『Abstract
A collection of 235 samples were taken from 115 sites (representing
a density of 1 sampling site ca. 130 km2) on rural
soils derived from the major rock types in the southern Iberian
Massif. The geochemical baselines of selected trace elements (As,
Co, Cr, Cu, Ni, Pb and Zn) were determined on the ＜2 mm soil fraction.
The sampling sites were not directly influenced by external pollution.
Soil geochemical baseline and threshold values were calculated
for each element in two geologically different zones: the Ossa-Morena
Zone (OMZ) and the South-Portuguese Zone (SPZ).
All the trace elements showed significantly high median concentrations
when compared to reference values for soils of Andalusia, the
European Union and the world indicative of regional scale enrichment
of topsoils, particularly with respect to As (24.7 mg kg-1),
Cu (32 mg kg-1) and Pb (37.9 mg kg-1) in
the SPZ, and Zn (78.5 mg kg-1) in the OMZ. The distribution
patterns of element concentrations are primarily influenced by
the lithology and geochemical nature of bedrock and the occurrence
of metallogenic belts in the survey area, notably the Iberian
Pyrite Belt. In the SPZ the highest median values of As (34.4
mg kg-1), Pb (56 mg kg-1) and Cu (57.4 mg
kg-1) were found in soils derived from acid igneous
rocks of the Iberian Pyrite Belt. By contrast, the soils developed
on carbonate rocks of the OMZ recorded the largest median values
for As (27.8 mg kg-1), Pb (44 mg kg-1) and
Zn (83.1 mg kg-1), probably regarded to base-metal
(SEDEX) deposits. These results indicate that regional geology
is an important determinant of soil geochemical baselines for
soil pollution assessment.
Keywords: Trace element baselines; Soil geochemical baselines;
South-West Spain』
1. Introduction
2. Study area
2.1. Geological setting
2.1.1. Ossa-Morena Zone (OMZ)
2.1.2. South-Portuguese zone (SPZ)
3. Sampling and analytical methods
4. Results
4.1. Abundance and distribution of trace elements in topsoil
4.1.1. Ossa-Morena Zone (OMZ)
4.1.2. South-Portuguese zone (SPZ)
4.2. Vertical distribution and relationship with parent rocks
4.3. Threshold values and baseline levels
4.3.1. Arsenic
4.3.2. Cobalt
4.3.3. Chromium
4.3.4. Copper
4.3.5. Nickel
4.3.6. Lead
4.3.7. Zinc
5. Conclusions
Acknowledgments
References