『Abstract
The continental area of Portugal is now entirely covered by a
soil geochemical survey (1 site/135 km2), taking as
the sampling media topsoils (upper mineral horizons, A) and organic
horizons (humus, O). Standard methods for sampling, sample preparation
and analysis were used in order to achieve high quality and consistent
data. Each sample was analyzed for 32 chemical elements, pH, electrical
conductivity and organic matter content.
The main purpose of the survey was to obtain baseline levels
for various chemical elements. The compilation of all data (nearly
45,000 individual data) in an organised way, led to the production
of the first Soil Geochemical Atlas of Portugal. In this Atlas
it is possible to find for each chemical element a set of information
statistics (basic statistical parameters, boxplots, cumulative
frequency curves, etc.), maps of spatial distribution, among other
information of geochemical and environmental interest. This paper
gives an overview of the Soil Atlas and examples of application.
The data were used to calculate reference values for 9 elements
of environmental importance and to obtain empirical formulae allowing
the estimation of elements in the coarse fraction of soils (<2.00
mm) from known concentration in a finer fraction (<0.18 mm).
Keywords: Geochemical mapping; Soils; Geochemical atlas; Geochemical
baselines; Portugal』
1. Introduction
2. The study area
3. Methods
3.1. Sample collection and treatment
3.2. Analysis and analytical quality control
3.3. Statistical processing and mapping
4. Results and discussion
4.1. General interpretation
4.2. Evaluation of quality standards for soils
4.3. Comparative analysis of data based on different size fractions
4.3.1. Regression models
5. conclusions
Acknowledgements
References