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TECHNICAL REPORTS
Heavy Metals in the Environment

Adsorption–Desorption Behavior of Copper at Contaminated Levels in Red Soils from China

S. Yu, Z.L. He^,*, C.Y. Huang, G.C. Chen and D.V. Calvert

Dep. of Resource Science, College of Environmental and Resource Sciences, Huajiachi Campus, Zhejiang Univ., Hangzhou, China 310029

* Corresponding author (zhe{at}mail.ifas.ufl.edu)

Received for publication June 25, 2001.

	ABSTRACT

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Adsorption–desorption of copper (Cu²⁺) at contaminated levels in two red soils was investigated. The red soil derived from the Quaternary red earths (clayey, kaolinitic thermic plinthite Aquult) (REQ) adsorbed more Cu²⁺ than the red soil developed on the Arenaceous rock (clayey, mixed siliceous thermic typic Dystrochrept) (RAR). The maximum adsorption values (M_A) that are obtained from the simple Langmuir model were 25.90 and 20.17 mmol Cu²⁺ kg^-1 soil, respectively, for REQ and RAR. Adsorption of Cu²⁺ decreased soil pH, by 0.8 unit for the REQ soil and 0.6 unit for the RAR soil at the highest loadings. The number of protons released per Cu²⁺ adsorbed increased sigmoidally with increasing initial Cu²⁺ concentration for the RAR soil, but the relationship was almost linear for the REQ soil. The RAR soil released about 2.57 moles of proton per mole of Cu²⁺ adsorbed at the highest Cu²⁺ loading and the corresponding value for the REQ soil was 1.12. The distribution coefficient (K_d) decreased exponentially with increasing Cu²⁺ loading. Most of the adsorbed Cu²⁺ in the soils was readily desorbed in the NH₄Ac. After five successive extractions with 1 mol L^-1 NH₄Ac (pH 5.0), 61 to 95% of the total adsorbed Cu²⁺ in the RAR soil was desorbed and the corresponding value for the REQ soil was 85 to 92%, indicating that the RAR soil had a greater affinity for Cu²⁺ than the REQ soil at low levels of adsorbed Cu²⁺.

Abbreviations: C, equilibrium concentration of dissolved ion • K_d, distribution coefficient • M_A, maximum adsorption level • q, adsorbed concentration • RAR, red soil developed on Arenaceous rock (clayey, mixed siliceous thermic typic Dystrochrept) • REQ, red soil developed on Quaternary red earths (clayey, kaolinitic thermic plinthite Aquult)

	INTRODUCTION

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COPPER enters agricultural ecosystems through applications of Cu-containing fungicides, stable manures (e.g., pig slurry), and liquid or solid wastes from Cu-related mining and manufacturing. Worldwide, approximately 70000 Mg of Cu as Bordeaux mixture [a Cu-containing fungicide: Ca(OH)₂ + CuSO₄] is annually sprayed on fruit orchards and other crops (Baker, 1990). The accumulated Cu concentrations in agricultural soils have reached 110 to 1500 mg kg^-1, compared with 20 to 30 mg kg^-1 background levels (Baker, 1990). Copper concentrations have reached contaminating levels in soils from old vineyards in France (Delas, 1963, cited by Mocquot et al., 1996) and old citrus groves in the USA (Reuther and Smith, 1953).

Red soils are a type of highly weathered variable-charge soil with a low pH value. They are widely distributed in southern China and other subtropical regions and contain great amounts of Fe and Al oxides and kaolinite. However, these soils have a relatively low affinity and low adsorption capacity for Cu²⁺, as compared with lateritic soils or Oxisols found in the tropical regions, which have more crystalline Fe and Al oxides and kaolinite. In addition, the adsorbed Cu²⁺ in the red soils is more readily released, probably due to low organic matter (Yu, 1981; Wu, 1989). In recent years, Cu contamination to soils has become an increasing concern in China due to rapid development of Cu-related industries such as mines and smelters. Copper toxicity to rice (Oryza sativa L.) plants and other crops has been reported to occur around the mining sites and smelters in the red soil regions.

