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Control of Pa/Th ratio by particulate chemical composition in the ocean
Author(s) -
Guo Laodong,
Chen Min,
Gueguen Celine
Publication year - 2002
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2002gl015666
Subject(s) - fractionation , particulates , chemical composition , carbonate , chemical fractionation , environmental chemistry , chemical oceanography , mineralogy , chemistry , analytical chemistry (journal) , geology , chromatography , organic chemistry , paleontology , microorganism , microbial biodegradation , bacteria
Controlled laboratory experiments were carried out using pure sorbents to examine the interactions of 234 Th (or 233 Pa) with particle surfaces and whether there is a fractionation between 234 Th and 233 Pa by particulate chemical composition. Our results show that the adsorption of 233 Pa and 234 Th on particle surfaces is highly selective and compound specific, resulting in a fractionation of 233 Pa/ 234 Th ratio, especially on SiO 2 (K d ratio, K d‐233Pa /K d‐234Th , = 10) and CaCO 3 (K d ratio, K d‐233Pa /K d‐234Th , = 0.01) surfaces. These new results agree well with previously published field observations that showed an increase of 231 Pa/ 230 Th ratio (or K d of 231 Pa) with increasing opal abundance and decreasing carbonate content in oceanic particles. In addition, they highlight the complications of using 231 Pa/ 230 Th ratio as a proxy and have implications for both oceanography and trace element geochemistry although more studies are needed to further examine the influence of natural organic matter on the fractionation of Th/Pa ratios.