Document Type : Research Article

Authors

Vali-e-Asr University of Rafsanjan

Abstract

Introduction: Soil contamination by heavy metals is a major concern throughout the world, due to persistence of metals in the environment and their toxicity and threat to all living organisms. Several strategies have been used to immobilize heavy metal ions in soils. Immobilization can be achieved by adding natural and synthetic amendments such as zeolites and organic materials. Because of large specific surface area, high cation exchange capacity (CEC), low cost and wide spread availability, zeolites are probably the most promising materials interacting with many heavy metal ions in contaminated soils and water. Organic amendments such as vermicompost contains a high proportion of humified organic matter (OM), may decrease the bioavailability of heavy metals in soil by adsorption and by forming stable complexes with surface functional groups, thus permitting the re-establishment of vegetation on contaminated sites. Recent studies showed that the co-application of zeolite and humic acids could be effective in reducing the available fraction of Pb in a garden polluted soil. Fractionation of heavy metals cations in amended polluted-soils is needed to predict elemental mobility in soil and phyto-availability to plants. Therefore, the objective of this study was to investigate the effects of co-application of zeolite and vermicompost on Zn redistribution in a contaminated soil.
Material and Methods: A contaminated soil was collected from the top 20 cm in the vicinity of zinc mine in Zanjan province, western north of Iran. The soil sample was air-dried, passed through 2-mm sieve and stored at room temperature. The soil sample was thoroughly mixed to ensure uniformity. Sub-samples were then digested using the hot-block digestion procedure for total Zn concentration. The experiment was conducted under greenhouse condition. The polluted soil was put in polyethylene pots and mixed well vermicompost and zeolite at the rate of 0, 50 and 100 g kg-1 soil. The treatments were evaluated in a 3 × 3 factorial design and were arranged in a randomized block design with three replications. After incubation for 45 days, five seeds of corn were sown in each pot. After germination the seedlings were thinned to 3 per pot. Plants were grown for 2 months under control conditions. After the corn had been harvested, soil samples were air-dried, and analyzed for pH, cation exchange capacity (CEC), and electrical conductivity (EC). Chemical fractionations of Zn in soils collected after the pot trial were investigated using the procedure of Salbu et al. (1998). This procedure subdivides the heavy-metal distribution into an water-extractable+exchangeable fraction, a form bound to carbonates, a form bound to Fe and Mn oxides, a form bound to organics, and a residual form. An analysis of variance was used to test significance (P≤0.05) of treatment effects and Duncan multiple range test (P≤0.05) was used to compare the means (SAS, 2002).
Results and Discussion: Soil pH gradually decreased with application of both vermicompost and zeolite amendments. This may be due to degradation of organic matter and releasing of organic and inorganic acids such as carbonic, citric and malic acids as well as H+ produced from mineralization of nitrogen in the organic matter. Electrical conductivity (EC) of soils increased with increasing amounts of vermicompost and zeolite applications. The highest EC was observed in pots containing 10% w/w zeolite and 10% w/w vermicompost. Addition of zeolite significantly increased soil CEC. The overall distribution of Zn in different fractions was in the sequence residual (38.6%)> Fe and Mn oxides bound (31.0 %) > carbonated (21.6%)> organic (4.3%)≈exchangeable +water soluble (4.4 %). The application of vermicompost significantly decreased concentration of Zn in water+exchangeable fraction as compared to the control soil. Although singly zeolite amendment had not significant effect on water+exchangeable Zn concentration, this form decreased significantly with co-application of vermicompost and zeolite. This may be due to redistribution of Zn from this form to less available forms (e.g. organic and residual fractions). The addition of vermicompost had not significant effect on the carbonated fraction of Zn, whereas co-application of zeolite and vermicompost significantly decreased concentration of Zn bound in carbonates. Singly zeolite and co-application of amendments decreased the concentration of Zn in Fe and Mn oxides bound. Although singly compost and zeolite amendments increased concentration of Zn bound to organics, this form decreased furthest with co-application of them. Zeolite and vermicompost alone had not significant effect on mobility factor (MF) of Zn over the un-amended soil. Co-application of vermicompost and zeolite to polluted soil resulted in a significant decrease in MF values of Zn compared to control.
Conclusion: Co-application of vermicompost and zeolite to polluted soil resulted in redistribution of Zn from available forms (exchangeable +water soluble) to less available form (e.g. organic), thus may be useful for the immobilization of Zn from polluted sites.

