『Abstract
Lead forms stable compounds with phosphate and the immobilized
Pb becomes less available to soil biota. In this study, we tested
the bioavailability of Pb using earthworms (Eisenia fetida)
and plants after immobilization of Pb by a soluble P compound
and an insoluble rock phosphate compound in the presence of phosphate-solubilizing
bacteria (Enterobacter sp.). Rock phosphate in the presence
of phosphate-solubilizing bacteria and a soluble P compound enhanced
Pb immobilization as measured by NH4NO3-extractable Pb concentration, thereby reduced
its bioavailability as evaluated by earthworm Pb loading and sunflower
(Helianthus annuus) Pb uptake under greenhouse conditions.
However, soluble P treatment increased the concentration of Pb
in soil solution thereby inhibited the root elongation of mustard
(Brassica hirta) seedlings. Sunflower plants in the Pb-spiked
soil without P amendments showed symptoms of necrosis and stunting
because of Pb toxicity. Both soluble and insoluble P treatments
significantly increased shoot and root weight and decreased Pb
concentration in shoot by more than 50% compared to the control.
However, high Pb concentration in soil solution was found in soluble
P treatment, which can be attributed to dissolved organic carbon-Pb
complex formation, thereby increasing Pb mobility. The inoculation
of phosphate-solubilizing bacteria can facilitate phytostabilization
of Pb-contaminated site.
Keywords: Bioavailability; Pb immobilization; Phosphate-solubilizing
bacteria; Rock phosphate; Earthworm』
1. Introduction
2. Methods
2.1. Soils used
2.2. Preparation of bacterial suspension
2.3. Incubation of soils with P amendments
2.4. Germination test
2.5. Earthworm ecotoxicity test
2.6. Phytoavailability test
2.7. Statistical analysis
3. Results and discussion
3.1. Lead immobilization in soil
3.2. Seed germination
3.3. Earthworm Pb loading
3.4. Plant growth and lead uptake
4. Conclusions
Acknowledgment
References