Characterizing Pb Mobilization from Upland Soils to Streams Using 206Pb/207Pb Isotopic Ratios

Julian James Charles Dawson, Doerthe Tetzlaff, Anne-Marie Carey, Andrea Raab, Christopher Soulsby, Kenneth Stuart Killham, Andrew Alexander Meharg

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

Anthropogenically deposited lead (Pb) binds efficiently to soil organic matter, which can be mobilized through hydrologically mediated mechanisms, with implications for ecological and potable quality of receiving waters. Lead isotopic (Pb-206/Pb-207) ratios change down peat profiles as a consequence of long-term temporal variation in depositional sources each with, distinctive isotopic signatures. This study characterizes differential Pb transport mechanisms from deposition to streams at two small catchments with contrasting soil types in upland Wales, U.K., by determining Pb concentrations and Pb-206/Pb-207 ratios from soil core profiles, interstitial pore waters, and stream water. Hydrological characteristics of soils are instrumental in determining the location in soil profiles of exported Pb and hence concentration and Pb-206/Pb-207 ratios in surface waters. The highest Pb concentrations from near-surface soils are mobilized, concomitant with high dissolved organic carbon (DOC) exports from hydrologically responsive peat soils with, preferential shallow subsurface flows, leading to increased Pb concentrations in stream water and isotopic signatures more closely resembling recently deposited Pb. In more minerogenic soils, percolation of water allows Pb, bound to DOC, to be retained in mineral horizons and combined with other groundwater sources, resulting in Pb being transported from throughout the profile with a more geogenic isotopic signature. This study shows that Pb-206/Pb-207 ratios can enhance our understanding of the provenances and transport mechanisms of Pb and potentially organic matter within upland soils.

Original languageEnglish
Pages (from-to)243-249
Number of pages7
JournalEnvironmental Science & Technology
Volume44
Issue number1
Early online date2 Dec 2009
DOIs
Publication statusPublished - 1 Jan 2010

Keywords

  • DISSOLVED ORGANIC-CARBON
  • HEAVY-METALS
  • MESOSCALE CATCHMENT
  • CONTAMINATED SOILS
  • LEAD CONTAMINATION
  • RUNOFF PROCESSES
  • RESIDENCE TIMES
  • PEAT CATCHMENT
  • NE SCOTLAND
  • UK

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