-DOC和Δ ¹⁴ C-POC）跨过主干和MRB的主要支流，包括19个不同的位置，以识别控制因素河流OC源的空间格局。的Δ ¹⁴ C-DOC和Δ ¹⁴C‐POC的变化范围很大，分别为-179.9‰至62.9‰和-728.8‰至−9.0‰。我们的数据显示Δ之间的正空间耦合¹⁴ DOC和POC横跨MRB，由此大部分Ç ¹⁴ C-贫水都从MRB山区西银行发行。这^14种C贫化的DOC和POC可能源自与基岩中存在干酪根的岩石成因源和通过冻土融化而动员的生物源。我们的分析还表明Δ之间的关系耐人寻味¹⁴DOC和POC的C具有浊度，水稳定同位素比和集水高程，表明水文和地貌是了解该景观中河流OC来源的关键。建议仔细检查产生这些关系的特定机制。目前，这项研究提供了这个快速变化的流域主要OC来源的路线图。