(ii) the top soil level (Ts), corresponding to the soil layer at the top
of the pot, i.e., immediately under the sludge layer, and with a
depth of 5 cm; and
(iii) the bottom soil level (Bs), corresponding to the soil layer at
the bottom of the pot with a depth of 5 cm.
The samples were oven-dried at 60 C for 48 h before being
crushed and sieved to 2 mm