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Particle (C p ) Results

This study examines the sources of variability in Cp results and particle size distribution in ocean optics research conducted in 2004. It investigates spatial and temporal differences, sub-sampling techniques, and calibration of instruments. The study also discusses the impact of different cleaning techniques and storage methods on Cp variability. The results suggest that the hyperbolic slope of the particle size distribution is sensitive to the fraction of large particles in the water samples.

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Particle (C p ) Results

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  1. Particle (Cp) Results Ocean Optics 2004 Julia Uitz & Eric Rehm

  2. Sources of Cp Variability • Spatial • Different Dock locations • Temporal • Different sampling days • Times were close • Sample • Sub-sampling technique • Possible settling in carboy

  3. Sources of Cp Variability • Calibration of AC-9 • Two instruments • Cleanliness of attenuation flow tube may differ • Different cleaning techniques: • Emmanuel’s groups cleaned flow tubes with soap, in addition to ethanol and D-I water. • For water blanks, Emmanuel’s groups used tubing that passed only D-I water.

  4. Sources of Cp Variability • Other sources • Yes: How water was subsampled and stored between Emmanual’s and Collin’s Groups • Collin’s sea water was poured off the top of the carboy used by Emmanuel’s group. “Top water” may have had less large particles due to settling. • Collin’s carboy had a tap 1” from the bottom, where as Emmanuel’s had a Teflon tube to the bottom. Large particles in Collin’s carboy may have settled below the tap, while the deeper Teflon tube in Emmanuel’s carboy probably didn’t have this problem

  5. Thurs Boss Roesler Tues

  6. Particle Size Distribution • Particle Size Distribution Model N(D) = N0(D/D0)- e • Model of Cp using hyperbolic slope g is related to PSD: e = g + 3 • Intuition: • Smaller e  flatter slope  larger fraction of large particles • Larger e  steeper slope  smaller fraction of large particles • “Typical ocean waters” (Mobley): e = 4

  7. PSD Results

  8. PSD Discussion • Lab values were in range of published values • Shape of PSD (hence size fraction N(D)/N0) is sensitive to hyperbolic slope rather than absolute value of Cp • Hyperbolic slope g (hence e, and PSD) was similar for all groups (but see next slide…) • Note that absolute value of N(D) (controlled by N0) does depend on the absolute value of Cp  PSD of Damariscotta River is very similar across sampling days

  9. PSD Discussion • g (hence e) was larger for results from Groups A and D (Collin’s Group) • This indicates a PSD with a smaller fraction of large particles. • Subsampling and carboy discussion indicate that Collin’s water may have had less larger particles. • Therefore, experimental results are consistent with the e derived from the data.

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