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10 Phytostabilization as Soil Remediation Strategy 179

providing micronutrients (as well as macronutrients) to growing plants. These
essential micronutrients are boron (B), copper (Cu), iron (Fe), manganese (Mn),
molybdenum (Mo), and zinc (Zn). The accumulation of these micronutrients by
plants generally follows the order of Mn > Fe > Zn > B > Cu > Mo. This order
may change among plant species and growth conditions. However, at elevated
bioavailable concentrations in soil and when taken in excessive amounts, all metals
ions may cause toxic effects on plants and animal organisms, including humans
(Fig. 10.1) (Ku ¨pper and Kroneck 2005). In this chapter, the focus is on essential and
nonessential elements that will be a risk for environment and humans and that result
from industrial activities.

10.1.1 Copper

Copper is the third most used metal in the world (VCI 2011). Copper ranks 26th
behind zinc in abundance on the lithosphere, and it is a naturally occurring element,
which can be found in all environmental media: air, soil, sediment, and water
(Alloway 1995). Concentrations of Cu in soils range from about 2 to 100 mg kg 1
with a mean of 30 mg kg 1 (Mortvedt 2000). Cu is mostly found in silt and clay
fractions of soil and usually present in carbonate fractions in alkaline soils and in Fe
oxide fractions in acid soils. Also, it occurs in numerous minerals including cuprite,
tenorite, malachite, azurite, and native copper. Copper forms sulfides, sulfates,
sulfosalts, carbonates, and other compounds and occurs in reducing environments
as the native metal. In the soil, Cu strongly complexes to the organic implying that
only a small fraction of copper will be found in solution as ionic copper, Cu(II). Cu
is an essential micronutrient required in the growth of both plants and animals. In
humans, it helps in the production of blood hemoglobin. In plants, Cu is especially
important in seed production, disease resistance, and regulation of water. Copper is
indeed essential, but in high doses it can cause anemia, liver and kidney damage,
and stomach and intestinal irritation.

10.1.2 Zinc

Zinc is the second most abundantly distributed element in the body after iron. Zinc
1
occurs naturally in soil (about 70 mg kg in crustal rocks), but Zn concentrations
are rising unnaturally, due to anthropogenic additions. Water-soluble Zn that is
located in soils can contaminate groundwater. In effect, some fish can accumulate
Zn in their bodies, and it is able to biomagnify up the food chain. Plants often have
a Zn uptake that their systems cannot handle, due to the accumulation of Zn in soils.
Zn catalyzes enzyme activity, contributes to protein structure, and regulates gene
expression. Also, zinc is involved in the carbohydrate transformation (consumption
of sugars) and in plant development regulation. Finally, Zn can interrupt the activity