Remote sensing of inland water quality
Outbreaks of cyanobacteria in inland water bodies, especially water sources, can pose a serious threat to public health. Studies have shown that public exposure or ingestion of cyanobacterial cells and toxins can cause a series of harmful health consequences, such as skin irritation, allergic reactions, mucous membrane blistering, muscle and joint pain, gastroenteritis, lung consolidation, liver and kidney damage, and various neurological effects. Furthermore, the outbreak of cyanobacteria can cause factory shutdowns and tremendous economic losses. Therefore, the scientific value and socio-economic significance of inland water quality remote sensing monitoring and early warning research are beyond doubt. Chlorophyll-a and phycocyanin are important indicators for monitoring and early warning of outbreaks of cyanobacteria in inland water bodies with remote sensing because both pigments exhibit diagnostic absorption spectral features in the visible spectral region. Over the last 15 years, my research group has been making efforts to improve remote sensing approaches to monitoring inland water quality. Particularly, the effort was put in deriving the absorption and scattering coefficients of optically active substances (OACs) in water from remote sensing reflectance spectra and decomposing the total absorption of OACs to achieve the separation of the absorption coefficients of algal pigments from other constituents such as soluble organic matter and suspended sediment. An accurate retrieval of pigment absorption coefficients makes it possible to reliably map chlorophyll-a and phycocyanin and assess inland water quality. This would provide water management authorities and managers with an effective remote sensing tool for dealing with the outbreak of cyanobacteria in inland water bodies, Last but not least, the development of high-precision remote sensing algorithms is a collaborative and multi-disciplinary research and relies on our better understanding of aquatic systems and climate effects on them, knowledge on light transfer and optical properties of OACs in the water column as well as modelling skills.