title: Changes in toxicity and bioavailability of lead in contaminated soils to the earthworm Eisenia fetida (Savigny 1826) after bone meal amendments to the soil.
abstract: The effect of bone meal (Ca5(PO4)3OH) amendments on lead (Pb) bioavailability to Eisenia fetida (Savigny 1826) was investigated. A standard uncontaminated soil was amended with Pb(NO3)2 solution to give Pb concentrations of 7,000 microg/g of soil. After one week, bone meal was added to one half of the soil in the ratio 1:20 bone meal:soil. Immediately after addition of the bone meal, survival times of E. fetida were 23 and 41 h in the bone meal-free and bone meal-amended soil, respectively. Twenty-eight days after addition of the bone meal, survival times of Eisenia fetida were 67 h in the bone meal-free soil and more than 168 h in the bone meal-amended soil. In a second experiment, a standard Organisation for Economic Co-operation and Development reproduction toxicity test was carried out, but in addition to Pb(NO3)2 solution, bone meal was added to the soil in the ratio 1:20 bone meal:soil. The bone meal-free soil was left for five weeks before addition of E. fetida. In the bone meal-amended soil, bone meal was added to the soil one week after addition of the Pb. The soil was left for a further four weeks before addition of Eisenia fetida. Calculated toxicities were significantly lower for the bone meal-amended soil than those calculated for the bone meal-free soil. Twenty-eight-day median lethal concentrations (LC50s; concentration that is statistically likely to kill 50% of the exposed test organism within a given time period +/- 95% confidence intervals) of Pb were 4,379 +/- 356 microg/g of soil for bone meal-free soil and 5,203 +/- 401 microg/g of soil for bone meal-amended soil. Twenty-eight-day median effect concentrations (EC50s; concentration causing a reduction by 50% of a stated parameter) of Pb for weight change were 1,408 +/- 198 microg/g of soil for bone meal-free soil and 3,334 +/- 731 microg/g of soil for bone meal-amended soil and EC50s for cocoon production were 971 +/- 633 microg/g of soil for bone meal-free soil and 1,814 +/- 613 microg/g of soil for bone meal-amended soil. Significant mortalities occurred at Pb concentrations of 2,000 microg/g of soil in the bone meal-free soil and 5,000 microg/g of soil in the bone meal-amended soil. Earthworm Pb body load was lower in the bone meal-treated soil than in the bone meal-free soil up to a Pb concentration of 5,000 microg/g of soil. Earthworm Pb body load was approximately 100 microg/g of worm in surviving earthworms in both experiments when significant mortality occurred. Water and diethylenetriamine pentaacetic acid-extractable soil Pb showed good correlations with earthworm Pb body load. These extractions could be used as estimates for Pb bioavailability.
authors.affiliation: Department of Soil Science, University of Reading, P.O. Box 233, Whiteknights, Reading, Berkshire RG6 6DW, United Kingdom.
authors.forename: Nicola A
authors.initials: NA
authors.lastname: Davies
authors.forename: Mark E
authors.initials: ME
authors.lastname: Hodson
authors.forename: Stuart
authors.initials: S
authors.lastname: Black
mesh_terms: D000818:Animals; D001673:Biodegradation, Environmental; D001682:Biological Availability; D001688:Biological Products; D007854:Lead / Q000493:pharmacokinetics* / Q000633:toxicity*; D007928:Lethal Dose 50; D008903:Minerals / Q000737:chemistry*; D009835:Oligochaeta; D012989:Soil Pollutants / Q000493:pharmacokinetics* / Q000633:toxicity*; D013534:Survival; D014018:Tissue Distribution
chemical_list: D001688:Biological Products; D008903:Minerals; D012989:Soil Pollutants; D007854:Lead; C027762:bone meal