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臺北市酸雨趨勢與特性分析
The Characteristic of Acid Precipitation in Taipei
摘要
本研究利用1980年6月至1990年12月植物園之雨水資料分析臺北市雨水性質。利用體積權重法求得pH平均值為4.47，範圍介於3.15和7.22之間，於701場降雨中有522場雨水的pH值小於5.65，卽植物園附近的雨水75%有酸化的現象。年總沉降量方面，硝酸根年平均沉降量爲3.63 g/m^2，由每年1.52 g/m^2增加至4.21 g/m^2，有逐年增加趨勢，至於硫酸根於施測期間則變化不大，平均值爲12.12 g/m^2。由離子比率分析得知鈉離子及鈣離子對陽離子的供獻最大，佔了58%，而對陰離子供獻最大者爲硫酸根離子和氯離子佔了87%。鈣離子、鎂離子、鈉離子、及pH值之月平均值呈明顯季節性變化。而除氟離子外，雨量與各成分的濃度之間呈明顯反比之關係，至於連日豪雨可能因缺少某些物質之中和，如銨根離子等，雨水則有愈降愈酸的趨勢。
並列摘要
Precipitation samples on event basis at Taipei Botanical Garden from June 1980 to December 1990 were collected and characterized for their chemistry. The volume weighted pH value averaged 4.47, ranging from 3.15 to 7.22, of which about three quarters or 552 out of 701 rainfall events had pH values below 5.65. Total annual deposition of dissolved nitrate averaged 3.63 g/m^2 and increased gradually from 1.52 to 4.21 g/m^2 during study period. The sulfate, however, remained relatively stable throughout the study period with an average of 12.12 g/m^2. From the analysis of ionic ratios, it revealed that calcium and sodium were major cations which consisted of 58% of total cations. The major anions were sulfate and chloride consisting of 87% of total anion. Monthly volume-weighted means of pH value and concentrations of calcium, sodium, potassium, magnesium and chloride showed clearly seasonal patterns of variation. The amount of precipitation correlated inversely with ionic concentrations. The acidity of precipitation tended to increase during prolonged rainstorm events indicating, perhaps, absence of substances, such as ammonia for neutralization during latter stage of the storm event.