Water sources (fingerprinting)


There are a number of different possible sources of water, such as seawater, domestic water, distilled water, brackish water, river water, spring water, production (oilfield) water etc, and each source of water will vary depending on the geographical location.


The following comments are useful in determining the type/source of any water associated with a dry or liquid cargo:


●


Production (oilfield) waters have very high sodium and chloride levels, which are significantly higher than the levels found in seawater.


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The calcium levels in production waters are significantly higher than the magnesium levels, which are the reverse for seawater, where the magnesium levels are higher. The calcium/ magnesium ratio is a useful indicator as to whether the water is seawater or production origin.


●


River waters will vary in cation and anion levels, depending on whether it is tidal and the levels will vary during the day depending upon the state of the tide.


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Domestic tap water would be expected to have a chloride level of less than 100 ppm. However, other salts, such as magnesium, calcium etc, will vary, depending upon whether a hard or soft water area.


●


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The individual metal/cation concentrations will vary in seawater, depending upon the geographical location and it is possible that this type of analysis can indicate the location of the seawater. For example, the typical concentrations noted below vary significantly and the levels found say, in the Black Sea, are very much lower.


The major cations and anions of seawater and some typical values are as shown below:


Chloride Sodium


(Cl) (Na)


Magnesium (Mg) Sulphate (SO4


but


Calcium (Ca) Potassium (K) Bromide


(Br)


Carbonate (CO3 Strontium


(Sr) ●


18,980 mg/kg 10,561 mg/kg 1,272 mg/kg


) 884 mg/kg (as S)


2,652 mg/kg (as SO4 400 mg/kg


380 mg/kg 65 mg/kg


) 140 mg/kg 13 mg/kg


Brackish water is defined as water having a chloride content in excess of 2,000 ppm.


)


Glossary of terms


Anion: A negative ion. Cation: A positive ion, molecule or radical.


Chromatography: A method for the separation of trace constituents of the sample by passing gaseous mixture through a column of finely divided powder which selectively absorbs the constituents in one or


more sharply divided bands.


Chromatogram: The array of distinctive bands produced by chromatography.


Eluent: The aqueous carrier of the sample through an ion chromatography system.


Ion: An electrically charged atom, radical or molecule formed by the dissolution of an electrolyte.


Molarity: Gram molecular weight, concentration of a solution.


ppm: Parts per million.


Spectroscopy: The science and practice of using spectrometers and spectroscopes in chemical analysis and studies of atoms, molecules, ions etc.


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