With the exception of site 9, there was no significant difference
in soil IHg concentrations between the two depths (p b 0.05).
These soils are regularly plowed by the local farmers contributing
to this homogeneous distribution of the soil mercury pool within
the surface soil layers. For samples 9a, 9b and 9c collected from
inside “Vala de S. Filipe” relatively higher IHg levels were found at
the 0–10 cm layer (140–210 mg kg−1 d.w.), compared to the 10–
20 cm depth (12–65 mg kg−1 d.w.) that is related with the significantly
higher organic carbon contents of the 0–10 cm layer as well
as with the sandy nature of the 10–20 cm layer (N90% sand). Such
soil characteristics contribute to a higher retention of Hg in the 0–
10 cmlayer when compared with the 10–20 cm.