富营养化水体中黑水团的吸收及反射特性分析

对黑水团水体光学特性进行研究,是利用遥感技术监测和评估黑水团事件的前提.针对2015年7月在太湖发生的黑水团现象,采集了太湖黑水团区(区域一)、蓝藻水华区(区域二)、清水区(区域三)共36个水样,对这3个区域的水体遥感反射率以及吸收特性进行对比分析.结果表明:1区域一水体的总颗粒物、色素颗粒物和非色素颗粒物吸收系数比区域二、区域三高出1~2倍,在400~500 nm之间,区域一CDOM吸收系数相比另外两个区域的水体高出2倍左右.导致黑水团区域水体具有很低的遥感反射率,被人眼感知时呈现为黑色;2黑水团区域水体M值低于滇池、巢湖和太湖的M值变化范围,说明黑水团中CDOM的腐殖酸含量较高.此外,叶绿素a浓度与CDOM在350 nm处吸收系数之间具有很好的相关性,表明蓝藻的降解可能是黑水团中CDOM的一个主要来源;3在380 nm之后,黑水团区域的水体总吸收以色素颗粒物占主导,但在短波350~380 nm处,CDOM对总吸收的贡献率高于色素颗粒物和非色素颗粒物.

Absorption and Reflection Characteristics of Black Water Blooms in the Eutrophic Water

Studying on optical properties of black water blooms, is the precondition for using remote sensing technology to monitor and evaluate the black water blooms event. Black water blooms occurred in Taihu Lake in July 2015. A total of 36 water samples were observed in the three water regions of Taihu Lake, the region 1 with black water blooms characteristics, region 2 with cyanobacterial bloom characteristics, and regional 3 with characteristics of clean lake water. The reflectance spectra and absorption coefficient of these three regions were analyzed, and the results show that:1 The absorption coefficients of the total particles, the pigment particles and the non-pigment particlesin black water blooms are 1 to 2 times higher than the other two areas. The absorption coefficient of CDOM between 400-500 nm in region 1 is about 2 times higher than the other two areas, which lead the black water area with a very lower reflectance, and presents as black color. 2 The range of M value in black water blooms is lower than Dianchi Lake and Chaohu Lake, which means the humic acid content of CDOM with black water characteristics is higher. A significant positive correlation is found between chlorophyll a (Chl-a) and the CDOM absorption coefficient at 350 nm, indicating that algae degradation is likely to be the primary source of CDOM in black waters. 3 The contribution of each optically active component indicates that the water absorption of region 1 strongly controlled by CDOM below 380 nm, but by Chla absorption between 380 nm and 700 nm.