Spatial Distribution of Natural Enrichments of Arsenic, Selenium, and Uranium in a Minerotrophic Peatland, Gola di Lago, Canton Ticino, Switzerland

Gola di Lago is a small (ca. 3 ha), minerotrophic peatland in Canton Ticino, southern Switzerland. Chemical analyses of peat show remarkable concentrations of As, Se, and U. Coring at regular intervals (19 sites) revealed several zones of pronounced accumulation, with As concentrations up to 350 mg kg-1 (2000 mg kg-1 on a mineral matter basis). Both Fe and S are also enriched at this depth, suggesting that redox-related transformations have affected all three elements. High concentrations of Se (up to 28 mg kg-1) and U (up to 470 mg kg-1) were also detected, representing on a mineral matter basis 350 and 2900 mg kg-1, respectively. An intermittent stream entering the peatland contained up to 400 μg of As L-1, but the permanent stream leaving the mire contains