Abstract: Historic and recent observational data of SO2 and NOx from Lin誥n and Longfengshan background stations, located in the Yangtze Delta and the Northeast Plain region, respectively, are analyzed in order to study the differences in concentrations of these climate-relevant acidic gases between the two regions, and the impacts of anthropogenic emissions on the gases since about one decade ago. The past and more recent concentration levels of the gases are compared between the two sites, long-term changing trends of the gases at both sites are estimated, and the NOx/SO2 ratios for the two sites are obtained using the correlation method. The results show that as early as middle 1990s, concentration levels of SO2 and NOx have been considerably high already at the background station of the Yangtze Delta region, and since then anthropogenic emissions have caused a significant increase in NOx concentration, making NOx another major pollutant in addition to SO2. Data from Longfengshan station suggest that levels of acidic gases in the Northeast Plain region were originally very low in the past, and are still considerably low at present. However, levels of the two acidic gases in this less polluted region have increased at very high rates, therefore, the future levels of these gases in the region are not optimistic.

Key words: climate-relevant acidic gases, sulfur dioxide, nitrogen oxides, anthropogenic emission, Yangtze Delta, Northeast Plain