Isotopic Signature and Impact of Car Catalysts on the Anthropogenic Osmium Budget

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• 作者：Andr&eacute ; Poirier and Cl&eacute ; ment Gari&eacute ; py
• 刊名：Environmental Science & Technology
• 出版年：2005
• 出版时间：June 15, 2005
• 年：2005
• 卷：39
• 期：12
• 页码：4431 - 4434
• 全文大小：107K
• 年卷期：v.39,no.12(June 15, 2005)
• ISSN：1520-5851

文摘

Higher osmium concentrations and lower ¹⁸⁷Os/¹⁸⁸Osratios in sediments from urban areas have been linked toanthropogenic osmium sources. Automobile catalyticconverters that use platinum group metals (PGM) are apotential source for this Os pollution. We present the firstdirect Os concentrations and isotopic measurements ofcatalytic converters for major automobile brands to test theassumption that car catalysts release Os with a distinctsignature in the environment. The analysis of four new catalyticconverters yields similar low ¹⁸⁷Os/¹⁸⁸Os ratios (0.1-0.2),suggesting a similar source for the PGM. The Osconcentrations measured are in the ppt range (6-228ppt). From our results, the osmium contribution of the carcatalysts to the environment through attrition (wearingand grinding down of the catalyst by friction) is predictedto be low, <0.2 pg Os/m²/year in highly urbanizedenvironment. We show that Os loss from catalysts asvolatile OsO₄ is important at car catalyst operatingtemperatures. Moreover, we estimate that car catalystsmay be responsible for up to ~120 pg Os/m² deposited peryear in urban areas and that part of it may be exportedto sedimentary sinks. Car catalytic converters are thus animportant anthropogenic osmium source in denselypopulated areas. The NIST car catalyst standard (SRM-2557, made from recycled used catalysts) yields higherconcentrations (up to 721 ppt Os) and a more radiogenicisotopic composition (~0.38), perhaps indicative of Oscontamination during its preparation.