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

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. 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 charge-coupled device, 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.