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

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• 作者：Zayre I. Gonzá ; lez A. ; Michael Krachler ; Andriy K. Cheburkin ; William Shotyk
• 刊名：Environmental Science & Technology
• 出版年：2006
• 出版时间：November 1, 2006
• 年：2006
• 卷：40
• 期：21
• 页码：6568 - 6574
• 全文大小：366K
• 年卷期：v.40,no.21(November 1, 2006)
• ISSN：1520-5851

文摘

Gola di Lago is a small (ca. 3 ha), minerotrophic peatlandin Canton Ticino, southern Switzerland. Chemical analysesof peat show remarkable concentrations of As, Se, and U.Coring at regular intervals (19 sites) revealed severalzones of pronounced accumulation, with As concentrationsup to 350 mg kg^-1 (2000 mg kg^-1 on a mineral matterbasis). Both Fe and S are also enriched at this depth,suggesting that redox-related transformations have affectedall three elements. High concentrations of Se (up to 28mg 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 peatlandcontained up to 400 g of As L^-1, but the permanentstream leaving the mire contains <2 g L^-1. A three-dimensional map of the spatial distribution of As showsthat the main source of As is the intermittent stream andnot the basal, mineral sediment underlying the peatland.Arsenic is highly enriched not only in shallow peat layersat the interface between the stream and peatland todaybut also in deeper peat layers in the center of the mire, atwhat must have been the stream-peat interface in thepast. By sequential extraction of fresh peat samples, 100%of the As could be extracted from a shallow sample butonly 19% from a sample taken from the deeper layers. In bothcases, most of the As was associated with the organicmatter fraction (73% and 57% respectively). Although thispeatland is an effective geochemical trap for As in thestream waters, the mechanisms of removal remain unclear.