Particle backscattering efficiency as an indicator of suspended particle composition and size in the Pearl River Estuary

Particle backscattering efficiency (Qbbe(lambda)) relates closely to particle type and links light backscattering with biogeochemical properties. However, knowledge gaps about Qbbe(lambda) persist in the Pearl River Estuary (PRE). We measured Qbbe(lambda) within the three transects in the PRE and investigated its relationships with particle composition and size. The results show that particle size influences Qbbe(lambda) more than composition. Vertical heterogeneity of Qbbe(lambda) was observed; high Qbbe(lambda) values spanned vertical columns due to dynamic river-sea interactions, showing distinct layers with higher concentrations at the surface and bottom, but lower mid- layer values unaffected by rivers. Transects influenced by river discharge showed elevated Qbbe(lambda) due to high inorganic particle inputs, while coastal currents influenced bottom values via sediment resuspension. This enhanced understanding of Qbbe(lambda)'s spatial-temporal variations in the South China Sea is vital for better predicting particle characteristics from optical data.