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An integrated model for simulating and diagnosing water quality based on the system dynamics and Bayesian network (BN) is presented in the paper. The research aims to connect water monitoring downstream with outlet management upstream in order to present an efficiency outlet management strategy. The integrated model was built from two components: the system dynamics were used to simulate the water quality and the BN was applied to diagnose the reason for water quality deterioration according to the water quality simulation. The integrated model was applied in a case study of the Songhua River from the Baiqi section to the Songlin section to prove its reasonability and accuracy. The results showed that the simulation fit to the variation trend of monitoring data, and the average relative error was less than 10%. The water quality deterioration in the Songlin section was mainly found to be caused by the water quality in the upper reach and Hadashan Reservoir drain by using the diagnosis function of the integrated model based on BN. The relevant result revealed that the integrated model could provide reasonable and quantitative support for the basin manager to make a reasonable outlet control strategy to avoid more serious water quality deterioration.

Bi-N-TiO 2 nanoparticles were synthesized via anneal after a simple sol-gel combined hydrothermal method. X-ray diffraction (XRD), UV-Visible diffuse reflectance spectra, Scanning Electron Microscope (SEM) and X-ray photoelectron spectra (XPS) confirm that the grain sizes are almost uniform diameters of about 11 nm, the response to light extends to visible region, the doped ions substitute some of the lattice titanium atoms, and furthermore Bi 3? and Bi 4? ions coexist. The photodegradation of acid orange 7 (AO7) is used to evaluate the photocatalytic activity of the prepared Bi-N-TiO 2 nanoparticles. The experiments indicated that Bi-N-TiO 2 showed higher photocatalytic activity than that of P25, TiO 2 , N-TiO 2 and Bi-TiO 2 in the visible light area and ultraviolet light. The improvement of photocatalytic activity of Bi-N-TiO 2 is more likely because the N doping causes the visible light response and improves the quantum yield and photocatalytic activity of TiO 2 , and Bi doping causes the enhancement of the separation of photogenerated charges.