Speciation of Pb-210/Po-210 in aquatic systems and their deposits

• Published in: Science of the total environment 1988, Vol.69, p.191-209
• Main Authors: El-Daoushy, Farid, Garcia-Tenorio, Rafael
• Format: Article
• Language: English
• Subjects: Applied sciences; Brackish; Continental surface waters; Exact sciences and technology; Freshwater; Marine; Natural water pollution; Pollution; Water treatment and pollution
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/0048-9697(88)90343-9

Lead-210 speciation was carried out on previously examined aquatic deposits of known ages and geochemical histories. The main separated fractions were fulvic, humic, humin and mineral-bonded humics. these organic components were wet-oxidized and their 210Po was extracted by coprecipitation with Fe 3+, distillation at 450°C and self-deposition on silver-discs. The 210Po activities were determined by isotope dilution and alpha spectrometry techniques. Nineteen samples from three lakes and one ombrotrophic peat-hummock in southern Sweden; and three fjords of Skagerrak, North Sea, were investigated. Humic materials proved to trap and preserve aquatic unsupported 210Pb, especially in lakes and peats. Fulvic compounds, on the other hand, seem to enhance the mobility of unsupported 210Pb particularly under acidic conditions. However, the fulvic fraction of marine sediments showed higher amounts of unsupported 210Pb. Our results show that the supported 210Pb is incorporated with the organo-mineral complexes, the NaOH-insoluble fraction. The 210Pb activity of this fraction was found to converge to the expected supported 210Pb of sediment samples older than 100 years or so. Some younger sediments may also show the last mentioned observation. This might serve as an alternative for evaluating the supported 210Pb in 210Pb dating.