北投溫泉地區磺港溪底泥中重金屬砷鉛濃度分佈之探討

Distribution of Arsenic and Lead in the Sediments in Hot Spring Area of Huang Gang Creek, Beitou

陳威智(Wei-Chin Chen)

指導教授 ： 張尊國

國立臺灣大學/生物資源暨農學院/生物環境系統工程學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.01021

摘要

2006年11月台大生態工程研究中心於北投關渡平原發現面積達百餘公頃農地土壤砷含量異常的現象，並認為其砷來源肇因於地熱谷含砷之溫泉水隨灌溉系統擴散於農田，並同時於北投溪(磺港溪的支流)河岸與河床中首次在台灣發現含有砷鉛鐵礬礦物。本研究目的為探討磺港溪底泥不同粒徑中的砷、鉛濃度之分佈關係。本研究方法係將磺港溪(地熱谷-磺港溪下游)的河川底泥通過五種不同尺寸的篩號，分別為16號(1.19 mm)、20號(0.84 mm)、100號(0.15 mm)、200號(0.075 mm)、300號(0.05 mm)，利用X射線螢光分析儀(XRF)檢測河川底泥重金屬(砷、鉛)含量。研究結果發現磺港溪底泥中的砷、鉛濃度皆會隨著顆粒細粒化而明顯地增加。河川底泥粒徑介於0.84-1.19 mm之平均砷濃度為229 (中位數136) mg kg-1，平均鉛濃度為182 (中位數119) mg kg-1；粒徑小於0.05 mm之平均砷濃度增加至790 (中位數601) mg kg-1，平均鉛濃度則上升至807 (中位數636) mg kg-1。由本研究結果得知底泥中砷濃度大於鉛濃度，兩者重量比(砷/鉛)介於1.29~1.40之間，莫耳數比(砷/鉛)介於3.58~3.88之間，與砷鉛鐵礬理想化學式之莫耳數比(砷/鉛) (1：1)有很大的差異。同時比較粒徑小於0.05 mm的農田土壤與河川底泥中的砷濃度，結果顯示農田土壤最高砷濃度值為444 mg kg-1仍低於河川底泥之平均砷濃度，因此本研究認為北投地區的農田砷汙染由底泥顆粒帶入所造成的機率極低

關鍵字

砷 ； 鉛 ； 底泥 ； 粒徑 ； 溫泉

並列摘要

Over 100 hectare paddy soils were found heavily polluted by arsenic through long-term irrigation with the water mixed with hot spring, in 2006 at Beitou, Taiwan. Moreover, in Taiwan it is the first time the beudantite was found on the bank and streambed of a nearby Huang Gang creek. The objective of this study is to investigate the distribution of arsenic and lead concentrations in the sediments of Huang Gang creek. 49 samples were collected along the creek about 4.6 km long. All samples were sieved to fine-grained fractions: 1.19-0.84 mm, 0.84-0.15 mm, 0.15-0.075 mm, 0.075-0.05 mm and<0.05 mm, prior to analysis. The results show that finer grained sediment samples tend to have higher concentrations of As and Pb. Samples were sieved to 1.19-0.84 mm had the mean concentrations of As and Pb 229 (with median 136) mg kg-1, and 182 (with median 119) mg kg-1 respectively; while the samples sieved to 0.05 mm had the mean concentrations of As and Pb 790 (601) mg kg-1, and 807 (636) mg kg-1. In general, the concentration of arsenic is higher than that of lead in all sediment samples, and the ratio is in the range between 1.29-1.4; the molar ratio is between 3.58-3.88. It is apparently different from the molar ratio (ratio=1) of beaudantite. The samples from paddy soils and stream sediments with the same particle size, <0.05mm, are compared with the As and Pb content, and it shows that the difference is marked. Therefore, the major cause of the As and Pb pollution of paddy soils seems to be not from sediments

並列關鍵字

Arsenic ； lead ； sediment ； particle-size ； hot spring

參考文獻

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