Copper, like other microelements, is essential to plants, animals, and microorganisms, but is toxic when its concentration exceeds a certain critical level (Baker, 1990). Total Cu concentration in soil solution is normally low (0.01–0.6 µmol L^-1), due to copper's high affinity to organic and inorganic soil colloids. Soluble copper at concentrations > 1.5 to 4.5 µmol L^-1 causes damage and even death to roots of growing plants (Baker, 1990). A significant decrease in root and leaf biomass of young maize (Zea mays L.) was observed at 10 µmol Cu²⁺ L^-1 in solution culture (Mocquot et al., 1996). To control heavy metal contamination to soil and food, the USEPA and the European Union have established maximum heavy metal limits for soil and for industry by-products such as biosolids and composts to be applied to fields. The current soil cleanup criteria for Cu in the USA is 600 mg kg^-1 (USEPA, 1999), and the upper limit of total soil Cu set by the European Union for receiving Cu-containing sewage sludge is 140 mg kg^-1 (Department of Environment, The Ministry of Agriculture, Fisheries and Food, 1993).

There are two types of minerals that are involved in the adsorption–desorption of Cu²⁺ in soils: permanent charge and variable charge. Permanent-charge minerals such as montmorillonite carry a negative charge as a result of ion substitution during the formation of the minerals. Variable-charge minerals such as Fe, Mn, and Al oxides carry charges varying from negative to positive, depending on pH. Adsorption and desorption of Cu²⁺ in soil are affected by the proportion of these two types of minerals. Moreover, the Fe, Al, and Mn oxides have a relatively strong affinity (pH dependent) for Cu²⁺ and other heavy metal cations and the adsorption of Cu²⁺ on these oxides is considered to be inner-sphere complex through a chemisorption process (Bertsch and Seaman, 1999). Therefore, adsorption of Cu²⁺ in the variable-charge soils is generally pH dependent (Atanassova, 1995; Atanassova and Okazaki, 1997; McBride, 1981; Wang et al., 1995). On the other hand, soil organic matter has a strong affinity for Cu²⁺ at low levels of Cu²⁺ (Buffle, 1988). Recently, Alcacio et al. (2001) provided spectroscopic evidence for the hypothesis proposed by McBride (1994) for possible binding configurations of Cu²⁺ on complexes of oxide minerals and organic matter: (i) Cu²⁺ is bonded to the mineral surfaces only (inner-sphere complex); (ii) Cu²⁺ is bonded to the organic matter that is adsorbed by the oxides at high levels (Type B ternary complex); and (iii) Cu²⁺ acts as a bridge cation between the oxides and the organic matter that is adsorbed at low levels (Type A ternary complex). Therefore, Fe, Al, and Mn oxides and organic matter are considered to play a very important role in the adsorption–desorption of Cu²⁺ in the variable-charge soils.

For most agricultural soils, bioavailability of Cu²⁺ is controlled by adsorption–desorption process (Xie, 1996). Remediation of Cu-contaminated soils requires an understanding of Cu²⁺ adsorption–desorption behavior and the major factors. Adsorption of Cu²⁺ in soils is often coupled with proton release (Padmanabham, 1983; Wang et al., 1995; Wu, 1989; Wu and Chen, 1983). A significant drop of solution pH has been reported to accompany Cu²⁺ adsorption, H⁺ being replaced by Cu²⁺ (Aoyama et al., 1993; Aoyama and Itaya, 1995; Speir et al., 1999). Soil components vary greatly in their adsorption capacity for Cu²⁺. Adsorption capacity decreases in the order: organic matter > Fe, Al, and Mn oxides >>> clay minerals (Adediran and Kramer, 1987, cited by Baker, 1990).

Adsorption of Cu²⁺ on soil and soil components can be described by a linear (McLaren et al., 1990), a Langmuir, or a Freundlich adsorption model (Wu, 1989; Atanassova, 1995; Atanassova and Okazaki, 1997). Although there are some different opinions regarding the use of Freundlich and Langmuir models for interpreting the adsorption of metal cations in soils (Sparks, 1995), some parameters from these models, such as maximum adsorption (M_A) and the distribution coefficient (K_d = q/C, where q is the amount of the adsorbed Cu²⁺ and C is the equilibrium Cu²⁺ concentration in solution), are useful in characterizing Cu²⁺ adsorption in soils (Atanassova, 1995; Wang et al., 1995; Basta and Tabatabai, 1992). However, most of the previous studies were conducted on other types of soils or pure oxide minerals using low concentrations of Cu²⁺ or a single rate of Cu²⁺, and the obtained information may not be transferable to variable-charge soils, particularly those at high levels of Cu contamination.

