Fractionation of surface sediment fines based on a coupled sieve-SPLITT (split flow thin cell) method

Area of Science:

• Environmental Science
• Geochemistry
• Analytical Chemistry

Background:

• Traditional sieve techniques fail to fractionate fine organic matter (< 38 micrometers).
• Existing high-capacity split flow thin cell (HC-SPLITT) instruments have limitations in throughput and particle size range.

Purpose of the Study:

• To evaluate the efficacy of an extra high capacity split flow thin cell (EHC-SPLITT) instrument for sediment fractionation.
• To further fractionate fine sediment particles (< 38 micrometers) hydrodynamically.
• To assess the EHC-SPLITT's utility in analyzing sediment composition from distinct biogeochemical regimes.

Main Methods:

• Coupling sieve separation with EHC-SPLITT for sediment fractionation.
• Calibration of EHC-SPLITT using particle standards.
• Fractionation of fine surface sediments using two cutoff velocities (1 and 6 m d(-1)).
• Analysis of organic (POC) and inorganic (Si, Fe, Al) parameters in sub-fractions.

Main Results:

• Sieve-SPLITT method demonstrated satisfactory mass recovery (80-97%).
• Particles < 38 micrometers constituted 70-90% of the sediment, highlighting the need for advanced fractionation.
• EHC-SPLITT-mediated sub-fractions showed distinct compositions based on organic and inorganic analyses.
• Good agreement between theoretical predictions and experimental results for particle standards.

Conclusions:

• The EHC-SPLITT instrument offers a significant advancement for fractionating fine sediment particles.
• This technique provides valuable insights into benthic boundary layer transport and off-shelf export processes.
• EHC-SPLITT aids in understanding how geochemical signals are fractionated during transport.