Characteristics of Natural and Urban Soils - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 93

such as arsenic and copper (from fungicides), and organic contaminants such as
DDT and dieldrin (from pesticides).
3. Urban soils from an anthropogenic origin (Technosols, FAO 2006 ), usually
deposited, consisting of technogenic man-made material or of both technogenic
and natural material (Deposols in German nomenclature). These soils are very
likely to contain contaminants, as they are often waste soils from excavations
at urban sites and can contain almost anything, from rubble to mine waste and
fly ash.

The second and third group belong to the anthropogenic soils. The FAO-Unesco
( 1998 ) soil classification system World Reference Base (WRB) refers to the second
group as Anthrosols (soils with long and intensive agricultural use), and the third
one is called Technosols (soils containing many artefacts).
The second group, associated with long-term horticultural or agricultural use,
indicates man-made profile changes. The soils, however, are based on natural par-
ent material. Typically, the humic topsoil is deeper than the usually ploughed soil
depth of 30 cm. We can distinguish between several kinds of soils within this group
(Meuser and Blume 2004 ):

• Garden soil , significant in residential areas with gardens surrounding detached

houses, row houses, or exclusive residences, as well as for allotments. Continuous
organic matter application (e.g., compost, manure), combined with frequent dig-
ging procedures, leads to humic top soils with an enhanced biological activity.
Based upon the German nomenclature, garden soils with a humic topsoil of at
least 40 cm are termed Hortisols . Different from garden soils, there are soils of
cemeteries and churchyards, indicative of deep digging activities to a depth of
180 cm and ultimately humus accumulation.

• Moreover, there are so-called plaggen soils occupying large areas of the northern

parts of Germany and the Netherlands. They result from long-term agricultural
use in time periods between the 14th and 19th century, when farmers used organic
manure only, leading to a raised soil surface in the course of time. They are of
importance at urban sites as well, since they are mostly located close to built-up
areas, in particular in the peri-urban area.

Generally, the cultivated soils of concern show enhanced contaminant concentra-
tion due to atmospheric input (air pollution) and artificial amendments like sewage
sludge or ashes. For instance, many urban garden soils have been fertilized with
ashes derived from domestic home heating processes, leading to a high concen-
tration of heavy metals compared with neighbouring cropland sites (Meuser and
Anlauf 2007 ) (Fig. 2.1 ).
Anthropogenic soils, or Deposols, can be subdivided according to distinct kinds
of deposits (Fig. 2.2 ). In the landscape, deposits consisting of mining heaps, waste
landfills, dumps, and linear structures such as dikes, dams, and sound-isolating earth
walls, are easily recognisable. The fill materials, however, result from excavations