A number of extractants including 0.1 mol HCl L^-1, 0.01 mol CaCl₂ L^-1 (Sauve et al., 1997), Mehlich 3 reagent (Mehlich, 1984; Grazebisz et al., 1997), 1 mol NH₄Ac L^-1 (pH 4.8) (Sakal et al., 1984; Brun et al., 2001), DTPA (Bertoni et al., 2000; Brun et al., 2001), and EDTA (Schramel et al., 2000; Brun et al., 2001) have been proposed for use in estimating the relationships between plant uptake of Cu and the extractable amount of soil Cu. Among frequently used extractants, 1 mol NH₄Ac L^-1 is most widely used for measuring soil Cu availability due to its extractable Cu being closely correlated with plant uptake of Cu. However, 0.01 mol CaCl₂ L^-1 is often employed for characterizing desorption of Cu²⁺ in soils (McLaren and Crawford, 1974; Cavallaro and McBride, 1984; Atanassova, 1995). Information is lacking on the relationship between the bioavailability of Cu to plants and the adsorption–desorption characteristics of Cu²⁺ in soils.

The overall objective of this study is to quantify Cu²⁺ adsorption–desorption behavior and soil pH change in two acidic soils at contaminated levels of Cu²⁺. Adsorption isotherms were measured and modeled at relatively high Cu concentrations. Proton release and pH changes during Cu²⁺ adsorption were determined to understand adsorption–desorption mechanisms, including H⁺–Cu²⁺ exchange stoichiometry. A 1 mol NH₄Ac L^-1 (pH 5.0) solution was used to extract a portion of the adsorbed Cu in an attempt to evaluate the relationship between the potential Cu²⁺ availability and the adsorbed Cu.

	MATERIALS AND METHODS

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Soils
Two red acidic soils were used in this study: the RAR soil (clayey, mixed siliceous thermic typic Dystrochrept), derived from Arenaceous rock, and the REQ soil (clayey, kaolinitic thermic plinthite Aquult), developed on Quaternary red earths. Soil samples were collected at 0 to 20 cm from Longyou County (119°02'120°20' E, 28°44'29°17' N), Zhejiang Province, southeastern China. Composite samples of the soils were air-dried, ground, and passed through a 60-mesh sieve prior to use. Some basic physicochemical properties of the soils are given in Table 1 . Based on X-ray diffraction analysis of powder samples, the dominant clay minerals in both soils were kaolinite, iron and aluminum oxides, and quartz. However, the RAR soil contained also small amounts of chlorite and illite. Both soils contained considerable amounts of crystalline and noncrystalline Fe and Al oxides (Table 1). The RAR soil had significantly greater amounts of exchangeable H⁺ and Al³⁺, consistent with its lower pH, but the REQ soil had a greater cation exchange capacity (CEC) (Table 1).

View this table: [in this window] [in a new window]   Table 1. Basic properties of the tested soils.

Adsorption of Copper Ion and Proton Release
Portions of 2.0 g air-dried soil were placed into 100-mL polypropylene centrifuge tubes, and 50 mL of 0.01 mol NaNO₃ L^-1 (pH 5.0) solution containing 0, 15.75, 31.50, 78.74, 157.48, 314.96, 629.92, and 1259.84 µmol Cu²⁺ L^-1 (equal to 0, 25, 50, 125, 250, 500, 1000, and 2000 mg Cu²⁺ kg^-1soil) [as Cu(NO₃)₂] were added to each tube. The suspensions were shaken at 200 rpm for 2 h at 25°C and then equilibrated in a dark incubator for an additional 22 h. No pH control was imposed. At the end of the designated time, the suspensions were centrifuged at 2500 x g relative centrifugal force for 10 min and filtered through 0.45-µm filter paper (Fisherbrand, Pittsburgh, PA). Ten milliliters of the filtrate were transferred into a 10-mL polypropylene centrifuge tube for measuring Cu²⁺ concentration using atomic absorption spectrometry. Total amounts of adsorbed Cu²⁺ (q) were calculated by the difference between the total applied Cu²⁺ and the soluble Cu²⁺ in the equilibrium solution.

