Remote sensing technology is promising for the future development of “pulse diagnosis” in lakes

Song Kaishan, a researcher in Northeast Geography and Agroecology of the Chinese Academy of Sciences, and his team and partners used remote sensing technology and other means to monitor the degree of eutrophication of water bodies, which could give early warning of blue-green algae outbreaks in advance and quantitatively estimate the content of algal toxins in water bodies. This achievement has been put into use in the Taihu Lake Lake and Chaohu Lake.

Eutrophication of water bodies is mainly reflected in the large amount of nutrients such as nitrogen and phosphorus entering the water, leading to rapid proliferation of algae. When algae die, a large amount of dissolved oxygen is consumed in the water, leading to the death of fish and other organisms, and the collapse of the aquatic ecosystem. The mass death of algae can cause the water to emit a foul odor, and some algae (blue-green algae) can also produce toxins, causing serious pollution.

Song Kaishan's team, together with Duan Hongtao and Shi Kun, researchers of the Chinese Academy of Sciences Nanjing Institute of Geography and Lakes, built a remote sensing model to calculate the water transparency, chlorophyll, total nitrogen and total phosphorus content through the combination of satellite remote sensing and actual distribution of points, so as to monitor the eutrophication degree of lakes and reservoirs, and also estimate the content of algal toxins. Song Kaishan said that the innovation lies in adding a key variable - the indicator pigment phycocyanin unique to blue-green algae - to the model. Phycocyanin not only has excellent spectral characteristics that can be recognized by remote sensing technology, but also accurately reflects the concentration of blue-green algae, improving the accuracy of remote sensing technology in calculating blue-green algae concentration, and is also the key to estimating algal toxins.

Satellite remote sensing survey has the characteristics of high viewpoint, wide field of view, fast data collection, repetition, and continuous observation. The obtained data is digital and can directly enter the user's computer image processing system. Satellite remote sensing surveys have advantages that traditional survey methods cannot match. Satellite remote sensing surveys have broad application prospects in land resources, forest resources, geological and mineral resources, water resources surveys, and crop yield estimation.

A remote sensing platform is a vehicle that carries remote sensing sensors during the remote sensing process. It is like a tripod for placing cameras during ground photography, and is a device for placing remote sensing sensors in the air or space. The main remote sensing platforms include high-altitude balloons, airplanes, rockets, artificial satellites, manned spacecraft, etc. Remote sensing is an instrument that can sense environmental radiation or reflected electromagnetic waves from distant objects. In addition to visible light cameras, infrared cameras, and ultraviolet cameras, there are also infrared scanners, multispectral scanners, microwave radiation and scattering meters, side view radars, thematic imagers, imaging spectrometers, etc. Remote sensing is developing towards multispectral, multipolar, miniaturized, and high-resolution directions. The digital and image information received by remote sensors is usually recorded in three ways: film, image, and digital magnetic tape. Its information is provided to users through optical processing or image digital processing processes such as correction, transformation, decomposition, and combination, for analysis and interpretation, or with the support of geographic information systems and expert systems, thematic maps or statistical charts are made, providing information services for resource exploration, environmental monitoring, land surveying and military reconnaissance. China has successfully launched and recovered more than 10 remote sensing and meteorological satellites, obtained panchromatic and infrared color images, established satellite remote sensing ground stations and satellite meteorological centers, developed image processing systems and computer-aided mapping systems. From the infrared cloud images obtained from the Fengyun-2 meteorological satellite, we can watch the meteorological situation on the TV every day.

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