Can earthworm-secreted calcium carbonate immobilise Zn in contaminated soils?

TY - JOUR

T1 - Can earthworm-secreted calcium carbonate immobilise Zn in contaminated soils?

AU - Brinza, Loredana

AU - Schofield, Paul

AU - Mosselmans, J Frederick W

AU - Donner, Erica

AU - Lombi, Enzo

AU - Paterson, David

AU - Hodson, Mark Edward

N1 - Copyright © 2014 Elsevier Ltd.

PY - 2014/7

Y1 - 2014/7

N2 - We investigated the interaction of soil Zn with calcium carbonate granules secreted by the earthworm Lumbricus terrestris. Earthworms were kept in agricultural soil amended with ZnSO4 to give Zn concentrations up to 750 mg / kg and in two former mine site soils containing 500 and 120 mg Zn / kg. After 21-42 days the earthworms accumulated 260-470 mg Zn / kg. Granule production was 0.027 - 2.11 mg CaCO3 / earthworm / day and was positively correlated with soil and soil solution pH (r = 0.66 and 0.85 respectively, p < 0.01). Granule Zn concentration was 34 -163 mg / kg. Granules collected from Zn-free control soil and left in Zn-bearing soil for 28 days contained 49-60 mg Zn / kg suggesting that the majority of Zn associates with granules after their secretion. However, synchrotron X-ray fluorescence indicates some incorporation of Zn into granules during their formation. X-ray diffraction and X-ray absorption spectroscopy indicate that the granules are predominantly calcite and the spectroscopy suggests that the Zn is either adsorbed to, or incorporated into, the calcite lattice. X-ray diffraction of the outer c. 35 micron of the granules supports incorporation of Zn into the calcite lattice. The low granule production rates in the mine site soils and the granule Zn concentrations suggest that earthworm secreted calcium carbonate is unlikely to impact significantly on Zn mobility in soils.

AB - We investigated the interaction of soil Zn with calcium carbonate granules secreted by the earthworm Lumbricus terrestris. Earthworms were kept in agricultural soil amended with ZnSO4 to give Zn concentrations up to 750 mg / kg and in two former mine site soils containing 500 and 120 mg Zn / kg. After 21-42 days the earthworms accumulated 260-470 mg Zn / kg. Granule production was 0.027 - 2.11 mg CaCO3 / earthworm / day and was positively correlated with soil and soil solution pH (r = 0.66 and 0.85 respectively, p < 0.01). Granule Zn concentration was 34 -163 mg / kg. Granules collected from Zn-free control soil and left in Zn-bearing soil for 28 days contained 49-60 mg Zn / kg suggesting that the majority of Zn associates with granules after their secretion. However, synchrotron X-ray fluorescence indicates some incorporation of Zn into granules during their formation. X-ray diffraction and X-ray absorption spectroscopy indicate that the granules are predominantly calcite and the spectroscopy suggests that the Zn is either adsorbed to, or incorporated into, the calcite lattice. X-ray diffraction of the outer c. 35 micron of the granules supports incorporation of Zn into the calcite lattice. The low granule production rates in the mine site soils and the granule Zn concentrations suggest that earthworm secreted calcium carbonate is unlikely to impact significantly on Zn mobility in soils.

KW - earthworms

KW - calcite

KW - zinc

KW - calcium carbonate

U2 - 10.1016/j.soilbio.2014.01.012

DO - 10.1016/j.soilbio.2014.01.012

M3 - Article

SN - 0038-0717

VL - 74

SP - 1

EP - 10

JO - Soil Biology and Biochemistry

JF - Soil Biology and Biochemistry

ER -