Use of U-isotope disequilibrium to evaluate the weathering rate and fertilizer-derived uranium in São Paulo state, Brazil

• Published in: Environmental earth sciences Vol. 44; no. 4; pp. 408 - 418
• Main Authors: CONCEICAO, F. T, BONOTTO, D. M
• Format: Journal Article
• Language: English
• Published: Berlin Springer 01.07.2003; Springer Nature B.V
• Subjects: Anthropogenic factors; Climatic conditions; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Fertilizers; Geochemistry; Isotopes; Mineralogy; Pollution, environment geology; River basins; Rivers; Rocks; Silicates; Soil and rock geochemistry; Sugarcane; Uranium; Water geochemistry; Weathering; Brazil; Sao Paulo Brazil; South America; impact statements; rivers; fertilizers; river discharge; Weathering rate; Phosphate and anthropogenic influences; weathering; concentration; rain water; human activity; sandstone; U-238/U-234; erosion rates; sedimentary rocks; drainage basins; claystone; hydrochemistry; dendrograms; phosphates; Brazil; dissolved materials; uranium; clastic rocks
• ISSN: 0943-0105; 1866-6280; 1432-0495; 1866-6299
• DOI: 10.1007/s00254-003-0775-4

The U-disequilibrium method was utilized to evaluate the velocity of alteration of rocks and fertilizer-derived uranium in the Corumbataí River basin, São Paulo state, Brazil. The Corumbataí River basin is affected by the continuous use of fertilizer-derived uranium utilized in sugar cane crops, increasing the dissolved uranium concentration in the Corumbataí River (Santa Terezinha station) in the wet period to 43%. The weathering rate in the Corumbataí River basin utilizing the U-isotope modeling was 0.0265 mm/year (corresponding to 38,000 years to weather 1 m of rock under actual climatic conditions). However, when the inputs of anthropogenic uranium were considered, then a weathering rate of 0.022 mm/year (corresponding to 45,500 years to weather 1 m of rock) was determined. The removed material in the Corumbataí River basin is mainly from two sub-basins (the Cabeças River and Passa Cinco River), where the sandstones weather easier than the siltstones and claystones in the basin.[PUBLICATION ABSTRACT]