Extractable organic compounds in the clay mineral sealing of a waste disposal site

Today, clay mineral sealings are often used for the construction of new waste disposal sites in order to protect the ground water from contamination by hazard seepage waters. In 1977 one part of the newly constructed waste disposal site in Geldern-Pont near Mönchengladbach, western Germany was reserved in order to investigate the long-term stability of such sealings. After 8 years, the clay sealing of the dump, filled only with conventional domestic waste, was sampled in order to study its geochemical alteration. In the present study a core of the clay linear was investigated using conventional organic geochemical methods. Results showed that the upper half of the 46 cm thick sealing has accumulated abundant organic matter. The extractable part is primarily composed of long-chain aliphatic hydrocarbons and polar compounds. The dominant constituents are odd-numbered n-alkanes and even numbered n-alkanols associated with minor amounts of long-chain odd-numbered n-alkan-2-ones and even-numbered n-aldehydes. The composition is similar to that of natural waxes of higher plants. Aromatic compounds, present in the original clay, disappeared from the sealing as shown by quantitation of phthalic acid esters, linear alkylbenzenes and phenanthrenes. Several parameters indicate that the activity of anaerobic microorganisms, in the dump and in the upper part of the sealing, governed the geochemical composition observed after 8 years. Aliphatic constituents resisted biodegradation and replaced the aromatic compounds present in the interlayer space of silicate layers.