Page 195 - Geochemistry of Oil Field Waters

182 ORGANIC CONSTITUENTS IN SALINE WATERS

Wilson et al. (1970) found that ethylene, propylene, and carbon
monoxide are produced in illuminated sea water to which dissolved phyto-
plankton was added. Higher saturated gaseous hydrocarbons and methane
were not produced.
Bonoli and Witherspoon (1968) measured the diffusion coefficients of
methane, ethane, propane, n-butane, n-pentane, benzene, toluene, ethyl-
benzene, cyclopentane, methylcyclopentane, and cyclohexane in pure water
at temperatures ranging from 2" to 60°C using the capillary-cell method. The
effect of sodium chloride was studied, and the largest decrease in diffusion
coefficients was found for the paraffin hydrocarbons. They attributed the
decrease to the effects of ions in water acting as structure breakers as well as
obstacles to diffusion because of obstructions and hydrations.

Hydrocarbons containing nitrogen

Chromatographic techniques were developed for determining humic acids,
amino acids, and indoles in saline waters and in sediments (Degens and
Reuter, 1964). Arginine was found in the particulate matter in sea water and
decreased in concentration with depth. Relatively abundant concentrations
of ornithine, serine, and glycine were found in sea water.
The total concentrations of amino acids found in some petroleum-
associated waters ranged from 20 to 230 pg/l (Degens et al., 1964). In
general, the amino acid content increased with salinity. Adjustment of the
salinity of the brines to that of modern sea water indicated a similarity
between the amino acid spectra in the two. High concentrations of serine
and the presence of threonine and phenylalanine and glutamic and aspartic
acids were found in the petroleum-associated waters. It was postulated that
the amino acids occurred in the petroleum waters in a combined state as
nonproteinaceous acid complexes and that the solubility of these complexes
probably is a function of salinity. This postulate was based on information
which indicated that serine is thermally unstable. More recent information
indicates that serine, lysine, threonine, glycocol, histine, isoleucine, and
leucine are fairly stable up to 180°C (Califet and Louis, 1965).
Liquid-exchange chromatography was used to determine the amounts of
amino acids in some saline waters (Siege1 and Degens, 1966). The results
indicated the bulk of the amino acids dissolved in the sea are tied up in
complexes and are not in a free form.
A study of the organic solutes in sea water led to the conclusion that
coprecipitation methods are the most versatile for their isolation (Chapman
and Rae, 1967). Some of the organics that can be isolated by this method
include glucose, glutamic acid, aspartic acid, citric acid, succinic acid, glycol-
late, glycine, and lysine. The percent of recovery of these solutes by this
method varied from 16 to 90%. The method involved the coprecipitation of
these organic solutes with iron or copper.
Most of the nitrogen in humic acid is located in the large and intermediate