Use this URL to cite or link to this record in EThOS:
Title: Impact of earthworms on metal mobility and availability
Author: Sizmur, Tom
ISNI:       0000 0004 2717 8298
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2011
Availability of Full Text:
Access from EThOS:
To assess the risks that contaminated soils pose to the environment properly a greater understanding of how soil biota influence the mobility of metal(loid)s in soils is required. Experiments have been undertaken to determine if earthworms affect the mobility, speciation and bioavailability of metals in contaminated soils. The majority of experiments involved inoculating Lumbricus terrestris (but also Eisenia veneta, Allolobophora chlorotica and Eisenia fetida) in laboratory microcosms containing soils contaminated with As, Cu, Pb and Zn. Metal(loid) availability to plants and mobility measured in porewater and soil extractions revealed that earthworms increased metal mobility, changed the speciation to a more available form and increased bioavailability to plants. The mechanism for these effects is the degradation of organic matter due to passage through the earthworm gut and subsequent release of organically bound metals into solution. Passage through the earthworm gut also increased the soil pH and the concentration of labile organic carbon which then had an impact on the distribution of metal(loid)s between the soil constituents and the soil solution. The precise effect depends on the chemistry of the element in question, but usually resulted in an increase in mobility. The secretion of earthworm mucus decreased the mobility of metals in soils, but this effect was not as great as passage through the earthworm gut. When earthworms were inoculated into soil that has been remediated with biochar and/or compost, they did not re-mobilise sequestered metals. Instead, the remedial amendment buffered the impact of the earthworm. The mobilisation of metal(loid)s in the environment by earthworm activity may allow for increased leaching or uptake into biota and should therefore be considered in the risk assessment of contaminated soils that contain earthworms.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available