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With the acceleration of urbanization in China, the urban surface thermal environment has undergone significant changes. This work aims to calculate the urban thermal comfort index using a temperature and humidity model with the land surface temperature and relative humidity. It also aims to explain the association between the land use/land cover change (LUCC) and urban surface thermal environment of the Beijing–Tianjin–Hebei (BTH) Region, the Guangdong–Hong Kong-Macao Greater Bay Area (GBA) and the Yangtze River Delta (YZD) in 2020, 2015, 2010 and 2005 using geographically weighted regression. The results reveal that (1) the three urban agglomerations have substantial heat island intensity regions, which are clustered and zonally distributed, and the annual average rates of the heat island area growth in the three regions are 1.01%, 1.41% and 1.09%, respectively. (2) Many uncomfortable areas exist in the three urban agglomerations, with an exponential growth trend in summer, and the annual average proportion of the uncomfortable areas in the three regions are 60.8%, 56.8% and 49.4%, respectively. (3) From the spatial point of view, the high-thermal comfort index areas of Beijing, Tianjin, Hebei, Guangdong, Hong Kong and Macao expand to the coast, and the high-index areas of the Yangtze River Delta expand to the inland. In terms of time, the annual distribution of thermal comfort in Beijing–Tianjin–Hebei is discrete, but the annual distribution of thermal comfort in Guangdong, Hong Kong, Macao and the Yangtze River Delta is concentrated. (4) In LUCC, the change intensity in construction land has a remarkable effect on the change in thermal comfort. The areas where the thermal comfort index increases positively correlate with the areas where the construction land increases. This study enriches the research on the impact of LUCC on urban ecological performance, and thus provides the necessary scientific basis for urban environment construction. [ABSTRACT FROM AUTHOR]

In recent years, coal combustion by-products have attracted much attention because of their large production volume, adverse environmental effects of potentially toxic elements, and as potential sources of critical metals. In order to better evaluate the leaching characteristics of alkaline coal combustion by-products, the Leaching Environment Assessment Framework (LEAF) proposed by the United States Environmental Protection Agency was adopted in this study. Depending upon the properties of the samples, the test methods used in this paper mainly included Methods 1313, 1314, and 1316. The liquid-solid partitioning curves of samples were drawn according to the results of chemical analysis. Samples were collected from the coal-fired Sunzhuang Power Plant, Hebei Province, China. The leaching characteristics of coal combustion by-products are discussed from three aspects: pH values, liquid--solid ratios, and accumulated liquid-solid ratios. According to the trend of the liquid-solid partitioning curves, the modes of occurrence and causes of mobility of trace elements in the coal combustion by-products are discussed. To assess the potential environmental risk of hazardous elements leached from coal combustion by-products, the maximum leaching values of hazardous elements were compared to the upper limit value of the Type III Chinese groundwater quality standard, suggesting that in the eluates of Method 1313, arsenic, selenium, beryllium, thallium, nickel, and lead contents in the eluates of fly ash and bottom ash exceed the recommended upper limit. However, in the eluates of Methods 1314 and 1316, selenium, molybdenum, barium, and nickel exceed the recommended upper limit. [ABSTRACT FROM AUTHOR]