跳到主要內容 :::

年度	100	專案性質	實驗性質
專案類別	研究專案	研究主題	調查
申請機構	國立台灣大學	申請系所	生物環境系統工程學系
專案主持人	張尊國	職等/職稱	教授
專案中文名稱	台灣地區油品之穩定性鉛同位素鑑定技術發展與應用
中文關鍵字	穩定性鉛同位素；汽油；環境鑑識
專案英文名稱
英文關鍵字	stable lead isotopes；gasoline；environmental forensics
執行金額
執行期間	2011/11/26 至 2012/11/25
計畫中文摘要	「環境鑑識（Environmental forensics）」定義為以系統性及科學性評估物理、 化學以及歷史信息等層面，目的為要針對污染物來源及排放至環境中之時序，展 現具有科學效力之法律認定。 鉛（lead, Pb）原子序為 82，原子量為 207.2 u，廣泛用於建築、鉛蓄電池、彈 藥、度量衡、合金冶煉等。流行病學研究顯示鉛會對人類神經系統造成危害，目 前國際癌症組織將無機鉛化合物列為疑似人類致癌物。 鉛具有四種穩定性同位素，包含：分別衰變自238U、235U、232Th的放射性成因 穩定性鉛同位素206Pb、207Pb、208Pb與非放射性成因之204Pb。將過長時期的研究和 發展，穩定性鉛同位素已於地質科學領域之中完善建構，近年來也開始廣受環境 科學應用。環境污染鑑識領域遭遇到的難題在於：單單就污染物質鉛濃度與熱區 （hotspot）的資訊，僅能協助瞭解污染規模並無法明確指向污染來源，而鉛同位 素特徵作為環境化學指紋將能協助克服之。國際間穩定性鉛同位素於含鉛油品污 染鑑定已行之有年，目的是為釐清油品環境污染事件的責任歸屬。 西元 1940 至 1980 年代，含鉛汽油的大量使用，導致全球性大規模的環境污 染。1970 開始提倡與落實禁止使用含鉛汽油添加劑。由於各地鉛礦具有相異之鉛 同位素特徵，因此，透過對汽油烷基鉛添加劑的鉛同位素瞭解，不僅能夠關鍵性 地鑑識汽油來源，更可辨識汽油燃燒後對環境所造成的影響。1980 年後，汽油含 鉛量大幅下降，今日無鉛汽油中所帶有的 ppb 等級鉛，係來自原油產地與精煉過 程中之微量添加。國際經驗亦告訴我們，由汽油的鉛同位素也可窺視當地之經濟 狀況，亦即，對鉛礦資源的仰賴度與掌握度。 由於設置高解析度儀器的昂貴成本與精細實驗技術的困難，在穩定性鉛同位 素鑑定議題上臺灣起步落後。本團隊於參與環保署委託「營運中含鉛製程事業之 土壤污染潛勢調查計畫」執行期間，已建立農地土壤與水稻植株之穩定性鉛同位 素分析技術，並成功鑑別土壤之污染源。結合離子交換樹酯分離純化與運用多頻 道感應耦合電漿質譜儀，建立了高精確度分析技術，且與國際各知名實驗室測量 結果一致，有信心將此研究案順利推行並得到顯著結果。臺灣地區自 1983 起開始將含鉛汽油之使用轉換至無鉛汽油，並於 2000 年起 停止含鉛汽油之供應，主要油品供應商為中油公司與台塑石化公司，現售無鉛汽 油中含鉛量低於 0.013 g L-1 。為協助釐清臺灣地區加油站或自用儲油系統是否有漏 油污染發生與增加污染來源鑑識之可行性，首要之務為建構一套適用於油品之穩 定性鉛同位素分析技術。唯有瞭解並掌握臺灣市售 92 無鉛汽油、95 無鉛汽油、98 無鉛汽油與柴油的鉛同位素組成特徵，方能夠為環境鑑識之研究與應用發展與油 品洩漏鑑識帶來新曙光。 研究結果發現，臺灣油品之鉛濃度為 5 ng g-1 至 50 ng g-1 之間。各鉛同位素比 值利用T檢定（T-test）分析數據得知，在不考慮油品類別之情況下，中油公司及台 塑公司兩種廠牌市售各油品的208Pb/206 Pb鉛同位素特徵具鑑別度（p < 0.001）。以油 類 銷售比例及 廠牌市佔率 加權，估算整體 油 品 各鉛同位素比 值，208Pb/207Pb、207Pb/206Pb分別為 2.4269、0.8710，與臺北地區氣膠之鉛同位素比 值特徵 2.4270、0.8720 極為相似，顯示臺北地區氣膠中鉛來源受地域性之油品影 響。
計畫英文摘要	“Environmental forensics” is defined as the systematic and scientific evaluation of physical, chemical and historical information for the purpose of developing defensible scientific and legal conclusions regarding the source or age of a contaminant release into the environment. Lead is a transitional element with symbol Pb (Latin: plumbum). Lead has the atomic number 82, the standard atomic mass is 207.2 u. Metallic lead does occur in nature. Lead compounds exist naturally in the earth’s crust, rocks and soil. Today, lead is used widely in many aspects, such as building construction, lead-acid batteries, bullets and shot, weights, and is part of solder, pewter, and fusible alloys. Unfortunately, lead poisoning has been actually linked to the fall of the Roman Empire. Several lines ofevidence demonstrate that both the central and peripheral nervous systems are principal targets for lead toxicity. The International Agency for Research on Cancer considered the overall evidence for the carcinogenicity of lead to human to be inadequate. Lead has four stable isotopes: 204Pb, 206Pb, 207Pb, and 208Pb. The last three are radiogenic isotopes and are produced by the radioactive decay of 238U, 235U, and 232Th, respectively (204Pb is non-radiogenic). Investigative studies of lead isotope compositions are well-established in geochemistry and geochronology and are increasingly used in environmental science. Knowing only the total concentrations and chemical/mineralogy position of lead is not sufficient for a precise evaluation of contamination sources. Lead isotopes have thus been introduced as “fingerprints” of environmental pollution. Each source of lead can have distinct or sometimes overlapping isotopic ratio ranges. Lead isotopic analyses proved to be a very efficient tool for tracing the sources of local and global lead pollution. Furthermore, stable lead isotope fingerprints of gasoline have been carried out to identify/determine sources of lead contamination in developed countries for a couple years. The former use of leaded gasoline had represented one of the main sources of global lead pollution in the period between the 1940s and the 1980s. Lead pollution has become a cause of major concern since the early 