NEAR-IR SPECTROSCOPIC MEASUREMENT OF SEAWATER SALINITY

Seawater salinity has been determined by near-IR spectroscopy based on the perturbations of water bands by sea salts. The measurements are made using a cuvette or a fiber-optic probe. The models expressing the salinity are developed by linear or multilinear regression of the absorbances at selected wavelengths and by principal component regression using the entire spectra. Temperature has a strong effect on the water bands and will interfere with the measurement of salinity. However, this effect can be removed by using the absorbances at isosbestic points in the linear model, or it can be accounted for by principal component regression. A standard error of 0.22 parts per thousand is attainable by this method. This technique can potentially be used in remote sensing of seawater salinity.