Quantification of heavy and trace metal contamination in soil can be arduous, requiring the use of lengthy and intricate extraction procedures which may or may not give reliable results. Of the many procedures in publication, some are designed to operate within specific parameters while others are designed for more broad application. Most procedures have been modified since their inception which creates ambiguity as to which procedure is most acceptable in a given situation. For this study, the Tessier, Community Bureau of Reference (BCR), Short, Galán, and Geological Society of Canada (GCS) procedures were examined to clarify benefits and limitations of each. Modifications of the Tessier, BCR, and GCS procedures were also examined. The efficacy of these procedures is addressed by looking at the soils used in each procedure, the limitations, applications, and future of sequential extraction. 1. Introduction Soils are the reservoir for many harmful constituents, elemental and biological, including heavy metals and trace metals, henceforth referred to as just metals [1]. Total metal content of soils is useful for many geochemical applications but often the speciation (bioavailability) of these metals is more of an interest agriculturally in terms of what is biologically extractable [2]. Speciation is defined by Tack and Verloo [3] as “the identification and quantification of the different, defined species, forms or phases in which an element occurs” and is essentially a function of the mineralogy and chemistry of the soil sample examined [4]. Quantification is typically done using chemical solutions of varying, but specific, strengths and reactivities to release metals from the different fractions of the examined soil [5]. In terms of bioavailability, various species of metals are more biologically available than others [6]. If bioavailability and the mobility of metals are related, then the higher the concentration of mobile toxic metals (Cu, Pb, Cd, and Al) in the soil column which increases the potential for plant uptake, and animal/human consumption [3, 7, 8]. Determination of metals in soil can be accomplished via single reagent leaching, ion exchange resins, and sequential extraction procedures (SEP), the latter under controversy. The number of available extraction techniques developed over the last three decades begs inquiry as to which technique is preferable over another. Moreover, the nonselectivity of the reagents used, handling of sediment prior to extraction, sediment-reagent ratio, and length of extraction all have an effect on data
References
[1]
A. Cottenie and M. Verloo, “Analytical diagnosis of soil pollution with heavy metals,” Fresenius' Journal of Analytical Chemistry, vol. 317, no. 3-4, pp. 389–393, 1984.
[2]
A. Cottenie, R. Camerlynck, M. Verloo, and A. Dhaese, “Fractionation and determination of trace elements in plants, soils and sediments,” Pure and Applied Chemistry, vol. 52, no. 1, pp. 45–53, 1980.
[3]
F. M. G. Tack and M. G. Verloo, “Chemical speciation and fractionation in soil and sediment heavy metal analysis: a review,” International Journal of Environmental Analytical Chemistry, vol. 59, pp. 225–238, 1995.
[4]
A. Tessier, P. G. C. Campbell, and M. Blsson, “Sequential extraction procedure for the speciation of particulate trace metals,” Analytical Chemistry, vol. 51, no. 7, pp. 844–851, 1979.
[5]
P. C. Ryan, S. Hillier, and A. J. Wall, “Stepwise effects of the BCR sequential chemical extraction procedure on dissolution and metal release from common ferromagnesian clay minerals: a combined solution chemistry and X-ray powder diffraction study,” Science of the Total Environment, vol. 407, no. 1, pp. 603–614, 2008.
[6]
A. Nelson and P. Donkin, “Processes of bioaccumulation: the importance of chemical speciation,” Marine Pollution Bulletin, vol. 16, no. 4, pp. 164–169, 1985.
[7]
W. Lund, “Speciation analysis—why and how?” Fresenius' Journal of Analytical Chemistry, vol. 337, no. 5, pp. 557–564, 1990.
[8]
T. Ratuzny, Z. Gong, and B.-M. Wilke, “Total concentrations and speciation of heavy metals in soils of the Shenyang Zhangshi Irrigation Area, China,” Environmental Monitoring and Assessment, vol. 156, no. 1–4, pp. 171–180, 2009.
[9]
F. Rapin, A. Tessler, P. G. C. Campbell, and R. Carignan, “Potential artifacts in the determination of metal partitioning in sediments by a sequential extraction procedure,” Environmental Science and Technology, vol. 20, no. 8, pp. 836–840, 1986.
[10]
X.-Q. Shan and B. Chen, “Evaluation of sequential extraction for speciation of trace metals in model soil containing natural minerals and humic acid,” Analytical Chemistry, vol. 65, no. 6, pp. 802–807, 1993.