Keywords

1- Abbaspour A., and Golchin A. 2011. Immobilization of heavy metals in a contaminated soil in Iran using di-ammonium phosphate, vermicompost and zeolite. Environmental Earth Sciences, 63: 935-943.
2- Achiba W.B., Gabteni N., Lakhdar A., Laing G. D., Verloo M., Jedidi N., and Gallali T. 2009. Effects of 5-year application of municipal solid waste compost on the distribution and mobility of heavy metals in a Tunisian calcareous soil. Agriculture Ecosystems and Environment, 130: 156–163.
3- Alison L.E., and Moodie C.D. 1965. Soil chemical analysis, advance course. University Wisconsin. Collage Agriculture, Department Soils, Madison, USA.
4- Alloway B.J. 1995. Heavy metal in soils. 2nd ed., Blackie Academic and Professional Publisher, London.
5- Coppola E., Battaglia G., Bucci M., Ceglie D., Colella A., Langella A., Buondonno A., and Colella C. 2003. Remediation of Cd- and Pb-polluted soil by treatment with organo-zeolite conditioner. Clay and Clay Minerals, 51: 609-615.
6- Edwards C.A., and Burrows I. 1988. The potential of earthworm composts as plant growth media. p. 211-219. In C.A. Edwards and E.F. Neuhauser (eds.). Earthworms in waste and environmental management. SPB Academic Publ. Co., The Hague, The Netherlands.
7- Gholamhoseini M., Aghaalikhani M., Khodaei-Joghan A., Zakikhani H., and Dolatabadian A. 2012. How zeolite controls nitrate leaching and modifies canola grain yield and quality. Agricultural Research and Reviews, 1: 113 -126.
8- Gupta S.K., Vollmer M.K., and Krebs R. 1996. The importance of mobile, mobilisable and pseudototal heavy metal fractions in soil for three-level risk assessmentand risk management. Science Total Environment, 178: 11-20.
9- Hamidpour M., Afyuni M., Kalbasi M., Khoshgoftarmanesh A.H., and Inglezakis V.J. 2010. Mobility and plant-availability of Cd(II) and Pb(II) adsorbed on zeolite and bentonite. Applied Clay Science, 48: 342-348.
10- Hamidpour M., Afyuni M., Khadivi E., Zorpas A., and Inglezakis V. 2012. Composted municipal waste effect on chosen properties of calcareous soil. International Agrophysics Journal, 26: 365-374.
11- He M.M., Tian G.M., Liang X.Q., Yu Y.T., Wu J.Y., and Zhou G.D. 2007. Effects of two sludge application on fractionation and phytotoxicity of zinc and copper in soil. Journal of Environmental Sciences, 19: 1482–1490.
12- He Z.L., Calvert D.V., Alva A.K., Li Y.C., and Banks D.J. 2002. Clinoptilolite zeolite and cellulose amendments to reduce ammonia volatilization in a calcareous sandy soil. Journal of Plant and Soil, 247: 253-260.
13- Ijagbemi C.O., Tbeak M., and Kim D. 2009. Montmorillonite surface properties and sorption characteristics for heavy metal removal from aqueous solutions. Journal of Hazardous Materials, 166: 538-546.
14- Leggo P.J., Ledesert B., and Christie G. 2006. The role of clinoptilolite in organo-zeolitic-soil systems used for Phytoremediation. Science of the Total Environment, 363: 1– 10.
15- Madrid F., Lopez R., and Cabrera F. 2007. Metal accumulation in soil after application of municipal solid waste compost under intensive farming conditions. Agricultural Ecosystem Environment, 199: 249–256.
16- Puschenreiter M., Horak O., Friesl W., and Hartl W. 2005. Low-cost agricultural measures to reduce heavy metal transfer into the food chain: a review. Journal of Plant Soil and Environment, 51: 1-11.
17- Salbu B., Krekling T., and Oughton D.H. 1998. Characterization of radioactive particles in the environment Analyst, 123: 843-849.
18- Shi W.Y., Shao H.B., Li H., Shao M.A., and Du S. 2009. Co-remediation of the lead-polluted garden soil by exogenous natural zeolite and humic acids. Journal of Hazardous Materials, 167: 136–140.
19- Sparks D.L. 2003. Environmental soil chemistry. Academic Press, San Diego.
20- Udom B.E., Mbagwu J.S.C., Adesodun J.K., and Agbim N.N. 2004. Distributions of zinc, copper, cadmium and lead in tropical ultisol after long-term disposal of sewage sludge. Environment International, 30: 467–470.
21- Westerman R.L. (ed.) 1990. Soil testing and plant analysis. 3rd ed. Soil Sci. Soc. Am. Madison, WI, USA.
22- Zhang M., and Pu J. 2011. Mineral materials as feasible amendments to stabilize heavy metals in polluted urban soils. Journal of Environmental Sciences, 23: 607–615.
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