Estimation of the hazard of landfills through toxicity testing of leachates : 2. Comparison of physico-chemical characteristics of landfill leachates with their toxicity determined with a battery of tests

Twenty-two landfill leachates were tested on a battery of aquatic organisms (microalgae, daphnids, rotifers, crustaceans, protozoans, luminescent bacteria) and analysed for various physico-chemical parameters (pH, conductivity, alkalinity, chemical oxygen demand, dissolved organic carbon, organic nitrogen, total ammonia, K+, Na+, Cl−, SO42−, Ca2+, Mg2+, Fe, Zn, Cu). Principal Components Analyses (PCA) and regression analyses were performed on both types of variables in order to find possible explanations for the observed toxicity. The results of multivariate analyses showed a general relationship between both data sets, namely the most (or least) contaminated samples were also generally the most (or least) toxic. These analyses also suggested that ammonia, alkalinity, and chemical oxygen demand (COD) were associated with increasing toxicity. Simple and multiple regression analyses allowed to confirm the importance of ammonia and alkalinity for causing toxicity to most organisms. Luminescent bacteria, however, were found to be more sensitive to the organic load of the leachates. The results are discussed in the context of risk assessment of various types of landfills.