Size Spectrum of Suspended Particulate Matter in the Bohai Sea

Abstract

We investigate the distribution and dynamics of suspended particulate matter (SPM) concentration in the Bohai Sea in China. Previous research in the area was limited to sampling analyzed in the laboratory, distorting the SPM size spectrum as smaller particles are cohesive and larger particles dissociate. The LISST-100B, an advanced optical device, allows for <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> measurement of the SPM size spectrum. These measurements are analyzed during a period of low Yellow River discharge, including a size spectrum analysis of SPM distribution and a time-series analysis. Areas of high SPM concentration are found in the western Laizhou Bay and in the western Bohai Sea. SPM in the region is determined to be due to resuspension of particulate matter from the Yellow River before 1996. Unlike previously thought, the present-day Yellow River delta does not significantly affect SPM concentration levels as the water output contains low SPM and as resuspension is local in nature. The majority of SPM are particles smaller than 6 microns in volume-equivalent diameter (VED). Areas further from the Yellow River have a greater percentage of larger particles. For the first time, the size limit of resuspension is determined to be around 210 microns in VED. This provides a basis for finding the relationship between tidal currents and the critical velocity for resuspension with respect to particle size