基于原位观测的黄河水下三角洲悬浮物浓度叠加锯齿模型

The superposed sawtooth model of suspended sediment concentration in the Yellow River subaqueous delta based on in-situ observation

利用海底原位三脚架搭载水动力观测仪器,在黄河水下三角洲进行了为期134天的原位观测,获取了该海域波浪、潮汐、海流、海水温度、浊度等相关数据。并利用观测点海域的表层沉积物进行室内测试,发现该海域表层沉积物以粉砂为主,悬浮物浓度与海水浊度存在良好的线性关系,底层(距离海床约50cm处)悬浮物浓度在2~4g/L范围内变化。切应力计算结果与原位观测结果表明,强浪过程中波浪对泥沙起动起控制作用,进而显著提高悬浮物浓度;其余时间段,海流控制泥沙起动,悬浮物浓度随流速动态波动。该海域悬浮物浓度表现为叠加锯齿模型。因波浪作用而形成大锯齿,因海流作用而形成小锯齿。切应力计算结果可以较好地解释该模型。

The time series of waves,tides,currents,temperatures and turbidities were measured for 134 days in the Yellow River subaqueous delta with a submarine in situ tripod equipped by various instruments.The samples taken from the study site are analyzed in the laboratory for sediment grain size and the relationship between the suspended sediment concentration and turbidity.The sediment studied is mainly composed of silt,and a good linear relationship between the suspended sediment concentration and turbidity has observed.The suspended sediment concentration varies from 2 g/L to 4 g/L in the Yellow River subaqueous delta.Both the in-situ observation and the shear stress calculation show that the sharp rise in suspended sediment concentration is attributed to the episodic high waves,and the quotidian currents are responsible for the periodic fluctuation in suspended sediment concentration.Above all,a superposed sawtooth model of suspended sediment concentration influenced by waves and currents is proposed and the shear stress can explain the reason why episodic waves account for large sawteeth and currents are responsible for the small sawteeth.