A Practical Approach for Site Investigation - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 140

Exploratory Investigation ...................................

3.7 152

3.8 Main Investigation ....................................... 158

Sampling Patterns ....................................... 3.9 160

3.10 Sampling Techniques ..................................... 161

Literature ................................................

162

3.1 Introduction

Historically, the investigation of soil quality had an agricultural background and was
the domain of agriculturally oriented soil science. During the 1980s, soil contam-
ination became an important issue, thus a new type of soil investigation had to be
developed: the investigation of (potentially) contaminated sites. This proved to be a
fundamentally different type of soil investigation compared to what was previously
common practice in agricultural science. Different not only because its aim is to
find contaminants in the soil rather than nutrients but, for example, also different
due to the presence of buildings, roads and sealed surfaces on the site which hin-
der sampling on every randomly chosen location. Different also because knowledge
of former (industrial) processes had to be implemented in the process of choosing
where to sample, as well as for identification of the contaminants that had to be
investigated.
Some decades later, the investigation of the soil quality of (potentially) con-
taminated sites in industrialised countries has become an area that employs far
more people than the original agricultural investigations. Given the volume of work
related to this type of soil investigation, both strategies and techniques for the
investigation of potentially contaminated sites have been developed and have been
standardized both on a national and an international level.

3.2 Not an Easy Task

Investigating soil contamination is not an easy task. Contaminants are most often
distributed highly heterogeneously in the soil, due to both the way the contaminants
get into the soil (e.g. industrial spilling, accidental spills or dumping) and to natu-
ral processes in the soil like groundwater transport. Moreover, we can only see the
surface of the soil, while the soil itself can be highly variable, for example when
small layers of sand, peat and clay alternate with each other. Variations in soil type
will result in different behaviour of contaminants, showing, for example, prefer-
ential pathways in sandy soils and a high degree of retention in clay layers. The
differences in interaction between various (combinations of) contaminants, the nat-
ural processes and the variations in the soil itself, altogether will result in a complex
distribution of the contaminant in the soil.
Given that complexity, non-experts should be aware of the fact that there is no
easy way to cope with these kinds of investigations. Although this article is partly
based on standardized approaches, expert knowledge is always an important factor