Introduction to Contaminated Site Management - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 23

1.3.3.2 Other Inorganic Contaminants (Other than Metals and Metalloids)

A specific case of other inorganic contaminants are the co-called nutrients . With
regard to plant nutrition and, hence, soil contamination, the most relevant nutrients
are the macro-nutrients nitrogen, phosphorus, potassium, and sulphur. These nutri-
ents are needed in relatively large quantities in agricultural management, and are
usually applied as nitrate, phosphate, potassium salts, and sulphate. Since this topic
does not primarily focus on agricultural practices, no further attention will be given
to (the consequences of) nutrients.
A representative of the category of other inorganic contaminants often found in
soils is cyanide, since cyanides are frequently found at former gas work sites, often
in (inner) cities. Cyanide is a contaminant that contains a cyano group (C N) as a

functional group, often found as the anion CN − . Many organic contaminants feature
cyanide as a functional group. Of the many kinds of cyanide contaminants, some are
gases, while others are solids or liquids. Those that can release the cyanide ion CN −
are highly toxic.
Although it has been shown that rhizobacteria are cyanogenic (that is, able to
synthesize cyanides), and hence negatively impact the seedling root growth of var-
ious plants (Kremer and Souissi 2001 ), most cyanide in soil has an anthropogenic
origin. However, since cyanide is mainly present as iron cyanide complexes at gas
work sites, the risk of effects on humans from exposure to cyanides often seems to
be of minor relevance (Kjeldsen 1999 ).

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1.3.3.3 Polycyclic Aromatic Hydrocarbons

Polycyclic Aromatic Hydrocarbons (PAHs) form also an extremely important group
in regard to soil contamination, since they are among the most widespread contam-
inants found in soils, worldwide. They are characterised by a fusion of aromatic
rings and do not contain many heteroatoms (atoms other than carbon or hydrogen).
PAHs are primarily formed by incomplete combustion of carbon-containing fuels
such as wood, coal, diesel, fat, tobacco, or incense (Fetzer 2000 ), and are concen-
trated in oil, tar and coal. Common PAHs in soil are naphthalene, phenanthrene,
anthracene, fluoranthene, benzo[a]anthracene, benzo[k]fluoranthene indeno[1,2,3-
cd]pyrene, benzo[g,h,i]perylene and benzo[a]pyrene. PAHs in soils might show
local or diffuse (due to atmospheric deposition) contamination patterns. Different
types of combustion yield different combinations of PAHs, both in terms of relative
amounts of individual PAHs and with regard to the isomers that are produced.
Some PAH representatives are known or suspected to be carcinogenic, muta-
genic, or teratogenic.

1.3.3.4 Monocyclic Aromatic Hydrocarbons

Some monocyclic aromatic hydrocarbons are frequently found in soil and ground-
water. The representatives most often found are usually categorized as BTEX