| dc.description.abstract | In this study, the long-term (2008-2017) winter precipitation chemistry at three sites in northern Taiwan, including Pengjia islet, Anbu, and Taipei, was analyzed. The major aims of this study are: report the characterization of inorganic component concentrations in rainwater, discuss the spatial distribution, and evaluate the long-term trends of the precipitation chemistry and the effect of weather type on rainfall composition at these sampling locations. The Mann-Kendall test and Sen’s estimation of the slope were employed to detect the long-term trends. Over the entire period, a mean pH of 4.91, 4.73, and 4.70 was found at Taipei, Anbu, and Pengjia islet, respectively. pH of the rainwater samples was strongly related to the concentration of NO3-, non-sea-salt (nss-) SO42- and acid-neutralizing compounds such as NH4+, K+, Mg2+, and Ca2+. Sea salt ions, NO3-, and nss-SO42- were all higher at Pengjia islet than Anbu and Taipei. This can, in part, be explained by the difference in sampling location as well as characteristics of the precipitation. Long-term trends in the precipitation chemistry indicated a significant increase in pH at all sites and could be attributed to a significant increase in Ca2+. At Pengjia islet and Anbu, the decrease in nss-SO42- concentration may have also contributed to the increase in pH, while Taipei showed a different pattern likely due to the impact of local emission. In addition, changes in anthropogenic emissions and the regional transport pattern of air masses may have contributed as well, impacting the precipitation chemistry at all three sites. Rainfall type also contributed to the difference in precipitation chemistry. Precipitation caused by the North-east monsoon (NE) showed a greater ion concentration than precipitation caused by frontal systems (FS) because of the lower precipitation amount in the former. Even so, the contribution fraction of major ions was similar between precipitation stemming from these two types of weather systems, suggesting similar anthropogenic emission sources during both. Effects on precipitation chemistry from the long-range transport of dust at Anbu was assessed through examining high Ca2+ events analysis. Two types of events are classified: 96% of events are associated with the mixing of dust and anthropogenic emission during transport and 4% of events may be considered as pure dust transportation. A haze event can be considered as a factor contributing to the difference between the two event types because of its negative effect on vertical mixing of anthropogenic emissions. | en_US |