桃園南崁溪沉積物岩芯中重金屬分布之研究

Study of heavy metal distribution in sediment cores of the Nankan River, Taoyuan

李安昇(An-Sheng Lee)

指導教授 ： 劉雅瑄

國立臺灣大學/理學院/地質科學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201703435

摘要

桃園南崁溪因流經發展了60年以上的人口密集城市、大範圍農地與數個工業區；尤其工業區的大量電路板、金屬處理工廠排放廢汙水相當嚴重，致使該河流嚴重污染，然而該河流底泥中污染物的縱向分布以及污染物相了解尚未有完整研究。本研究於南崁溪中游與出海口兩地採集數根岩芯，使用Itrax-XRF 岩芯掃描儀(以下簡稱Itrax-XRF)掃描而取得高解析半定量多種化學元素組成圖譜，並利用ICP-OES 針對特定污染潛勢區間進行重金屬(鉻、銅、錳、鎳、鉛、鋅)定量分析確認以及粒徑、孔隙水中重金屬含量分析。多變量分析步驟係先將原始Itrax-XRF數據進行中心對數比轉換(centred Log-ratio transformation)，再以主成分分析(principal component analysis)進行資料結構的簡化，求出較少之維度來描述底泥特性；並依據其結果利用群集分析(cluster analysis)將底泥進行分群，解析出各元素之相關特性與分布。根據多變量統計分析結果顯示南崁溪底泥中可能受到重金屬相關污染，搭配視覺化之呈現可以清楚看出不同污染潛勢熱區之分布；重金屬污染熱區中重金屬含量明顯超標且與細顆粒底泥、錳共伴存在，另有可能與含鉛汽油、農藥相關的污染。底泥與孔隙水中重金屬含量的測定顯示重金屬主要以穩定固態相存在而非溶解於水中。雖有鉛-210進行定年分析，然因河川沉積特性而無法得到可信年代。藉由多變量統計分析可以充發揮 Itrax -XRF 資料高解析度之優點，將岩芯污染物詳細分層解析出相關特性，並透過一系列沉積物特性分析技術得到確認。

關鍵字

河川與出海口底泥 ； 重金屬污染 ； 主成份分析 ； 群集分析 ； 對數比轉換

並列摘要

Decades of economic development has cost most rivers in Taiwan polluted at various levels. The Nankan River, as the main river in Tauyuan City, Taiwan, flows through several concentrated industrial areas, crowded cities and a wide range of agricultures. The electronic and mechanical manufacturers in this area are highly productive. Nevertheless, pollutants in sediments and water bodies have not been well surveyed. Two series of sediment cores were taken along the Nankan River in sections of stable deposition. High-resolution physico-chemical properties of these cores were yielded from Itrax-XRF Core Scanner and grain size analysis. The data were pretreated with centred log-ratio transformation to mitigate the asymmetry problem of ratio and to achieve normality of data distribution, and then subjected to multivariate analyses. The results of principal component analysis and cluster analysis exhibit the spatial distribution of heavy metals (Cr, Cu, Mn, Ni, Pb and Zn) in sediment as well as the affinity of heavy metals to fine grains and manganese. Meanwhile, the level of heavy metals pollution in sediment of the Nankan River was assessed. We found that the heavy metals have remained in solid phase stably. The Pb-210 dating was carried out but difficult to make reliable chronology. In conclusion, the combination of sediment analysis and multivariate analysis provides a high-resolution pattern showing the occurrence and distribution of potential metal polutions in sediments of the Nankan River.

並列關鍵字

Riverine and estuary sediments ； Heavy metals ； Pollution ； Principal component analysis ； Cluster analysis ； Centred log-ratio transformation

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