1970s, which led to the banning of lead additives in gasoline in the western world since the mid-1970s. The knowledge about the origin of gasoline, i.e. about the origin and age of lead ore used for alkyl-lead antiknock additives is vital for a precise identification of lead originating from leaded gasoline combustion. The isotopic composition of lead ores used thus reflects the composition of leaded gasoline. With the efforts to legislation that limits concentrations of lead in gasoline and the increased market penetration of unleaded gasoline, lead levels in gasolines have dropped significantly since the early 1980s; current part-per-billion levels are attributable to natural crude oil sources plus any minute amount of lead added during the refining process. The isotopic composition of gasoline was to some extent dependent on economical factors, such as the availability and price of lead ores and has evolved due to the different lead ores used. Due to the expensive set-up cost of the instruments and the high technology, there is no investigation or research on the lead isotope fingerprints in Taiwan before 2008. According to our former experiences from the project, “Soil pollution investing nearby the active factories with lead-containing processes,” authorized by Environmental Protection Administration (EPA), applying stable lead isotope ratios analysis to trace the possible sources of lead contamination in farmland soil is available. Moreover, we have built-up and improved the chemistry and instrumental methodology to approach a reliable procedure for subnanogram-quantity determination of lead isotopes ( 204Pb, 206Pb, 207Pb, and 208Pb) on multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS, Thermo Electron NEPTUNE), equipped with a high efficiency desolvation nebulization system, Cetac ARIDUS, housed at the Department of Geosciences, National Taiwan University. Chinese Petroleum Corporation, Taiwan (CPC) and Formosa Petrochemical Corporation (FPCC) are the major source of gasoline sold in Taiwan. Taiwanese government policy on phasing lead out of gasoline started from 1983; unleaded gasoline accounted for 100 percent of total local sales in 2000. The cord blood lead level was significantly decreased, with the averages of 7.48±2.25, 3.28±1.52, 2.35±1.12 and 1.39±0.06 μg/dL obtained from the surveys conducted in 1985-1987, 1990-1992, 2001-2002 and 2004-2005, respectively. Nowadays, 92 unleaded gasoline, 95 unleaded gasoline, 98 unleaded gasoline, and super diesel (CPC)/environmental protection diesel (FPCC) are the most common products. The lead content of the unleaded gasoline are below 0.013 g L-1 . More recently, in the unleaded gasoline era, the lead isotopic variations of gasolines inherited from their crude oil sources and subsequent processingmake it possible to fingerprint different manufacturers' products. In order to gain insight into lead pollution of gasoline leaks in Taiwan, the most essential steps is to establish the lead isotope analytical method suitable for the gasoline sold in Taiwan, and thus the preliminary, reliable database can be constructed. Only when the acquired isotopic data for gasoline of different brands are presented, the candidate contamination sources can be identified and environmental liability at contaminated sites can be unraveled with the help of this state-of-art technology. The lead concentrations in gasoline ranged from 5 ng g-1 to 50 ng g-1 . There is significant difference between two brands of gas products on its lead isotopic ratio, 208Pb/207Pb (p < 0.001). To estimate the lead isotope ratios of overall vehicle exhaust based on sales ratio and gas stations number, the recalculated lead isotope ratios, 208Pb/207Pb and 207Pb/206Pb, are 2.4269 and 0.8710, respectively. It’s very similar to that of aerosols in Taipei area, 2.4270 and 0.8720, respectively. Represent that the lead in Taipei area aerosols mainly from local gasoline combustion