| ^210Pb chronology and trace metal geochemistry at Los Tuxtlas, Mexico, as evidenced by a sedimentary record from the Lago Verde crater lake |
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| 摘 要： | Lago Verde is a fresh water maar found in the San Martin volcano, at the Sierra of Los Tuxtlas, Mexico, currently the northernmost remnant of the tropical rain forest in America. A sediment core from Lago Verde was analyzed for ^210Pb and ^137Cs in order to assess the evolution of the accretion rates in the lake and to reconstruct the historical fluxes of heavy metals （Ag, Cd, Cu, Pb, Hg and Zn） to the site during the last -140 years. C/N ^13C were used to evaluate the provenance of the organic atomic ratios and matter accumulated in the sediments. Modem sediments from Lago Verde were found enriched in Pb （26-fold natural concentration level, NCL＇s） and moderately enriched in Cd〉Cu〉Zn and Hg （6, 5, 4 and 4 fold corresponding NCL＇s）. The excess fluxes of Cu, Hg, Pb and Zn have importantly increased during the last 60 years, with peak ratios of total modem to preindustrial fluxes （FR） of 11, 11, 19 and 49, respectively. The lake occupies a relatively pristine, non-industrialized basin, surrounded mostly by pasture lands and sugar cane fields; therefore the increased metal fluxes recorded in the sediment core are most likely related to the enhanced rate of erosion within the watershed, promoted by changes in land use and the irrational deforestation of the tropical rain forest, which have occurred during the past.
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| 关 键 词： | 地质年代学 火山 湖泊 沉淀物 热带雨林 |
^210Pb chronology and trace metal geochemistry at Los Tuxtlas, Mexico, as evidenced by a sedimentary record from the Lago Verde crater lake |
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| Abstract: | |
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| Keywords: | ^210Pb geochronology ^137Cs crater lake sediment Los Tuxtlas tropical rain forest trace metal fluxes |
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