A critical review of the variation in rainwater acidity in 24 Chinese cities during 1982–2018

Rainwater is an essential pathway to remove fine particulate matter and dissolved atmospheric pollutants (e.g., SO2, HNO3, NH3). Acid rain (pH < 5.6) has been a severe environmental issue in China since the 1970s, adversely impacting ecosystem health. This study focuses on influence of anthropogenically induced anions (SO42– NO3–) alkaline cations (Ca2+ NH4+) acid Chinese cities. In this review, cities with high population density east Hu Huanyong Line that divides geographically according its uneven economic development were studied. Coastal central areas line are characterized by much faster developing economy rapid urbanization. The observed trends spatial variability acidity chemical composition rainwater discussed relation industrialization changes China. Over past 3½ decades, precipitation pH urban regions exhibited reduced acidity. A mixed nitric–sulfuric type become prominent due significant decrease SO42– via desulfurization. Ca2+ levels have decreased, while NH4+ increased slightly more vehicular transportation. addition, neutralization capacity decreased from north south. Overall, problem alleviated recent years.