Two models for absorption by coloured dissolved organic matter (CDOM)

Oceanologia

关键词: CDOM;    Gelbstoff;    Ocean colour;    UV absorption;   

DOI  :  

来源: DOAJ

【 摘 要 】

The standard exponential model for CDOM absorption has been applied to data from diverse waters. Absorption at 440 nm (a_g440) ranged between close to zero and 10 m^-1, and the slope of the semilogarithmic absorption spectrum over a minimum range of 400 to 440 nm (s440) ranged between < 0.01 and 0.04 nm^-1. No relationship was found between a_g440 or s440 and salinity. Except in the southern Baltic, s440was found to have a broad distribution (0.0165 ± 0.0035), suggesting thatit should be introduced as an additional variable in bio-optical models whena_g440 is large. An alternative model for CDOM absorptionwas applied to available high quality UV-visible absorption spectra fromthe Wisla river (Poland). This model assumes that the CDOM absorption spectrumcomprises distinct Gaussian absorption bands in the UV, similar to thoseof benzene. Five bands were fit to the data. The mean central energy of allbands was higher in early summer (E~7.2, 6.6, 6.4, 6.2 and 5.5 eV or 172,188, 194, 200 and 226 nm) than in winter. The higher energy bands were foundto decay in both height and width with increasing salinity, while lower energybands broadened with increasing salinity. s440was found to be correlated with shape parameters of the bands centred at6.4 and 5.5 eV.While the exponential model is convenient for optical modellingand remote sensing applications, these results suggest that the Gaussianmodel offers a deeper understanding of chemical interactions affecting CDOMmolecular structure.

【 授权许可】

Unknown