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Rhizosphere effect on Pb solubility and phytoavailability in Pb-Contaminated soils
Xinxin Li1, Samantha Huang1, M B McBride1
1Section of Soil and Crop Sciences, Cornell University, Ithaca, NY, 14850, USA.
Environmental Pollution (Barking, Essex : 1987)
|October 29, 2020
Summary
Plant roots significantly increase lead (Pb) solubility in contaminated soils, especially in historically polluted orchard soils. This rhizosphere effect enhances lead uptake by plants, impacting bioavailability.
Area of Science:
- Environmental Science
- Soil Science
- Plant Biology
Background:
- Lead (Pb) contamination in soils poses risks to ecosystems and human health.
- Understanding factors influencing Pb solubility and bioavailability is crucial for risk assessment.
- The rhizosphere, the soil zone influenced by plant roots, can alter metal speciation and mobility.
Purpose of the Study:
- To investigate the impact of plant roots on lead (Pb) solubility and bioavailability in two distinct contaminated soil types.
- To compare the rhizosphere effect on Pb solubility in a historically contaminated orchard soil versus a Pb phosphate-spiked soil.
- To assess the uptake of Pb by radish plants from these contaminated soils.
Main Methods:
- Measurement of soluble Pb and dissolved organic carbon (DOC) in soil solutions.
- Analysis of Pb content in radish shoots grown in contaminated soils.
- Comparison of rhizosphere soil with unplanted control soil.
- Soil pH adjustment in Pb phosphate-spiked soil.
Main Results:
- Soluble Pb and DOC were significantly higher in the rhizospheres of both contaminated soils compared to unplanted soils.
- The rhizosphere effect increased soluble Pb 15-fold in the historically contaminated orchard soil, but was less pronounced in the Pb phosphate-spiked soil.
- Rhizosphere effect on Pb solubility persisted even after pH adjustment in the spiked soil.
- Pb uptake by radish shoots occurred from both soil contamination sources.
- Solubility of other trace metals (Al, Fe, Cu, Ni) increased in the rhizosphere, while alkali and alkaline earth metals decreased.
Conclusions:
- Plant roots, through the rhizosphere effect, can substantially increase the solubility of Pb in soils contaminated by legacy sources and insoluble Pb phosphate.
- The magnitude of the rhizosphere effect on Pb solubility varies depending on the soil contamination type and properties.
- Plant uptake of Pb is possible from various soil Pb sources, highlighting the importance of root activity in metal bioavailability.
Keywords:
BioavailabilityDissolved organic carbon (DOC)Pb phosphatePb phytoavailabilityRaphanus sativusMore Related Videos
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