G. M. Cartwright, C. T. Friedrichs, and L. P. Sanford

IN SITU CHARACTERIZATION OF ESTUARINE SUSPENDED SEDIMENT

IN THE PRESENCE OF MUDDY FLOCS AND PELLETS

Mud Flocculants FecalPellets

SandD~ 5 – 10 µmWs< to <<0.1 mm/sec

D ~ O(λ)Microflocs < 160 µmMacroflocs >160 µmWs

D~ 10s – 100s µm Ws

Ws ~0.1–10 mm/s

D= 63 – 500 µmWs = 2.3–60 mm/s

Ws α D λ Turbulence

λλ% Organic

Settling Velocity

Fugate and Friedrichs (2003)

Sherwood (2007)Anderson (2001), Sanford et al (2005) Taghon et al (1984), Wheatcroft et al (2005)

Mud Flocculants FecalPellets

SandD~ 5 – 10 µmWs< to <<0.1 mm/sec

D ~ O(λ)Microflocs < 160 µmMacroflocs >160 µmWs

D~ 10s – 100s µm Ws

Ws ~0.1–10 mm/s

D= 63 – 500 µmWs = 2.3–60 mm/s

Ws α D λ Turbulence

λλ% Organic

Settling Velocity

Fugate and Friedrichs (2003)

Sherwood (2007)Anderson (2001), Sanford et al (2005) Taghon et al (1984), Wheatcroft et al (2005)

STUDY SITENSF MUltiDisiplinary Benthic

Exchange Dynamics

Claybank area on York River Chesapeake Bay, VA

Micro tidal ( 0.7 to 1 meter)

Secondary Channel ~ 5 meter depth

Neap TideSeabed > 75% mud

~10% OrganicsSand D50 ~100 µm

<30% PelletsKraatz, (2010, personal comm), Rodriguez-Calderon (2010)

LISST

ADV

CTDS2E

Real-time Communication

Cables

RipsCam

METHOD 25 hour Study Period

LISST 100X

15 min burst interval100 records @ 1 Hz(10 samples/record)

Distribution measured2.5 – 500 µm

RipsCam

1 hour “burst” interval5 flash exposures at 1 min interval

Focal depth ~1mm

Distribution measured~60 µm – 1.3 mm

ADV

15 min burst interval2 min @ 10 Hz

15 18 21 00 03 06 09 12 15 18 210

50

100

150

200

Conc

entra

tion

from

ADV

(mg/

L)

15 18 21 00 03 06 09 12 15 180

200

400

600

800

Date (July 28, 2009 (17:00 EST) - July 29, 2009 (18:00 EST) )

Volu

me

Conc

entra

tion

(ul/L

)

LISST Total volume concLISST Volume Conc > 60 micronsRIPScam Volume Conc/10

B

A

15 18 21 00 03 06 09 12 15 18 210

20

40

60

Salin

ity (P

SU)

Velo

city

(cm

/s)

VelocitySalinity

18 21 00 03 06 09 12 15 180

0.1

0.2

0.3

0.4

Date (July 28, 2009 (17:00 EST) - July 29, 2009 (18:00 EST) )

Stre

ss (P

asca

ls)

EBB FLOOD C

D

FLOODEBB A

B

C

D

Currents, Stress and Concentration

Concentrationby weight(mg/L)

correspondswith peak currents

Concentrationby volume (µm/L)

doesn’t

0 0.5 1 1.5 2 2.5 3 3.5 4 4.50

20

40

60

80

100LISST D16 = 21 µmLISST D50 = 85 µmLISST D84 = 218 µmLISST Peak = 104 µm RIPScam D16 = 117 µmRIPScam D50 = 197 µmRIPScam Peak = 201 µm

LISST time = 28-Jul-2009 19:55:12 EST Camera time = 100 GMT

(Log10) Particle Size (µm)

Volu

me

Conc

entra

tion

(µl/L

)

