Summary: | 碩士 === 國立東華大學 === 自然資源管理研究所 === 86 === Rainfall samples collected at the Taipei Botanical Garden from 1981 to 1997 were analyzed for pH, specific conductivity, and major ions. Basic statistics, seasonal patterns, deposition flux of the chemicals, and correlation among ions were examined to provide a baseline data for Taipei. Average of volume-weighted pH value of the rainfall was 4.91 and ranged from 3.15 to 7.66. Among the total 1089 rainfall events, 78% of them had pH value below 5.65. Monthly averages of the pH value were highest in October and lowest in July. In general, the pH values had an increased trend over the past 17 years in Taipei. The seasonal difference of pH values between summer and winter was significant. Both the pH value and ion concentrations were lower in summer and higher in winter. Annual total deposition of ammonium gradually increased from 10.2 kg/ha/y in 1981 to 45.7 kg/ha/y in 1997. Nitrate was also gradually increased from 3.5 kg/ha/y to 12.9 kg/ha/y over these years. The most contribution anions were sulfate, chloride and nitrate. For the cations, calcium, ammonium and sodium were the most contribution ones. Major neutralization ions in the precipitation were calcium, ammonium and magnesium. The equivalent ratio of NO3-/SO42- was comparable with the Northeast of United States and Europe region.
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