PII S0016-7037(00)00610-X Transport of U- and Th-series nuclides in a Baltic Shield watershed and the Baltic Sea

• Main Authors: D. Porcelli, P. S. Andersson, M. Baskaran, G. J. Wasserburg
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 1999
• Subjects: Arctic; Kalix
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.569.6288; http://www.clas.wayne.edu/multimedia/usercontent/File/Geology/instructors/baskaran/publications/60-GCA-2001-Porcelli etal.pdf

Abstract—The transport of Th, Ra, and 210Pb from a continental source region and through an estuarine environment was investigated. Unlike previous studies, here both short- and long-lived nuclide data were obtained for river inputs, river water, and estuarine waters. The mire-rich Kalix River drainage basin was chosen as a typical northern shield area because this river may represent typical waters flowing into the Arctic and northern seas. Groundwaters from bedrock and glacial tills have comparable Th isotope concentrations and do not exhibit significant Th isotopic shifts relative to host rocks. The extensive peat deposits of the basin receive groundwater discharges and concentrate Th and U (but not Ba and Ra), which cause high 230Th/232Th ratios in mire waters. However, mire outflows do not have a significant impact on Th and Ra isotopic compositions of the river. Overall weathering characteristics for the basin are obtained from the river data. The 230Th/232Th, 228Ra/226Ra, and 226Ra/Ba river ratios are comparable to those of source rocks, consistent with similar release rates of these nuclides from U-, Th-, and Ba-bearing minerals. River ratios of (230Th/238U)AR and (226Ra/ 238U)AR are,1, so that Th and possibly Ra are accumulating in the weathering regions, and the weathering profile is still evolving. Low (228Ra/232Th)AR and (226Ra/230Th)AR ratios indicate that Th is preferentially