Variations In Optical Properties And Water Color During The Formation Of Black Bloom Waters

Algal in eutrophic lake largely breakouts then accumulate in water surface and finally degrade under suitable hydrologic and meteorological conditions. And this contributes to the bloom of black water occurred, which lead to rapid deterioration in water quality and do harm to the ecosystem. Considering that the black bloom can be exist in any area and in any time, it is difficult to monitor in field. Up till now, there are no other methods except for separate human field monitoring. And this makes remote -sensing monitoring essential.The main character of black bloom is the water turn black and smelly. But it does not mean all these change can be regard as the black bloom. The change of water can be a strong proof of the occurring of black bloom because it can be regard as a progress of water color change, which makes remote sensing monitoring possible. So it is essential to get better understanding of the change rule of water optical properties to identify the optical monitoring index to accurately monitoring this phenomenon. We focus on water optical character variation during black bloom and analysis the main factors which contributes to "black" based on in field measurements and laboratory experiment. Hydrolight and CIE color matching simulation also play an important role in the research. And the research can give scientific prove to remote sensing based monitoring of black bloom. The main conclusions are as follows.During black water bloom formation:CDOM absorption increased significantly, while absorption from suspended particulate inorganic matter decreased. Phytoplankton pigments absorption (aph) varied over time. Simulated water-leaving radiance and remote sensing reflectance decreased. Chlorophyll-a concentration varied over time while both absorption and scattering of SPIM contributes to the small variation of Lw in different band. In conclusion, CDOM is a major factor leading to the variation of Lw. CDOM values were significantly correlated with the blackness of water color (R2= 0.63, p< 0.01). Water-leaving radiance was simulated under different CDOM conditions by Hydrolight and transposed using the CIE color matching functions. This showed a transition from green to brown which closely followed the increase in CDOM absorptionFe2+、S2- were regard as the major factor for the black bloom in geochemistry field. Our research results showed ag(443) is highly correlated to Fe2+、S2-(R2=0.67, R2=0.88) so we can use ag(443) to study the variation of Fe2+、S2-. In conclusion, the variation of CDOM concentration can monitoring the formation of black blooms both in optical and chemical field. This also has been proved by in field measurements with CDOM concentration of black bloom water is much higher than other no polluted water.From these results, we clearly show that CDOM is a major factor leading to the formation of black blooms, and can be used to monitor their dynamics over time.