Assessment of landfill leachate toxicity using the duckweed Lemna minor

Leachates from 10 landfills receiving municipal or industrial wastes were tested chemically and their toxicity tested on duckweed. Six duckweed specimens each of 2 fronds were exposed to 6 dilutions of each leachate. Net frond increase and dry weight increase were measured for 5 d and observations made on plant damage. Three assays were performed with each leachate. Many leachates stimulated growth at low concentrations and were toxic at higher values, producing increasing damage as their concentrations rose. The nature of the damage and the effect on biomass yield could help differentiate the leachates. Toxicities were explained principally by conductivity, alkalinity and ammonia content. Further work was necessary to understand the role of conductivity and alkalinity in toxicity.