Evidence for the presence of PCDD/Fs in the environment prior to 1900 and further studies on their temporal trends.

Alcock, Ruth E. and McLachlan, M. S. and Johnston, A. E. and Jones, Kevin C. (1998) Evidence for the presence of PCDD/Fs in the environment prior to 1900 and further studies on their temporal trends. Environmental Science and Technology, 32 (11). pp. 1580-1587. ISSN 0013-936X

Abstract

This paper presents evidence for the existence of PCDD/Fs in the environment prior to the widespread development of the chloroaromatics and chlorine industry, by the analysis of a previously unopened bottle of soil collected in 1881 from a controlled long-term agricultural experiment at Rothamsted Experimental Station. Great care was taken to avoid contamination of the sample from dust or by exposure to modern air; an experiment was conducted to investigate the potential for contamination of the sample by such exposure. The 1881 soil sample (from the plowed 0−23 cm depth layer) contained 0.7 ng of ∑TEQ/kg soil, and there were no detectable changes in its ∑PCDD/F composition when aliquots of it were exposed over 32 days in a laboratory at Lancaster University. Modern soil sampled from the same field plot (which has never received any fertilizers or amendments) now contains 1.4 ng of ∑TEQ/kg, an increase resulting from cumulative atmospheric deposition of PCDD/Fs retained in the surface layers of the soil. Post-collection contamination issues were also addressed by PCDD/F analysis of dust and paper bags used to store more recent samples. The ∑TEQ concentration of archived herbage samples collected year-on-year from Rothamsted between 1980 and 1995 have trended downward by a factor of 3−4, implying a recent decline in the atmospheric deposition of PCDD/Fs and supporting a previously reported (Kjeller et al. Environ. Sci. Techol. 1996, 31, 458−463) longer term decline. The significance of these results is discussed.