LISST 100XRIPSCAM./10

Increasing stress toward Ebb

Slack after Ebb

EXAMPLE DISTRIBUTIONS

Dominant Floc size ~315 µm

0 0.5 1 1.5 2 2.5 3 3.5 4 4.50

20

40

60

80

100LISST D16 = 21 µmLISST D50 = 85 µmLISST D84 = 218 µmLISST Peak = 104 µm RIPScam D16 = 117 µmRIPScam D50 = 197 µmRIPScam Peak = 201 µm

LISST time = 28-Jul-2009 19:55:12 EST Camera time = 100 GMT

(Log10) Particle Size (µm)

Volu

me

Conc

entra

tion

(µl/L

)

LISST 100XRIPSCAM./10

Increasing stress toward Ebb

Slack after Ebb

EXAMPLE DISTRIBUTIONS

Dominant Pellet size~102 µm

0 0.5 1 1.5 2 2.5 3 3.5 4 4.50

20

40

60

80

100LISST D16 = 21 µmLISST D50 = 85 µmLISST D84 = 218 µmLISST Peak = 104 µm RIPScam D16 = 117 µmRIPScam D50 = 197 µmRIPScam Peak = 201 µm

LISST time = 28-Jul-2009 19:55:12 EST Camera time = 100 GMT

(Log10) Particle Size (µm)

Volu

me

Conc

entra

tion

(µl/L

)

LISST 100XRIPSCAM./10

Increasing stress toward Ebb

Slack after Ebb

EXAMPLE DISTRIBUTIONS

Dominant Floc size~205 µm

slack EBB slack Flood slack Ebb slack Flood slack

STUDY PERIOD DISTRIBUTIONSµl/L

Low Stress

Dominate floc size~ 315 µm

LISST PeakLISST D84

RIPScam D50

High Stress

Pellets~ 102 µm

LISST PeakLISST D50

RIPScam D16

Dominate floc size~ 205 µm

LISST D84RIPScam PeakRIPScam D50

20 40 60 80 100 120 140 1600

5

10

15

< C > (mg/L)

< C'

w' >

(m

g/L)

(cm

/sec

)

y = 0.0924*x - 3.41

15 18 21 00 03 06 09 12 15 18 210

1

2

3

Date (July 28, 2009 (17:00 EST) - July 29, 2009 (18:00 EST) )

Fall V

eloc

ity (m

m/s

ec)

ratio calc methodslope calc method

A

B15 18 21 00 03 06 09 12 15 18

0

10

20

30

40

50

60

Date (July 28, 2009 (17:00 EST) - July 29, 2009 (18:00 EST) )

Vol

ume

Con

c (u

l/L)

87.9 µm280 µm

15 18 21 00 03 06 09 12 15 180

20

40

60

Date (July 28, 2009 (17:00 EST) - July 29, 2009 (18:00 EST) )

Volu

me

Conc

(ul/L

)

87.9 µm280 µm

C

slack EBB slack Flood slack Ebb slack Flood slack

Settling Velocity and Volume Concentration

Pellets

Increase stressIncrease eff. WsIncrease vol conc

Flocs

Decrease stressDecrease eff. WsIncrease vol conc

Conclusions and Future work• The LISST can be used to identify different suspended sediment populations• LISST Peak grainsize or D84 during maximum stress is the dominant resilient

grainsize• LISST Peak grainsize or D50 during slack periods is the dominant flocculent size

(larger will occur but at levels that are averaged out during burst averaging)• LISST D50 during maximum stress represents the dominant minimum

flocculent size• Future work needs to look at LISST distributions during spring tide and episodic

events to discover how the higher stress change the sizes and populations in suspension

• Calibrations, with the Total Suspended Solids broken into resilient and non resilient portions, needs to be done to convert volume concentration to mass concentration so the density of the dominant particles can be determined

• Time averaged burst statistics can be used to determine the effective fall velocity of the sediment in suspension• Once the mass concentration of the dominant particles are identified further

work can be done to calculate effective fall velocity of these size classes.

Acknowledgements

Students,Vessel and Lab personnelAt UMCES and VIMS

Specifically:

Tim GassWayne ReisnerSteve SuttlesKim YongEmily MillerLindsey KraatzKelsey FallCarissa Wilkerson