Digital economy and synergy effect of pollution reduction and carbon emission reduction: Based on the threshold effect analysis of environmental penalty and pollution intensity

Abstract Under the dual circumstances of the “dual carbon” goal promotion and the deep development of the digital economy (DE), clarifying the influence mechanism of the DE on the synergy effect of pollution reduction and carbon emission reduction (SEPRCER) is of great practical significance for promoting the green and high-quality development of the region. This paper is based on the panel data of 108 cities in the Yangtze River Economic Belt (YREB) from 2011 to 2023. It systematically analyzes the evolution characteristics of the DE and the SEPRCER, and empirically examines the influencing mechanism between the two. The results show: (1) The level of the DE in the YREB shows an overall upward trend, while the level of the SEPRCER shows a slight downward trend. Both form a distribution pattern with the Yangtze River Delta (YRD) as the core and multiple growth poles coexisting in space; (2) The influence of the DE on the SEPRCER presents a significant "U" shape relationship, and this conclusion still holds after robustness and endogeneity tests; (3) The relationship between the two shows heterogeneity characteristics. The “U” shape feature is more prominent in the lower reaches of the Yangtze River (LRYR), urban agglomerations, non-resource-based cities, and regions with high economic levels; (4) Both the environmental protection penalty intensity (EPPI) and the pollution intensity (PI) exhibit a significant single-threshold. As the EPPI crosses the threshold value, the turning point of the “U” shape curve for the DE and the SEPRCER will be reached earlier, while the opposite is true for the PI; (5) From the two threshold variables interaction grouping perspective, in the combination of high EPPI and low PI, the “U” shaped inflection points for the DE and the SEPRCER is the earliest. The research conclusions provide theoretical basis for improving the SEPRCER in the YREB.