| dc.description.abstract | In this study, long-term precipitation chemistry monitoring data from the Chiayi Acid Rain Station from 2004 to 2020 were analysed. The results of the analysis showed that the long-term rainfall-weighted average pH of precipitation in the Chiayi region was 5.20. The correlation analysis between pH and pAi showed no significant relationship. This indicates a significant neutralization effect in precipitation chemistry. The primary neutralizing factor was found to be NH4+, which is likely associated with frequent agricultural activities in the Chiayi region. The main acidifying factor, SO42-, showed a significant decreasing trend in the rainfall-weighted average concentration over the years. On the other hand, the long-term yearly concentration trend of NO3- exhibited noticeable variability, but the concentration values did not show a significant decrease, and the long-term trend was not significant. The long-term S deposition in the Chiayi region showed a decreasing trend with a slope of -0.374(P = 0.0013<0.05), indicating statistical significance. The deposition of N was mainly contributed by NH4+, and although the long-term trends of N, N-NH4+, and N-NO3- deposition showed a decrease, they were not statistically significant.
The factor analysis classified three factors. Factor 1 represents a combination of agricultural activities, traffic pollution, and dust, among other factors. Factor 2 shows a high correlation between Cl-, Na+, and Mg2+, related a marine source. Factor 3 shows a high correlation with K+ and moderately correlated with Cl-, associated with agriculture, and dust-related influences. The estimated pollution sources suggest three main airflow source regions. Cluster 2 may be attributed more to the long-range transport pollutants, accounting for 28 % of the total samples. Cluster 1 and Cluster 3, comprising 72 % of the total samples, are likely to be associated with local/regional pollutants surrounding Taiwan. The analysis of high concentration precipitation events indicates that, in addition to the long-range transport pollutants, the Chiayi region may also be influenced by higher pollutant emissions from the Taichung area, which affect local precipitation. | en_US |