title: Soil-solution speciation of Cd as affected by soil characteristics in unpolluted and polluted soils.
abstract: Total metal content by itself is insufficient as a measure to indicate actual environmental risk. Understanding the mobility of heavy metals in the soil and their speciation in the soil solution is of great importance for accurately assessing environmental risks posed by these metals. In a first explorative study, the effects of general soil characteristics on Cd mobility were evaluated and expressed in the form of empirical formulations. The most important factors influencing mobility of Cd proved to be pH and total soil content. This may indicate that current legislation expressing the requirement for soil sanitation in Flanders (Belgium) as a function of total soil content, organic matter, and clay does not successfully reflect actual risks. Current legal frameworks focusing on total content, therefore, should be amended with criteria that are indicative of metal mobility and availability and are based on physicochemical soil properties. In addition, soil-solution speciation was performed using two independent software packages (Visual Minteq 2.23 and Windermere Humic Aqueous model VI [WHAM VI]). Both programs largely were in agreement in concern to Cd speciation in all 29 soils under study. Depending on soil type, free ion and the organically complexed forms were the most abundant species. Additional inorganic soluble species were sulfates and chlorides. Minor species in solution were in the form of nitrates, hydroxides, and carbonates, the relative importance of which was deemed insignificant in comparison to the four major species.
authors.affiliation: Ghent University, Applied Analytical and Physical Chemistry, Coupure Links 653, Room B-623, Ghent, Oost-Vlaanderen 9185, Belgium. erik.meers@ugent.be
authors.forename: Erik
authors.initials: E
authors.lastname: Meers
authors.forename: Virginia
authors.initials: V
authors.lastname: Unamuno
authors.forename: Michiel
authors.initials: M
authors.lastname: Vandegehuchte
authors.forename: Karolien
authors.initials: K
authors.lastname: Vanbroekhoven
authors.forename: Wouter
authors.initials: W
authors.lastname: Geebelen
authors.forename: Roeland
authors.initials: R
authors.lastname: Samson
authors.forename: Jaco
authors.initials: J
authors.lastname: Vangronsveld
authors.forename: Ludo
authors.initials: L
authors.lastname: Diels
authors.forename: Ann
authors.initials: A
authors.lastname: Ruttens
authors.forename: Gijs
authors.initials: G
authors.lastname: Du Laing
authors.forename: Filip
authors.initials: F
authors.lastname: Tack
mesh_terms: D001530:Belgium; D002104:Cadmium / Q000032:analysis / Q000737:chemistry* / Q000592:standards; D019015:Geologic Sediments / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D018570:Risk Assessment; D012984:Software; D012987:Soil / Q000032:analysis*; D012989:Soil Pollutants / Q000032:analysis* / Q000592:standards; D012995:Solubility
chemical_list: D012987:Soil; D012989:Soil Pollutants; D002104:Cadmium