Use of a column leaching test to study the mobility of chlorinated HOCs from a contaminated soil and the distribution of compounds between soluble and colloid phases

An equilibrium and recirculation column test for hydrophobic organic chemicals (ER-H test) was used to study the leaching behaviour of chlorophenols (CPs), polychlorinated diphenyl ethers (PCDEs), polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo-p-dioxins (PCDDs) from contaminated soil. A 50% increase in the pore water velocity was shown to have little or no effect on the mobility of CPs, PCDEs, PCDFs and PCDDs. The standard deviations of truly dissolved compounds, CPs, were between 19% and 65% between the tests. However, the repeatability of the ER-H test decreased with increases in the hydrophobicity of the studied compounds; the standard deviations for PCDEs, PCDFs and PCDDs ranged from 53% to 110%, 57% to 77% and 110% to 130%, respectively. The influence of colloids on the release of these compounds was also examined. Up to 30% of the CPs in the soil were leached, of which 1-3% were associated with colloids. The PCDEs, PCDFs and PCDDs were found to be preferably associated with the particulate fraction of the leachate, and less than 0.2% of these compounds were mobilised.