This study was conducted to assess the monometal and competitive adsorption of Cd, Ni, and Zn in the soil incubated with different contents of decayed cow manure ( : 0, : 25, and : 50？tha？1) for 90-d at 25°C. Sorption isotherms were characterized using the linear Freundlich equation. Most sorption isotherms were well described by the Freundlich equation (maximum and minimum ) and the monometal and competitive adsorption isotherms of Zn, Cd, and Ni followed the L-curve type (L-2). Results showed that the mono- and multimetal sorption amounts increased with an increase in organic amendment content as the sorption capacities for Cd, Ni, and Zn followed the following sequence: . This sequence was consistent with the CEC and particularly pH for the three soils. All soils showed greater sorption capacity for Zn than the other trace elements as the sorption sequence in was , while in both and was . Therefore, the metal-binding sites in OM were more selective for Zn and Ni than Cd. Competition significantly reduced metals , especially for Cd and Ni. 1. Introduction Heavy metal pollution of soils has become a dangerous problem in agricultural production around the world in the past few decades, as a result of anthropogenic activities, such as mining or industrial activities and improper use of heavy metal-enriched materials in agriculture, including chemical fertilizer and pesticides, industrial effluents, sewage sludge, and wastewater irrigation [1, 2]. Anthropogenic trace elements are easily accumulated in the surface soil [3], leading to serious environmental concerns [4]. There is concern that increased anthropogenic inputs of trace elements in soils may result in transport of these metals in the soil profile, leading to the increased concentrations of trace elements in the ground or surface waters [5]. The movement of trace elements in soil is greatly affected by their physicochemical forms in the soil solid phase [6] and adsorption [4]. The most important process that affects heavy metal availability and mobility is sorption onto soil solid phases. Sorption of heavy metals by soil depends on factors such as the nature and content of the mineral and organic constituents, the nature and concentration of the metal, the composition of the soil solution, and pH [7, 8]. Organic matter is one of the major contributors to the ability of soils for retention of heavy metals in an exchangeable form. Moreover, organic matter also improves soil fertility and structure and other soil properties. The effect of organic matter on the reduction of metals in soil solutions
References
[1]
S. Kuo, M. S. Lai, and C. W. Lin, “Influence of solution acidity and CaCl2 concentration on the removal of heavy metals from metal-contaminated rice soils,” Environmental Pollution, vol. 144, no. 3, pp. 918–925, 2006.
[2]
M. A. E. Ramadan and E. A. Al-Ashkar, “The effect of different fertilizers on the heavy metals in soil and tomato plant,” Australian Journal of Basic and Applied Sciences, vol. 1, pp. 300–306, 2007.
[3]
D. L. Baker, “Copper,” in Heavy Metals in Soils, B. J. Alloway, Ed., pp. 151–176, Blackie, London, UK, 1990.
[4]
W. R. Berti and L. W. Jacobs, “Distribution of trace elements in soil from repeated sewage sludge applications,” Journal of Environmental Quality, vol. 27, no. 6, pp. 1280–1286, 1998.
[5]
P. S. Hooda and B. J. Alloway, “Effects of time and temperature on the bioavailability of Cd and Pb from sludge-amended soils,” Soil Science, vol. 44, pp. 97–110, 1993.
[6]
L. Zhenbin and L. M. Shuman, “Redistribution of forms of zinc, cadmium and nickel in soils treated with EDTA,” Science of the Total Environment, vol. 191, no. 1-2, pp. 95–107, 1996.
[7]
V. Antoniadis and B. J. Alloway, “The role of dissolved organic carbon in the mobility of Cd, Ni and Zn in sewage sludge-amended soils,” Environmental Pollution, vol. 117, no. 3, pp. 515–521, 2002.
[8]
J. J. Msaky and R. Calvet, “Adsorption behavior of copper and zinc in soils: influence of pH on adsorption characteristics,” Soil Science, vol. 150, no. 2, pp. 513–522, 1990.
[9]
？. Alm？s, B. R. Singh, and B. Salbu, “Mobility of cadmium-109 and zinc-65 in soil influenced by equilibration time, temperature, and organic matter,” Journal of Environmental Quality, vol. 28, no. 6, pp. 1742–1750, 1999.
[10]
R. P. Narwal and B. R. Singh, “Effect of organic materials on partitioning, extractability and plant uptake of metals in an alum shale soil,” Water, Air, and Soil Pollution, vol. 103, no. 1–4, pp. 405–421, 1998.
[11]
S. M. Ross, “Retention, transformation and mobility of toxic metals in soils,” in Toxic Metals in Soil-Plant Systems, S. M. Ross, Ed., pp. 63–152, John Wiley & Sons, New York, NY, USA, 1994.
[12]
L. M. Shuman, “Organic waste amendments effect on zinc fractions of two soils,” Journal of Environmental Quality, vol. 28, no. 5, pp. 1442–1447, 1999.
[13]
S. Staunton, “Direct and indirect effects of organic matter on metal immobilisation in soil,” Developments in Soil Science, vol. 28, pp. 79–97, 2002.
[14]
D. J. Walker, R. Clemente, A. Roig, and M. P. Bernal, “The effects of soil amendments on heavy metal bioavailability in two contaminated Mediterranean soils,” Environmental Pollution, vol. 122, no. 2, pp. 303–312, 2003.
[15]
V. Antoniadis, J. S. Robinson, and B. J. Alloway, “Effects of short-term pH fluctuations on cadmium, nickel, lead, and zinc availability to ryegrass in a sewage sludge-amended field,” Chemosphere, vol. 71, no. 4, pp. 759–764, 2008.
