Predicting Cd partitioning in spiked soils and bioaccumulation in the earthworm Eisenia fetida

• Published in: Applied soil ecology : a section of Agriculture, ecosystems & environment Vol. 42; no. 2; pp. 118 - 123
• Main Authors: Li, Lian-Zhen, Zhou, Dong-Mei, Wang, Peng, Allen, Herbert E., Sauvé, Sébastien
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 01.06.2009; [Amsterdam]: Elsevier Science; Elsevier
• Subjects: Agronomy. Soil science and plant productions; bioaccumulation; Biochemistry and biology; Biological and medical sciences; Cadmium; calcium; Chemical, physicochemical, biochemical and biological properties; Earthworms; Eisenia fetida; Fundamental and applied biological sciences. Psychology; iron; magnesium; partition coefficients; Physics, chemistry, biochemistry and biology of agricultural and forest soils; polluted soils; provenance; simulation models; Soil and water pollution; Soil ligand model; soil pH; soil pore water; Soil properties; Soil science; uptake mechanisms; Zoology (interactions between soil fauna and agricultural or forest soils); China; Cadmium; K p; Soil ligand model; Soil properties; Earthworms; Fauna; Ligand; Prediction; Property of soil; Ecology; K; Modeling; Annelida; Lumbricidae; Oligochaeta; Heavy metal; Earthworm; Soils; Macrofauna; Soil science; Eisenia fetida; Invertebrata; Biological accumulation
• ISSN: 0929-1393; 1873-0272
• DOI: 10.1016/j.apsoil.2009.02.007

Multiple linear regression analysis yielded a statistically based, semimechanistic model describing Cd partitioning coefficients ( K p ) in nine Cd-spiked soils. The Ca, Mg and Fe content in pore water and soil pH were the main variables that account for the variation in Cd partitioning between the soil solid phase and pore water. The affinity constants of Ca 2+ (log K Ca-s = 1.47), Mg 2+ (log K Mg-s = 2.04), Fe 3+ (log K Fe-s = 5.78) and H + (log K H-s = 5.59) binding to active sites on the soil surfaces were evaluated based on the soil ligand modeling approach (SLM), which was derived from the concept of the biotic ligand model (BLM). Cadmium uptake by the earthworm Eisenia fetida was only weakly related to total pore water Cd concentrations ( R 2 = 0.26, P < 0.01) or free Cd activities ( R 2 = 0.21, P < 0.05) in pore water. Introduction of pore water pH as an explanatory variable increased R 2 to 0.45, indicating that Cd uptake by E. fetida may be moderated by the presence of other cations in pore water, especially H + ions. A competitive equilibrium model based on the free ion activity model (FIAM) was developed to quantify the effects of H + ions on the uptake of Cd by earthworms. One of the model parameters is the conditional binding constant of H + (log K H-w = 6.06) to the biotic uptake sites on the surface of the earthworm E. fetida. The results indicated that pH-adjusted free Cd 2+ was a better predictor of tissue concentration in E. fetida than unadjusted free Cd 2+.