title: Bioavailability of heavy metals in soils: definitions and practical implementation--a critical review.
abstract: Worldwide regulatory frameworks for the assessment and remediation of contaminated soils have moved towards a risk-based approach, taking contaminant bioavailability into consideration. However, there is much debate on the precise definition of bioavailability and on the standardization of methods for the measurement of bioavailability so that it can be reliably applied as a tool for risk assessment. Therefore, in this paper, we reviewed the existing definitions of heavy metal bioavailability in relation to plant uptake (phytoavailability), in order to better understand both the conceptual and operational aspects of bioavailability. The related concepts of specific and non-specific adsorption, as well as complex formation and organic ligand affinity were also intensively discussed to explain the variations of heavy metal solubility and mobility in soils. Further, the most frequently used methods to measure bioavailable metal soil fractions based on both chemical extractions and mechanistic geochemical models were reviewed. For relatively highly mobile metals (Cd, Ni, and Zn), a neutral salt solution such as 0.01 M CaCl2 or 1 M NH4NO3 was recommended, whereas a strong acid or chelating solution such as 0.43 M HNO3 or 0.05 M DTPA was recommended for strongly soil-adsorbed and less mobile metals (Cu, Cr, and Pb). While methods which assessed the free metal ion activity in the pore water such as DGT and DMT or WHAM/Model VI, NICA-Donnan model, and TBLM are advantageous for providing a more direct measure of bioavailability, few of these models have to date been properly validated.
authors.affiliation: Soil and Groundwater Research Division, National Institute of Environmental Research, 42 Hwangyong-ro, Inchon, 404-708, Republic of Korea.
authors.forename: Rog-Young
authors.initials: RY
authors.lastname: Kim
authors.affiliation: Soil and Groundwater Research Division, National Institute of Environmental Research, 42 Hwangyong-ro, Inchon, 404-708, Republic of Korea.
authors.forename: Jeong-Ki
authors.initials: JK
authors.lastname: Yoon
authors.affiliation: Soil and Groundwater Research Division, National Institute of Environmental Research, 42 Hwangyong-ro, Inchon, 404-708, Republic of Korea.
authors.forename: Tae-Seung
authors.initials: TS
authors.lastname: Kim
authors.affiliation: Department of Biological Environment, Kangwon National University, 1 Kangwondaehak-gil, Chuncheon, 200-701, Republic of Korea.
authors.forename: Jae E
authors.initials: JE
authors.lastname: Yang
authors.affiliation: Environmental Contaminants Group, Mawson Institute, University of South Australia, Mawson Lakes, SA, 5095, Australia.
authors.forename: Gary
authors.initials: G
authors.lastname: Owens
authors.affiliation: Department of Agronomy and Medicinal Plant Resources, Gyeongnam National University of Science and Technology, Jinju, 660-758, Republic of Korea. kimkr419@gntech.ac.kr.
authors.forename: Kwon-Rae
authors.initials: KR
authors.lastname: Kim
mesh_terms: D000327:Adsorption; D006863:Hydrogen-Ion Concentration; D019216:Metals, Heavy / Q000737:chemistry* / Q000378:metabolism; D008962:Models, Theoretical; D010944:Plants / Q000378:metabolism; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000737:chemistry* / Q000378:metabolism; D012995:Solubility
chemical_list: D019216:Metals, Heavy; D012987:Soil; D012989:Soil Pollutants
keywords: Bioaccessibility; Complex formation; Free metal ion activity; Mobility; Phytoavailability; Specific adsorption
references.citation: Environ Monit Assess. 2010 Sep;168(1-4):215-22
references.pmid: 19669583
references.citation: Environ Pollut. 2007 Jun;147(3):713-22
references.pmid: 17055630
references.citation: Ecotoxicol Environ Saf. 2007 Jun;67(2):163-79
references.pmid: 17445889
references.citation: Environ Pollut. 2007 Sep;149(1):59-69
references.pmid: 17289232
references.citation: Environ Sci Technol. 2003 Mar 15;37(6):1175-82
references.pmid: 12680672
references.citation: Ecotoxicol Environ Saf. 2004 Jan;57(1):39-47
