Characteristics of atmospheric precipitation chemistry and deposition in typical regions of China during 2000-2021

Based on the data of atmospheric precipitation in 10cities of the Northeast, North, East, Southeast, Northwest, and Southwest China from 2000 to 2021, a long-term variation trend was studied on precipitation amount, pH value, electrical conductivity, water-soluble ion concentration, and nitrogen and sulfur wet deposition in various regions. The ion neutralization of precipitation components in typical sites was also analyzed. The pH values of each site in China generally showed an upward trend from 2000 to 2021, but the annual average pH in Chongqing and Shanghai had not yet reached 5.6. The electrical conductivity showed a significant downward trend in Jinan, Xi'an, and Chongqing. The terrestrial characteristics were more obvious in the Northwest with a higher concentration of Ca2+ (up to 1035.2µeq/L). The concentration of NO3− showed an upward trend in Chongqing, which was related to the growth of motor vehicle ownership. The concentration of NH4+ decreased in all regions. The relatively high concentrations of Na+ and Cl− occurred in Southeast, where was influenced by sea salt. The sulfur and nitrogen wet deposition in the Northwest and the Southwest was significantly higher than that in the Southeast. The ratio of NH4+-N to NO3−-N showed a downward trend in all regions, but the annual average ratio was commonly greater than 1, indicating that reduced nitrogen was dominated in nitrogen deposition. The acidity of precipitation in Southeast China was relatively higher, but the concentration of acidic ions (SO42− and NO3−) was lower, indicating that the acidity of precipitation was also influenced by the alkaline ions (Ca2+ and NH4+). The annual changes in concentrations of NO3−, NSS-SO42− and NH4+ were not significant in Xiamen and Xi'an, while the pH value and the ratio of the neutralizing potential to the acidifying potential (NP/AP) showed a significant upward trend. The value of NP/AP in Xi'an was significantly higher, reflecting that the neutralization capacity in dust in Xi'an was higher than that in the Southeast China. © 2024 Chinese Society for Environmental Sciences. All rights reserved.