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

Particle backscattering efficiency (Q_bbe(λ)) relates closely to particle type and links light backscattering with biogeochemical properties. However, knowledge gaps about Q_bbe(λ) persist in the Pearl River Estuary (PRE). We measured Q_bbe(λ) within the three transects in the PRE and investigated its relationships with particle composition and size. The results show that particle size influences Q_bbe(λ) more than composition. Vertical heterogeneity of Q_bbe(λ) was observed; high Q_bbe(λ) 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 Q_bbe(λ) due to high inorganic particle inputs, while coastal currents influenced bottom values via sediment resuspension. This enhanced understanding of Q_bbe(λ)'s spatial-temporal variations in the South China Sea is vital for better predicting particle characteristics from optical data.