ADP与OBS观测悬沙浓度实验对比研究

Comparison between measurements of suspended sediment concentration using ADP and OBS

光学(OBS)和声学方法(ADP/ADCP)进行现场悬沙浓度观测,是目前悬沙浓度变化研究的重要方法。在长江河口,利用ADP、OBS对水体悬浮泥沙浓度进行大、小潮周期现场定点同步观测:(1)在水平方向上,ADP、OBS观测悬沙浓度具有同步峰值变化,但ADP峰值变化要比OBS平缓;(2)在垂向上,从表层到近底层,悬沙浓度逐渐增加,增加幅度在不同特征时刻、不同水层有较大差异;(3)大、小潮期间,ADP、OBS观测的悬沙浓度与传统方法得到的悬沙浓度的平均相对误差都小于20%;(4)ADP声强信号与OBS浊度、ADP与OBS观测的悬沙浓度,分别具有较好的相关性。主要结论,OBS可观测传感器附近的悬沙浓度,具有较高的精确度;ADP在观测不同水层水动力参数的同时,可同步提取不同水层的悬沙浓度信息,并且对周围水动力环境没有干扰;在特征时刻取悬沙水样率定OBS和ADP,也可用OBS率定ADP,ADP和OBS观测悬沙浓度结果可以相互验证。可见,利用声学与光学仪器进行现场联合观测,可以提高现场悬沙浓度观测的时空分辨率和准确度,同时,也为深入研究悬沙浓度变化的机制、机理,以及悬沙通量计算提供了一个有效而可靠的途径。

Field measurement of suspended sediment concentration（SSC） using ADP and OBS was carried out in the Changjiang（Yangtze） Estuary during the spring and neap tides on June,6-12,2005.（1） In the horizontal direction,the curves of SSC by ADP and OBS changed in phase,respectively.Nevertheless,the curves of ADP were smoother than that of OBS.（2） In the water column,the change in SSC by ADP and OBS increased from the surface to near the bed,but the range of change depended on the different tidal phases and water layers.（3） The average relative errors of SSC by ADP and OBS were no more than 20%.（4） The SSC by ADP and OBS,the amplitude of signal and NTU had close correlation,respectively.Therefore,OBS can be used to study the changes in SSC near the sensor which has high precision.ADP can be used to study the changes in SSC and can obtain the information of current profiles in synchrony without interference in the surrounding environment in the field.Calibration of the OBS was made using the water samples obtained from the different tidal phases,and then the OBS was used to calibrate the ADP.This method could not only reduce the working load in the field,but also ensure the precision of SSC by ADP.The results of ADP and OBS can be validated each other.Thus,the combining observation by ADP and OBS is a way of efficiency and credibility for studying the changes in SSC and the suspended sediment transport processes.