Long range transport of nitrate in the low atmosphere over Northeast Asia

- Source-receptor relationships were established for surface nitrate in Northeast Asia.
- The local contribution of nitrate was higher than that of sulfate.
- The local ammonia helped transform trans-boundary gaseous nitric into nitrate.

In this study, the source-relationships were established for surface nitrate concentrations in Northeast Asia, using the Particulate Matter Source Apportionment Technology (PSAT) in the CAMx (a regional chemical transport model). Both of the local emissions and Chinese emissions were important among the sources of the particle nitrate in Japan and South Korea, accounting for 27.9-62.9% and 22.9-50.5% respectively. The local contributions of nitrate were 4-20% higher than the figures of sulfate, and this was caused by the different chemical processes and emissions involved. The seasonal variation of the nitrate concentration in East Asia led to different amounts of nitrate being attributed to long-range transport, and was higher in winter (>53%) than in summer (<41%). The interactions between ammonia/ammonium, sulfate and nitrate were also discussed. The distribution of degree of sulfate neutralization (DSN) and the adjusted gas ratio (AdjGR) in East Asia suggested that the particle nitrate concentration was most sensitive to changes in the total ammonia in most parts of Japan and some regions of South Korea. And that was different in most parts of East Asia, where there were large quantities of ammonia. The ammonia from local emissions were most likely responsible for some particulate nitrate being transformed from trans-boundary gaseous nitric, which signified that local emissions of ammonia increased the contribution of China to the nitrate concentrations in Japan and South Korea.