Effects of liming on uptake of lead and cadmium by Raphanus sativa

Abstract

Although liming soil to reduce the heavy metal uptake by plants has been recommended generally, there is some disagreement with the practice based on the results of recent studies. Radishes, Raphanus sativa L. var. Paekyong, were grown in greenhouse pots which were filled with soils treated with 1.52 mg kg(-1) Cd and 25.37 mg kg(-1) Pb, respectively and amended with lime at five rates of 0, 0.25, 0.5, 1.0, and 2.0% by dry soil weight. Plants were harvested three times at 25, 50, and 75 days after sowing and the roots and shoots separated. After the plant samples were digested with HNO3-HClO4, Cd was analyzed by flame AAS and Pb by graphite furnace AAS. A large amount of Cd was translocated into the radishes, which accumulated dramatically with time. Compared to Cd, Pb uptake was very low and accumulated slowly. Cd contents were very much higher in the shoots than the roots, but Pb was not significantly different. Liming or increased soil pH decreased Cd uptake markedly with increased lime level; Pb influence was negligible. Yields were decreased with excessive liming, but not by the levels of Cd or Pb added.

Effect of soil pH on cadmium phytoavailability in some New Zealand soils

“…There have been a number of studies showing the effect of soil pH changes on plant uptake of Cd. Han & Lee (1996) showed Cd uptake in radishes was significantly decreased after liming. Guttormsen et al (1995), examined the effect of soil pH on Cd uptake by cabbage and carrot during 3 years in a field trial, and at pH 5.5, Cd concentrations in cabbage and carrot were 23 and 46% higher than at pH 6.5.…”

“…However, soil pH is often regarded as the major variable controlling Cd uptake from soils (Chaney & Hornick 1978). A number of studies have shown that with increasing soil pH, there is a corresponding decrease in plant Cd concentrations (e.g., Han & Lee 1996). In contrast, however there have been several field trials in which liming to increase soil pH has resulted in no change in plant Cd concentrations (e.g., Sparrow et al 1993) and in some instances liming soil has increased plant Cd concentrations (e.g., Maier et al 1997;Singh & Myhr 1998).…”

“…As a soil property that is relatively easy to manipulate, soil pH may be important in the management and control of plant Cd concentrations. However, although there have been several previous studies examining the relationship between plant uptake of Cd and soil pH, the vast majority of these have been carried out using soils to which Cd in the form of soluble inorganic salts has been added (Cieslinski et al 1996;Han & Lee 1996), or using soils which have been contaminated with Cd from sewage sludge application (e.g., Smith 1994;. In consequence, the concentrations of Cd used are orders of magnitude higher than those found in New Zealand agricultural soils where Cd has accumulated slowly through the use of phosphate fertilisers.…”

Role of assisted natural remediation in environmental cleanup

“…Hydroxyapatite Increased immobilization through cation exchange, adsorption, surface complexation, precipitation and co-precipitation (Jeanjean et al, 1995;Mandjiny et al, 1998;Xu et al, 1994;Boisson et al, 1999;Seaman et al, 2001) Rock phosphate Increased immobilization through adsorption and precipitation Chen et al, 1997) K 2 HPO 4 Increased immobilization through phosphate-induced adsorption and precipitation (Pierzynski and Schwab, 1993;Pearson et al, 2000) KH 2 PO 4 Increased immobilization through phosphate-induced adsorption (Bolan et al, 1999b;Naidu et al, 1994) Ca(H 2 PO 4 ) 2 Increased immobilization through phosphate-induced adsorption (Bolan et al 1999b) (NH 4 ) 2 HPO 4 Increased adsorption due to an increase in pH, precipitation of Cd 3 (PO 4 ) 2 (Pierzynski and Schwab, 1993;Levi-Minzi and Petruzzelli, 1984;McGowen et al, 2001) CaCO 3 Increased immobilization through adsorption and precipitation; decreased plant uptake (Andersson and Siman, 1991;Bingham et al, 1979;Brown et al, 1997;Han and Lee, 1996;Chaney et al, 1977;He and Singh, 1994;Hooda and Alloway, 1996;John and Van Laerhoven, 1976;John et al, 1972;Lehoczky et al, 2000;Maclean, 1976;Oliver et al, 1996;Singh and Myhr, 1998;Singh et al, 1995;Tyler and Olsson, 2001) Ca(OH) 2 Decreased bioavailability (Basta and Sloan, 1999;Chaney et al, 1977;Brallier et al, 1996;Gray et al, 1999a) CaO Decreased phytoavailability (Vasseur et al, 1998) MgCO 3 Decreas...…”

Short-term in situ immobilization of Cd and Ni by beringite and steel shots application to long-term sludged plots

“…Oliver et al [26] found that the effect of soil pH on the Cd concentration in wheat and barley grain was very small. Excessive liming may lead to a depression in crop yield [13]. In [2,10,11,28].…”