The amounts of protons released during Cu²⁺ adsorption were quantified by titrating another 10 mL of the filtrate with standardized NaOH solution (0.004 mol NaOH L^-1, diluted from 0.02 mol NaOH L^-1 freshly prepared and standardized before use). The remaining solution was used for measuring pH.

Desorption of Adsorbed Copper Ion by 1 mol NH₄Ac L^-1 (pH 5.0)
The residue of Cu²⁺–enriched soil separated from the supernatant solution by centrifugation, from the above adsorption experiment, was rinsed several times with 95% ethanol (vortexing and shaking at 200 rpm for 15 min and centrifuging for 10 min at 2500 x g relative centrifugal force) to remove Cu²⁺ in the entrapped solution until no Cu²⁺ was detected. The mass balance was performed for each tube and the lost weight was recorded. Fifty milliliters of 1 mol NH₄Ac L^-1 (pH 5.0) were added to each tube containing the Cu-enriched soil residue. The suspensions were shaken at 200 rpm for 2 h at 25°C and equilibrated for an additional 10 h. The equilibrated suspensions were then centrifuged at 2500 x g relative centrifugal force for 10 min and then filtered. Ten milliliters of the filtrate were pipetted into a 10-mL polypropylene centrifuge tube for measuring Cu²⁺ concentration. In order to estimate the affinity of Cu in soils, the desorption process was repeated five times (D1 to D5). The non-extractable fraction of the adsorbed Cu²⁺ in soils was obtained by the difference between the total adsorbed Cu²⁺ and the total recovered Cu²⁺ by five successive extractions with the NH₄Ac solution (pH 5.00 ± 0.02).

Statistical Analysis
All data were processed by Microsoft Excel (Microsoft, 2000), and the regression of linear and nonlinear and other statistical analyses were conducted using the programs of SAS Release 6.12 (SAS Institute, 1996).

	RESULTS AND DISCUSSION

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Adsorption Isotherms of Copper and its Effect on Soil pH and Proton Release
Adsorption of Cu²⁺ increased steeply with Cu²⁺ concentration in the equilibrium solution at the low concentration range (0–10 mg L^-1), then the slope of the isotherm decreased at equilibrium Cu²⁺ concentrations > 10 mg L^-1 (Fig. 1 and Table 2) , possibly because Cu²⁺ adsorption in soils involves multiple adsorbing sites (McBride, 1995; Alcacio et al., 2001). The REQ soil adsorbed more Cu²⁺ than the RAR soil at the same Cu²⁺ equilibrium concentrations. At the highest level of added Cu²⁺ (2000 mg Cu²⁺ kg^-1 soil), the RAR soil adsorbed approximately 50% of the applied Cu²⁺ and the REQ soil adsorbed more than 68% of the applied Cu²⁺ (Table 2), suggesting that the REQ soil might not reach its maximum adsorption even at the designed highest Cu²⁺ loading. The difference in Cu²⁺ adsorption between the two soils may be attributed to the higher concentrations of organic matter (approximately 50% higher), clay, and exchangeable bases, and higher CEC and soil pH of the REQ soil, as compared with the RAR soil (Table 1). These results were in agreement with previous reports (Padmanabham, 1983; Wu, 1989; Atanassova, 1995; Wang et al., 1995; Atanassova and Okazaki, 1997).

View larger version (15K): [in this window] [in a new window]   Fig. 1. Isotherms of Cu2+ adsorption in the two red soils. RAR, red soil developed on Arenaceous rock (clayey, mixed siliceous thermic typic Dystrochrept); REQ, red soil developed on Quaternary red earths (clayey, kaolinitic thermic plinthite Aquult).

View this table: [in this window] [in a new window]   Table 2. Characteristics of Cu2+ adsorption and desorption with 1 mol NH4Ac L-1 (pH 5.0) in two red acidic soils.

