Similar cities, but diverse carbon controls: Inspiration from the Yangtze River Delta megacity cluster in China

Addressing global uneven urban development and the urgent need to reduce carbon emissions (CE), this study presents a new method for calculating urban socioeconomic development indexes using a variety of data sources. Using the Yangtze River Delta as an example, we categorize urban areas into core, transitional, and peripheral cities. With the help of extended Kaya-index decomposition models, we evaluate the effects of regional industrial growth, consumer markets, and spatial expansion on urban CE. The research explores differences in CE drivers across and within these city categories. Our findings reveal that in core cities, 31.5 % of CE is due to the industrial structure and 14.9 % due to population density. In transitional cities, CE increases by 60.22 % primarily due to industrial structure and consumer consumption. Peripheral cities, on the other hand, have a complex set of causes for CE, with per capita living, spatial expansion, population size, urbanization, and consumption limitation contributing to 91.97 %, 10.73 %, 14.2 %, 9.34 %, and 24.92 % of CE respectively. Varied factors influence CE intensity differences within each city group. Cleaner production technologies and potential carbon reductions in consumption and industry are identified as key strategies for compensating CE reduction. We propose the adoption of carbon function zoning in urban clusters to leverage the role of carbon function in each area. Territorial spatial planning should ensure a balanced layout of production, living, and ecological functions. Residents' consumption, being the key factor driving CE, must transition toward green, low-carbon consumption, reinforced by societal norms and responsibilities. This research provides valuable theoretical and practical insights into urban classification and CE reduction strategies.

Photochemical ozone pollution in five Chinese megacities in summer 2018

To investigate photochemical ozone (O₃) pollution in urban areas in China, O₃ and its precursors and meteorological parameters were simultaneously measured in five megacities in China in summer 2018. Moderate wind speeds, strong solar radiation and high temperature were observed in all cities, indicating favorable meteorological conditions for local O₃ formation. However, the unusually frequent precipitation caused by typhoons reaching the eastern coastline resulted in the least severe air pollution in Shanghai. The highest O₃ level was found in Beijing, followed by Lanzhou and Wuhan, while relatively lower O₃ value was recorded in Chengdu and Shanghai. Photochemical box model simulations revealed that net O₃ production rate in Lanzhou was the largest, followed by Beijing, Wuhan and Chengdu, while it was the lowest in Shanghai. Besides, the O₃ formation was mainly controlled by volatile organic compounds (VOCs) in most cities, but co-limited by VOCs and nitrogen oxides in Lanzhou. Moreover, the dominant VOC groups contributing to O₃ formation were oxygenated VOCs (OVOCs) in Beijing and Wuhan, alkenes in Lanzhou, and aromatics and OVOCs in Shanghai and Chengdu. Source apportionment analysis identified six sources of O₃ precursors in these cities, including liquefied petroleum gas usage, diesel exhaust, gasoline exhaust, industrial emissions, solvent usage, and biogenic emissions. Gasoline exhaust dominated the O₃ formation in Beijing, and LPG usage and industrial emissions made comparable contributions in Lanzhou, while LPG usage and solvent usage played a leading role in Wuhan and Chengdu, respectively. The findings are helpful to mitigate O₃ pollution in China.