| In July of 2008,under the natural condition of sea water,the Laser in-situ scattering and transmissometry (LISST-100X Type C) was used to measure grain size distribution spectrum and volume concentration of total suspended matter in the sea water,including flocs at different layers of 24 sampling stations at Changjiang Estuary and its adjacent sea. The characteristics and its forming mechanism on grain size distribution of total suspended matter were analyzed based on the observation data of LISST-100X Type C,and combining with the temperature,salinity and turbidity of sea water,simultaneously observed by Alec AAQ1183. The observation data showed that the average median grain size of total suspended matter was about 4.69φ in the whole measured sea area,and the characteristics of grain size distribution was relatively poor sorted,wide kurtosis,and basically symmetrical. The conclusion could be drawn that vertically average volume concentration decreased with the distance from the coastline,while median grain size had an increase trend with the distance,for example,at 31.0°N section,the depth-average median grain size had been increased from 11 μm up to 60 μm. With the increasing of distance from the coast,the concentration of fine suspended sediment reduced distinctly,nevertheless some relatively big organic matter or big flocs appeared in quantity,so its grain size would rise. The observation data indicated that the effective density was ranged from 246 kg/m3 to 1 334 kg/m3,with average was 613 kg/m3. When the concentration of total suspended matter was relatively high,median grain size of total suspended matter increased with the water depth,while effective density decreased with the depth,because of the faster settling velocity and less effective density of large flocs that of small flocs. As for station 37 and 44,their correlation coefficients between effective density and median grain size were larger than 0.9. |
