IN-SITU AND LABORATORY STUDIES ON THE FATE OF SPECIFIC ORGANIC-COMPOUNDS IN AN ANAEROBIC LANDFILL LEACHATE PLUME .2. FATE OF AROMATIC AND CHLORINATED ALIPHATIC-COMPOUNDS

The transformation of specific organic compounds was investigated by i n situ and laboratory experiments in an anaerobic landfill leachate po llution plume at four different distances from the landfill. In a prev ious paper (Part 1, also published in this issue) we described the in situ microcosm and laboratory batch microcosm experiments performed fo cusing on redox conditions, microbiology and the fate of 7 phenolic co mpounds. In this paper we present the results on the fate of 8 aromati c compounds and 4 chlorinated aliphatic compounds. Nitrobenzene was tr ansformed at all distances from the landfill in methanogenic, and Fe(I II)-and NO3--reducing conditions. Toluene was transformed slowly in on e out of three in situ experiments at the distance of 250 m from the l andfill in the Fe(III)-reducing part of the plume after a lag phase of similar to 3 months. Benzene, o-xylene, p-dichlorobenzene, o-dichloro benzene, naphthalene and biphenyl were not transformed at any of the i nvestigated distances from the landfill, neither in in situ nor in lab oratory experiments. In the methanogenic part of the aquifer 2 m from the landfill, 1,1,1-trichloroethane, tetrachloromethane and tetrachlor oethene were transformed in in situ experiments while trichloroethene was not. Lag phase periods were up to 40 days for 1,1,1-trichloroethan e and up to 100 days for tetrachloroethene. No or only short lag phase s (<10 days) were observed for tetrachloromethane. Tetrachloromethane was furthermore transformed at distances of up to 250 m from the landf ill in Fe(III)-reducing conditions but not in NO3--reducing conditions at 350 m from the landfill. Abiotic processes apparently contributed to the transformation of tetrachloromethane. A local variation in the transformation of the chlorinated aliphatic hydrocarbons was observed at 2 m from the landfill. In general, good accordance with respect to compound transformation was observed between in situ and laboratory ex periments, but in a few cases more compounds were transformed in in si tu experiments than in the corresponding laboratory experiments.