No abstract

To reduce carbon emissions, the Chinese government is considering introducing a differentiated industrial carbon tax on enterprises outside the carbon trading market in the future. An efficient carbon tax must consider not only how carbon taxes impact the current economy but also how the size of the tax should be adjusted across time due to external changes. To calculate the optimal industrial carbon tax for China which is subject to certain constraints, this paper investigates the economic and environmental effects of four possible industrial carbon tax rate models under carbon intensity constraints from 2021 to 2030 by a dynamic input–output optimization model. The results show that the dynamic tax rate model leads to larger fluctuations in GDP growth than the other tax models, with a low initial tax rate in the beginning and a high tax rate exceeding ¥180/t in 2030. Second, a large quantity of capital stock is distributed across the energy-intensive industries, which leads the existing capital investment structure to be path-dependent. This offsets the performance of carbon taxes. Third, indirect energy-intensive industries such as construction and transport are insensitive to the industrial carbon tax. Finally, comparing the impacts of the four tax rate models, the optimal industrial carbon tax for China is found to be a fixed differentiated tax rate, in which energy-intensive sectors are taxed ¥75/t and low-carbon sectors are taxed ¥50/t. Supplementary Information The online version contains supplementary material available at 10.1007/s11356-022-19162-6.

China used to be a major destination of foreign direct investment (FDI) and Chinese firms have long been acquired by foreign companies. In the recent decade, after thirty years since the implementation of the "Reform and Opening-up" policy 1 , Chinese firms began to take an active part in investing abroad through cross-border M&As, a major form of internationalisation. Under the 1 The economic reform featured by "socialism with Chinese characteristics" and "socialist market economy" led by chairman Deng Xiaoping that started in December 1978.

Chinese Jin Great Wall Defensive Settlement, built earlier than Jin Boundary Moat, is an important component of the Jin Great Wall defensive system and is a hierarchical defensive system. It does not only have national characteristics but also have regional characteristics, but for years, the conservation of the Jin Great Wall defensive settlements has not been fully understood like that of boundary moats, which seriously restricts the value cognition and conservation planning of Jin Great Wall. This paper achieves the goal of expanding lineal cultural heritage resources and promoting the historical and cultural value through improving the past traditional ideas and technologies about Great Wall study and conservation, and provides a more comprehensive and powerful foundation for the integrated conservation principle and strategy of the Jin Great Wall.

Treatment of tailwater in intensive aquaculture has been a major issue that affects the utilization efficiency and pollution of water resources. In this study, the intensive farming of bullfrogs (Rana catesbeiana) was taken as an example to construct a tailwater treatment system consisting of a flotation tank, a biochemical tank and wetlands. The operating conditions of the biochemical tank were first optimized. The results showed that at an influent flow rate of 250 m3·h− 1, a hydraulic retention time of 6 h, and an aeration intensity of 2000 m3 h− 1, the levels of CODCr, ammoniacal nitrogen and total phosphorus in the effluent of the biochemical tank were reduced by 70%, 43% and 42%, respectively. Under these operating conditions, the efficiencies of the flotation tank, biochemical tank and constructed wetlands were 8.3%, 67.3% and 5.6% for CODCr removal, 4.2%, 40.4% and 70.5% for ammoniacal nitrogen removal, and 16.8%, 42.1% and 59.4% for total phosphorus removal, respectively. After one month of continuous operation, the following treatment results were obtained: 71.7% and 90% removal for CODCr and BOD5, 83% and 92% removal for ammoniacal nitrogen and nitrite nitrogen, 86.7% and 76.5% removal for reactive phosphorus and total phosphorus, and 95.1% removal of suspended solids. The dissolved oxygen level increased from 1.2 mg·L− 1 (influent) to 3.5 mg·L− 1 (effluent), indicating significantly improved water quality that met the Grade 1 national wastewater discharge standard and the criteria of recycled water utilization in bullfrog farming. This system thus realized the regeneration and utilization of tailwater in intensive aquaculture.