Taking Huancheng River in Hefei City as the study site, machine learning models such as linear regression, random forest, support vector regression, and lasso regression were utilized to establish the relationship between Landsat8 satellite data and water quality parameters, model the reflectance and water quality parameters of remote sensing image values, and compare the performance of four different models. Results showed that the random forest model performed best, and the accuracy of the inversion models for total nitrogen (TN), total phosphorus (TP), and ammonia nitrogen (NH3-N) was above 0.7. The concentration distribution map of water quality parameters showed that the pollution of TN and TP was the most significant in the northeast section of Huancheng River, while NH3-N was most present in the southwest section. The water eutrophication distribution map shows that the water body in the eastern section of the Huancheng River showed a moderate nutrition state.
To judge ecosystem health of the shallow lakes along the shores of Taihu Lake in the process of ecological restoration, water body of Jinshugang polder was investigated during 2022. The comprehensive assessment index system of water ecological health was constructed, consisting of the target layer, criterion layer, and index layer, of which the criterion layer was composed of three items: function, integrity, and stability. The index layer was composed of 14 major items such as comprehensive water quality and nutritional status and 28 small items such as pH, temperature, and dissolved oxygen. The results showed that during the process of ecological restoration, functional evaluation index reached the highest in autumn, integrity evaluation index was better than that in spring and summer, stability evaluation index was the best in summer, with 70% of the points at the “healthy” level, and the comprehensive evaluation index of aquatic ecological health continued to increase. The results and system of comprehensive evaluation of water ecological health formulated for shallow lakes in Taihu Lake are not only important for subsequent restoration and management, but also provide a reference for water ecological restoration and evaluation of other lakes.
Industrial park wastewater is characterized by various components, changeable water quality, complex pollutant factors, poor biodegradability, and high emission standards. A full-scale industrial park wastewater treatment plant in Deqing was used as an example to investigate the technical-economic feasibility of a process combining hydrolysis acidification, anaerobic-anoxic-oxic-anoxic-oxic (A2/O+AO), and Fenton oxidation in treating wastewater from various enterprises, primarily printing and dyeing, food manufacturing, and metal processing factories. The effluent chemical oxygen demand, ammoniacal nitrogen, total nitrogen, and total phosphorus stably met the required discharge limits for Urban Sewage Treatment Plants (DB33/2169—2018), while other indicators reached Grade A standard for Urban Sewage Treatment Plants (GB18918—2002). The engineering investment and actual operation costs of the wastewater treatment plant were 8200 and 2.39 yuan/m3, respectively.
Suppressing water glint pollution from remote sensing images and reconstructing image information are effective ways to improve the quality of UAV (unmanned aerial vehicle) remote sensing information and increase water environment monitoring areas. It is difficult to apply traditional glint information reconstruction algorithms to UAV hyperspectral images. This study proposes an algorithm for automatic glint detection, removal, and information reconstruction. First, NDWI (normalized difference water index) was used to extract the water body, and the lowest value of the sum of grayscale images in the entire band was used as a threshold to segment the glint, and the Laplace operator was used to extract the glint texture. The difference between the two areas was calculated through multiple rounds of morphological expansion and threshold updates. The lowest difference occurrence frequency was obtained by voting, and the best threshold was obtained in reverse to remove the glint automatically. Then, we determined the matching bands based on principal component analysis and compared the minimum similarity of matching blocks of different sizes to obtain the best size of the image blocks. Finally, we used an improved Criminisi algorithm to reconstruct the flare removal region. The removal algorithm was applied to four real glint scenarios with a removal rate > 99%; the reconstruction algorithm results are superior to those of other algorithms both subjectively and objectively, and the difference between the variation coefficient of each band of the glint reconstruction for water and normal water was within 1%, indicating good spectral application capability.
中国综合性科技类核心期刊(北大核心)
