EVOLUTION OF CHEMICALS WITHIN THE DUMP PROFILE IN A CONTROLLED LANDFILL

Abstract.- The chemical composition of horizontal soil barriers in an active landfill have been evaluated to determine the degrece of the refuse decomposition following a two year active management period. The analysis performed include the distribution of inorganic elements and the composition and mounts of the suite of chemicals found in the water soluble and lipid fractions from the soil layers taken at different depths. The total content of organic matter, as well as of carbohydrates, volatile fatty acids (VFAs), and humic-like substances, increases with depth whereas the amounts of amino acids and lipids follow irregular trends. The similar patterns of VFAs in the different samples analyzed indicate that similar conditions prevail through the dump profile. On the other hand, the progressive transformation u dergone by the lipids from fresh organic matter, mostly produced by microbial activity, is reflected in the distribution patterns of n-alkanes and n-alkanoic acids. Among the most relevant xenobiotic ompounds only dialkyl phthalates and traces of a series of polychlorinated biphenyls (PCBs) were detected. Understanding the origin and fate of organic ompounds in contemporary and ancient environments is one of the key concerns of environmental biogeochemistry. In agreement with Bracke et al. (1991), modern waste disposal sites could be considered as "biochemical reactors", i.e., dynamic systems ideal for monitoring biogeochemical processes. No other natural system offers such advantages to provide short-turm information on the rate of organic matter degradation with respect to aerobic/anaerobic metabolism and varying redox conditions, which therefore may simulat