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

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.