Variation characteristics of acid rain in Zhuzhou, Central China over the period 2011-2020.

• Long-term analysis on the rainwater chemistry during 2011–2020. • Despite the improvement, the situation of acid rain frequency and precipitation pH in Zhuzhou City are still serious comparied to other cities in China. • The changs of nss-SO 4 2−/NO 3 − ratio reveals the acid type in Zhuzhou is gradually changing from sulfuric acid type to the compound type of both sulfuric acid and nitric acid. • Analysis on the rainwater chemistry shows The Zhuzhou municipal government should be cautious in implementing ammonia emission control measures. Zhuzhou was one of the most polluted cities in China with the serious acid rain. Due to the implementation of air pollution control measures from 2016 to 2018, the acid rain pollution in this city has reduced. In order to understand the recent situation, a comprehensive study on the acid rain was carried out from January 2011 to December 2020. The pH values during the study period varied from 3.3 to 7.5, with a volume-weighted mean value of 4.7. The predominant acidic components of the precipitation were SO 4 2− and NO 3 −, accounting for 89.3% of the total anions. The ratio of non-sea-salt SO 4 2− to NO 3 − showed a decreasing trend, revealing that the pollution type of acid rain changed from sulfuric acid type to sulfuric acid and nitric acid compound type. The correlation analysis (p < 0.05) showed that SO 4 2− was positively correlated with NH 4 +, Ca2+, and Mg2+; hence, it predominated in precipitation as (NH 4) 2 SO 4 , NH 4 HSO 4 , CaSO 4 , and MgSO 4. Significant positive correlation of Ca2+ with Mg2+ shows that they may originated mainly from crust. Significant positive correlation between SO 4 2− and F− and Cl− indicate that their source may be related to the non-ferrous metal smelting industry in Zhuzhou. Further correlation analysis shows that emissions from the non-ferrous metal smelting industry in the area have a large significant on SO 4 2− and F− in precipitation, while Cl− may still be emitted from other anthropogenic sources. [Display omitted] [ABSTRACT FROM AUTHOR]