references.pmid: 14659365
references.citation: Environ Geochem Health. 2014 Jun;36(3):409-19
references.pmid: 24026571
references.citation: J Hazard Mater. 2009 Mar 15;162(2-3):1261-8
references.pmid: 18650011
references.citation: Environ Toxicol Chem. 2009 Aug;28(8):1704-10
references.pmid: 19374472
references.citation: Environ Pollut. 2004 Oct;131(3):461-8
references.pmid: 15261410
references.citation: Chemosphere. 2006 Dec;65(11):2304-12
references.pmid: 16797672
references.citation: Sci Total Environ. 2005 Jan 20;337(1-3):175-82
references.pmid: 15626388
references.citation: Environ Pollut. 2005 Jan;133(1):103-16
references.pmid: 15327861
references.citation: Environ Int. 2009 Jan;35(1):142-56
references.pmid: 18691760
references.citation: Environ Sci Technol. 2008 Feb 15;42(4):1123-30
references.pmid: 18351082
references.citation: Ecotoxicol Environ Saf. 2003 Sep;56(1):52-62
references.pmid: 12915140
references.citation: Sci Total Environ. 2012 Jun 1;426:120-31
references.pmid: 22542230
references.citation: Environ Sci Technol. 2004 Jun 15;38(12):228A-231A
references.pmid: 15260315
references.citation: Ecotoxicol Environ Saf. 2000 Oct;47(2):195-200
references.pmid: 11023698
references.citation: Anal Chim Acta. 2007 Oct 17;602(1):131-40
references.pmid: 17936117
references.citation: Environ Pollut. 2009 Aug-Sep;157(8-9):2435-44
references.pmid: 19345457
references.citation: Environ Toxicol Chem. 2006 Mar;25(3):643-51
references.pmid: 16566147
references.citation: J Environ Qual. 2007 Aug 31;36(5):1420-8
references.pmid: 17766821
references.citation: Environ Sci Technol. 2006 Nov 15;40(22):7085-93
references.pmid: 17154020
references.citation: Environ Pollut. 2005 Sep;137(2):316-23
references.pmid: 15913857
references.citation: Environ Sci Technol. 2004 Aug 15;38(16):4390-5
references.pmid: 15382869
references.citation: Environ Sci Technol. 2003 Aug 1;37(15):295A-302A
references.pmid: 12966964
references.citation: Environ Sci Technol. 2009 Aug 15;43(16):6196-201
references.pmid: 19746713
references.citation: J Hazard Mater. 2011 Apr 15;188(1-3):98-104
references.pmid: 21316851
references.citation: Ecotoxicol Environ Saf. 2003 Sep;56(1):45-51
references.pmid: 12915139
references.citation: Environ Pollut. 2006 Dec;144(3):736-45
references.pmid: 16647172
references.citation: Environ Pollut. 2003;125(2):213-25
references.pmid: 12810315
references.citation: Ecotoxicol Environ Saf. 1991 Oct;22(2):164-74
references.pmid: 1769350
references.citation: Ecotoxicol Environ Saf. 1997 Jul;37(2):163-72
references.pmid: 9262956
references.citation: Environ Pollut. 2007 Jun;147(3):626-33
references.pmid: 17134808
references.citation: Chemosphere. 2006 May;63(5):762-71
references.pmid: 16213570
references.citation: Environ Monit Assess. 2012 Apr;184(4):2275-84
references.pmid: 21590301
references.citation: Environ Sci Pollut Res Int. 2013 Aug;20(8):5665-72
references.pmid: 23456945
references.citation: J Environ Qual. 2005 Mar-Apr;34(2):496-507
references.pmid: 15758102
references.citation: Environ Sci Technol. 2001 Nov 15;35(22):4436-43
references.pmid: 11757598
references.citation: Environ Sci Technol. 2005 Sep 15;39(18):7176-84
references.pmid: 16201646
references.citation: Environ Pollut. 2007 Nov;150(2):209-17
references.pmid: 17428595
references.citation: New Phytol. 2005 Mar;165(3):703-10
references.pmid: 15720681
references.citation: Planta. 1976 Jan;132(3):209-14
references.pmid: 24425083
references.citation: J Environ Sci (China). 2010;22(12):1960-5
references.pmid: 21462716
references.citation: J Environ Qual. 2004 Mar-Apr;33(2):522-31
references.pmid: 15074803
references.citation: Sci Total Environ. 2007 Nov 15;387(1-3):220-7
references.pmid: 17804039
references.citation: Environ Pollut. 2001;111(2):293-302
references.pmid: 11202733
references.citation: Environ Toxicol Chem. 2006 May;25(5):1239-45
references.pmid: 16704054
references.citation: Anal Chem. 2005 May 1;77(9):2852-61
references.pmid: 15859602
references.citation: Environ Pollut. 2007 Jan;145(1):121-30
references.pmid: 16777287