[Effects of Land Use Types on Water Quality at Different Buffer Scales: Tianjin Section of the Haihe River Basin as an Example].

It is important to explore the relationship between land use types and water quality to improve the surface water environment. Based on monthly water quality monitoring data from 16 nationally controlled surface water quality monitoring stations in Tianjin and land use data in 2021, GIS spatial analysis and mathematical and statistical methods were used to study the influence of land use types on surface water quality in buffer zones at different scales. The results showed that:① the land use types in the study area were mainly construction land, farmland, and water areas, which had significant effects on river water quality. Except for water temperature (WT) and pH, the farmland, construction land, and water areas were negatively correlated with each water quality indicator; forest land and grassland were positively correlated with dissolved oxygen (DO) and total nitrogen (TN) and negatively correlated with other water quality indicators. ② The water quality indicators showed obvious spatial differences in different seasons. The pH, DO and TN concentrations were higher in the dry season, whereas the permanganate index, ammonia nitrogen (NH4+-N), and total phosphorus (TP) concentrations were higher in the rainy season. ③ The results of the RDA analysis showed that the 800 m buffer zone land use had the greatest explanatory power for water quality changes in the dry season (50.4%), whereas the 3 000 m buffer zone land use could explain the water quality changes in the rainy season to the greatest extent (49.6%); from the average explanation rate of the dry and rainy seasons, the 3 000 m buffer zone was the best impact scale (50.0%) on water quality indicators in Tianjin. ④ The partial least squares regression (PLSR) analysis showed that the most important variables affecting surface water quality changes were construction land, farmland, and water areas. The predictive ability of the PLSR model of most water quality indicators was stronger in the dry season than that in the rainy season. In the dry season, all water quality indicators, except WT and pH, were most influenced by farmland. In the rainy season, construction land had the greatest influence on WT and NH4+-N concentrations, and the most important influencing factor for the remaining water quality indicators was still farmland. This study showed that the rational planning of land use types within 3 000 m of rivers or lakes was beneficial to improving the water quality of surface water.

Application of beta-(2-chloroaroyl) thioacetanilides in synthesis: an unusual and highly efficient access to thiochromeno[2,3-b]pyridine derivatives.

A series of unusual fused tricyclic thiochromeno[2,3-b]pyridines were successfully synthesized by tandem [3 + 3] annulation and SNAr of beta-(2-chloroaroyl) thioacetanilides with activated 4-arylidene-2-phenyloxazol-5(4H)-ones or aromatic aldehydes and ethyl 2-cyanoacetate under microwave irradiation, respectively. Because of the existence of the o-chloro atom of beta-(2-chloroaroyl) thioacetanilides, these reactions were very mild, convenient, and ortho-selective to form new fused tricyclic target molecules. In the domino processes, at least seven reactive distinct chemical sites were involved and up to three new covalent bonds and one tricycle with only cis configuration were generated. A synthetic study and mechanistic proposal for these transformations are presented.

2-Anilino-3-benzoyl-4-(2,5-dichloro-phen-yl)-7,7-dimethyl-5-oxo-5,6,7,8-tetra-hydro-4H-benzo[b]pyran.

The title compound, C(30)H(25)Cl(2)NO(3), was prepared by the reaction of 3-oxo-N,3-diphenyl-propane-thio-amide, 2,5-dichloro-benzaldehyde and 5,5-dimethyl-1,3-cyclo-hexa-nedione (1:1:1) in ethanol. The cyclohexene ring adopts a half-chair conformation. The crystal structure exhibits intra-molecular N-H⋯O and C-H⋯O, and inter-molecular C-H⋯O inter-actions.

7-Chloro-4-(2,5-dichloro-phen-yl)-1-phenyl-1H-thio-chromeno[2,3-b]pyridine-2,5(3H,4H)-dione.

In the crystal structure of the title compound, C(24)H(14)Cl(3)NO(2)S, the tetra-hydro-pyridine ring adopts a half-chair conformation and both pendant benzene rings are oriented nearly perpendicular to the thio-chromeno[2,3-b]pyridine system.