Principle and implementations of a refracto-nephelo-turbidimeter for seawater measurements

Bo Hou (1) , Philippe Grosso (2) , Jean-Louis de Bougrenet de La Tocnaye (1) , Marc Le Menn (3)

1 OPT - Département Optique
2 FOTON - Fonctions Optiques pour les Technologies de l'informatiON
3 SHOM - Service Hydrographique et Océanographique de la Marine

Salinity and turbidity are two important seawater properties in physical oceanography. The study of physical oceanography requires a compact high-resolution in-situ salino-turbidimeter to measure these two parameters in different ocean zones. Refractometry has proved to be an effective method to measure seawater salinity with a high resolution. Previous studies have shown that the transmission and scattering of light in a turbid medium impact the light beam deviation measurements, which makes the combination of salinity and turbidity measurements with the same sample mandatory. In this paper, we analyze the requirements and challenges of a refracto-turbidimeter design from their measurement principles and correlations. According to these requirements, we propose a miniature refracto-nephelo-turbidimeter with a CCD, providing a salinity measurement resolution of 2 mg.kg-1 and a turbidity measurement resolution of 1 % of the measurement range. Based on this refracto-nephelo-turbidimeter, different embodiments are discussed to meet the different requirements for different ocean zones.

Mots clés: Turbidity; Salinity; Refractometer; Nephelometer; Transmissiometer; Seawater measurement

Domaines: Optique [physics.optics]

Bo Hou, Philippe Grosso, Jean-Louis de Bougrenet de La Tocnaye, Marc Le Menn. Principle and implementations of a refracto-nephelo-turbidimeter for seawater measurements. Optical Engineering, 2013, 52 (4), pp.044402-6. ⟨10.1117/1.OE.52.4.044402⟩. ⟨hal-00940400⟩