PARTICULATE ORGANIC MATTER IN SEA WATER
41
apparatus phosphate was removed exponentially. They furthermore
found that preliminary extraction of the sea water with xylol reduced
the effectiveness of the bubbling process and suggested that organic
substances adsorbed on the bubbles served as anion binders. Their
conclusion was that phosphate could be transported toward the
surface by rising bubbles. Part of it could be ejected with the aerosol
droplets, but materials remaining in the surface film or released by
dissolution of bubbles before they reached the surface could produce
the observed vertical gradient in phosphate.
Sutcliffe et al. (1963) pursued this subject further, and their attention was now focused primarily on the organic component and its
possible biological significance in the sea. Experiments testing the
surface activity of the adsorbed material and partitioning of the phosphate by dialysis led to the conclusion that some of the phosphate is
bound to organic substances with a molecular weight in excess of 300.
Their hypothesis regarding the mode of formation of organic particles
was as follows : " Such large organic-active molecules adsorb to bubbles
and produce monomolecular films which may be aggregated into insoluble organic particles in the following way: in the foam produced
by aeration the ever increasing area of the adsorbed monomolecular
films causes them to fold into polymolecular layers and to form colloidal
micellae or to collapse into fibers (Goldacre, 1958). The agitation of
foaming produces repeated collisions and results in multiple-layer
coalescence of colloidal particles to produce a semi-stable suspension
of organic material. Many of the larger particles undergo further
aggregation and settle out."
Subsequent studies have brought to light certain aspects of the
aggregation process which are not fully in agreement with this early
hypothesis. The evidence will be examined in a later discussion;
however, the experimental work and theoretical implications developed
by these investigators were directly responsible for a rapid expansion
of programmes of enquiry into various aspects of this subject.
Because of the fact that these experimental studies stemmed from
earlier meteorological work, it was natural that the problem was
approached from an aerosol point of view. Experimental devices were
designed to catch droplets above the water surface or to drain off surface
foam. We now know that methods of this type give the largest continuing yield of any method thus far discovered.
As primary interest shifted from studies of the immediate surface
film to problems involving a larger portion of the water column,
experimental methods changed. Most investigators bubbled a volume
of water for a given length of time, allowing the particles to accumulate
41
apparatus phosphate was removed exponentially. They furthermore
found that preliminary extraction of the sea water with xylol reduced
the effectiveness of the bubbling process and suggested that organic
substances adsorbed on the bubbles served as anion binders. Their
conclusion was that phosphate could be transported toward the
surface by rising bubbles. Part of it could be ejected with the aerosol
droplets, but materials remaining in the surface film or released by
dissolution of bubbles before they reached the surface could produce
the observed vertical gradient in phosphate.
Sutcliffe et al. (1963) pursued this subject further, and their attention was now focused primarily on the organic component and its
possible biological significance in the sea. Experiments testing the
surface activity of the adsorbed material and partitioning of the phosphate by dialysis led to the conclusion that some of the phosphate is
bound to organic substances with a molecular weight in excess of 300.
Their hypothesis regarding the mode of formation of organic particles
was as follows : " Such large organic-active molecules adsorb to bubbles
and produce monomolecular films which may be aggregated into insoluble organic particles in the following way: in the foam produced
by aeration the ever increasing area of the adsorbed monomolecular
films causes them to fold into polymolecular layers and to form colloidal
micellae or to collapse into fibers (Goldacre, 1958). The agitation of
foaming produces repeated collisions and results in multiple-layer
coalescence of colloidal particles to produce a semi-stable suspension
of organic material. Many of the larger particles undergo further
aggregation and settle out."
Subsequent studies have brought to light certain aspects of the
aggregation process which are not fully in agreement with this early
hypothesis. The evidence will be examined in a later discussion;
however, the experimental work and theoretical implications developed
by these investigators were directly responsible for a rapid expansion
of programmes of enquiry into various aspects of this subject.
Because of the fact that these experimental studies stemmed from
earlier meteorological work, it was natural that the problem was
approached from an aerosol point of view. Experimental devices were
designed to catch droplets above the water surface or to drain off surface
foam. We now know that methods of this type give the largest continuing yield of any method thus far discovered.
As primary interest shifted from studies of the immediate surface
film to problems involving a larger portion of the water column,
experimental methods changed. Most investigators bubbled a volume
of water for a given length of time, allowing the particles to accumulate