1. Wayne Slade Ocean Optics Summer 2004
Dock Observatory – Estimating Total Suspended Matter from Particle Backscatter
Wayne Slade
Ocean Optics Summer 2004

2. Total Suspended Matter
Comprised of sediments, dead or decaying plant and animal bits, and still living particles
Basic indicator of water turbidity and “water quality”
Light penetration affects photosynthesis
Makes fish unhappy (gills)
Makes people unhappy (aesthetics, water supply)
More suspended material  more scattering (and maybe absorption)
Therefore, optical methods offer potential for use as proxies for TSM
Goal of our (Mike & Wayne) project  Establish a functional relationship between hard to measure TSM and plentiful dock observations of bbp(700)

3. Optical Proxies for TSM
cp(630) (m-1)
Bergmann et al. 2004
In situ TSM is time consuming  optical methods for “continuous” observation
Many relationships between optical quantities and TSM are available
Examples
Bergmann et al. 2004
Babin et al L&O
bp = (bp*) TSM
Mass-specific particle scatter
(bp*) ~ m2g-1
Babin et al. 2003

4. After Week 1 We looked at relating TSM with IOP…
With the data collected so far, a relationship is not apparent
Note that results are typically given log-log
Relationship between TSM and bbp was not clearly visible…
Revisit the problem with more dock sampling!

5. (1) Dock Measured bbp
BB2F measures optical backscatter at two wavelengths
(λ = blue 470nm, red 700nm) and chl fluorescence, θ = 117°
β(117°,λ) = scale(λ)*DN(λ) + offset(λ)
bbp (λ) = 2π [β (117°,λ) - βw(117°,λ)] Xp(117°)
bbp values seem odd:
Dock samples for bp(700) were ~1-2 m-1
bbp/bp ~ 10% ??

6. (2) Bottle Samples for TSM
Routine (~daily) sampling
Many sources of error and strife!
SALTS!
Sometimes not enough dried filters!
~8 samples (3 reps/sample)

7. (3) Matching Dock bbp(700) to TSM
Typical dock sample time was 1300
Sample median values of dock TSM were matched with observatory bbp
Observatory bbp are median of values from 1230 to 1330
High variability in both TSM and bbp is present…

8. (4) Linear Regression Results
TSM [g m-3] = (48.3) bbp(700)
TSM [g m-3] = (71.4) bbp(700)
bbp(700) [m-1] = (0.012) TSM
More dynamic range would
be nice!
We find (bbp*) ~ 0.01 m2 g-1
Reasonable compared to
Babin? (bp*)~ m2g-1
(bbp*) = Bp * (bp*)
(~0.01 m2g-1) = (~0.01)(1.0 m2g-1) ☺

9. Observatory TSM Product

10. Discussion Results show link a between bbp(700) and TSM
Need more dynamic range of in situ samples to show that the model is valid for all bbp observed at dock observatory
2 samples /day, at different times of day, across full tidal range
Higher quality TSM would be nice (i.e. consistent lab technique, proper rinsing protocol)
Should regression of TSM and bbp be forced to pass through origin?