Accumulation of arsenic and zinc in the rhizosphere of wetland plants

• DOI: 10.1007/bf00212403
• Publication Date: 2004-09-30T10:36:35Z
• Authors: M. L. Otte; C. C. Kearns; M. O. Doyle
• Keywords: Analysis of Variance; Iron; Pilot Projects; 15. Life on land; Plant Roots; 01 natural sciences; 6. Clean water; Arsenic; Soil; Zinc; Oxidation-Reduction; Soil Microbiology; Rhizobium; 0105 earth and related environmental sciences

Oxidation of the rhizosphere by wetland plants leads to precipitation of iron oxyhydroxides (ironplaque) in the rhizosphere and on the root surface of the plants. Arsenic and zinc have a high binding affinity for iron oxyhydroxides and were found to accumulate in ironplaque on roots of Aster tripolium L. It was argued that rhizosphere oxidation and formation of an ironplaque would favor the accumulation of iron, arsenic and zinc in the rhizosphere. Oxidation of ferrous iron to its ferric form would lead to precipitation of iron oxyhydroxides in the rhizosphere, which in turn would lead to a decreasing concentration gradient of dissolved iron towards the plant roots. The iron oxyhydroxides in turn would bind arsenic and zinc, again creating a decreasing concentration gradient of both elements towards the roots. These gradients would lead to the diffusion of iron, arsenic and zinc in the direction of the roots. Assuming that uptake of the elements by the roots is slower than supply through diffusion, an increase in concentrations of all three elements would be expected to occur in the solid phase of the rhizosphere. The plant-induced processes in wetland soils may not only affect the availability of zine and arsenic to plantsmore » but also may play an important role in the sink function of wetlands for metals and metalloids. This paper reports the results of a pilot field study which compared concentrations of the metals in ironplaque, rhizosphere soil and bulk soil under Spartina anglica and Halimione portulacoides. 20 refs., 3 figs., 2 tabs.« less