Ammonium may emerge as the primary driver of future aerosol acidity, replacing the historical role of sulfate over the coastal area of North China: Insights from a megacity (Qingdao) - Wenshuai Li; Yaoyu Song; Tianshu Chen; Yuxuan Qi; Guanru Wu; Xinshuo Wang; Wenwen Xie; Lifang Sheng; Wencai Wang; Wenjun Qu; Yang Zhou (Atmospheric Environment, 2026)