Long-term changes in wet nitrogen and sulfur deposition in Nanjing

Abstract

The concentration and deposition of acid from precipitation in Nanjing in the Yangtze River Delta are presented, and their long-term trends are detected based on ground measurements. The wet SO42− deposition was 18.1 kg S ha−1 yr−1 from 2015 to 2016, which is much lower than the average across China; and the NO3− deposition was 8.5 kg N ha−1 yr−1, which is higher than the national average. Both SO42− and NO3− depositions were relatively high in spring, summer, and autumn, with the lowest occurring in winter. From 1990 to 2016, the averages of SO42− deposition during each Five-year Plan gradually decreased from the 8th (1991–1995) to 12th Five-year Plan (2011–2015), although the annual value did not show a significant decreasing trend due to large variations. Both the annual value and averages of NO3− deposition during each Five-year Plan showed significant increasing trends from 1990 to 2016. The SO42− deposition during the 12th Five-year Plan decreased by 26.5% while the NO3− deposition increased by 182.9% relative to that of the 8th Five-year Plan. These results confirmed that NO3− deposition is still high in the Yangtze River Delta.