Abstract In the past several decades, anthropogenic changes throughout drainage basins have threatened physical, hydrological and ecological river-to-ocean continuum balances. Dams are one of these anthropogenic influences that can seriously affect sediment fluxes to the ocean. Here, we investigate the formation and dispersion of a high-concentration mud suspension (HCMS) at a river mouth due to a tailing dam failure. In November 2015, the Fundao dam (Mariana-MG, Southeast Brazil) failure released approximately 39.2 million m3 of tailings into the Doce River system. The slurry travelled 660 km down to the river mouth, reaching the Atlantic Ocean. Pre- and Post-dam failure surveys were used to investigate temporal and spatial changes in Suspended Particulate Matter (SPM) concentration, seabed sediment grain size and seabed sediment bulk density along the inner shelf. Results indicate that the combination of the tailing dam failure with an extremely dry seasonal condition led to the formation of a HCMS, altering, at least in a short term, the sedimentary processes along the inner shelf, leading to high sedimentation rates and low seabed sediment bulk density. Changes in particle size defined by an increase in clay content, a significant increase in SPM concentration in the inner shelf and a decrease in seabed sediment bulk density were observed as a result of the dam failure. SPM concentrations were higher near the seabed than at the surface, reaching up to 9000 mg/l. The highest SPM concentration measured during a major flood in January 2014 reached around 100 mg/l, The combination of a HCMS with tailings high clay content resulted in low values of seabed sediment bulk density and the formation of fluid mud along the inner shelf. In the first week after the tailings arrival, a 5 cm thick tailing fluid mud was observed. In this stage of bed formation, bed strength is lower, easing particle reentrainment by waves or currents. Thus, tailings could be advected, spreading the impact along the coast.

中文翻译：

---

尾矿坝溃决对巴西东部内陆架沉积的影响

摘要 在过去的几十年里，整个流域的人为变化已经威胁到河流到海洋的自然、水文和生态连续体平衡。大坝是这些人为影响之一，可严重影响流入海洋的沉积物通量。在这里，我们调查了由于尾矿坝溃决而在河口形成和分散的高浓度泥浆悬浮液 (HCMS)。2015 年 11 月，Fundao 大坝（巴西东南部马里亚纳-MG）发生故障，向多切河系统排放了约 3,920 万立方米的尾矿。泥浆向下流到河口 660 公里，到达大西洋。大坝溃坝前和溃坝后调查用于调查悬浮颗粒物 (SPM) 浓度的时间和空间变化，沿内陆架的海底沉积物粒度和海底沉积物容重。结果表明，尾矿坝溃决与极度干燥的季节性条件相结合导致 HCMS 的形成，至少在短期内改变了内陆架的沉积过程，导致高沉积率和低海底沉积物体积密度。由于大坝溃决，观察到由粘土含量增加、内陆架中 SPM 浓度显着增加和海底沉积物容重降低所定义的粒度变化。海床附近的 SPM 浓度高于海面，高达 9000 毫克/升。在 2014 年 1 月的一次大洪水期间测得的最高 SPM 浓度达到了 100 毫克/升左右，HCMS 与尾矿的高粘土含量相结合，导致海底沉积物容重值较低，并且沿内陆架形成了流体泥浆。在尾矿到达后的第一周，观察到5厘米厚的尾矿泥浆。在地层形成的这个阶段，地层强度较低，减轻了波浪或水流对颗粒的再夹带。因此，尾矿可能会平流，沿海岸传播影响。