PAH contamination (sum of 16 US-EPA PAHs and sum of 15 available PAHs) over time (at T₀ and at T₃₇) and depending on the plant species (orange: alfalfa, Alf; green: ryegrass, Rye).

<p>Values are means and standard deviations of 15 and 56 replicates (PAHs), and 4 and 16 replicates (available PAHs) for the T₀ and T₃₇ conditions, respectively. The effects of time and plant species were evaluated separately using Student t-tests (p<0.05). Green and orange asterisks indicate significant changes in PAH concentrations between T₀ and T₃₇ in the ryegrass and alfalfa rhizotrons, respectively. Black asterisks indicate significant differences in PAH concentrations between the ryegrass and alfalfa rhizotrons at T₃₇.