Suspended particle property variations in Gaoping Submarine Canyon

1. Suspended particle property variations in Gaoping Submarine Canyon Ray T. Hsu and James T. Liu Institute of Marine Geology and Chemistry, National Sun Yat-sen University, Kaohsiung, Taiwan, R.O.C.

2. Estuarine system: River plume Biogenic production Flocculation & deflocculation Canyon Channel: Landslides Debris flows Turbidity current Nepheloid layers Gaoping river-sea system Shelf Region: Biogenic production Resuspension

3. Shelf margin Internal tide C. Benthic nepheloid layer Particle settling A. Hypopycnal plume B. Hyperpycnal plume

4. Diversities of suspended particles in coastal water > 500 μm > 250 μm > 10 μm > 63 μm Optical microscopy

5. Study area 8/27-28/2006 N M 6/18/2004 Gaoping River Gaoping Submarine Canyon Taiwan Strait

6. Investigation scheme

7. Particle filtration procedure CatNet filtration 2004/6/18 cruise 2006/8/27-28 cruise Filtering on board 10 L water sample 153 µm 500 µm stainless steel sieve 63 µm 250 µm stainless steel sieve 10 µm 63 µm nylon net 3 µm Filtering in the lab 0.7 µm 10 µm nylon net All filtered particles were dried in the oven at 50 ℃ and then weighed rendering suspended sediment concentration in mg/l

8. Results: • Mean diameter profile • Floc porosity profile • Floc density profile

9. Sea level elevation Julian day (2006)

10. Sea level elevation Julian day (2006)

11. Floc model Avoid in floc (VIS) Floc volume (Vf) Volume of interstitial water（VIS）： ( Krone, 1986. From W. Van Leussen, 1989. Estuarine macroflocs and their roles in fine-grained sediment transport. )‏

12. Formula for floc porosity (f) estimation Bulk volume of floc (Vf) Interstial volume in floc (VIS)

13. Compare floc porosity data in two cruises

14. Averaged floc porosity profile < 10 µm Average floc porosity • 0.4-10 µm: 46.96 % • 10-63 µm: 63.95 % • 63-250 µm: 85.87 % > 63 µm 10-63 µm

15. Floc density estimation • Deduced density formula • Two assumptions: • 1. The primary particle density (p) was 2.65 g/cm3 • 2. The pore water in flocs was sea water (w=1.025 g/cm3)

16. Average bulk density profile Average Bulk density • 0.4-10 µm: 1.89 g/cm3 • 10-63 µm: 1.61 g/cm3 • 63-250 µm: 1.25 g/cm3 > 63 µm < 10 µm 10-63 µm

17. Bulk floc density 0.4-10 µm: 1.89 g/cm3 10-63 µm: 1.61 g/cm3 63-250 µm: 1.25 g/cm3 Order of Aggregation Wilmington District Brunswick Harbor Gulfport Channel San Francisco Bay White River (in salt water)‏ 0 1 2 3 4 5 6 1.250 1.132 1.093 1.074 1.164 1.090 1.067 1.056 1.205 1.106 1.078 1.065 1.269 1.179 1.137 1.113 1.098 1.087 1.079 1.212 1.109 1.079 1.065 Properties of suspended aggregates (Krone, 1978)‏ Density in salt water 1.025 g/cm3

18. Summary Particles in river plume can be identified from its grain size distribution. The results from the 2004 data were not as good as those from 2006 due to the difference of on-board filtration which reduces the chance of breakage of fragile flocs storage and transport. The average calculated floc densities of 0.4-10, 10-63, 63-250 µm were 1.89, 1.61, 1.25 g/cm3, respectively. And the floc porosities were 46.96, 63.95, 85.87 %, respectively. This approach is different from the traditional floc density estimation derived from settling velocity according to Stokes law.