Root-Induced Cycling of Lead in Salt Marsh Sediments
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- 作者：Bj
//pubs.acs.org/images/gifchars/oslash.gif" border="0">rn Sundby ; Miguel Caetano ; Carlos Vale ; Charles Gobeil ; George W. Luther ; III ; and Donald B. Nuzzio
- 刊名：Environmental Science & Technology
- 出版年：2005
- 出版时间：April 1, 2005
- 年：2005
- 卷：39
- 期：7
- 页码：2080 - 2086
- 全文大小：249K
- 年卷期：v.39,no.7(April 1, 2005)
- ISSN：1520-5851
文摘
A gold-mercury amalgam microelectrode was used insitu to measure Pb(II) by anodic stripping voltammetryand O2, Fe(II), Mn(II), and HS- by square-wave voltammetryin sediment pore water in a Haliomione portulacoidesstand in a Tagus estuary salt marsh. The measurementswere made in spring, summer, and fall, and were supplementedwith analysis of Pb in solid phases and stable isotopeanalysis of Pb. In spring, the pore water was anoxic,Fe(II) reached concentrations as high as 1700 
mol/L, andPb(II) was undetectable (<0.1 mol/L). However, insummer, the pore water was oxic, Fe(II) was undetectable,and Pb(II) was present throughout the 20 cm deep rootzone in concentrations reaching 6 mol/L. In fall, low levelsof O2 and Pb(II) were detected in the upper half of theroot zone, and low concentrations of Fe(II) were detectedin the lower half. The annual cycle of Pb is controlledby the growth and decay of roots. Roots deliver oxygen,which oxidizes lead-bearing solid phases and releasesPb(II) to the sediment pore water. Iron oxides, which formin the rhizosphere when Fe(II) is oxidized, are apparentlynot efficient sorbents for Pb(II) under the organic-richconditions in this sediment. This allows Pb(II) to remainsoluble and available for uptake by the roots. In fall andwinter, when roots decay and the oxygen flux to the sedimentstops, Pb is released from the decaying roots andreturned to and precipitated in the anoxic sediment, likelyas a sulfide. On an annual basis more than 20% of thetotal mass of Pb in the root zone cycles between root tissueand inorganic sediment phases. Depending on location,anthropogenic Pb constitutes 30-90% of total Pb in TagusEstuary salt marshes.
mol/L, andPb(II) was undetectable (<0.1 mol/L). However, insummer, the pore water was oxic, Fe(II) was undetectable,and Pb(II) was present throughout the 20 cm deep rootzone in concentrations reaching 6 mol/L. In fall, low levelsof O2 and Pb(II) were detected in the upper half of theroot zone, and low concentrations of Fe(II) were detectedin the lower half. The annual cycle of Pb is controlledby the growth and decay of roots. Roots deliver oxygen,which oxidizes lead-bearing solid phases and releasesPb(II) to the sediment pore water. Iron oxides, which formin the rhizosphere when Fe(II) is oxidized, are apparentlynot efficient sorbents for Pb(II) under the organic-richconditions in this sediment. This allows Pb(II) to remainsoluble and available for uptake by the roots. In fall andwinter, when roots decay and the oxygen flux to the sedimentstops, Pb is released from the decaying roots andreturned to and precipitated in the anoxic sediment, likelyas a sulfide. On an annual basis more than 20% of thetotal mass of Pb in the root zone cycles between root tissueand inorganic sediment phases. Depending on location,anthropogenic Pb constitutes 30-90% of total Pb in TagusEstuary salt marshes.