Biophysical flocculation reduces variability of cohesive sediment settling velocity
Biophysical flocculation reduces variability of cohesive sediment settling velocity
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DOI：
10.1038/s43247-023-00801-w
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发表时间：
2023-04
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通讯作者：
Ye;Springer Science;Business Media;L. Ye;J. A. Penaloza-Giraldo;A. Manning;J. Holyoke;T. Hsu
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作者：
Ye;Springer Science;Business Media;L. Ye;J. A. Penaloza-Giraldo;A. Manning;J. Holyoke;T. Hsu
生物物理凝聚力主要由胞外聚合物（ExtracellularPolymericSubstances，EPS）在水中矿物絮凝过程中产生，在形态动力学、生态地球化学循环和生态系统过程中起着重要作用。然而，EPS如何与粘性颗粒一起发挥作用并影响沉降行为的机制仍然知之甚少。测定了矿物和人工合成的EPS（黄原胶）混合物的初始絮凝率、絮体尺寸和沉降速度。从这些和以前的研究结果相结合，表明连贯的EPS相关的絮凝相比，纯矿物和石油矿物混合物的强化。重要的是，EPS的存在从根本上改变了絮凝体结构，降低了沉降速度的变化。实测数据表明，纯矿物絮体的微絮体和大絮体沉降速率比为3.9，但由于生物EPS的加入，微絮体和大絮体的沉降速率比大大降低到最低值1.6。由于EPS的参与，沉降速度的低变异性解释了以前在现场和实验室研究之间观察到的看似不一致的结果。
Biophysical cohesion, introduced predominantly by Extracellular Polymeric Substances (EPS) during mineral flocculation in subaqueous environments, plays important role in morphodynamics, biogeochemical cycles and ecosystem processes. However, the mechanism of how EPS functioning with cohesive particles and affects settling behaviors remain poorly understood. We measure initial flocculation rate, floc size and settling velocity of mineral and artificial EPS (Xanthan gum) mixtures. Combining results from these and previous studies demonstrate coherent intensification of EPS-related flocculation compare with those of pure mineral and oil-mineral mixtures. Importantly, the presence of EPS fundamentally changes floc structure and reduces variability of settling velocity. Measured data shows that ratios of microfloc and macrofloc settling velocity for pure mineral flocs is 3.9 but greatly reduced to a lowest value of 1.6 due to biological EPS addition. The low variability of settling velocity due to EPS participation explains the seemingly inconsistent results previously observed between field and laboratory studies.