River discharge has an important influence on the chemistry of Arctic shelf seas and surface waters. In this study, we examined the changes in nutrient, trace metal, dissolved organic matter, dissolved inorganic carbon, alkalinity, and radium isotope distributions across the Mackenzie River delta and estuary in June 2016, and estimated trace element and isotopes fluxes from the Mackenzie River to the Western Arctic Ocean. While inorganic nutrient, dissolved inorganic carbon, alkalinity, trace metal, and radium levels remained fairly constant through the delta, dissolved organic matter concentrations were 2–3.5 times higher at the mouth of the river, reflecting inputs from the delta. In the estuarine mixing zone, radium isotope ratios indicated that both desorption from suspended sediments and benthic inputs affected solute concentrations. Similarly, most of the measured trace metals (Ba, Co, Cu, Mn, Ni) exhibited non-conservative addition in the freshwater-saltwater transition zone, while Pb was removed and U was mixed conservatively. Inorganic nutrients were affected by both addition and removal processes in the estuary. Dissolved inorganic carbon and alkalinity exhibited net removal, likely due to a combination of biological uptake, gas exchange, CaCO₃ precipitation, and surface ion exchange processes. Approximately 45% and 60% of dissolved organic carbon and nitrogen, respectively, were removed rapidly at low salinities, in contrast with previous studies suggesting conservative mixing through Arctic estuaries. This study highlights the need to take deltaic and estuarine processes into account when determining the flux of riverine solutes to the coastal ocean.

河流排放对北极大陆架海和地表水的化学性质具有重要影响。在这项研究中，我们研究了2016年6月整个麦肯锡河三角洲和河口的养分，微量金属，溶解的有机物，溶解的无机碳，碱度和镭同位素分布的变化，并估算了麦肯齐河的微量元素和同位素通量到北冰洋西部。尽管整个三角洲的无机养分，溶解的无机碳，碱度，痕量金属和镭的含量保持相当稳定，但河口的溶解有机物浓度却高出2–3.5倍，反映了三角洲的投入。在河口混合区，镭的同位素比值表明悬浮沉积物的解吸和底栖生物输入都影响溶质浓度。同样，大多数测量的痕量金属（Ba，Co，Cu，Mn，Ni）在淡水-盐水过渡区中显示出非保守添加，同时Pb被去除并且U保守地混合。河口的无机营养物质受添加和去除过程的影响。溶解的无机碳和碱度表现出净去除，这可能是由于生物吸收，气体交换，CaCO₃沉淀和表面离子交换过程。在低盐度下，大约有45％和60％的溶解有机碳和氮迅速被去除，这与之前的研究表明通过北极河口进行保守混合形成了鲜明的对比。这项研究强调在确定河流溶质向沿海海洋的通量时需要考虑三角洲和河口过程。