Page 24 - Soil and water contamination, 2nd edition

General introduction 11

bacteria absorb pollutants directly from soil or water. Subsequently, when animals or humans
eat these plants as part of their diet, the absorbed chemicals may be transferred to higher
trophic level s. Foodstuffs may also become contaminated due to, for example, atmospheric
deposition , application of pesticides , or food processing. In addition, contaminants may
enter the bodies of humans and animals through drinking water, inhalation of contaminated
airborne dust, or via the skin. Contaminants that are not stored in body tissues leave the
body in urine and faeces. The extent to which pollutants accumulate over time in the tissues
of organisms (e.g. leaves, roots, bones, body fat) through any route, including respiration ,
ingestion, or direct contact is referred to as bioaccumulation . Some pollutants have a short
biological half-life (i.e. the time it takes to remove 50 percent of the quantity of a substance

in a specified tissue, organ, or any other specified biota as a result of biological processes),
which means that they are excreted soon after intake and do not have the opportunity to
bioaccumulate. Other pollutants have a long biological half-life and they accumulate in
the organism’s tissues. Whereas bioaccumulation refers to the storage of pollutants in an
individual organism, the term biomagnification is commonly used for the increasing
concentrations as the pollutant passes through the food chain.

1.5 SPATIAL AND TEMPORAL VARIABILITY AND THE CONCEPT OF SCALE

This book is to do with the analysis and prediction of the formation and dynamics of spatial
contaminant patterns in our environment and their impact on the environment. To study
the response of the spatially complex and heterogeneous natural environment to the large-
scale stresses of environmental pollutants the approach must be interdisciplinary, integrating
various subdisciplines of earth and life sciences, such as geochemistry , hydrology , soil science ,
geomorphology , meteorology , ecotoxicology , classical and spatial statistics , and geographic
information science . The water flow and solute transport models developed by hydrologists,
soil scientists, and geochemists are essential simulation tools for assessing potential temporal
and spatial changes in the fate and movement of pollutants in soil, groundwater, and surface
water. Classical statistics is valuable for model validation and assessing data uncertainty,
whereas spatial statistics is helpful for examining the spatial variability and spatial structure
by analysing both spatial trends and spatial correlation. Geographical information systems
(GIS ) serve as a means of storing, manipulating, retrieving, and displaying spatial data
associated with environmental pollution.
Spatial and temporal variability are key issues in studies of the environment. The
characteristics of spatial and temporal variation influence which spatial and temporal scale is
chosen for the systematic description of the sources and processes that govern the patterns of
chemicals in the environment. The concept of scale arises from the notion that the properties
of phenomena or processes vary when measured over different spatial or temporal extents
or different levels of resolution (Bierkens et al., 2000). The extent refers to the size or scope
of the study area or duration of time; the resolution refers to the detail of measurement
(Figure 1.2), which is determined by both sampling interval (distance or time lag between
two samples) and so-called sample support , i.e. physical size or extent of the sample (area,
volume, or mass). Extent and resolution are thus both characteristics of scale, but scale
usually refers to the spatial or temporal extent . All environmental issues are defined within
a spatial and temporal framework and can thus be investigated at different scales, depending
on the objectives of the research: management, planning, or restoration. For example, river
water quality can be monitored or simulated at a range of temporal scales from hours or
days (e.g. studies of the response of phosphorus concentration to a heavy rainfall event in
a small catchment ), months and years (e.g. studies of seasonal or year-to-year variation of
phosphorus load from a river basin). If historical records are used, the scale can be extended

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