[11]
Q. Tu, X.-Q. Shan, J. Qian, and Z.-M. Ni, “Trace metal redistribution during extraction of model soils by acetic acid/sodium acetate,” Analytical Chemistry, vol. 66, no. 21, pp. 3562–3568, 1994.
[12]
I. Maiz, I. Arambarri, R. Garcia, and E. Millán, “Evaluation of heavy metal availability in polluted soils by two sequential extraction procedures using factor analysis,” Environmental Pollution, vol. 110, no. 1, pp. 3–9, 2000.
[13]
A. M. Ure, P. H. Quevauviller, H. Muntau, and B. Griepink, “Speciation of heavy metals in soils and sediments. An account of the improvement and harmonization of extraction techniques undertaken under the auspices of the BCR of the commission of the European communities,” International Journal of Environmental Analytical Chemistry, vol. 51, pp. 135–151, 1993.
[14]
G. E. M. Hall, G. Gauthier, J.-C. Pelchat, P. Pelchat, and J. E. Vaive, “Application of a sequential extraction scheme to ten geological certified reference materials for the determination of 20 elements,” Journal of Analytical Atomic Spectrometry, vol. 11, no. 9, pp. 787–796, 1996.
[15]
H. Zeien and G. W. Brümmer, “Chemische extraktion zur bestimmung von schwermetallbindungsformen in b？den,” Metteilungen der Deutschen Bodenkundlichen Gesellschaft, vol. 39, pp. 505–510, 1989.
[16]
W. P. Miller, D. C. Martens, and L. W. Zelazny, “Effect of sequence in extraction of trace metals from soils,” Soil Science Society of America Journal, vol. 50, no. 3, pp. 598–601, 1986.
[17]
G. R. R. Rauret and J. F. Lopez Sanchez, “Optimization of Tessier procedure for metal solid speciation in river sediments,” International Journal of Environmental Analytical Chemistry, vol. 36, pp. 69–83, 1989.
[18]
G. Rauret, J. F. Lopez Sanchez, A. Sahuquillo, et al., “Improvement of the BCR three step sequential extraction procedure prior to the certification of new sediment and soil reference materials,” Journal of Environmental Monitoring, vol. 1, no. 1, pp. 57–61, 1999.
[19]
E. D？lsch, B. Deroche, and V. Van de Kerchove, “Impact of sewage sludge spreading on heavy metal speciation in tropical soils (Réunion, Indian Ocean),” Chemosphere, vol. 65, no. 2, pp. 286–293, 2006.
[20]
I. Maiz, M. V. Esnaola, and E. Millán, “Evaluation of heavy metal availability in contaminated soils by a short sequential extraction procedure,” Science of the Total Environment, vol. 206, no. 2-3, pp. 107–115, 1997.
[21]
E. Galán, J. L. Gómez Ariza, I. González, J. C. Fernández Caliani, E. Morales, and I. Giráldez, “Utilidad de las tecnicas de extraccion secuencial en la mejora de la caracterización mineralogica por DRX de suelos y sedimentos con altos contenidos de oxidos de hierro,” in Libro de Conferencias y Resumenes de la XV Reunion Cientifica de la Sociedad Espa？ola de Arcillas, vol. 15, pp. 68–69, 1999.
[22]
L. N. Benitez and J.-P. Dubois, “Evaluation of the selectivity of sequential extraction procedures applied to the speciation of cadmium in soils,” International Journal of Environmental Analytical Chemistry, vol. 74, no. 1–4, pp. 289–303, 1999.
[23]
E. D？lsch, G. Moussard, and H. Saint Macary, “Fractionation of tropical soilborne heavy metals—comparison of two sequential extraction procedures,” Geoderma, vol. 143, no. 1-2, pp. 168–179, 2008.
[24]
L. Rodríguez, E. Ruiz, J. Alonso-Azcárate, and J. Rincón, “Heavy metal distribution and chemical speciation in tailings and soils around a Pb-Zn mine in Spain,” Journal of Environmental Management, vol. 90, no. 2, pp. 1106–1116, 2009.
[25]
M. A. Hossain, H. Furumai, and F. Nakajima, “Competitive adsorption of heavy metals in soil underlying an infiltration facility installed in an urban area,” Water Science and Technology, vol. 59, no. 2, pp. 303–310, 2009.
[26]
J. Kierczak, C. Neel, U. Aleksander-Kwaterczak, E. Helios-Rybicka, H. Bril, and J. Puziewicz, “Solid speciation and mobility of potentially toxic elements from natural and contaminated soils: a combined approach,” Chemosphere, vol. 73, no. 5, pp. 776–784, 2008.
