Stable strontium accumulation by earthworms: A paradigm for radiostrontium interactions with its cationic analogue, calcium

• Published in: Environmental toxicology and chemistry 2001-06, Vol.20 (6), p.1236-1243
• Main Authors: Morgan, John E., Richards, Sarah P. G., Morgan, A. John
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Animals; Applied ecology; Biological and medical sciences; Body Burden; Calcium; Calcium - pharmacokinetics; Concentration factor; Discrimination coefficient; Earthworms; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on protozoa and invertebrates; Fundamental and applied biological sciences. Psychology; Kinetics; Oligochaeta - metabolism; Soil - analysis; Soil Pollutants - pharmacokinetics; Spectrophotometry, Atomic; Strontium; Strontium - pharmacokinetics; Strontium Radioisotopes
• ISSN: 0730-7268; 1552-8618
• DOI: 10.1002/etc.5620200612

The accumulation of stable strontium and its chemical analogue calcium by four species of earthworm, representing three distinct ecophysiological groups inhabiting celestite (SrSO4)‐rich natural soils, was investigated. An increase in soil strontium concentration over a four‐orders‐of‐magnitude range was accompanied by an increase in earthworm tissue strontium concentration. In contrast, no relationship between soil and tissue calcium concentrations was apparent, indicating that this essential cation is strongly regulated within earthworm tissues but that nonessential strontium burdens are not physiologically regulated. Concentration factors for strontium ranged from 0.1 to 1.42, with an inverse relationship between this parameter and soil strontium concentration. The use of concentration factors and discrimination coefficients lead to the conclusion that earthworms discriminate against strontium accumulation at increased soil calcium concentrations, such that strontium would be predicted to be more efficiently accumulated by worms inhabiting acidic, calcium‐poor soils. Although few consistent trends in strontium and calcium concentration were apparent between earthworm species, the species with the highest calcium turnover (i.e., the litter‐inhabiting Lumbricus rubellus) typically accumulated higher concentrations of strontium than representatives of contrasting ecophysiological classes. These findings are considered in the context of the distribution, retention, and cycling of radiostrontium in soils.