Xenobiotic organic compounds in leachates from ten Danish MSW landfills—chemical analysis and toxicity tests

A monitoring program comprising chemical analysis and biological toxicity testing of leachate samples from 10 Danish landfills (six engineered and four uncontrolled) revealed the presence of 55 different xenobiotic organic compounds (XOCs) and 10 degradation products of XOCs. The compounds belong to the following groups: BTEX, C3-benzenes, bicyclo compounds, napthalenes, chlorinated aliphatics, phenols (chloro-, methyl-, dimethyl, nonyl-), pesticides, and phthalates. Concentrations of single XOCs ranged from <0.1 to 2220 μg/L. A pesticide screening including 101 different compounds resulted in detection of 18 pesticides and three degradation products. The findings of degradation products of toluene, phenols, phthalates, pesticides, and nonylphenol ethoxylates show that degradation occurred inside the landfills. In biotests with bacteria and algae it was found that the non-volatile organic compounds were toxic as the samples only needed to be pre-concentrated from 1.3 to 9.4 times to give 50% inhibition of the test organisms. One of the ten samples proved to be genotoxic in the umuC test after 141 times pre-concentration. A major part of the organic chemicals causing toxicity remains unknown and it is recommended to combine chemical analyses and biotests in future monitoring programs.