南海北部内孤立波影响海域悬浮颗粒物特征变化研究

Characteristics of suspended particulate matter in the northern South China Sea affected by internal solitary waves

悬浮颗粒物在“源-汇”沉积体系中扮演着关键角色,而南海常见的动力现象—内孤立波,则被证实是影响悬浮颗粒物分布和沉积过程的重要因素。该项研究于2022年9月在吕宋海峡至东沙群岛海域开展,采用LISST-deep与CTD设备进行同步观测,以研究悬浮颗粒物的粒径及体积浓度分布。通过调查期内的卫星遥感数据,划定了内孤立波的影响范围,并结合海床基观测内孤立波影响悬浮颗粒物分布过程,从动力学的角度揭示了内孤立波对悬浮颗粒物在输运过程中特征变化的影响。研究发现:(1)在内孤立波的振幅深度区间(6~79 m)内,以较小粒径的悬浮颗粒物(15~25μm)分布为主,且越接近内孤立波的波谷深度,出现较小粒径悬浮颗粒物的频率越高。(2)悬浮颗粒物分布由内孤立波波峰线中心区域扩散到两侧,在中心为体积浓度低值区(≤91μL/L),而波峰线两侧区域与内孤立波传播路径远端区域为体积浓度高值区(≥500μL/L)。此外,研究进一步揭示了内孤立波通过改造作用使聚集状态的悬浮颗粒物被分解为粒径较小、组成单一的颗粒,通过控制作用改变悬浮颗粒物在波峰线不同位置、传播路径和振幅深度上的体积浓度分布,为理解南海源-汇沉积体系提供了重要的理论依据。

Suspended particulate matter(SPM)plays a key role in the“source-sink”deposition system,and intern-al isolated waves,a common dynamical phenomenon in the South China Sea,have been shown to be an important factor influencing the distribution of SPM and the deposition process.The study was carried out in September 2022 in the sea area from Luzon Strait to Dongsha Islands,using LISST-deep and CTD equipment for simultaneous ob-servation to study the distribution of suspended particulate matter in terms of particle size and volume concentra-tion.The satellite remote sensing data during the investigation period were used to delineate the influence range of internal isolated waves and to reveal the influence of internal isolated waves on the characterization changes of sus-pended particulate matter during transport from a kinetic point of view.It was found that:(1)the distribution of sus-pended particulate matter of smaller sizes(15-25μm)was dominated in the amplitude depth interval(6-79 m)of the inner isolated wave,and the closer the depth of the trough of the inner isolated wave was,the higher the fre-quency of the occurrence of suspended particulate matter of smaller sizes.(2)The distribution of suspended particles spreads from the center of the inner isolated wave crest line to both sides,forming a low volume concentra-tion zone(≤91μL/L)in the center,and forming a high concentration zone(≥500μL/L)on both sides of the crest line and the distal end of the propagation path of the inner isolated wave.In addition,the study further reveals that the internal isolated wave breaks down the aggregated suspended particles into smaller size and single composition particles through modification,and changes the volume concentration distribution of the suspended particles at dif-ferent locations of the crest line,propagation path and amplitude depth through control,which provides an import-ant theoretical basis for the understanding of the South China Sea source-sink deposition system.