Source–receptor relationships of nitrate in Northeast Asia and influence of sea salt on the long-range transport of nitrate

We conducted a source–receptor relationship (SRR) analysis of the total deposition of nitrate (TDN; dry + wet, gas + aerosol) in Northeast Asia using an aerosol chemical transport model. Six regions were included in the study: North China, Central China, South China, South Korea, Japan, and Ocean. More than 95% of the TDN across China consisted of contributions from Chinese emissions. The largest intra-regional contributions and the second largest contributions were attributed to the Central China region. The contribution of the three China regions accounted for approximately 50–60% of the TDN in South Korea and Japan and 75% of the TDN in the Ocean region, respectively. The spatial distributions of the SRR indicated that the sub-regional high was more than twice the regional averages of the TDN. We also investigated the effects of sea salt on the transport and deposition of nitrate. During the long-range transport from the Asian continent over the ocean, nitric acid gas condenses on sea-salt particles to form NaNO3. The presence of sea-salt particles increased the TDN over the downwind regions of the Asian continent by approximately 10–25% in South Korea and Japan and by up to 40% in the Ocean region. However, the sea-salt effects on the SRR of the TDN were small (the absolute differences were smaller than approximately 10%).