Absorption Property of Non-algal Particles and Contribution to Total Light Absorption in Optically Complex Waters, a Case Study in Yangtze Estuary and Adjacent Coast

Abstract

The investigation on inherent optical properties (IOPs) of coastal water-color components at regional scale, is very crucial in developing coastal bio-optical algorithms for remote sensing of ocean color. In contrast to chromophoric dissolved organic matters (CDOM) and phytoplankton, the variability in absorption property of no-algal particles (NAP) in highly turbid estuarine and coastal waters was less described. For this investigation on bio-optical properties of estuarine and coastal waters, water samplings were taken monthly in 2009 within the Yangtze Estuary and three cruise campaigns were conducted off the Yangtze Estuary seawards during May, August and November 2009. Absorption spectrum of each water component was then measured by a spectrophotometer in laboratory. It is found that The NAP absorption spectrum is subject to degradation of exponential law with increasing wavelength, similar to regularity of CDOM absorption. The NAP absorption has a significant contribution to total light absorption in estuarine waters and the ratio of the two reaches a percentage of 50-90. The percentage decreases mostly to 20 in the coastal waters. The NAP absorption and the ratio in the estuarine waters can be affected by seasonal variations in river sediment discharges.