| The purpose of this research was to characterize the chemical composition and biological effects of leachates from MSW landfills in Florida. Samples were collected from 16 engineered landfills to encompass a cross-section of leachate quality and characteristics. The MSW landfill leachates were tested using a suite of bioassays, which included the chronic Pseudokirchneriella subcapitata and the acute Ceriodaphnia dubia, D. pulex, and Microtox™. Leachates were tested with MetPLATE, a heavy metal specific assay. Additionally, using a yeast reporter assay, the leachates were tested for hormonal activity.; Landfill leachates are complex mixtures of organic and inorganic contaminants with compositions heavily influenced by site-specific parameters (e.g. waste composition and age). The chemical composition of the Florida landfill leachates varied widely. In some leachates, high levels of un-ionized ammonia, inorganic components, CBOD, and COD were recorded. The corresponding toxicity at these sites was high. Significant relationships were shown between the ammonia content of the leachates and toxicity as determined by the C. dubia (R2 = 0.62) and P. subcapitata (R2 = 0.69). The assays were ranked for their sensitivities to the MSW landfill leachates as follows: C. dubia ≈ D. pulex > P. subcapitata (125-ml) ≈ P. subcapitata (25-ml) > Microtox™.; The heavy metal toxicity/bioavailability and heavy metal binding capacity (HMBC) of landfill leachates was determined with MetPLATE. The heavy metal toxicity was low, which was attributed to the presence of complex-forming ligands. The magnitude of the HMBC was investigated with the metals copper, zinc, and mercury. The results showed that the HMBC ranged from 3 to 115, 5 to 93 and 4 to 101 for HMBC-Cu+2, HMBC-Zn+2, and HMBC-Hg+2, respectively. The leachates were chemically/physically treated to reduce or fractionate their complexity. Fractionation of selected leachates revealed that HMBC was influenced by the solid, organic, and hardness content of the tested leachates. Additionally, other unidentified components influenced the HMBC of the landfill leachates.; The leachates were evaluated for their hormonal activity using a yeast reporter assay. The hormonal activity of the raw MSW landfill leachates was highly variable, with an E2 equivalent range from 2.6 to 45.7 ng E2/L. A similar range from 6.2 to 59.7 ng E2/L was reported for the methanol extracts of the leachates. The presence of unidentified substances in the leachates reduced the recovery of hormonal activity. Treatment processes utilizing powdered activated carbon (PAC) removed hormonal activity. |
