Tank experiment and simulation of sunken hazardous and noxious substances detection using high frequency active sonar

Abstract

Hazardous and Noxious Substances are defined as substances that are likely to create hazards to the marine ecosystem and human health when they are released into the sea. Because even a small amount of leakage may cause a fatal effect, it is important to develop a technology to handle effectively the HNS spill incidents. Especially, it is difficult to detect or monitor the HNS deposited on the seabed after HNS spill incident using a direct observation method. In this paper, the remote sensing technique using underwater acoustic method is suggested as an alternative method to observe effectively the HNS sunk to ocean bottom. First, to examine the detection possibility of underwater acoustic method, tank experiment was carried out using 200-kHz active sonar. The target HNS was chloroform, which is one of major sunken HNS. However, castor oil having a similar acoustic impedance with the chloroform was used as an alternative substance due to the toxicity of chloroform. Second, a computer simulation to investigate the availability of side scan sonar to detect the sunken HNS was carried out. It is assumed that the chloroform and tetrachloride, which is another sunken HNS, are randomly distributed on the several types of seabed. The simulation algorithm is based on the difference of backscattering strengths from the ocean bottom interface and the sunken HNS.