Department of Civil Engineering, TKM College of Engineering Kollam, Kerala, India; APJ Abdul Kalam Technological University, Kerala, India.
Department of Civil Engineering, TKM College of Engineering Kollam, Kerala, India; APJ Abdul Kalam Technological University, Kerala, India.
Environ Res. 2024 Jun 15;251(Pt 1):118590. doi: 10.1016/j.envres.2024.118590. Epub 2024 Mar 2.
Estuaries are fragile environment that are most affected by climate change. One of the major consequences of climate change on estuarine processes is the enhancement in salt intrusion leading to higher salinity values. This has several implications on the estuarine sediment dynamics. Of the various factors that affect the flocculation of cohesive sediments, salinity and turbulence have been recognized as to have great significance. Many of the estuaries are contaminated with heavy metals, of which, the concentration of Iron (Fe (II)) are generally on the higher range. However, the influence of Fe (II) on the flocculation of cohesive sediments at various estuarine mixing conditions is not well known. The present study investigated the influence of Fe (II) on the flocculation of kaolin at various concentration of Fe (II), salinity and turbulence shear. The results indicated that Fe (II) and salinity have a positive influence on kaolin flocculation. The increase in turbulence shear caused an initial increase and then a decrease in floc size. In case of sand-clay mixtures, that are observed in mixed sediment estuarine environments, a reduction in the floc size was observed, which is attributed to the breakage of flocs induced by the shear of sand. Breakage coefficient, which is a measure of break-up of flocs, is generally adopted as 0.5 assuming binary breakage. The present study revealed that the breakage coefficient can take values from 0 to 1 and is a direct function of Fe (II) and salinity and an inverse function of turbulence and sand concentration. Thus, a new model for breakage coefficient with the influencing parameters has been proposed, which is an improvement of existing model that is expressed in terms of turbulence alone. Sensitivity analysis showed that the proposed model can very well predict the breakage coefficient of Fe (II) - kaolin flocs. Thus, the model can quantify the breakage coefficient of flocs in estuaries contaminated with Fe (II) that is a vital parameter for population balance models.
河口是受气候变化影响最严重的脆弱环境之一。气候变化对河口过程的主要影响之一是盐入侵加剧，导致盐度值升高。这对河口泥沙动力有几个影响。在影响粘性泥沙絮凝的各种因素中，盐度和紊流已被认为具有重要意义。许多河口都受到重金属污染，其中铁 (Fe (II)) 的浓度通常处于较高范围。然而，在各种河口混合条件下，Fe (II) 对粘性泥沙絮凝的影响尚不清楚。本研究研究了不同浓度的 Fe (II)、盐度和紊流剪切对高岭土絮凝的影响。结果表明，Fe (II) 和盐度对高岭土絮凝有积极影响。紊流剪切的增加导致絮体粒径先增加后减小。在混合泥沙河口环境中观察到的砂-粘土混合物的情况下，观察到絮体粒径减小，这归因于砂的剪切引起的絮体破碎。破碎系数是衡量絮体破碎的一种度量，通常假定为二进制破碎的 0.5。本研究表明，破碎系数可以取 0 到 1 之间的值，并且是 Fe (II) 和盐度的直接函数，是紊流和砂浓度的反比函数。因此，提出了一个新的破碎系数模型，该模型考虑了影响参数，是仅基于紊流的现有模型的改进。敏感性分析表明，所提出的模型可以很好地预测 Fe (II) -高岭土絮体的破碎系数。因此，该模型可以量化受 Fe (II) 污染的河口中絮体的破碎系数，这是质量平衡模型的一个重要参数。
