| 摘要: | 北港溪、朴子溪及急水溪下游河段為雲嘉地區受汙染較嚴重的河川。本研究針對採樣自三條河川不同深度泥樣,利用連續萃取法(Sequential extraction procedure)進行分析,推求鎳(Ni)、鉻(Cr)、銅(Cu)、鋅(Zn)、鈷(Co)及鉛(Pb),在各深度泥樣中與五種鍵結型態(可交換態、碳酸鹽鍵結態、錳氧化物鍵結態、鐵氧化物鍵結態及有機物鍵結態)的分布。了解重金屬在泥樣中鍵結量與泥值原始化學組成分之相關性及蓄積的時空變化。存在五種鍵結型態的重金屬總量稱為總可萃取量(TEHMs)。另針對北港溪、朴子溪混合底泥重金屬進行化學可利用性(Chemical availability)試驗,了解重金屬在河川底泥中受主要環境因子---氧化還原電位(ORP)影響而被釋出或轉換化學鍵結型態的程度。 結果顯示,各種重金屬在三條河川泥樣之五種鍵結型態分布皆非常相似。Zn主要和有機物、鐵氧化物及碳酸鹽鍵結,隨著底泥中Zn汙染量增加,與碳酸鹽鍵結百分比增加。80%的TEHMCu和有機物鍵結。Co在底泥中含量最低(8.2mg/kg)濃度也沒有隨著底泥沈積時間而變化,表示流域中沒有Co汙染源。Cr與有機物及與鐵氧化物鍵結量約佔總可萃取重金屬量的95%。Ni主要和有機物鍵結(約52-68%),次為與鐵氧化物與碳酸鹽鍵結。將底泥pH固定(pH7.0),改變底泥ORP值(-288,+316mV),Cu、Ni、Co、Pb、Zn之總可萃取重金屬量變化不大,在各種鍵結態間也沒有明顯互相轉移的現象。
Lower sections of Peikang, Potzu, and Chishui rivers, locate in area of Yunliu and Chiayi, have been heavily polluted. This study aims to investigate the binding fractions of Nickel (Ni), Chromium (Cr), Copper (Cu), Zinc (Zn), Cobalt (Co), and Lead (Pb) in different sediment depth of the three rivers. The binding fractions include exchangeable, bound to carbonates, bound to Mn oxides, bound to Fe oxides and bound to organic matters. The sum of heavy metals exist in five binding fractions defines as TEHMs. Sequential extraction procedure (SEP) was used to study both binding and transformation behaviors of heavy metals in sediments. Results show that the percentages of heavy metals in five binding fractions were similar in sediments of three rivers. Zn was primarily bound to organic matters, Fe oxides, and Carbonates. The percentage of Zn bound to carbonates increased with TEHMZn in the sediment. 80% of TEHMCu was bound to organic matters. The content of Co was lowest (8.2mg/kg) in the sediment and didn't change with the sediment depth. This meant that no Co pollution sources existed in the basin. The percentage of Cr bound to organic and Fe oxides fractions was about 95% of TEHMCr. The batch chemical availability tests of heavy metals under different ORP values were carried out for contaminated sediments of Potzu and Peikang rivers. Those showed that the increase of ORP did not significantly change the binding fractions of heavy metals (Ni, Cu, Zn, Co and Pb) in river sediments when ORP increased from -288mV to 275mV at Potzu river sediments or from 3mV to 316mV at Peikang river sediments. |
