OCCURRENCE OF POLYCHLORINATED DIBENZO-p-DIOXINS AND DIBENZOFURANS AS IMPURITIES IN WOOD PRESERVATIVE CONTAMINATED AND REMEDIATED SOIL.

K. Kalevi¹, A. Donner¹, H. Kiviranta², T. Vartiainen², K.S. Jørgensen¹, ¹Finnish Environment Institute, P.O. Box 140, FIN-00251 Helsinki, Finland, ²National Institute of Public Health, P.O. Box 95, FIN-70701 Kuopio, Finland

Spills and work with wood preservatives have been the reason for contamination of many sawmills and wood impregnation plants around the world. In Finland a commercial chlorophenol mixture, Ky  5, has been generally used for more than 40 years, until it was banned in 1988. The chlorophenol formulation Ky 5 was, however, not very pure, and impurities of polychlorinated biphenyls (PCBs), polychlorinated phenoxyphenols (PCPPs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) have later been detected in the pure formulation as well as in contaminated soil. These compounds have not, however, been routinely measured in site investigations mainly due to the complexity and expensiveness of analysis.

Due to the solubility and mobility of chlorophenols, they have often been found to contaminate ground water and the general public concern has been directed towards the chlorophenols due to their acute toxicity. Even though PCDD/Fs are some of the most toxic compounds, they do not exhibit acute toxicity and they are very tightly bound to particles and do not leach. During the 1980s the contaminated sites in Finland were registered and remediation of around 50 sawmill sites have been remediated during the late 1980s and in the 1990s with regard to chlorophenols. Around 500 sites are still to be cleaned up.

The most common remediation methods in Finland for chlorophenol-contaminated soil has been composting in biopiles off or on site. To a lesser extent soil has been isolated on landfills or thermically treated. The bioremediation technology has worked out excellent with regard to chlorophenols. After the completion of many remediation events it has become evident that extremely high concentrations of PCDD/Fs can still be found. The purpose of this study was to thoroughly investigate the presence of PCDD/Fs at 5 sites that were remediated with regard to chlorophenols with state support from 1988 to 1996. The investigation covered both bioremediated soil and what might be left on the original site.

PCDD/Fs were analyzed by high resolution mass spectrometry (HRGC/HRMS) and chlorophenols were analyzed by GC-ECD. The preliminary results are given in Table 1. The main components of the PCDD/Fs are PCDFs (usually more than 98 %) and mainly hexa-, hepta- and octa-chlorinated. The results are given as international 2,3,7,8-TCDD toxicity equivalents (I-TEQ). The target value in Finland for remediation actions is 500 ng/kg I-TEQ, and the limit value for non contaminated areas is 20 ng/kg I-TEQ. In soil remaining at sawmill sites the concentrations of PCDD/Fs were found to be from 1 to 12 000 ng/kg I-TEQ. At same time the soil that was digged up from sawmill area contained PCDD/Fs from 200 to 1 954 000 ng/kg I-TEQ. Bioremediated soil contained 500 - 13 000 ng/kg I-TEQ PCDD/Fs. The high concentrations in the bioremediated soil is due to the original presence of the PCDD/Fs in the chlorophenol contaminated soil. In the remediated areas we found concentrations of PCDD/Fs that exceeded both the remediation limit value and the target limit value for clean soil.

The appearance of these high concentrations of PCDD/Fs requires important decisions for the land use and for the remediation technologies to be used. Before that can be done a very thorough risk evaluation both with regard to the exposure to humans and to the environment has to be carried out. Today there are very few remediation technologies available for the removal of PCDD/Fs, only very expensive incineration or isolation at hazardous waste landfills seem to be safe methods at the moment, so here is a great challenge for remediation technology developers.