Osmium Isotopes Demonstrate Distal Transport of Contaminated Sediments in Chesapeake Bay

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• 作者：George R. Helz ; Jordan M. Adelson ; Cherie V. Miller ; Jeffrey C. Cornwell ; James M. Hill ; Mary Horan ; and Richard J. Walker
• 刊名：Environmental Science & Technology
• 出版年：2000
• 出版时间：June 15, 2000
• 年：2000
• 卷：34
• 期：12
• 页码：2528 - 2534
• 全文大小：117K
• 年卷期：v.34,no.12(June 15, 2000)
• ISSN：1520-5851

文摘

Because the isotopic composition of anthropogenic Os isnormally distinctive in comparison to continental crustand is precisely measurable, this platinum-group elementis attractive as a tracer of transport pathways forcontaminated sediments in estuaries. Evidence herein andelsewhere suggest that biomedical research institutionsare the chief source of anthropogenic Os. In the ChesapeakeBay region, uncontaminated sediments bear a crustal ¹⁸⁷Os/¹⁸⁸Os signature of 0.73 ± 0.10. Slightly higher ¹⁸⁷Os/¹⁸⁸Osratios occur in Re-rich Coastal Plain deposits due to post-Miocene ¹⁸⁷Re decay. The upper Susquehanna Basinyields sediments also with higher ¹⁸⁷Os/¹⁸⁸Os. Beginning inthe late 1970s, this signal was overprinted by a low ¹⁸⁷Os/¹⁸⁸Os (anthropogenic) source in the lower Susquehanna Basin.In the vicinity of Baltimore, which is a major center ofheavy industry as well as biomedical research, anthropogenicOs has been found only in sediments impacted by theprincipal wastewater treatment plant. Surprisingly, a mid-Bay site distant from anthropogenic sources containsthe strongest anthropogenic Os signal in the data set, havingreceived anthropogenic Os sporadically since the mid-20th Century. Transport of particles to this site overrodethe northward flowing bottom currents. Finding anthropogenicOs at this site cautions that other particle-borne substances,including hazardous ones, could be dispersed broadlyin this estuary.