EXTRACTABLE ORGANIC-COMPOUNDS IN THE CLAY MINERAL SEALING OF A WASTE-DISPOSAL SITE

Today, clay mineral sealings are often used for the construction of ne w waste disposal sites in order to protect the ground water from conta mination by hazard seepage waters. In 1977 one part of the newly const ructed waste disposal site in Geldern-Pont near Monchengladbach, weste rn Germany was reserved in order to investigate the long-term stabilit y of such sealings. After 8 years, the clay sealing of the dump, fille d only with conventional domestic waste, was sampled in order to study its geochemical alteration. In the present study a core of the clay l iner was investigated using conventional organic geochemial methods. R esults showed that the upper half of the 46 cm thick sealing has accum ulated abundant organic matter. The extractable part is primarily comp osed of long-chain aliphatic hydrocarbons and polar compounds. The dom inant constituents are odd-numbered n-alkan-2-ones and even-numbered n -alkanols associated with minor amounts of long-chain odd-numbered n-a lkan-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 quanti tation of phthalic acid esters, linear alkylbenzenes and phenanthrenes . Several parameters indicate that the activity of anaerobic microorga nisms, 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 i n the interlayer space of silicate layers.