Comparison of the spectral-angular properties of light scattered in the Baltic Sea and oil emulsions

Abstract

Angular distributions of scattered light, which are described by one of two forms, i.e. the Volume Scattering Function (VSF) or the phase function, are the least-known optical properties of seawater. This is because there is currently no commercially available instrument commonly used for such measurements. In particular, little is known about the spectral variability of VSF. The spectral properties of VSF can be presented by linear slopes of a scattering spectrum separately for all scattering angles. Through research conducted using a prototype Volume Scattering Meter (VSM), the linear slopes were determined for three Baltic Sea marine regions: open Baltic Sea waters, the Gulf of Gdańsk and the mouth of the Vistula River. In this paper, the spectral slopes of VSFs of those waters are compared with VSFs of oil-in-water emulsions. The optical properties of crude oil extracted from the Baltic seabed, called Petrobaltic, were taken for calculations. The results show that VSFs of oil emulsions differ from those of natural waters, especially close to the perpendicular direction of scattering. For scattering angles between 70° and 120° there is an increase observed for oil emulsions which distinguishes them from VSFs of Baltic waters. While the spectral slopes of VSFs of oil emulsions differ from those of Baltic water across almost the entire angular range, excluding backward directions close to 180°.