In situ holographic measurements of the sizes and settling rates of oceanic particulates

A free-floating sediment trap equipped with a holographic particle velocimeter (HPV) was deployed for 14.4 hours at a depth of 30 m in the western North Atlantic Ocean. The system recorded the in situ sizes, shapes, orientations, and settling rates of microscopic particles moving through the laser beam. The primary data reduction revealed particles from the system's lower limit of resolution, 15 micrometers in diameter, to 250 micrometers in diameter with settling velocities ranging from 0.0190 to 0.2302 cm/s (16--198 m/day). Individual particle densities, calculated from a modified Stokes equation, ranged from 1.37 to 5.10 g/ml. The presence of high density particles was independently corroborated through individual particle analysis of the trapped material with a computer-controlled, scanning electron microscope equipped with an energy dispersive X-ray analyzer. In the future, in situ holographic systems might be used to further our understanding of primary productivity, sediment erosion/deposition, and particle aggregation/disruption/dissolution.

[1]  B. Thompson,et al.  Application of hologram techniques for particle size analysis. , 1967, Applied optics.

[2]  K. Carder,et al.  Elimination of fine suspensoids in the oceanic water column , 1977 .

[3]  D. Ketten,et al.  The chemistry, biology, and vertical flux of particulate matter from the upper 400 m of the equatorial Atlantic Ocean , 1977 .

[4]  M. Dacey,et al.  Stokes’ Settling and Chemical Reactivity of Suspended Particles in Natural Waters , 1974 .

[5]  Kendall L. Carder,et al.  New Optical Techniques For Particle Studies In The Bottom Boundary Layer , 1980, Other Conferences.

[6]  P. Wiebe,et al.  Particulate matter sinking to the deep-sea floor at 2000 M in the Tongue of the Ocean, Bahamas, with a description of a new sedimentation trap , 1976 .

[7]  M. Silver,et al.  In situ and laboratory measurements on macroscopic aggregates in Monterey Bay, California 1 , 1978 .

[8]  H. Schrader.  Fecal Pellets: Role in Sedimentation of Pelagic Diatoms , 1971, Science.

[9]  D. C. Gordon.  A microscopic study of organic particles in the North Atlantic ocean , 1970 .

[10]  S. Fowler,et al.  SINKING RATES OF EUPHAUSIID FECAL PELLETS , 1972 .

[11]  J. Bishop.  The chemistry, biology, and vertical flux of oceanic particulate matter. , 1977 .

[12]  Paul Dunn,et al.  Particle Sizing Using Far-Field Holography: New Developments , 1980 .

[13]  T. Smayda.  Normal and accelerated sinking of phytoplankton in the sea , 1971 .

[14]  Kenneth W. Bruland,et al.  Fluxes of particulate carbon, nitrogen, and phosphorus in the upper water column of the northeast Pacific , 1979 .

[15]  Kendall L. Carder.  Holographic Microvelocimeter For Use In Studying Ocean Particle Dynamics , 1979 .