From the point of view of flocculation, the mechanisms of particle formation and size distribution in situ are reviewed and discussed.
In the sea, particles of different sizes are controlled by two forces; one is the cohesive force due to bacterial associations, chemical interactions and electrokinetic forces acting on particles, and the other is the destructive force mainly due to shearing stress in turbulent motion. When some agitations such as the forces accompanied with sampling and mixing are applied, particles which are in equilibrium under the two forces possibly change their size distribution. Accordingly, the size determination by a microscope and/or a Coulter Counter may possibly fail to show the real size distribution in situ. Some opinions stressed that the large visible flocculent particle do not make up a significant bulk of either organic or inorganic particles in water. However, considering the possibility that the flocculent particles in situ may be sinking with repeated coagulation and disintegration corresponding to the change of conditions mentioned above, the particle size in situ should be investigated with respect to sedimentation and the metabolism of chemical substances.
