Solubility and Plant Uptake of Cadmium in Soils Amended with Cadmium and Sewage Sludge

Abstract

Adsorption and precipitation of Cd2+ in soil suspensions were investigated as possible factors controlling Cd2+ levels in soils. Both adsorption of Cd2+ onto soils surfaces and possibly precipitation of cadmium minerals were evident in this study. At low cadmium levels solubility relationships in soils are best described by adsorption and fit the empirical Freundlich adsorption isotherm. Based on current thermodynamic data the solid phases CdCO3 (log Ksp = −12.07) and Cd3(PO4)2 (log Ksp = −32.61) most likely limit Cd2+ activities in soils. Under alkaline conditions, Cd2+ activity decreased approximately 100‐fold for each unit increase in pH. In this study, CdCO3 precipitated in sandy soils, having low cation exchange capacity (CEC), low organic matter, and pH values >7.0.DTPA‐extractable cadmium levels in soils were highly correlated (r = 0.96) with Cd concentrations in corn (Zea mays L.) seedlings grown on soils amended with Cd solutions, sewage sludge, or Cd‐spiked sewage sludge. Increasing Cd additions to the soil increased plant Cd regardless of the form of Cd added. Addition of inorganic Cd to the soil increased the Cd concentration of corn seedlings more than equivalent Cd additions in the form of sewage sludge or Cd‐spiked sludge.

Factors influencing metal bioavailability in soils: preliminary investigations for the development of a critical loads approach for metals

“…Cotter-Howells et al (1994) found pyromorphite to be the major Pb bearing phase in a study of mine waste soils. Precipitation of Cd in the carbonate, phosphate, sulphate and chloride forms has also been reported, generally in non-acidic conditions (Street et al, 1977;Jones and Jarvis, 1981;Moir, 1992). Whilst recognising the importance of precipitation in the partition of metals between the solid and solution phases, there are analytical and theoretical problems in extrapolating the concept of solubility products to precipitation reactions in natural soils.…”

“…Organic matter content showed no correlation with Pb uptake (John, 1972), positive associations with Zn uptake (MacLean, 1976;Martin et al, 1982) and negative associations with Cd uptake (MacLean, 1976;Street et al, 1977). Similarly, the effect of soil organic matter on metal mobility has been investigated.…”

Adsorption du cadmium dans les sols calcaires du Sud-Est de l'Espagne

“…Vis-à-vis (Street et al, 1977;Singh, 1979;Jarvis et (Singh, 1979;Mc Bride et al, 1981) ainsi que de leur faculté à prévenir l'adsorption du métal par la plante (Miller et al, 1976;Mc Bride et al, 1981;Hinesly et al, 1982 …”

Adsorção de cádmio em dois Latossolos ácricos e um Nitossolo

“…(Pombo, 1995;Gray et al, 1998;Filius et al, 1998 (Street et al, 1977;Naidu et al, 1994). É reportada também na literatura a complexação de Cd com matéria orgânica dissolvida, principalmente entre pHs 4 e 6 (Sauvé et al, 2000).…”