Fractionation of copper and cadmium and their binding with soil organic matter in a contaminated soil amended with organic materials

State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070 People’s Republic of China
Journal of Soils and Sediments (Impact Factor: 2.14). 09/2010; 10(6):973-982. DOI: 10.1007/s11368-010-0199-1


PurposeThe contamination of agricultural soils by heavy metals is a worldwide problem. Organic amendments can be used for the immobilization
and binding of heavy metal ions in soils by complexation, adsorption, and precipitation. A field trial was carried out to
evaluate the influence of some low-cost organic materials such as rice straw (RS), green manure (GM), and pig manure (PM)
on the distribution of Cu and Cd and the retention of these metals by organic matter fractions in heavy metal-polluted soils.

Materials and methodsThe experiment was conducted in Miaoyunao Village, Daye County, Hubei province, China. PM, GM (peanut plants), and RS were
obtained from a farm close to the village. Sixteen treatments with three replicates were designed. Soil chemical properties
such as soil pH, electrical conductivity (EC), organic matter (OM), and available P were measured by standard methods. Soluble/exchangeable,
organic-bound, inorganic precipitates and residual Cu and Cd in the soil were sequentially extracted and analyzed. The amounts
of Cu and Cd bound with soil particulate organic matter (POM) fractions and humic substances were also determined.

Results and discussionThe addition of organic amendments declined significantly the concentrations of soluble/exchangeable Cu and Cd, but increased
the amounts of these metals in organic-bound and inorganic precipitate forms in the soil. RS was more effective than GM and
PM in diminishing the solubility of Cu and Cd. The largest retention for Cu and Cd by humic substances and POM was noticed
in RS treatments, whereas the lowest was found in PM treatments. Humic substances showed higher potential in the fixation
of Cu and Cd than POM fractions. The conversion of soluble/exchangeable Cu and Cd to other insoluble forms after the application
of organic amendments may be ascribed to the increases of soil OM, pH, EC, and available P contents. The highest binding of
Cu and Cd with POM fractions and humic substances after the incorporation of RS mainly resulted from the greatest increase
of soil OM contents.

ConclusionsRS, GM, and PM can be employed as good and cheap substances for the immobilization of Cu and Cd in heavy metal-polluted soils.
RS was the best amendment in decreasing the solubility of Cu and Cd, and also in enhancing the retention of these metals by
humic substances and POM fractions in the soil. Futures studies should focus on the influence of these organic amendments
or their mixtures on the phytotoxicity of Cu and Cd for different plants in heavy metal-contaminated soils.

KeywordsFractionation-Heavy metal-Humic substances-Organic amendments-POM

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Available from: Ibrahim Mohamed, Feb 18, 2015
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    ABSTRACT: The aim of this study was to determine the mobility of metals in contaminated sediments in the water reservoir Ružín No.I, which is situated on the Hornád and Hnilec Rivers (Eastern Slovakia). Bottom sediments are contaminated above all by heavy metals, namely As, Cu, Cd, Cr, Hg, Mn and Zn, which were alluvial into the reservoir from localities of former mining activities, and thus they represent ecological load mainly at the inputs into reservoir. The mobilities and solid-state distributions of As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, and Zn ions in impoundment materials were investigated using a five-step sequential extraction procedure. The greatest quantity of Hg was released in the organic–sulfide fraction (F4), in the range of 75.2–87.6 % in both samples. The highest percentage of the total metal content for As, Cr, and Sb was between 82.0 and 94.6 % in the fifth step for both samples also. Cu and Pb were released in the greatest quantities in the third step in the reducible fraction, from 45 to 65.7 % in sample HN and up to 68–50 % in sample HR. High bioavailability was observed for copper, zinc, lead, and cadmium. Nickel, arsenic, antimony, and chromium were only extracted in the residue fraction and displayed low bioavailability. The bioavailability of the metals in the sediments followed the sequence: Cu > Hg > Pb > Cd > Zn > Ni > As > Cr > Sb. The sediment phytotoxicity was evaluated based on the germination of seeds and decreases in the root growth of the plant Sinapis alba. The percentage inhibition of seed germination was 8.9–41.1 % in the 2010–2011 HR samples and 9.1–45.1 % in the 2010–2011 HN samples, which was higher than the inhibition of root growth. In the majority of tested Sinapis alba seeds, the metals displayed no phytotoxic effect. This indicates that the Sinapis alba test still exhibited a strong tolerance to contaminated sediment as this plant species has developed distinct detoxification mechanisms.
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    • "Briefly, 5 g of sample was shaken with 25 ml of 0.005 M DTPA, 0.01 M CaCl 2 and 0.1 M TEA (triethanolamine) solution at pH 7.3, and then centrifuged at 5100 rpm for 30 min (Lindsay and Norvell, 1969). Concentrations of soluble and available Cd were measured by the flame atomic absorption spectrometry (Varian AA240FS) (Mohamed et al., 2010). "

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