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).


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


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


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:


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


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.