塑膠微粒污染於金門地區歐亞水獺與棲地水域關聯性之研究

Abstract

金門位於臺灣海峽中段，受洋流與季風的雙重影響，沿岸經常堆積來自中國沿海城市及東亞地區的海漂垃圾，其中以塑膠廢棄物為主。這些廢棄物在自然環境中風化與降解後，進一步形成直徑小於5毫米的塑膠微粒（microplastics）。大量海洋廢棄物已對當地生態系統造成衝擊，並對金門特有之保育類物種—歐亞水獺（Lutra lutra）的棲地構成潛在威脅。本研究自2023年7月起，每季定期採集金門地區歐亞水獺排遺及其棲地水域樣本，進行塑膠微粒污染分析。樣本經化學消化、密度分離與過濾處理後，透過顯微傅立葉轉換紅外光譜儀（Micro-Fourier Transform Infrared Spectroscopy, Micro-FTIR）進行聚合物識別，並輔以儀器內建光譜資料庫與OpenSpecy線上光譜庫進行比對驗證。後續依據塑膠微粒的材質、顏色、形狀與尺寸分類，進行定性與定量探討。結合統計分析與資料視覺化方法，描繪金門地區塑膠微粒污染的時空分布特性，並透過塑膠微粒綜合多樣性指數（Microplastic Diversity Integrated Index, MDII）與聚合物危害指數（Polymer Hazard Index, PHI）評估其潛在生態風險。 本研究共採集八季歐亞水獺排遺樣本，檢出塑膠微粒共68個，材質以低密度聚乙烯（47.1%）、聚丙烯與聚乙烯為主；形狀則呈碎片、顆粒與纖維三者分布均衡；顏色以透明（55.1%）與紅色（18.8%）為主。紅色塑膠可能因顏色鮮明而被水獺誤認為獵物，亦可能經由食物鏈傳遞所致。同期亦進行四季河水樣本採集，共檢出213個塑膠微粒，主要材質為聚丙烯（52.6%）、聚乙烯與低密度聚乙烯；形狀以碎片為主（52.8%）；顏色則以透明（48.8%）與綠色（17.8%）最常見。綠色塑膠多分布於金門西部市區，推測可能與漁業活動或特定塑膠製品的棄置有關。兩類樣本在尺寸分布上皆呈現尺寸越小、數量越多的趨勢，反映塑膠經環境中機械作用後易破碎為微小尺寸。 在時空分布方面，水獺排遺與河水樣本的塑膠微粒豐度並未呈現顯著差異，顯示金門地區整體塑膠污染分布相對均勻。然而，排遺樣本在金沙溪與湖尾溪流域的檢出頻率與總量較高，顯示此處為潛在污染熱區；河水樣本則以穿越市區的浯江溪流域豐度最高，顯示塑膠微粒污染與人為活動高度相關。此外，MDII與PHI數值較高者，集中於東北部的金沙溪水系與東南部的太湖流域，可能與高密度人為活動與水獺活動範圍重疊有關，突顯此區域的潛在生態風險。本研究揭示金門地區水獺及其棲地水體普遍受到塑膠微粒污染，且污染表現具有地域性差異，提供未來生態健康監測與塑膠污染治理策略的重要參考依據。

Kinmen Island, located in the central Taiwan Strait, is subject to the dual influence of ocean currents and monsoons, resulting in frequent accumulation of marine debris along its coastlines—primarily plastic waste originating from coastal cities in China and the broader East Asia region. As these plastics undergo weathering and degradation in the natural environment, they gradually break down into microplastics (particles <5 mm in diameter). The influx of marine debris has already impacted the local ecosystem and poses a potential threat to the habitat of the Eurasian otter (Lutra lutra), a protected species unique to Kinmen. Beginning in July 2023, this study conducted seasonal sampling of Eurasian otter feces and surrounding freshwater habitats in Kinmen to assess microplastic pollution. After undergoing chemical digestion, density separation, and filtration, samples were analyzed using Micro-Fourier Transform Infrared Spectroscopy (Micro-FTIR) to identify polymer types. Spectral identification was verified using both the instrument’s internal library and the OpenSpecy online database. Subsequently, microplastics were categorized and analyzed based on their material, color, shape, and size. Statistical analyses and data visualization techniques were employed to illustrate the spatiotemporal distribution of microplastic pollution in Kinmen. Furthermore, the potential ecological risks were evaluated using the Microplastic Diversity Integrated Index (MDII) and the Polymer Hazard Index (PHI). A total of eight seasonal collections of otter fecal samples yielded 68 microplastic particles. The dominant polymer type was low-density polyethylene (LDPE, 47.1%), followed by polypropylene (PP) and polyethylene (PE). In terms of shape, fragments, granules, and fibers were evenly distributed. The most common colors were transparent (55.1%) and red (18.8%). The prevalence of red plastics may be due to their visual attractiveness, leading to mistaken ingestion by otters or bioaccumulation through the food chain. Concurrently, four rounds of river water sampling detected 213 microplastics, primarily composed of PP (52.6%), PE, and LDPE. Fragments accounted for the majority (52.8%), with transparent (48.8%) and green (17.8%) as the predominant colors. Green plastics were mainly distributed in the island’s western urban area, potentially linked to fishing activities or specific plastic products. Both otter and river water samples exhibited a trend of higher counts in smaller particle size classes, indicating extensive fragmentation due to environmental mechanical forces. No significant differences in microplastic abundance were observed across sampling periods or regions, suggesting a relatively uniform distribution of microplastic pollution across Kinmen. However, elevated detection frequencies and quantities in otter feces were found in the Jinsha River and Huyi River, highlighting them as potential pollution hotspots. Among river water samples, the Wujian River, which flows through the urban center, showed the highest microplastic abundance, indicating strong correlations with human activity. Notably, higher MDII and PHI values were concentrated in the northeastern Jinsha River system and the southeastern Taihu Basin, where dense human activity coincides with otter habitat, suggesting elevated ecological risk. This study demonstrates that both the Eurasian otters and their freshwater habitats in Kinmen are widely affected by microplastic contamination, with region-specific patterns. The findings provide a scientific basis for future ecological health monitoring and the development of targeted pollution management strategies.