Document Type


Publication Date


Publication Title

Proceedings of the National Academy of Sciences of the United States of America


Department of Earth Sciences


Osmium is one of the rarer elements in seawater, with typical concentration of approximately 10 x 10(-15) g g(-1) (5.3 x 10(-14) mol kg(-1)). The osmium isotope composition ((187)Os/(188)Os ratio) of deep oceans is 1.05, reflecting a balance between inputs from continental crust (approximately 1.3) and mantle/cosmic dust (approximately 0.13). Here, we show that the (187)Os/(188)Os ratios measured in rain and snow collected around the world range from 0.16 to 0.48, much lower than expected (>1), but similar to the isotope composition of ores (approximately 0.2) that are processed to extract platinum and other metals to be used primarily in automobile catalytic converters. Present-day surface seawater has a lower (187)Os/(188)Os ratio (approximately 0.95) than deep waters, suggesting that human activities have altered the isotope composition of the world's oceans and impacted the global geochemical cycle of osmium. The contamination of the surface ocean is particularly remarkable given that osmium has few industrial uses. The pollution may increase with growing demand for platinum-based catalysts.



Original Citation

Chen C, Sedwick PN, Sharma M. Anthropogenic osmium in rain and snow reveals global-scale atmospheric contamination. Proc Natl Acad Sci U S A. 2009 May 12;106(19):7724-8. doi: 10.1073/pnas.0811803106. Epub 2009 Apr 24. PMID: 19416862; PMCID: PMC2683094.