Adsorption of Cu²⁺ significantly decreased soil pH (Fig. 2) . Greater decrease in pH was observed in the RAR soil than the REQ soil at low to medium adsorbed Cu²⁺ levels (<10.9 mmol Cu kg^-1), but the reverse was true at high levels of adsorbed Cu²⁺ (Fig. 2). This indicates that different mechanisms may be involved in Cu²⁺ adsorption at different levels of Cu²⁺ loading and between the two soils. The maximum decrease in pH was about 0.8 unit in the REQ soil and 0.6 unit in the RAR soil. The decrease in soil pH (pH) was linearly related with the amounts of Cu²⁺ adsorbed for the REQ soil (r² = 0.99, P < 0.01), but this relationship was curvilinear for the RAR soil (R² = 0.98, P < 0.01) (Fig. 2). At high levels of adsorbed Cu²⁺, pH decrease became less in the RAR soil, probably because of approaching maximum adsorption and limited availability of H⁺ (Table 2). The pH–Cu adsorption relationship from this study is consistent with previous findings by Atanassova and Okazaki (1997) and Speir et al. (1999). However, the REQ soil did not seem to reach the maximum Cu²⁺ adsorption even at the highest levels of added Cu²⁺ (2000 mg Cu²⁺ kg^-1 soil) (Fig. 1 and Table 2). If higher amounts of Cu²⁺ had been applied, the same curvilinear response might have occurred in the REQ soil, too.

View larger version (26K): [in this window] [in a new window]   Fig. 2. The pH changes and proton release in relation to Cu2+ adsorption in the two red soils. RAR, red soil developed on Arenaceous rock (clayey, mixed siliceous thermic typic Dystrochrept); REQ, red soil developed on Quaternary red earths (clayey, kaolinitic thermic plinthite Aquult).

The number of protons released per Cu²⁺ adsorbed increased with increasing initial Cu²⁺ concentrations and more protons per Cu²⁺ adsorbed were released in the RAR soil than the REQ soil (Fig. 3) . The relationship between H⁺ to Cu²⁺ ratio and initial Cu²⁺ concentration was sigmoidal for the RAR soil, but was quadratic for the REQ soil (Fig. 3). At the highest Cu²⁺ level, the H⁺ to Cu²⁺ ratio reached up to 2.57 for the RAR soil and 1.12 for the REQ soil. Basta and Tabatabai (1992) did not have the same observation for the two permanent-charge soils with four cropping systems in their study. They obtained an H⁺ to Cu²⁺ ratio of <1.0 from the slope of log₁₀ K_d vs. pH of the equilibrium solution at the rate of 2000 µM Cu²⁺ (equal to 3175 mg Cu²⁺ kg^-1 soil). Wang et al. (1995) obtained similar findings with the clay fraction from a red soil, the ratio close to 1.0 at 6270 mg Cu²⁺ kg^-1 soil clay. The difference in H⁺ to Cu²⁺ ratio between the reported value by Wang et al. (1995) and our results may be caused by the difference between pure clay and whole soil and different calculation approaches used.

View larger version (18K): [in this window] [in a new window]   Fig. 3. Effect of initial Cu2+ concentration on proton release per Cu2+ adsorbed (H+ to Cu2+ ratio) in the two red soils. RAR, red soil developed on Arenaceous rock (clayey, mixed siliceous thermic typic Dystrochrept); REQ, red soil developed on Quaternary red earths (clayey, kaolinitic thermic plinthite Aquult).

Distribution Coefficient of Copper
The distribution coefficient (K_d) is defined as the ratio of adsorbed Cu²⁺ to dissolved Cu²⁺. This parameter reflects the overall copper-surface affinity (Atanassova, 1995; Wang et al., 1995). The REQ soil had slightly higher K_d than the RAR soil (Fig. 4) . The K_d values at very low levels of added Cu²⁺ (<125 mg Cu²⁺ kg^-1 soil) were not measured because the added Cu²⁺ was almost completely adsorbed (Table 2) and Cu²⁺ concentrations in the equilibrium solution were below detection limits. The K_d values decreased exponentially with increasing initial Cu²⁺ concentrations in both soils (Fig. 4). This can be attributed to the high affinity of Cu²⁺ for those highly selective sites (specific adsorption) at low Cu²⁺ concentrations, followed by adsorption of Cu onto those less-selective sites at high Cu²⁺ loadings (nonspecific adsorption) (Basta and Tabatabai, 1992). Lehmann and Harter (1984) reported that Cu²⁺ was mainly adsorbed onto low binding energy sites at Cu²⁺ rates exceeding 100 mg Cu kg^-1 soil in a comparable soil. These sites can adsorb Cu²⁺ through electrostatic forces or by forming Type A or Type B ternary surface complexes (Alcacio et al., 2001). In this study, added Cu²⁺ levels (0, 25, 50, 125, 250, 500, 1000, or 2000 mg Cu²⁺ kg^-1 soil) were mostly above this level and therefore, adsorption of Cu²⁺ in the two red soils was mainly involved with the low binding energy adsorbing sites. The REQ soil had a greater concentration of organic matter, larger external surface, and higher pH and CEC (Table 1), and thus adsorbed more Cu²⁺ than the RAR soil.

