School of Marine Science and Engineering, University of Plymouth, Plymouth, Devon PL4 8AA, UK.
Mar Pollut Bull. 2010;61(1-3):37-51. doi: 10.1016/j.marpolbul.2009.12.012. Epub 2010 Feb 12.
This paper provides a review and critique of the distributions and characteristics of non-cohesive and cohesive sediments within the Severn Estuary, with particular reference to floc properties. The estuary is hyper-tidal and, consequently, highly turbid along most of its length and it generally has two turbidity maxima. In the upper reaches of the estuary, suspended particulate matter (SPM) concentrations can be in excess of 10 g l(-1) for river flows up to 50 m(3)s(-1), rising to over 50 g l(-1) during periods of lower river flow. The lower estuary turbidity maximum originates in the vicinity of Bridgwater Bay where SPM concentrations may vary between 0.1-200 g l(-1). The formation of fluid mud is coupled to the spring-neap cycle and strong vertical gradients in SPM concentrations produce turbulence damping and drag reduction effects, and hence impair the ability of the flow to transport sediments. Flocculation is an important mechanism for controlling the behaviour of fine sediments and mean settling velocities of flocs vary between 0.8-6 mm s(-1). A secondary consequence of flocculation is the formation of mud:sand mixtures in turbid suspensions. Improved understanding of the significance of flocculation processes is crucial as they may exert an influence on the mechanism by which adsorbed contaminants are transported in the system.
本文回顾和批判了塞文河口非粘性和粘性沉积物的分布和特征，特别提到了絮体特性。该河口潮汐强烈，因此在大部分长度上都非常浑浊，通常有两个浊度最大值。在上游河口，悬浮颗粒物 (SPM) 浓度在河流流量高达 50 立方米/秒时可超过 10 克/升，在河流流量较低时可超过 50 克/升。下游河口的浊度最大值起源于布里奇沃特湾附近，那里的 SPM 浓度可能在 0.1-200 克/升之间变化。流体泥浆的形成与潮汐周期有关，SPM 浓度的强烈垂直梯度会产生湍流阻尼和阻力降低效应，从而削弱水流输送沉积物的能力。絮凝是控制细颗粒沉积物行为的重要机制，絮体的平均沉降速度在 0.8-6 毫米/秒之间变化。絮凝的另一个后果是在浑浊悬浮液中形成泥-沙混合物。更好地了解絮凝过程的意义至关重要，因为它们可能会影响系统中吸附污染物的迁移机制。
