Developing analytical tools for measuring and characterizing environmental nanomaterials
|關鍵字:||奈米微粒採樣及化學分析;奈米微粒質量平衡;微粒有效密度;奈米物質環境安全衛生;nanoparticle sampling and analysis;mass closure of nanoparticles;effective density of particles;EHS of nanomaterials|
|摘要:||由於環境奈米微粒附著大量的有機物質、鹽類及重金屬，學者研究發現環境奈米微粒對細胞的毒性比一般工程製造的奈米粉體還高，因此準確地採集環境奈米微粒並分析其化學成分以做為暴露及風險評估之用十分重要。然而目前國際上尚沒有任何一個研究團隊能準確的採集並分析奈米微粒。透過本研究，本團隊已能準確地採集不同環境的奈米微粒並得到很好的化學質量平衡(主要化學成分的總質量比上秤重得到的質量)，主要化學成分包括有機碳(OC)、元素碳(EC)、水溶性離子(Ions)及金屬元素(Element)。過去學者無法得到好的微粒質量平衡是由於沒有修正濾紙吸附氣態有機碳所造成微粒有機碳(POC, particle organic carbon)濃度的高估，本研究則提出了一個使用QBQ (quartz behind quartz) +QBH (quartz behind HEPA)以修正POC的方法。研究結果已發表兩篇論文於Atmospheric Environment及Aerosol Science and Technology。本研究延續過去之成果，在一般民眾、駕駛乘客、遊客及作業勞工或工廠附近居民容易長時間暴露奈米微粒的地方如路旁、隧道、森林及粉體廠等，探究人體暴露奈米微粒的濃度，也於汽、柴油車及機車動力檢測中心及柴油車排煙檢測站進行車輛排放奈米微粒的測量。
在具國際水平的研究方面，我們領先使用VOC denuder於奈米微粒的採樣，將VOC denuder加裝於MOUDI (microorifice uniform deposit impactor)上游來移除氣態有機物，結果顯示此Denuder可大幅減低石英濾紙吸附VOC情形，預期PAHs及水溶性有機酸等較微量的有害物質的濃度將來亦可準確的量測出來。我們也設計並製造更平滑的MOUDI噴嘴，來減低微粒在噴嘴中的損失及避免因噴嘴阻塞造成採樣結果的錯誤，此設計目前也正在申請專利中。最後我們也設計了一濕度控制裝置來改變微粒進入MOUDI或其它採樣器的相對溼度，可徹底解決微粒在慣性衝擊器中彈跳的問題，增加奈米微粒採集的正確性。前些研究都至極具國際競爭力。
本研究團隊於前兩年的研究計畫中已針對環境中奈米物質未來暴露評估與風險評估可能的知識缺口進行文獻收集及整理，並列出部份主題的國內研究現況及缺口，且舉行了國內專家座談會，作了具體的結論及建議。根據這兩年的研究報告，及目前在ICON資料庫、Environmental Science and Technology及Nano Letters期刊收集的2008-2009年的文獻，本年度再進一步回顧以下十個相當重要的議題：奈米物質的毒性評估、美國及歐盟對奈米物質的管制近況、奈米物質對水生物及環境生態的影響、奈米物質的風險評估、奈米物質的皮膚穿透、奈米物質的生命週期評估、奈米物質的暴露評估、奈米物質的暴露評估、奈米物質的暴露控制分組方法、奈米物質環境暴露控制與管理對策及奈米物質量測分析與暴露評估技術，撰寫成國內奈米微粒暴露及風險評估缺口報告，分析國內研究能量，並提出行政面、法規面及技術面的具體建議。
By comparing the cellular toxicity, researchers found that environmental nanoparticles are more toxic than manufactured nanoparticles due to bounded organic compounds, inorganic salts as well as trace metals on the particles. Therefore, it is important to measure the concentration of environmental nanoparticles and quantify its chemical compositions accurately for the study of nanoparticle exposure and nanotoxicology. However, there hasn’t been any research team who is able to sample and analyze all chemical species of nanoparticles accurately. As the results of this study, we demonstrated that the samples of nanoparticles could be collected accurately and good chemical mass closure (CMC) could be obtained. The analyzed chemical species include OC (organic carbon), EC (elemental carbon), water-soluble ions and elements. Good CMC was not achieved by previous researches due to VOC adsorption by the sampling filter leading to positive artifact of particle OC. This study proposed a method based on the QBQ (quartz behind quartz) + QBH (quartz behind HEPA) to correct for the positive particle OC artifact. The research results were published in two journal papers in Atmospheric Environment and Aerosol Science and Technology, respectively. This year, we continued to conduct the samplings at the locations where city residents, students, drivers, tourists as well as workers are likely to expose to nanoparticles. In addition, the nanoparticle study was conducted at the dilution tunnel of a dynamometer and at an inspection station of diesel vehicles. In the aspect of developing world-class tools for measuring and characterizing nanomaterials, this study takes the lead in using the VOC denuder for nanoparticle sampling. The denuder was installed at the inlet of the MOUDI (micro-orifice uniform deposit impactor) to remove the gaseous VOCs. Test results showed that the denuder could reduce the adsorption of VOCs on the quartz filter effectively. It is foreseeable that the PAHs and trace organics could be quantified accurately in the future. We also made new micro-orifices for impactor nozzles which have smoother shapes than those of the MOUDI to reduce particle loss in the nozzles and prevent particles from clogging the nozzles. A patent application was filed for this invention. In addition, this study setup a humidify control system to reduce particle bounce in the MOUDI for increasing the accuracy of nanoparticle collection. These new researches are very competitive in the world. In the past two years, this study has reviewed the latest literature and written reports to bridge the domestic knowledge gaps on exposure and risk assessments of nanomaterials. Workshops on these topics were also held, where research capacity and knowledge gaps in our country were pointed out and suggestions for government were made. Based on the reports and latest literature in the ICON website, Environmental Science and Technology and Nano Letter journals from 2008-2009, we further reviewed the following ten topics including “toxicity assessment of nanomaterials”, “Current control strategy of nanomaterials in USA and EU”, “Influence of nanomaterials on ecology and organisms in water”, “Risk assessment of nanomaterials”, “dermal penetration of nanomaterials”, “Life cycle assessment of nanomaterials”, “control banding of nanomaterial exposure”, “strategy of nanomaterial exposure control” and “nanomaterials measurement and exposure assessment in the environment”. The report of the domestic knowledge gaps in exposure and risk assessment were written, the domestic research capacity was analyzed and finally the recommendations in the aspects of administration, regulation and technology development were made.
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