View larger version (15K): [in this window] [in a new window]   Fig. 4. Effect of initial Cu2+ concentration on Cu2+ distribution coefficient (Kd) in the two red soils. RAR, red soil developed on Arenaceous rock (clayey, mixed siliceous thermic typic Dystrochrept); REQ, red soil developed on Quaternary red earths (clayey, kaolinitic thermic plinthite Aquult).

Most of the adsorbed Cu²⁺ in the soils was readily desorbed by the NH₄Ac. After five successive extractions, 61 to 95% of the total adsorbed Cu²⁺ in the RAR soil was desorbed. The corresponding values for the REQ soil were 85 to 92% of the total adsorbed Cu²⁺ (Fig. 5 and Table 2). From 8 to 39% of the adsorbed Cu²⁺ in both soils was not recovered by the NH₄Ac extraction. The proportion of the adsorbed Cu²⁺ that was not desorbed (as percent residual Cu²⁺) increased with decreasing concentration of adsorbed Cu²⁺ (Fig. 5), implying that a portion of the Cu²⁺ was adsorbed with a high binding energy, and may not be available to plants. The proportion of the tightly bonded Cu²⁺ was significantly higher in the RAR soil than in the REQ soil at low Cu²⁺ loadings. At application rates 125 mg Cu²⁺ kg^-1 soil, the residual fraction accounted for 12 to 39% and 11 to 15% of adsorbed Cu²⁺, respectively, in the RAR and the REQ soil. At application rates > 125 mg Cu²⁺ kg^-1 soil, neither the RAR nor the REQ soil could retain more than 10% of the adsorbed Cu²⁺ after five successive extractions with 1 mol NH₄Ac L^-1 (pH 5.0) (Table 2). These findings agreed with the results of Lehmann and Harter (1984) that Cu²⁺ was adsorbed onto high binding energy sites only at the added Cu²⁺ levels < 100 or 125 mg Cu²⁺ kg^-1 soil.

View larger version (46K): [in this window] [in a new window]   Fig. 5. Fractions of five successive extractions and residual Cu2+ in the total adsorbed Cu2+. The terms D1 to D5 represent the fraction of desorbed Cu2+ from each of the five successive extractions and the residual Cu2+ represents the fraction of adsorbed Cu2+ that is not recovered by the five successive extractions with 1 mol L-1 NH4Ac (pH 5.0). RAR, red soil developed on Arenaceous rock (clayey, mixed siliceous thermic typic Dystrochrept); REQ, red soil developed on Quaternary red earths (clayey, kaolinitic thermic plinthite Aquult).

	CONCLUSIONS

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	ACKNOWLEDGMENTS

 
This study was, in part, supported by an Outstanding Young Scientist Fund grant (No. 40025104) and a research grant (No. 20177020) from The Natural Science Foundation of China. The authors thank Mr. Bingliang Zhu for his assistance in soil sampling.

	NOTES

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Florida Agricultural Experiment Station Journal Series no. R-08577.

(current address), Univ. of Florida, Institute of Food and Agricultural Sciences, Indian River Research and Education Center, 2199 S. Rock Road, Fort Pierce, FL 34945-3138.

