福山森林生態系之大氣酸沈降

Acidic Deposition in Fu-Shan Forest Ecosystem

林文龍(Wen-Lung Lin) ； 林能暉(Neng-Huei Lin)

《環境保護》 27卷2期 (2004/12) Pp. 242-258

https://doi.org/10.30017/EP.200412.0008

摘要

本研究旨在估算台灣福山試驗林大氣污染物的沈降量，藉以了解台灣低海拔山區大氣污染物影響森林生態的情形。在1993年至1996年採樣期間，由模式所計算而得之HNO3、SO2、NH(上標 + 下標 4)、SO(上標 2- 下標 4)及NO(上標 - 下標 2)乾沈降速度分別為0.64-1.75、0.19-0.38、0.07-0.27、0.08-0.31及0.10-0.38 cm s^(-1)。大致上可發現冬季時的沈降速度較大，而春季較小。硫酸鹽有較高的溼沈降量(10.7-36.6 kg•ha^(-1))，為美東地區之2倍以上，充沛的雨量是主因；硝酸鹽的溼沈降量為硫酸鹽沈降量的10-50%，乃因雨水中硝酸根離子濃度較低之故。硝酸與二氧化硫的季平均乾沈降通量範圍為0.04-1.45 與0.09-0.53 kg ha^(-1)，而銨鹽、硫酸鹽及硝酸鹽的乾沈降量分別是0.07-0.32、0.06-1.29及0.03-0.38kg ha^(-1)。日間的乾沈降通量比夜間大，主要來自風速及大氣穩定度的影響。在乾沈降對總沈降(乾＋溼沈降)貢獻的比例上，硫酸鹽約為3.37%，而硝酸鹽約為2.35%，顯然多雨、潮溼的福山亞熱帶森林，乾沈降的貢獻遠不如溼沈降重要。

關鍵字

乾沈降 ； 溼沈降 ； 沈降速度

並列摘要

The main purpose of this study is to estimate the deposition fluxes of acid pollutants in Fu-Shan forest in order to improve our understanding of their potential impact on forest ecosystems. During the 1993-1996 experimental periods, the model calculated dry deposition velocities of HNO3, SO2, NH(superscript + subscript 4), SO(superscript 2- subscript 4) and NO(superscript - subscript 3) ranged in 0.64-1.75, 0.19-0.38, 0.07-0.27, 0.88-0.31 and 01.0-0.38 cm s^(-1), respectively. It was found that the deposition velocities had the largest values in winter but smaller in spring. Seasonal wet depositions of sulfates were between 10.7-36.6 kg ha-1 which were more than twice that for eastern USA, primarily attributed to higher rainfall in Fu-Shan area. Seasonal wet depositions of nitrates were about 10-50% of those values of sulfates, owing to lower concentration levels of nitrates in rainwater. For seasonal dry deposition fluxes, NH3 and SO2 ranged in 0.04-1.45 and 0.09-0.53 kg ha^(-1), respectively, and 0.07-0.32, 0.06-1.29 and 0.03-0.38 kg ha^(-1) for NH(superscript + subscript 4), SO(superscript 2- subscript 4) and NO(superscript - subscript 3), respectively. Daytime dry deposition was larger than nighttime because of high wind speed and instability. As to the relative contribution of dry deposition to total deposition, it was 3.37% and 2.35% for sulfates and nitrates, respectively, indicating that wet deposition pathway is much more important than dry deposition in humid subtropical Fu-Shan forest.

並列關鍵字

Dry deposition ； wet deposition ； deposition velocity