Localized Metal Solubilization in the Rhizosphere of Salix smithiana upon Sulfur Application

A metal-accumulating willow was grown under greenhouse conditions on a Zn/Cd-polluted soil to investigate the effects of sulfur (S0) application on metal solubility and plant uptake. Soil porewater samples were analyzed 8 times during 61 days of growth, while DGT-measured metal flux and O2 were chem...

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Bibliographic Details
Published in:Environmental science & technology 2015-04, Vol.49 (7), p.4522-4529
Main Authors: Hoefer, Christoph, Santner, Jakob, Puschenreiter, Markus, Wenzel, Walter W
Format: Article
Language:English
Subjects:
Bioaccumulation
Biodegradation, Environmental
Hydrogen-Ion Concentration
Leaching
Mass Spectrometry
Metals
Metals - metabolism
Oxidation
Oxygen - metabolism
Rhizosphere
Salix - metabolism
Salix smithiana
Soil - chemistry
Soil Pollutants - metabolism
Soils
Solubility
Sulfates - metabolism
Sulfur
Sulfur - metabolism
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Summary:A metal-accumulating willow was grown under greenhouse conditions on a Zn/Cd-polluted soil to investigate the effects of sulfur (S0) application on metal solubility and plant uptake. Soil porewater samples were analyzed 8 times during 61 days of growth, while DGT-measured metal flux and O2 were chemically mapped at selected times. Sulfur oxidation resulted in soil acidification and related mobilization of Mn, Zn, and Cd, more pronounced in the rooted compared to bulk soil. Chemical imaging revealed increased DGT-measured Zn and Cd flux at the root-soil interface. Our findings indicated sustained microbial S0 oxidation and associated metal mobilization close to root surfaces. The localized depletion of O2 along single roots upon S0 addition indicated the contribution of reductive Mn (oxy)­hydoxide dissolution with Mn eventually becoming a terminal electron acceptor after depletion of O2 and NO3 –. The S0 treatments increased the foliar metal concentrations (mg kg–1 dwt) up to 10-fold for Mn, (5810 ± 593), 3.3-fold for Zn (3850 ± 87.0), and 1.7-fold for Cd (36.9 ± 3.35), but had no significant influence on biomass production. Lower metal solubilization in the bulk soils should translate into reduced leaching, offering opportunities for using S0 as environmentally favorable amendment for phytoextraction of metal-polluted soils.
ISSN:0013-936X
1520-5851
DOI:10.1021/es505758j