Suspended particle property variations in Gaoping Submarine Canyon
Ray T. Hsu
Institute of Marine Geology and Chemistry
National Sun Yat-sen University, Kaohsiung, Taiwan 804
ray@mail.nsysu.edu.tw
Co-author: James T. Liu
The hydrographic environment in submarine canyons is highly dynamic that affects the
physical properties of suspended particles in the water column. Some parameters relating to
the behavior and nature of the suspended matter such as the in-situ particle size distribution,
density, and settling velocity are of interest to oceanographers. Two cruises were conducted
on June 18, 2004 and August 27-28, 2006 for hourly CTD profiling with LISST-100 attached
and water samples collection at different depths in the Kaoping Submarine Canyon off
southwestern Taiwan. In the 2004 cruise, 10 L of water samples were filtered sequentially
through two stainless steel sieves (mesh size of 500 and 250 µm), two nylon mesh nets (63
and 10 µm), and finally the GF/C filter (0.4 µm) in the lab. A new-stacked filtering system,
CatNet, filtered 60 L water samples on board through 153, 63, and 10 µm stacked nylon nets.
The residual fitlered water filled up a 20 L plastic contaioner and was filtered through 2.7 and
0.7 µm filters in the lab. All filtered particles were dried in the oven at 50 °C and then
weighed rendering suspended sediment concentration (SSC) in mg/l.
The mean size of suspended particles in the water column was calculated from LISST-100
profile data. Profiles of particle mean size shows high fluctuations, especially when the
CTD rosset was stopped for taking water sample. The depth averaged mean grain size was
about 69 µm but the sorting was about 50 µm. The smoothed particle mean size increased
with depth in the surface layer.
Base on the Krone’s model, we suggested a new method to evaluate the in situ bulk floc
density of different particle-size classes. The concluding bulk density of this new estimation
was similar to the literature presented. The floc density of three grain-size classes indicated
that the smaller the size, the higher the density. The floc density profile showed a maximum
at the middle depth around 150 m and decreased toward the surface and bottom layer.
In this investigation, the physical properties of suspended particles in Gaoping Submarine
Canyon highly varied in the vertical water column. It is suggested that highly dynamic
environment will change the suspended particle properties, such as mean particle size and
density. The relationships between suspended particle properties variations and in situ
hydrodynamics will be further analyzed.