『Abstract
The distribution of As in a variety of sample materials was studied
at different scales, from continental to local, combining published
data sets with the aim, of delineating the impact and relative
importance of geogenic vs. anthropogenic As sources. Geochemical
mapping of As with a variety of sample materials demonstrates
that variation is high at all scales (local to continental) -
from sample densities of 400 sites per km2 to 1 site
per 5000 km2. Different processes govern the As distribution
at different scales. A high sample density is needed to reliably
detect mineralisation or contamination in soil samples. In both
cases the impact on the much larger geochemical background variation
is limited to a local scale. Distribution patterns in geochemical
maps on the sub-continental to continental scale are dominated
by natural variation. Given that the geochemical background is
characterised by a high variation at all scales, it appears impossible
to establish a reliable single value for “good soil quality” or
a “natural background concentration” for As for any sizable area,
e.g., for Europe. For such a differentiation, geochemical maps
at a variety of scales are needed.
Different sample materials can pick up dissimilar geochemical
sources and processes, even when collected from the same survey
area. Weathering (soil formation) leads to an As increase in soils
when compared to rocks. Soils and stream sediments return very
comparable median As concentrations. Plants are usually well protected
against As uptake. There are, however, plant species that can
accumulate unusually high As concentrations. The marine environment
is generally enriched in As. Several geochemical mapping projects
deliver indications for crustal as degassing as an important process
leading to As enrichment in the surface environment.
Keywords: Geochemical mapping; Exploration; Contamination; Background;
Soil; Sediment; Biogeochemistry』
Contents
1. Introduction
1.1. Geochemical mapping and scale
1.2. Some general properties of arsenic
2. Regional bedrock geochemistry
3. Soil geochemistry
3.1. Mineral exploration
3.1.1. Tampera, Finland, mineral exploration at three different
scales using soil samples
3.1.2. The Walchen Valley, Austria
3.2. Contamination
3.2.1. Urban geochemistry, Berlin, Germany
4. Regional impact of metal mining and smelting on a variety of
sample materials - the Kola ecogeochemistry project
5. (Sub)continental-scale geochemical mapping
5.1. The Barents project
5.2. The Baltic soil survey
5.3. The FOREGS (EuroGeoSurveys) geochemical Atlas of Europe
6. Discussion and conclusions
Acknowledgements
References