Industrial agglomeration and industrial SO2 emissions in China's 285 cities: Evidence from multiple agglomeration types

The environmental externalities of industrial agglomeration have generated intense debate, yet few studies have considered their effects and inner influence mechanism based on varied agglomeration types. This study distinguished between industrial density and proximity (spatially) and industrial specialization and diversity, as well as related variety and unrelated variety (organizationally). Using the panel data from China's 285 cities from 2003 to 2013, we examined the different effects of multiple agglomeration types of industrial agglomeration on industrial SO₂ emissions, and their inner influence mechanism from two aspects of industrial structure and technological progress. First, we found that various agglomeration types have different environmental externalities and that industrial density and proximity both have significant reduction effects on SO₂ emissions; diversity and related variety effectively reduce SO₂ discharges, but specialization and unrelated variety are linked to increased emissions. Second, technological progress and industrial structure are the critical channels of industrial agglomeration affecting pollution emissions while technological progress plays a greater role in the reducing emission effect of industrial agglomeration. Our findings reveal the importance of different agglomeration types and technological progress between industrial agglomeration and pollution emission.