Thermodynamic Modeling of Zinc, Cadmium, and Copper Solubilities in a Manured, Acidic Loamy‐Sand Topsoil

Hesterberg, Dean; Bril, J.; Castilho, P. del

doi:10.2134/jeq1993.00472425002200040008x

Cited by 44 publications

(16 citation statements)

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“…where M 2+ is the bivalent metal ion, L n – is the ligand ion or molecule, and ML 2 – n is the metal complex. In a typical Dutch arable soil bound ligand fractions were negligible, with bound dissolved organic carbon (DOC) fractions ranging from 0.033 to 0.014, and bound fractions of inorganic ligands not exceeding 0.0003 (Hesterberg et al . 1993).…”

Section: Methodsmentioning

confidence: 99%

General purpose Freundlich isotherms for cadmium, copper and zinc in soils

Elzinga

Grinsven

Swartjes

1999

European J Soil Science

101

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Summary Assessing the accumulation and transport of trace metals in soils and the associated toxicological risks on a national scale requires generally applicable sorption equations. Therefore Freundlich equations were derived for Cd, Zn and Cu using multiple linear regression on batch sorption data from the literature with a wide variety of soil and experimental characteristics, and metal concentrations ranging over five orders of magnitude. Equations were derived based on both total dissolved metal concentrations and free metal activities in solution. Free metal activities were calculated from total metal concentrations taking into account ionic activity, and inorganic (all metals) and organic complexation (Cu only). Cadmium and Zn were present in solution predominantly as free ions, while Cu was present as organic complexes. Since actual dissolved organic carbon (DOC) concentrations were not available they were estimated using an empirical field relation between DOC and organic matter content. The logarithmic transformation of the Freundlich constant for Cd was regressed on the logarithmic transformations of cation exchange capacity (CEC) (H+) and dissolved Ca, and for Zn with CEC and (H+). For Cu the log–log regression model of the Freundlich constant included the solid:solution ratio of the batch to account for dilution of DOC in the batch as compared with the field. The explained variance for the fitted Freundlich equations was 79% for Cd, 65% for Cu and 83% for Zn, using log‐transformed adsorbed concentrations and soil solution activities. The Freundlich adsorption models underestimated metal contents determined from 1 m HNO3 digestion on field samples, up to a factor of 6 (Cd and Cu) or 10 (Zn).

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Section: Methodsmentioning

confidence: 99%

General purpose Freundlich isotherms for cadmium, copper and zinc in soils

Elzinga

Grinsven

Swartjes

1999

European J Soil Science

101

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“…These results may assist in predicting Cu mobility in field soils, where models typically include sorption and complexation processes of Cu(II), but do not account for reduction of Cu(II) to Cu(I). Copper(II) reduction to Cu(I) has been invoked to explain model underestimations in dissolved Cu concentration (Hesterberg et al, 1993). A significant fraction of soil Cu(II) is typically complexed with naturally occurring organic ligands (McBride, 1994), which may affect its reactivity with dissolved Fe(II).…”

Section: Resultsmentioning

confidence: 99%

Reduction of Copper(II) by Iron(II)

et al. 2005

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Laboratory and field investigations have clearly demonstrated the important role of reduced iron (Fe(II)) in reductive transformations of first-row transition metal species. However, interactions of Fe(II) and copper (Cu) are not clearly understood. This study examined the reduction of Cu(II) by Fe(II) in stirred-batch experiments at pH 5.2 and 5.5 as influenced by chloride (Cl-) concentration (0.002-0.1 M), initial metal concentration (0.1-9.1 mM), and reaction time (1-60 min) under anoxic conditions. Reduction of Cu(II) to Cu(I) by dissolved Fe(II) was rapid under all experimental conditions and the stability of the products explains the driving force for the redox reaction. Under conditions of low [Cl-] and high initial metal concentration, >40% of total Cu and Fe were removed from solution after 1 min, which accompanied formation of a brownish-red precipitate. X-ray diffraction (XRD) patterns of the precipitates revealed the presence of cuprite (Cu2O), a Cu(I) mineral, based on d-spacings located at 0.248, 0.215, 0.151, and 0.129 nm. Fourier transform infrared (FTIR) spectroscopy corroborated XRD data for the presence of Cu2O, with features located at 518, 625, and 698 cm(-1). Increasing [Cl-] stabilized the dissolved Cu(I) product against Cu2O precipitation and resulted in more Fe precipitated from solution (relative to Cu) that appears to be present as poorly crystalline lepidocrocite (gamma-FeOOH). This process may be important in anoxic soil environments, where dissolved Fe(II) levels can accumulate.

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“…Thus, the desired overall increase in accuracy might not be achieved. Dissolved organic carbon (DOC) is probably one of the important model parameters in addition to pH, clay and organic matter content, (Del Castilho et al, 1993a,b;Hesterberg et al, 1993). The effect of including DOC in a sorption model for bioavailability is not clear at present.…”

Section: Resultsmentioning

confidence: 99%

Uptake of soil cadmium by three field crops and its prediction by a pH-dependent Freundlich sorption model

Castilho¹,

Chardon²

1995

Plant Soil

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Crop contamination with cadmium is a function of soil contamination. Here we study the applicability of the soil solution bioavailability hypothesis to Cd: that is, whether uptake of Cd was more directly related to its concentration or activity in the soil solution than in the soil solid phase. Experimental data from past soil-crop surveys for Cd were used to test this hypothesis. It was also investigated whether pH-dependent desorption of cadmium would be an important mechanism in affecting cadmium activity and thus uptake. To do so we calculated the correlation between the Cd transfer factor (ratio between Cd level in plant dry material and Cd level in the topsoil) and either the soil pH, or the calculated soil solution Cd concentrations.There was no correlation between the Cd contents of the soil and of the edible parts of leafy plants (endive, spinach and lettuce). There was a strong negative correlation between soil pH and the log transfer factor for Cd at pH 4.5-7.2 and thus plant content. There also was a negative correlation between soil pH and calculated cadmium concentrations in the soil solution. For spinach grown on soils with pH > 7.2 the transfer factor increased, which is tentatively ascribed to cadmium mobilization by dissolved organic matter.The soil solution hypothesis should be further tested by pot and field trials. Special attention should be paid to the role of pH and dissolved organic matter.

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Thermodynamic Modeling of Zinc, Cadmium, and Copper Solubilities in a Manured, Acidic Loamy‐Sand Topsoil

Cited by 44 publications

References 0 publications

General purpose Freundlich isotherms for cadmium, copper and zinc in soils

General purpose Freundlich isotherms for cadmium, copper and zinc in soils

Reduction of Copper(II) by Iron(II)

Uptake of soil cadmium by three field crops and its prediction by a pH-dependent Freundlich sorption model

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