	REFERENCES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 

• Adediran, S.A., and J.R. Kramer. 1987. Copper adsorption on clay, iron-manganese oxide and organic fractions along a salinity gradient. Appl. Geochem. 2:213–216.
• Alcacio, T.E., D. Hesterberg, W.Q. Chou, J.D. Martin, S. Beauchemin, and D.E. Sayers. 2001. Molecular scale characteristics of Cu(II) bonding in goethite–humate complexes. Geochim. Cosmochim. Acta 65:1355–1366.
• Aoyama, M., and S. Itaya. 1995. Effects of copper on the metabolism of ¹⁴C-labelled glucose in soil in relation to amendment with organic materials. Soil Sci. Plant Nutr. 41:245–252.
• Aoyama, M., S. Itaya, and M. Otowa. 1993. Effects of copper on the decomposition of plant residues, microbial biomass and ß-glucosidase activity on soils. Soil Sci. Plant Nutr. 39:557–566.
• Atanassova, I.D. 1995. Adsorption and desorption of Cu at high equilibrium concentrations by soil and clay samples from Bulgaria. Environ. Pollut. 87:17–21.[Medline]
• Atanassova, I.D., and M. Okazaki. 1997. Adsorption–desorption characteristics of high levels of copper in soil clay fractions. Water Air Soil Pollut. 98:213–228.
• Baker, D.E. 1990. Copper. p. 151–176. In B.J. Alloway (ed.) Heavy metals in soils. Blackie & Sons Ltd., London.
• Barrow, N.J. (ed.) 1987. Reactions with variable-charge soils. Martinus Nijhoff Publ., Dordrecht, the Netherlands.
• Basta, N.T., and M.A. Tabatabai. 1992. Effect of cropping systems on adsorption of metals by soils: II. Effect of pH. Soil Sci. 153:195–204.
• Bertoni, J.C., F.S.R. Holanda, J.G. de Carvalho, A.E. Neto Furtini, and M.P. de Assis. 2000. Effect of copper on growth of flooded rice and accuracy of the extractor DTPA in predicting copper availability. Ciencia-e-Agrotecnologia 24:62–73. (Abstract only).
• Bertsch, P., and J.C. Seaman. 1999. Characterization of complex mineral assemblages: Implications for contaminant transport and environmental remediation. Proc. Natl. Acad. Sci. USA 96:3350–3357.[Abstract/Free Full Text]
• Brun, L.A., J. Maillet, P. Hinsinger, and M. Pepin. 2001. Evaluation of copper availability to plants in copper-contaminated vineyard soils. Environ. Pollut. 111:293–302.[Medline]
• Buffle, J. (ed.) 1988. Complexation reactions in aquatic systems: An analytical approach. Ellis Horwood Publ., Chichester, UK.
• Cavallaro, N., and M.B. McBride. 1984. Zinc and copper sorption and fixation by an acid soil clay: Effect of selective dissolutions. Soil Sci. Soc. Am. J. 48:1050–1054.[Abstract/Free Full Text]
• Delas, J. 1963. La toxicité du cuivre accumulé dans les sols. Agrochimica 7:258–288.
• Grazebisz, W., W.Z. Kocialkowski, and B. Chudzinski. 1997. Copper geochemistry and availability in cultivated soils contaminated by a copper smelter. J. Geochem. Explor. 58:301–307.
• Kinniburg, D.G. 1983. The H⁺/M²⁺ exchange stoichiometry of calcium and zinc adsorption by ferrihydrate. J. Soil Sci. 34:759–768.
• Lehmann, R., and R. Harter. 1984. Assessment of copper-soil bond strength by desorption kinetics. Soil Sci. Soc. Am. J. 48:866–870.
• Liu, G., N. Jiang, L. Zhang, and Z. Liu (ed.) 1996. Methods of soil physicochemical analysis and profile description. Chinese Standard Press, Beijing.
• Lu, R. (ed.) 2000. Methods for soil and agricultural chemistry. Chinese Agric. Press, Beijing.
• Department of Environment, The Ministry of Agriculture, Fisheries and Food. 1993. Review of the rules for sewage sludge application to agricultural land: Soil fertility aspects of potentially toxic elements. Report of Independent Scientific Committee. PB 1561. MADD Publ., London.
• McBride, M.B. 1981. Forms and distribution of copper in solid and solution phases of soil. p. 25–45. In J.F. Loneragan et al. (ed.) Copper in soils and plants. Academic Press, Sydney, Australia.
