Luke Beesley: Ecotoxicity Screening of Biochars for Mine Soil Remediation

STSM at Universidad Autónoma de Madrid, Spain

Remediation of heavy metal contaminated soils is costly, and in-situ methods are preferable to avoid large scale engineering and removal of soils. Luke's STSM was a screening exercise designed to predict the usefulness of applying seven biochars to two metal contaminated mine soils; he used a simple petri-dish germination assay of biochars mixed with soils or extracts of water from soil and biochar mixtures.

Luke Beesley (James-Hutton-Institute, UK) was hosted by Eduardo Moreno-Jimenez at the Department of Agricultural Chemistry, Universidad Autónoma de Madrid (Spain).

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The first stage was to mix soils with biochars and place the mixtures in simple columns, to extract by suction soil water:

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Mixtures of soil and biochar were also placed in petri dishes for comparison:

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Soil water collected by the columns was used to irrigate a filter paper with 15 ryegrass seeds, as a growth medium. These could be compared with soil as a growth medium:

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Other samples were prepared for chemical analysis, centrifuging and filtering to remove particulate matter. These were checked for metal concentrations, dissolved organic carbon etc:

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This methodology proved rapid and could be used to quickly screen a number of biochars for their effects on individual soils, before field application; most tested biochars reduced soil toxicity, promoting an increased germination against the control, without biochar. The soil solution method was a sensitive indicator of toxicity.