藻源型湖泛发生过程水色变化规律

Variations in optical properties and water color during the formation of black bloom waters: a laboratory experiment

利用Y-型沉积物再悬浮发生模拟装置,模拟湖泛发生过程,分析水体吸收特性变化特征;同时,利用Hydrolight和CIE颜色匹配函数模拟水体颜色,分析湖泛水色变化规律.结果表明:在湖泛发生过程中,可溶性有色物质(CDOM)浓度(ag)不断增大,无机颗粒物浓度及吸收(ad)总体呈减小的趋势,而浮游植物色素浓度及吸收(aph)随时间变化不规律;基于Hydrolight模拟湖泛水体,离水辐亮度(Lw)和遥感反射比(Rrs)均随时间不断变小;3)另外,随SPIM或ag(443)的变大,水体颜色逐渐由绿色变为棕色.当SPIM增至40mg/L时,水体呈现棕色;当ag(443)达到10m-1时,水体呈现红棕色.通过研究湖泛发生过程水体光学特性和水色变化规律,有助于构建高精度的湖泛遥感监测模型.

In the summer of 2007,a bloom of black water in Lake Taihu entered into the potable water supply of Wuxi city and left more than 1million people lack of drinking water. Recent evidence shows that these blooms involve massive production of dissolved organic carbon,most likely from inorganic carbon fixed in cyanobacterial blooms. Because blooms have limited spatial and temporal distributions,it is difficult to monitor them in situ. Remote sensing provides a new opportunity to monitor this complex carbon transformation. However,little is known about the temporal dynamics of optical properties of black bloom formation. In this study,we analyzed the daily transformation of particulate organic material to dissolved organic material,closely monitoring optical changes and water color during the simulation of a black water bloom in the laboratory. Results showed that during black water bloom formation： 1） CDOM absorption increased significantly,while absorption from suspended particulate inorganic matter decreased. 2） Phytoplankton pigments absorption（aph） varied over time. 3） Simulated water-leaving radiance and remote sensing reflectance decreased,allowingto examine spectral variations and water color in relation to bloom formation. These changes in optical properties of black bloom provided new opportunities to monitor these processes in lake conditions using remote sensing.