The Amazon is Earth's largest river by volume output, making it an important source of trace metals and dissolved organic matter (DOM) to the Atlantic Ocean. Despite major recent anthropogenic disruptions to the Amazon catchment area, data for trace metals such as copper (Cu) in the Amazon River estuary and associated mixing plume are still rare. Furthermore, there is currently no existing data in this region for Cu-binding ligands, which govern the amount of bioavailable Cu. To understand trace metal mixing and transport processes, the GEOTRACES process study GApr11 (cruise M147 with RV Meteor) was conducted in 2018 in the Amazon and Pará River estuaries and mixing plume in the tropical North Atlantic Ocean during high river discharge. Size-fractionated surface samples were collected along the full salinity gradient for concentrations of Cu, apparent Cu-binding organic ligands (L_Cu) and corresponding conditional stability constants (K′_{CuL, Cu2+}^cond), electroactive humic substances (eHS), solid phase extractable organic Cu (SPECu), dissolved organic carbon (DOC), chlorophyll a (Chl a) and macronutrients. Dissolved (<0.2 μm) and soluble (<0.015 μm) Cu correlated negatively with salinity and largely followed values expected from conservative mixing. Cu was primarily in the soluble fraction, with the exception of a minor fraction of large colloidal Cu at low salinity (S ≤ 10). Organic ligands (log K′_{CuL, Cu2+}^cond = 12.6–15.6) were present in excess of Cu and likely played a role in solubilizing Cu and preventing Cu being affected by colloidal flocculation. Cu-associated DOM (measured as L_Cu, eHS and SPECu) correlated negatively with salinity and appeared to be primarily governed by river input and mixing with seawater. However, an increase in the colloidal fraction for L_Cu and eHS observed at S ~ 6–10 was attributed to possible additional autochthonous (phytoplankton) ligand production. In all dissolved samples, organic complexation kept free Cu below levels potentially toxic for phytoplankton (<1 pmol L⁻¹). Despite increasing anthropogenic activity over the past century, we find Cu concentrations remained similar to the 1970s, suggesting that the large overall river flow may so far minimize the impact of Cu pollution.

亚马逊河是地球上产量最大的河流，使其成为大西洋的微量金属和溶解有机物 (DOM) 的重要来源。尽管亚马逊流域最近发生了重大的人为破坏，但亚马逊河河口铜 (Cu) 等痕量金属和相关混合羽流的数据仍然很少。此外，目前该地区还没有关于铜结合配体的数据，这些配体控制着生物可利用的铜的数量。为了了解微量金属混合和运输过程，GEOTRACES 过程研究 GApr11（巡航 M147 与RVMeteor) 于 2018 年在亚马逊河和帕拉河河口进行，并在高河流流量期间在热带北大西洋进行混合羽流。沿全盐度梯度收集大小分级的表面样品，以获得 Cu 浓度、表观 Cu 结合有机配体 (L _Cu ) 和相应的条件稳定性常数 ( K ' _{CuL、Cu 2+} ^cond )、电活性腐殖质 (eHS)、固相可萃取有机铜 (SPE Cu)、溶解有机碳 (DOC)、叶绿素a (Chl a) 和大量营养素。溶解 (<0.2 μm) 和可溶性 (<0.015 μm) Cu 与盐度呈负相关，很大程度上遵循保守混合预期的值。Cu 主要在可溶部分，除了少量的低盐度 (S ≤ 10) 大胶体 Cu。有机配体（log K ′ _{CuL，Cu 2+} ^cond  = 12.6–15.6）存在于过量的Cu 中，并且可能在溶解Cu 和防止Cu 受胶体絮凝影响方面发挥作用。与铜相关的 DOM（以 L _Cu、eHS 和 SPE Cu 测量）与盐度呈负相关，似乎主要受河流输入和与海水混合的控制。然而，L 的胶体分数增加在 S ~ 6-10 观察到的_Cu和 eHS 归因于可能的额外本地（浮游植物）配体产生。在所有溶解的样品中，有机络合使游离铜保持在对浮游植物具有潜在毒性的水平以下（<1 pmol L ^-1）。尽管在过去的一个世纪里人为活动不断增加，但我们发现 Cu 浓度与 1970 年代相似，这表明迄今为止大的整体河流流量可能会将 Cu 污染的影响降至最低。