[16]
G. M. Hettiarachchi, J. A. Ryan, R. L. Chaney, and C. M. la Fleur, “Sorption and desorption of cadmium by different fractions of biosolids-amended soils,” Journal of Environmental Quality, vol. 32, no. 5, pp. 1684–1693, 2003.
[17]
G. R. Aiken, D. M. McKnight, and R. L. Wershaw, Humic Substances in Soil, Sediment, and Water, John Wiley & Sons, New York, NY, USA, 1985.
[18]
R. Clemente, á. Escolar, and M. P. Bernal, “Heavy metals fractionation and organic matter mineralisation in contaminated calcareous soil amended with organic materials,” Bioresource Technology, vol. 97, no. 15, pp. 1894–1901, 2006.
[19]
Y. Chen, “Organic matter reactions involving micronutrients in soils and their effect on plants,” in Humic Substances in Terrestrial Ecosystems, A. Piccolo, Ed., pp. 507–530, Elsevier, Amsterdam, The Netherlands, 1996.
[20]
R. D. Harter, “Competitive sorption of cobalt, copper, and nickel ions by a calcium- saturated soil,” Soil Science Society of America Journal, vol. 56, no. 2, pp. 444–449, 1992.
[21]
N. T. Basta and M. A. Tabatabai, “Effect of cropping systems on adsorption of metals by soils: III. Competitive adsorption,” Soil Science, vol. 153, no. 4, pp. 331–337, 1992.
[22]
B. Zhu and A. K. Alva, “Differential adsorption of trace metals by soils as influenced by exchangeable cations and ionic strength,” Soil Science, vol. 155, no. 1, pp. 61–66, 1993.
[23]
M. T. Morera, J. C. Echeverría, C. Mazkiarán, and J. J. Garrido, “Isotherms and sequential extraction procedures for evaluating sorption and distribution of heavy metals in soils,” Environmental Pollution, vol. 113, no. 2, pp. 135–144, 2001.
[24]
M. S. Yoo and B. R. James, “Zinc extractability as a function of pH in organic waste-amended soils,” Soil Science, vol. 167, no. 4, pp. 246–259, 2002.
[25]
R. D. Harter, “Micronutrient adsorption-desorption reactions in soils,” in Micronutrients in Agriculture, J. J. Mortvedt, F. R. Cox, L. H. Shuman, and R. H. Welch, Eds., vol. 4 of SSSA Book Series, pp. 59–87, SSSA, Madison, Wis, USA, 2nd edition, 1991.
[26]
G. Sposito, The Chemistry of Soils, Oxford University Press, New York, NY, USA, 1989.
[27]
N. T. Basta and J. J. Sloan, “Bioavailablility of heavy metals in strongly acidic soils treated with exceptional quality biosolids,” Journal of Environmental Quality, vol. 28, no. 2, pp. 633–638, 1999.
[28]
S. Brown, B. Christensen, E. Lombi et al., “An inter-laboratory study to test the ability of amendments to reduce the availability of Cd, Pb, and Zn in situ,” Environmental Pollution, vol. 138, no. 1, pp. 34–45, 2005.
[29]
A. Karaca, “Effect of organic wastes on the extractability of cadmium, copper, nickel, and zinc in soil,” Geoderma, vol. 122, no. 2–4, pp. 297–303, 2004.
[30]
F. Haghiri, “Plant uptake of cadmium as influenced by cation exchange capacity, organic matter, zinc, and soil temperature,” Journal of Environmental Quality, vol. 3, no. 2, pp. 180–183, 1974.
[31]
G. Petruzzelli, G. Guidi, and L. Lubrano, “Organic matter as an influencing factor on copper and cadmium adsorption by soils,” Water, Air, and Soil Pollution, vol. 9, no. 3, pp. 263–269, 1978.
[32]
J. O. Agbenin and L. A. Olojo, “Competitive adsorption of copper and zinc by a horizon of a savanna Alfisol as affected by pH and selective removal of hydrous oxides and organic matter,” Geoderma, vol. 119, no. 1-2, pp. 85–95, 2004.
[33]
Y. Yin, C. A. Impellitteri, S.-J. You, and H. E. Allen, “The importance of organic matter distribution and extract soil: solution ratio on the desorption of heavy metals from soils,” Science of the Total Environment, vol. 287, no. 1-2, pp. 107–119, 2002.
[34]
D. J. Walker, R. Clemente, and M. P. Bernal, “Contrasting effects of manure and compost on soil pH, heavy metal availability and growth of Chenopodium album L. in a soil contaminated by pyritic mine waste,” Chemosphere, vol. 57, no. 3, pp. 215–224, 2004.
[35]
N. Ram and M. Verloo, “Effect of various organic materials on the mobility of heavy metals in soil,” Environmental Pollution B, vol. 10, no. 4, pp. 241–248, 1985.
[36]
V. Antoniadis, C. D. Tsadilas, and D. J. Ashworth, “Monometal and competitive adsorption of heavy metals by sewage sludge-amended soil,” Chemosphere, vol. 68, no. 3, pp. 489–494, 2007.
[37]
N. C. Uren, “Forms, reactions, and availability of nickel in soils,” in Advances in Agronomy, D. L. Sparks, Ed., vol. 48, pp. 141–203, Academic Press, New York, NY, USA, 1992.
[38]
U. K. Saha, S. Taniguchi, and K. Sakurai, “Simultaneous adsorption of cadmium, zinc, and lead on hydroxyaluminum- and hydroxyaluminosilicate-montmorillonite complexes,” Soil Science Society of America Journal, vol. 66, no. 1, pp. 117–128, 2002.
