內洞國家森林遊樂區水環境化學

Study on Water Environmental Chemistry in Neidong National Forest Recreation Area

本研究主要針對林務局新竹林管處轄區內的內洞國家森林遊樂區進行水環境監測，藉以瞭解河川自淨能力與遊憩行為對森林遊樂區水化學的影響。調查項目包含林外雨和溪流水的pH值、電導度、溶氧量、無機陰離子和陽離子、溶解性有機碳、溶解性無機碳和總氮。本試驗地雨水pH值落在4~5之間，酸度主要是硫酸根的輸入。另一方面，溪流水pH值則是介於pH 7~8，且碳酸氫根當量濃度大於300 μeq L-1，可見內洞國家森林遊樂區內森林生態系對於酸雨有良好的緩衝能力。比較上游有人為開發的南勢溪和濱溪沿岸森林覆蓋完整的內洞溪的溪流水水化學，結果顯示在鎂離子、鈣離子、硫酸根離子和碳酸氫根離子都是以內洞溪的測值較為平穩，受到干擾而造成的波動比較小。因此可以證明溪流水上游需要維持健康森林覆蓋，方能使河川具有良好的自淨能力。 The obiectives of this monitoring study are to concern the buffer capacity of different source streams and the effects of recreational behaviors on water chemistry of forest ecosystems. The pH, electrical conductivity (EC), Inorganic cations (Na+ , NH4 + , K+ , Mg2+, Ca2+) and anions (F- , Cl- , NO3 - , SO4 2-, HCO3 - ) , dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and total nitrogen (TN) in the precipitation and streamwater samples were determined. The precipitationl pH was under 5.6 during the monitoring period, from 4 to 5, indicated the Neidong National Forest Recreation Area was affected by acid rain. SO4 2- accounted for the highest proportion of solute in the precipitation. However, the pH value was higher than 7 in all the sampling sites of streamwater, and the HCO3 - concentration was higher than 300 μeq L-1, indicating owned good capacities to acid precipitation in this area. Overall, although the watershed area of Nansi River was bigger than Neidong River and under more stress from tourists, but it did not threaten to pollution. It implied that forest watershed owned capacity to maintain good water quality.