2015 Volume 71 Issue 1 Pages 69-77
Field observations and indoor experiments were performed for quantitative elucidation of the effect of suspended particulate matter on seawater salinity based on electrical resistivity. Seawater salinity was found to decline with increasing suspended particulate matter concentration and with increasing sensor penetration into seafloor sediment. The results of the indoor experiments show that nominal salinity decreases linearly with rising suspended particulate matter concentration and that the rate of decrease increases with increasing salinity of filtered seawater. The results of experiments using montmorillonite and kaolinite indicate that this is caused by a decrease in seawater volume in the salinity sensor and by clay particle adsorption. The characteristic decrease of salinity by suspended particulate matter found in the indoor experiments and the vertical distribution of suspended particulate matter concentration near the seafloor estimated from salinity measurements using a multiparameter water quality sensor clearly show that a layer approximately 2 cm thick containing fluid mud at approximately 15,000 mg/L forms on the seafloor.