桃竹苗地區河川中氨氮輸出與土地使用方式改變之關係

Abstract

水質安全是本世紀重要議題，其中河水之氨氮濃度與集水區內人為活動息息相關，亦是現行法規判定水質是否受到污染之依據，然而過去台灣相關研究主要探討單一流域各子集水區水質之時空變化，鮮少有整合多個流域通透之探討，因此本研究以土地利用變化甚鉅之桃竹苗地區河川為研究對象，將1995及2005年兩時期之國土利用調查資料為基礎，配合環保署自1993至2015年於該區內54個水質測站資料，探討土地使用方式改變對於河川中氨氮濃度變化之時空關係。 本研究首先針對桃竹苗地區兩時期之人口密度、河水中氨氮濃度及各類土地利用進行主成分分析，結果顯示該10年內都市擴張與工業發展對水質有重要之影響；此外，透過計算1995年及2005年間各子集水區土地利用的轉移矩陣，配合群集分析中的二階段分析將54個水質測站分為高、低度開發兩組，結果顯示高度開發組26個測站集中在桃園與新竹市區等開發快速之地區，其中有19個水質測站於該十年內氨氮濃度有顯著升高之趨勢，顯示集水區水質受到人口快速增加集工業用地影響甚鉅，低度開發組28個測站則集中在苗栗及新竹郊區，其氨氮濃度呈下降趨勢。本研究計算得出各土地利用及人口氨氮輸出強度的研究結果中，1995年輸出強度以人口及建物為主，而2005年增加了工業輸出的影響，暗示工業土地使用類型的增加是造成桃園、新竹地區河川氨氮濃度增加的原因之一。Water quality issues are gradually getting more attentions recently. In stream water, ammonium concentration is highly affected by human activities, so it is usually served as a criterion to regulate water pollution. However, previous studies only focused on the temporal variation of water qualities within a single watershed, which cannot reflect the spatiotemporal relationships among the neighboring watersheds. In this study, we analyzed the spatiotemporal changes of ammonium concentration, which is monitored at 54 sites from 1993-2015, and linked to the changes of landuse types surveyed in 1995 and 2005 in Taoyuan, Hsinchu and Miaoli regions, where the landuse type of these region have changed significantly. The principle component analysis was conducted to determine the significant factors controlling the riverine ammonium concentration. The result shows that the urbanization and industry expansion have influenced the water quality for the past decade. The 54 sites were divided into high-development group (HG) and low-development group (LG) by applying the cluster analysis to the transition matrix of landuse type from 1995 to 2005. Of which, HG consists of 26 sites which are mostly located in Taoyuan and Hsinchu County, where population and industrial development increased rapidly. In terms of ammonium concentration, 19 of the 26 sites increase significantly, which indicates the ammonium concentration is highly effected by human activities. LG consists of 28 sites, mostly in Miaoli County, showing downward ammonium concentration due to few population growth and industrial development. According to results regarding the ammonium export coefficients of different land use types and population, the main contributors in 1995 are the population and the buildings. However, in 2005 the industry additionally contributes to the increased ammnomium concentration, implying the effects of industry expansion on water quality.