声学光学法泥沙浓度观测的对比研究

根据光学后散射传感器(Optical Backscatter Sensor,OBS)和声学后散射传感器(Acoustic Backscatting Sensor,ABS)估算悬浮沉积物质量浓度(Suspended sediment concentration,SSC)的原理,在水槽实验室不同波况产生较高悬浮沉积物质量浓度的条件下运用OBS仪器ASM-IV(激光边界层泥沙剖面仪)和ABS仪器AQUAscat1000(多频声学悬沙剖面仪)观测并记录数据。然后用水槽实验抽取的水样标定光学和声学仪器,反演得到高精度的垂向泥沙浓度分布剖面。结果表明,OBS仪器ASM-IV上的不同光学探头测得的浊度与SSC可以用同一个线性关系描述,相关系数高达0.996,进而能够高精度(垂向间距1cm)地反演垂向的SSC剖面;对于本组水槽实验的粉土底质和不同的波况而言,声学仪器比光学仪器的量测精度低;不同频率声学仪器换能器的量测值可相差几个数量级,不同波况条件下的声学仪器反演值与实测SSC的相关性系数在0.716~0.974变化。

A Comparative Study of Suspended Sediment Concentrations Observed With Acoustic and Optical Methods

Based on the principle of the estimation of suspended sediment concentration (SSC)by using optical backscatter sensor(OBS)and acoustic backscatter sensor(ABS), the suspended sediment concentrations have been measured and recorded by using OBS instrument ASM-IV and ABS instrument AQUAscat1000 under the conditions of high sediment concentration and different wave conditions in a water flume lab.Both the OBS and the ABS measurements are first calibrated with the water samples collected during the water flume experiments and then inverted to obtain the vertical SSC profiles with high accuracy.The results show that the turbidity and the SSC determined with differ-ent optical probes of ASM-IV can be described with the same linear relationship,with a correlation coefficient being as high as 0.996,indicating that the vertical SSC profile can possibly be inverted with a high accuracy (vertical interval 1 cm).For the silty bottom and wave conditions in the present flume experiment,the detection accuracy is lower with the ABS instrument than with the OBS instrument.The values measured by using the acoustic transducers with different frequencies can vary over several orders of magni-tude,and the correlation coefficients between the inverted and the measured SSC values vary from 0.716 to 0.974.