The aim of the current study was to determine the nature of the seasonal variability of the Suspended Particulate Matter (SPM) fluxes from the drainage basin to the estuary in a macrotidal region (Northeastern Brazil), and the estuarine response to a seawater intrusion regarding sediment deposition, which will support the understanding of the global transport of materials at the continent-ocean interface. Thermohaline structure data was acquired using a Conductivity, Temperature, and Depth (CTD) probe with a sampling frequency of 4 Hz. Suspended particulate material was measured by gravimetric measurements applied to exact filtered volume samples. The outflows were measured through the use of an Acoustic Doppler Current Profiler (ADCP) with frequency of 1.5 MHz. The horizontal thermal and saline gradients varied from warmer and less saline waters (2014) to cooler and saline waters (2015). The gradient behavior when linked to volume transport and SPM flows, suggests a minimization of the fluvial flows in 2015, easing the advance of coastal water (CW) towards the inner estuary, leading to an inversion of the baroclinic pressure gradient. The bottom saline front, generated by the entrance of coastal water masses, caused an increase in SPM concentrations due to increased fluid density, resuspension of previously deposited sediment, and erosion of banks. High concentrations of SPM indicate higher volume transport suggesting a hydraulic barrier due to the change/inversion of the baroclinic pressure gradient, resulting in water and material retention. Material deposition was observed during neap tide, while during spring tide the material is resuspended, increasing the concentration, generating cycles of deposition and erosion during the neap-spring tides. The sediment in suspension that reach the estuary, even with low fluvial volume, stay in this environment forming new islands because of deposition. High deposition rates or sediment cycling, if generated by the hydraulic barrier, may indicate that the flows of SPM from the continental drainage to the estuary and adjacent continental shelf are interrupted and the residence time is increased.

本研究的目的是确定大潮区（巴西东北部）从流域到河口的悬浮颗粒物（SPM）通量的季节性变化的性质，以及河口对沉积物对海水入侵的响应沉积，这将有助于了解大陆与海洋交界处的全球物料运输。使用电导率，温度和深度（CTD）探头以4 Hz的采样频率获取盐卤的结构数据。悬浮颗粒材料通过重量分析法测量，并应用于精确过滤的体积样品。通过使用频率为1.5 MHz的声学多普勒电流剖面仪（ADCP）来测量流出量。水平的热水和盐水梯度从温暖的和较少的盐水（2014年）到凉爽的和咸水（2015年）不等。与体积传输和SPM流量相关的梯度行为表明，2015年的河流流量最小化，缓解了沿海水（CW）向内河口的推进，从而导致了斜压梯度的反转。由沿海水团进入而产生的底部盐水前沿，由于流体密度增加，先前沉积的沉积物重新悬浮和河岸侵蚀而导致SPM浓度增加。高浓度的SPM表示较高的体积输运量，这表明由于斜压梯度的变化/反演而形成了水力屏障，从而导致水和物质的滞留。在潮汐期间观察到物质沉积，在春季潮汐期间，物料会重新悬浮，从而增加浓度，从而在轻度春季潮汐期间产生沉积和侵蚀的循环。即使河流流量很小，悬浮物到达河口的沉积物也会由于沉积而留在此环境中，形成新的岛。如果由水力屏障引起的高沉积速率或沉积物循环，可能表明SPM从大陆排水流向河口和邻近大陆架的流动被中断，并且停留时间增加了。