Bioremediation of soil contaminated with alkyllead compounds

Sandy soil, which was highly contaminated with alkyllead compounds, was taken from bore cores from a site of a former tetraalkyllead producing company. It was analyzed for its capacity to chemically and/or biologically degrade alkyllead contaminants. For this purpose, soil samples were supplied with oxygen or oxygen + minerals at different water saturation. For long-term elution, contaminated soil was packed into glass columns of 1.5m length and 10cm diameter. Oxygen-saturated water was recirculated in an upflow mode. Within a time span of 260 days tetraethyllead was completely eluted from the sandy soil and was apparently converted to triethyllead by chemical or microbiological reaction. The triethyllead concentration in the circulating water accounted for 60-80% of the maximal amount, that could be formed from tetraethyllead by a single dealkylation. This indicated that between 20-40% of the triethyllead were apparently further degraded. Only very little diethyllead accumulated in the water. The triethyllead concentration in the circulating water was highly toxic for non-adapted microorganisms. However, if a readily degradable carbon source was added, fast growth of indigenous soil bacteria was observed, but only little alkyllead degradation occurred.