Mechanisms of metal-phosphates formation in the rhizosphere soils of pea and tomato: environmental and sanitary consequences
- 499 Downloads
At the global scale, soil contamination with persistent metals such as lead (Pb), zinc (Zn), and copper (Cu) induces a serious threat of entering the human food chain. In the recent past, different natural and synthetic compounds have been used to immobilize metals in soil environments. However, the mechanisms involved in amendment-induced immobilization of metals in soil remained unclear. The objective of the present work was therefore to determine the mechanisms involved in metal-phosphates formation in the rhizospheric soils of pea and tomato currently cultivated in kitchen gardens.
Materials and methods
Pea and tomato were cultivated on a soil polluted by past industrial activities with Pb and Zn under two kinds of phosphate (P) amendments: (1) solid hydroxyapatite and (2) KH2PO4. The nature and quantities of metal-P formed in the rhizospheric soils were studied by using the selective chemical extractions and employing the combination of X-ray fluorescence micro-spectroscopy, scanning electron microscopy, and electron microprobe methods. Moreover, the influence of soil pH and organic acids excreted by plant roots on metal-P complexes formation was studied.
Results and discussion
Our results demonstrated that P amendments have no effect on metal-P complex formation in the absence of plants. But, in the presence of plants, P amendments cause Pb and Zn immobilization by forming metal-P complexes. Higher amounts of metal-P were formed in the pea rhizosphere compared to the tomato rhizosphere and in the case of soluble P compared to the solid amendment. The increase in soil-metal contact time enhanced metal-P formation.
The different forms of metal-P formed for the different plants under two kinds of P amendments indicate that several mechanisms are involved in metal immobilization. Metal-P complex formation in the contaminated soil depends on the type of P amendment added, duration of soil-plant contact, type of plant species, and excretion of organic acids by the plant roots in the rhizosphere.
KeywordsLow molecular weight organic acids Metal immobilization Phosphates Rhizosphere Speciation
This work has been supported by the National Research Agency under reference ANR-12-0011-VBDU and from ADEME, France.
- Austruy A (2012) Aspects physiologiques et biochimiques de la tolérance à l'arsenic chez les plantes supérieures dans un contexte de phytostabilisation d'une friche industrielle. Thèse de l'Université Blaise Pascal, Clermont Ferrand, 328 pGoogle Scholar
- Fritsch C, Giraudoux P, Cœurdassier M, Douay F, Raoul F, Pruvot C, Waterlot C, de Vaufleury A, Scheifler R (2010) Spatial distribution of metals in smelter-impacted soils of woody habitats: influence of landscape and soil properties, and risk for wildlife. Chemosphere 81:141–155CrossRefGoogle Scholar
- Lapied E, Nahmani JY, Moudilou E, Chaurand P, Labille J, Rose J, Exbrayat J-M, Oughton DH, Joner EJ (2011) Ecotoxicological effects of an aged TiO2 nanocomposite measured as apoptosis in the anecic earthworm Lumbricus terrestris after exposure through water, food and soil. Environ Int 37:1105–1110CrossRefGoogle Scholar
- Lopareva-Pohu A, Pourrut B, Waterlot C, Garçon G, Bidar G, Pruvot C, Shirali P, Douay F (2011) Assessment of fly ash-aided phytostabilisation of highly contaminated soils after an 8-year field trial: part 1. Influence on soil parameters and metal extractability. Sci Total Environ 409:647–654CrossRefGoogle Scholar
- Ministry of Environment Government of Japan (2007) Current status of the Brownfields Issue in Japan Interim Report, pp. 1–26. http://www.env.go.jp/en/water/soil/brownfields/interin-rep0703.pdf
- Panfili F, Manceau A, Sarret G, Spadini L, Kirpichtchikova T, Bert V, Laboudigue A, Marcus MA, Ahamdach N, Libert M-F (2005) The effect of phytostabilization on Zn speciation in a dredged contaminated sediment using scanning electron microscopy, X-ray fluorescence, EXAFS spectroscopy, and principal components analysis. Geochim Cosmochim Acta 69:2265–2284CrossRefGoogle Scholar
- Pourrut B, Shahid M, Dumat C, Winterton P, Pinelli E (2011) Lead uptake, toxicity, and detoxification in plants. Rev Environ Contam Toxicol 213:113–136Google Scholar
- Schreck E, Laplanche C, Le Guédard M, Bessoule J-J, Austruy A, Xiong T, Foucault Y, Dumat C (2013) Influence of fine process particles enriched with metals and metalloids on Lactuca sativa L. leaf fatty acid composition following air and/or soil-plant field exposure. Environ Pollut 179:242–249CrossRefGoogle Scholar
- Shahid M, Ferrand E, Schreck E, Dumat C (2013a) Behavior and impact of zirconium in the soil-plant system: plant uptake and phytotoxicity. Rev Environ Contam Toxicol 221:107–127Google Scholar
- Shahid M, Xiong T, Masood N, Leveque T, Quenea K, Austruy A, Foucault Y, Dumat C (2013d) Influence of plant species and phosphorus amendments on metal speciation and bioavailability in a smelter impacted soil: a case study of food-chain contamination. J Soils Sediments. doi: 10.1007/s11368-013-0745-8 Google Scholar
- Shahid M, Pinelli E, Pourrut B, Dumat C (2014c) Effect of organic ligands on lead-induced oxidative damage and antioxidant defence in the leaves of Vicia faba plants. J Geochem Explor. doi: 10.1016/j.gexplo.2014.01.008