PARTICTTLATE ORGANIC MATTER I N SEA WATER
39
Wangersky (1965) and Wangersky and Gordon (1966) were particularly conceriied with the geochemistry of calcium carbonate and
manganese. Their calculations indicated that the carbonate fraction
of organic particles could contribute significantly to the fine fraction
of carbonate in deep water sediments. Manganese was particularly
interesting. The presence of abundant deposits of manganese dioxide
as nodules, crusts, and layers in sediments has been a subject of debate
for many years. No known mechanism could account for the existence
of soluble manganous ion which could be oxidized in bottom waters to
produce these deposits. However, Wangersky and Gordon found that
organic aggregates in deep water contain manganous ion in concentrations of 0.0 1-0.06 pgllitre, and decomposition of this material could
liberate Mil++, which would then be available for oxidation and
precipitation.
The ability of particulate matter and associated clay particles to
adsorb trace elements is well known, yet little of the geochemical
literature shows much awareness of this problem. Some geochemists
use whole water samples for analysis ; others filter their samples. In
some cases various kinds of collections are indiscriminantly mixed,
and often the exact procedures are not stated. This lack of realization
that many of the problems are biogeochemical rather than merely
geochemical has slowed the development of the field.
The occurrence of inorganic substances in oceanic aggregates
obviously can result from either adsorption of ions or scavenging of
solid materials. The presence of manganous ion presumably is the
result of direct adsorption. Calcium carbonate could be scavenged
from the water column or formed as crystals on bubble surfaces or
possibly adsorbed. Wangeraky and Gordon (1 966) reported that
experimentally produced aggregates had a calcium carbonate content
that averaged about 2.5% of the dry weight. However, Siege1 and
Burke (1965), using tracer methods to study the uptake of various
cations on particulate matter formed by bubbling, found essentially no
calcium uptake. They reported that zinc, strontium, and manganese
were adsorbed t o a slight degree on particles that were formed both by
bubbling and on standing, but the amount was invariably less than
1 yo of the amount added. The amount added was not stated specifically
but was said to be negligible compared with the natural concentration
of the cation in sea water. This raises questions about the interpretation
of their results. In the case of calcium carbonate, for example, the
amount that Wangersky and Gordon found in their aggregates was a
significant component of the aggregates but was generally less than
0.2% of the amount normally found in sea water. I n this case one
39
Wangersky (1965) and Wangersky and Gordon (1966) were particularly conceriied with the geochemistry of calcium carbonate and
manganese. Their calculations indicated that the carbonate fraction
of organic particles could contribute significantly to the fine fraction
of carbonate in deep water sediments. Manganese was particularly
interesting. The presence of abundant deposits of manganese dioxide
as nodules, crusts, and layers in sediments has been a subject of debate
for many years. No known mechanism could account for the existence
of soluble manganous ion which could be oxidized in bottom waters to
produce these deposits. However, Wangersky and Gordon found that
organic aggregates in deep water contain manganous ion in concentrations of 0.0 1-0.06 pgllitre, and decomposition of this material could
liberate Mil++, which would then be available for oxidation and
precipitation.
The ability of particulate matter and associated clay particles to
adsorb trace elements is well known, yet little of the geochemical
literature shows much awareness of this problem. Some geochemists
use whole water samples for analysis ; others filter their samples. In
some cases various kinds of collections are indiscriminantly mixed,
and often the exact procedures are not stated. This lack of realization
that many of the problems are biogeochemical rather than merely
geochemical has slowed the development of the field.
The occurrence of inorganic substances in oceanic aggregates
obviously can result from either adsorption of ions or scavenging of
solid materials. The presence of manganous ion presumably is the
result of direct adsorption. Calcium carbonate could be scavenged
from the water column or formed as crystals on bubble surfaces or
possibly adsorbed. Wangeraky and Gordon (1 966) reported that
experimentally produced aggregates had a calcium carbonate content
that averaged about 2.5% of the dry weight. However, Siege1 and
Burke (1965), using tracer methods to study the uptake of various
cations on particulate matter formed by bubbling, found essentially no
calcium uptake. They reported that zinc, strontium, and manganese
were adsorbed t o a slight degree on particles that were formed both by
bubbling and on standing, but the amount was invariably less than
1 yo of the amount added. The amount added was not stated specifically
but was said to be negligible compared with the natural concentration
of the cation in sea water. This raises questions about the interpretation
of their results. In the case of calcium carbonate, for example, the
amount that Wangersky and Gordon found in their aggregates was a
significant component of the aggregates but was generally less than
0.2% of the amount normally found in sea water. I n this case one