A standard reference soil
(GRX2) was used to verify the digestion protocol and measurement accuracy. All the
results correspond to the mean of two replicates. Values were the following:
Pb ¼ 39800, Sb ¼ 2095, Zn ¼ 294, As ¼ 288, Cu ¼ 286 and Cd ¼ 18.36 mg kg1.