Microplastics (MPs) pollution in marine environments has received considerable attention over the past two decades due to the increased awareness of its potential risks to ecosystems. Numerical simulations can be used to provide estimates of MPs fate and distribution, but so far this approach has been largely applied to the open ocean. In this work, the distribution patterns of MPs in a prototype coastal upwelling environment (Ría de Vigo estuary, Spain) is investigated using a combined approach of field data and modelling. Water and sediment samples were collected at different locations along the Ría during both upwelling and downwelling conditions. Experiments using an idealized 2D-vertical model were conducted to explain the observed MP distribution and elucidate the relative importance of river discharge, wind-driven and density-driven circulation. Microplastics were found at all stations in all samples. The largest observed fraction of MPs corresponded to fibres followed by plastic paint sheets and fragments. The trapping or flushing of MPs was mainly controlled by the wind forcing, whose effects on the circulation normally exceeds those of the density-driven and river flows. During upwelling conditions, more MP items were collected near the surface at the outer half of the estuary than during downwelling. The seaward near-surface circulation induced by the wind and density gradient jointly contributed to flushing out floating MPs. Near the bottom, the landward wind-induced and gravitational circulation formed estuarine MP maxima (EMPM) inside the estuary. Pellets, fragments, and films were more efficiently trapped than fibres, as their EMPM were located more upstream. The results suggested that downwelling-favourable winds caused an overall landward (seaward) displacement of the distribution of floating (sinking) MPs. Modelling results indicate that winds dominate the circulation in the outer part of the estuary, whereas near the head the gravitational circulation takes over the control of the net flow. The particular location of the EMPM appears to be controlled by the competition of density-driven and wind-driven flows.

由于对生态系统潜在风险的认识不断提高，过去二十年来，海洋环境中的微塑料（MP）污染受到了广泛关注。可以使用数值模拟来估算海洋议员的命运和分布，但到目前为止，这种方法已广泛应用于公海。在这项工作中，采用现场数据和建模相结合的方法，研究了沿海原型上升流环境（西班牙里亚维戈河口）中MP的分布模式。在上涌和下涌条件下，沿Ría的不同位置收集了水和沉积物样本。进行了使用理想化2D垂直模型的实验，以解释观测到的MP分布并阐明河流流量的相对重要性，风驱动和密度驱动的循环。在所有样品的所有工位都发现了微塑料。观察到的MP的最大部分对应于纤维，其次是塑料油漆板和碎片。MPs的捕集或冲洗主要由风力控制，其对循环的影响通常超过了密度驱动和河流的影响。在上涌条件下，与下涌过程相比，在河口外半部表面附近收集到更多的MP物品。风和密度梯度引起的海面近地表环流共同推动了漂浮MP的冲刷。在底部附近，向风引起的重力和引力环流在河口内部形成了河口MP最大值（EMPM）。颗粒，碎片和薄膜比纤维更有效地被捕获，因为他们的EMPM位于上游。结果表明，向下的有利风导致了漂浮（下沉）海平面的总体向陆地（向海）位移。模拟结果表明，风支配着河口外部的循环，而在水头附近，重力循环接管了净流量的控制。EMPM的特定位置似乎受密度驱动流和风驱动流竞争的控制。而在头部附近，重力循环接管了净流量的控制。EMPM的特定位置似乎受密度驱动流和风驱动流竞争的控制。而在头部附近，重力循环接管了净流量的控制。EMPM的特定位置似乎受密度驱动流和风驱动流竞争的控制。