Evaluation of spiking procedures for the introduction of poorly water-soluble contaminants into soil

The purpose of this study was to assess the suitability of various spiking procedures for the introduction of persistent organic pollutants (POPs) into soil environments. 14C-radiolabeled analogues of two representative polycyclic aromatic hydrocarbons (PAHs), phenanthrene (Phe), and benzo[a]pyrene (B[a]P), were introduced into soil using different spiking techniques, and the homogeneity of compound distribution in subsamples was assessed. It was established that under analogous spiking procedures dry soil could be spiked with greater homogeneity than wet soil. The procedure which gave the most homogeneous distribution of compound involved a single spiking/rehydration operation conducted on dry soil. Relative standard deviations of 2.40% for 14C-9-Phe and 3.65% for 14C-7-B[a]P were obtained for this procedure. An optimum procedure for the spiking of wet soil was established, giving relative standard deviations of 4.1% for 14C-9-Phe and 3.7% for 14C-7-B[a]P. This procedure employed a highly spiked wet soil inoculum to distribute the compound throughout the soil system. The influence of carrier solvent on microbial cell numbers determined as colony forming units was also evaluated and shown to have a dramatic negative impact at high volumes.