• McBride, M.B. 1994. Environmental chemistry of soils. Oxford Univ. Press, Oxford.
• McBride, M.B. 1995. Toxic metal accumulation from agricultural use of sludge—Are USEPA regulations protective? J. Environ. Qual. 24:5–18.[Abstract/Free Full Text]
• McLaren, R.G., and D.V. Crawford. 1974. Studies on soil copper: III. Isotopically exchangeable copper in soils. J. Soil Sci. 25:111–119.
• McLaren, R.G., D.S. Hogg, and R.S. Swift. 1990. Some factors, affecting the availability of native and applied soil copper in New Zealand soils. For. Ecol. Manage. 37:131–142.
• Mehlich, A. 1984. Mehlich 3 soil test extractant: A modification of Mehlich 2 extractant. Commun. Soil Sci. Plant Nutr. 15:1409–1416.
• Microsoft. 2000. Excel 2000. Microsoft, Redmond, WA.
• Mocquot, B., J. Vangronsveld, H. Clijsters, and M. Mench. 1996. Copper toxicity in young maize (Zea mays L.) plants: Effects on growth, mineral and chlorophyll contents, and enzyme activities. Plant Soil 182:287–300.
• Padmanabham, M. 1983. Adsorption–desorption behaviour of copper (II) at the goethite–solution interface. Aust. J. Soil Res. 21:309–320.
• Reuther, W., and P.F. Smith. 1953. Effects of high copper content of sandy soil on growth of citrus seedlings. Soil Sci. 75:219–224.
• Sakal, R., A.P. Singh, B.P. Singh, and R.B. Sinha. 1984. Evaluation of some chemical extractants for predicting response of wheat grown in pots to copper in sub-Hlicuolayan soils. J. Agric. Sci. (Cambridge) 102:659–666.
• SAS Institute. 1996. SAS Release 6.12. SAS Inst., Cary, NC.
• Sauve, S., M.B. McBride, W.A. Norvell, and W.H. Hendershot. 1997. Copper solubility and speciation of in situ contaminated soils: Effects of copper level, pH and organic matter. Water Air Soil Pollut. 100:133–149.
• Schnitzer, M., and S.U. Khan (ed.) 1978. Soil organic matter. Elsevier Sci., New York.
• Schramel, O., B. Michalke, and A. Kettrup. 2000. Study of the copper distribution in contaminated soils of hop fields by single and sequential extraction procedures. Sci. Total Environ. 263:11–22.[Medline]
• Sparks, D.L. 1995. Environmental soil chemistry. Academic Press, San Diego, CA.
• Speir, T.W., H.A. Kettles, H.J. Percival, and A. Parshotam. 1999. Is soil acidification the cause of biochemical responses when soils are amended with heavy metal salts? Soil Biol. Biochem. 31:1953–1961.
• Stevenson, F.J., and A. Fitch. 1981. Reactions with organic matter. p. 69–95. In J.F. Loneragan et al. (ed.) Copper in soils and plants. Academic Press, Sydney, Australia.
• Sumner, M.E. 1998. Soil chemistry: Past, present, and future. p. 1–38. In P.M. Huang (ed.) Future prospects for soil chemistry. SSSA Spec. Publ. 55. SSSA, Madison, WI.
• Tessier, A., P.G.C. Campbell, and M. Bisson. 1979. Sequential extraction procedure for the speciation of particulate trace metals. Anal. Chem. 51:844–851.
• Tinsley, J. 1950. The determination of organic carbon in soils by dichromate mixtures. p. 161–164. In Trans. 4th Int. Congr. Soil Sci. Hoitsema Brothers, Amsterdam.
• USEPA. 1999. The EPA Region III risk-based concentration table. USEPA, Philadelphia, PA.
• Wang, W., Z. Shao, and Q. He. 1995. Study on adsorption affinities of Co, Cu, Pb and Zn for different red soil clays. Acta Pedologica Sinica 32:167–178.
• Wu, M. 1989. Study on the specific adsorption of copper ion by soils and its characteristics. Acta Pedologica Sinica 26:31–41.
• Wu, M., and J. Chen. 1983. Preliminary study on the specific adsorption characteristics of copper ion by soils. Chinese J. Environ. Chem. 2:61–67.
• Xie, Z. 1996. Chemical balance of soil copper. Adv. Environ. Sci. 4: 1–23.
• Xu, Z.Y., and J.F. Chen. 1980. Assay of amorphous Fe oxide in soils. Chinese J. Soil 6:32–34.
• Yu, T. 1981. Variable charge soil. Chinese J. Soil 5:40–45.

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