Incorporation of lead into calcium carbonate granules secreted by earthworms living in lead contaminated soils

TY - JOUR

T1 - Incorporation of lead into calcium carbonate granules secreted by earthworms living in lead contaminated soils

AU - Fraser, A.

AU - Lambkin, D. C.

AU - Lee, M. R.

AU - Schofield, P. F.

AU - Mosselmans, J. F. W.

AU - Hodson, M. E.

PY - 2011/5/1

Y1 - 2011/5/1

N2 - The influence of soil organisms on metal mobility and bioavailability in soils is not currently fully understood. We conducted experiments to determine whether calcium carbonate granules secreted by the earthworm Lumbricus terrestris could incorporate and immobilise lead in lead-and calcium-amended artificial soils. Soil lead concentrations were up to 2000 mg kg(-1) and lead: calcium ratios by mass were 0.5-8. Average granule production rates of 0.39 +/- 0.04 mg(calcite) earth-worm(-1) day(-1) did not vary with soil lead concentration. The lead: calcium ratio in granules increased significantly with that of the soil (r(2) = 0.81, p = 0.015) with lead concentrations in granules reaching 1577 mg kg(-1). X-ray diffraction detected calcite and aragonite in the granules with indications that lead was incorporated into the calcite at the surface of the granules. In addition to the presence of calcite and aragonite X-ray absorption spectroscopy indicated that lead was present in the granules mainly as complexes sorbed to the surface but with traces of lead-bearing calcite and cerussite. The impact that lead-incorporation into earthworm calcite granules has on lead mobility at lead-contaminated sites will depend on the fraction of total soil lead that would be otherwise mobile. (C) 2011 Elsevier Ltd. All rights reserved.

AB - The influence of soil organisms on metal mobility and bioavailability in soils is not currently fully understood. We conducted experiments to determine whether calcium carbonate granules secreted by the earthworm Lumbricus terrestris could incorporate and immobilise lead in lead-and calcium-amended artificial soils. Soil lead concentrations were up to 2000 mg kg(-1) and lead: calcium ratios by mass were 0.5-8. Average granule production rates of 0.39 +/- 0.04 mg(calcite) earth-worm(-1) day(-1) did not vary with soil lead concentration. The lead: calcium ratio in granules increased significantly with that of the soil (r(2) = 0.81, p = 0.015) with lead concentrations in granules reaching 1577 mg kg(-1). X-ray diffraction detected calcite and aragonite in the granules with indications that lead was incorporated into the calcite at the surface of the granules. In addition to the presence of calcite and aragonite X-ray absorption spectroscopy indicated that lead was present in the granules mainly as complexes sorbed to the surface but with traces of lead-bearing calcite and cerussite. The impact that lead-incorporation into earthworm calcite granules has on lead mobility at lead-contaminated sites will depend on the fraction of total soil lead that would be otherwise mobile. (C) 2011 Elsevier Ltd. All rights reserved.

UR - http://www.scopus.com/inward/record.url?scp=79953212890&partnerID=8YFLogxK

U2 - 10.1016/j.gca.2011.02.015

DO - 10.1016/j.gca.2011.02.015

M3 - Article

SN - 0016-7037

VL - 75

SP - 2544

EP - 2556

JO - Geochimica et Cosmochimica Acta

JF - Geochimica et Cosmochimica Acta

IS - 9

ER -