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.

The toxicity of different lead salts to Enchytraeus crypticus in relation to bioavailability in soil

“…Previous studies have also demonstrated that reproduction toxicity is often better related to internal metal concentration than to total soil concentrations [24,39,40]. In the present study, Bioavailability and toxicity of lead salts to enchytraeids Environ Toxicol Chem 36, 2017 mortality occurred when internal Pb concentration exceeded approximately 60 mg Pb/kg dry body wt, which is in agreement with the results observed by Davies et al [41]. Thus, it is likely that when the internal Pb concentration exceeds a physiological limit (the capacity of Pb detoxification mechanisms), the mortality of E. crypticus increases, while metal is slowly sequestered.…”

Single versus multiple occupancy—effects on toxcityp parameters measured on Eisenia fetida in lead nitrate–treated soil

“…The soil was air dried and sieved, and the <2‐mm fraction was retained for the experiment. The soil water holding capacity [1] was 27 ± 1% ( n = 5), the soil pH (0.01 M CaCl 2 [17]) was 6.7 ± 0.5 ( n = 3) (compared with the pH of the OECD standard soil of 6.0 ± 0.5), and the cation exchange capacity was 17.6 ± 9.2 centimoles of charge (cmol c )/kg ( n = 24) [18] (compared with 14 cmol c /kg for the OECD standard soil [19]). The earthworms were kept in a 3:1 mixture of Kettering loam soil and Irish moss peat (Westland Garden Health, Dungannon, County Tyrone, Ireland) for 14 days before the start of the tests.…”

“…At the end of the experiment, the surviving earthworms were depurated on moist filter paper for 48 h at 20°C in the dark, (with filter paper being changed every 12 h), frozen at −18°C, allowed to thaw, dried overnight at 40°C, and then digested in reagent‐grade AnalaR nitric acid [18]. Solutions were analyzed by ICP‐OES.…”

Treatment and Management of Closed or Inactive Small Arms Firing Ranges

“…Several recent studies have also reported that phosphate addition lowered the toxicity of the lead in the contaminated soils, primarily by making it less bioavailable (Yang et al 2001, Davies et al 2002, Hettiarachchi et al 2002, Maenpaa et al 2002. Yang et al (2001) added phosphoric acid at 1.25 to 10 g/kg phosphorous to smelter-contaminated urban soils.…”

“…This is commonly determined by in vivo tests on live organisms such as earthworms, weanling pigs, and rats, and by in vitro tests such as sequential extraction or physiological based extraction tests for "bioaccessible" lead (ITRC 2003). Several recent in vivo studies have compared the effect of phosphate treatment of lead-contaminated soils to a corresponding reduction in earthworm lead uptake and toxicity (Maenpaa et al 2002, Davies et al 2002, Nahmani et al 2007). In all cases, phosphate addition lowered the toxicity of the lead in the contaminated soils or increased the LC 50 and/or survival time of the earthworms exposed to the soil.…”