55
Zinc [Zn, 30]
55.1 INTRODUCTION
Zinc (Zn) is a metal of group 15 in the periodic table of elements, which also contains
Cd and Hg. Its abundance in the Earth’s crust is about 75 mg/kg, within the given
range of 50–80 mg/kg. Its highest contents are in mafic rocks (<120 mg/kg), and it
may be also concentrated, up to about 120 mg/kg, in some argillaceous sedimentary rocks. The lowest Zn amounts, 10–25 mg/kg, are in calcareous rocks. In coal
its amounts vary highly, from about 50 to 19,000 mg/kg, and in fly ash it is usually
around 200 mg/kg. Crude oils may contain Zn up to about 90 mg/kg.
Zinc occurs mainly at +2 oxidation state. It reveals chalcophilic affinity, and is
often associated with carbonates, organic compounds, and clay minerals. Common
Zn minerals are sphalerite (αZnS), wurzite (βZnS), zincite (ZnO), smithonite
(ZnCO 3 ), willemite (Zn 2 SiO 4 ), and hemimorphite [Zn 2 Si 2 O 7 (OH) 2 ·H 2 O]. All these
minerals contain about 50% of Zn, present in the geosphere.
World Zn production from mines (rounded) in 2010 was 12,000 kt, of which
3,500 t was produced in China, 1,520 t in Peru, 1,450 t in Australia, 750 t in India,
and 720 t in the United States (USGS 2011). Of the total Zn consumed, about 55%
is used in galvanizing, 21% in Zn-based alloys, 16% in brass and bronze, and 8% in
other uses, including chemical, paint, rubber, and plastic industries. It is applied in
some batteries, automotive equipments, pipes, and various household devices. Some
Zn compounds are also used in agriculture. Different Zn compounds have dental and
medical applications.
55.2 SOILS
Average Zn contents of worldwide soils range from about 30 to 100  mg/kg
(Table  55.1). Its amounts are, in general, closely associated with soil texture, and
usually the lowest are in light sandy soils. It may be elevated in some calcareous
and organic soils. However, mean Zn content in organic surface soils of Norway is
60.8 mg/kg, and is a bit lower than the mean value (62.4 mg/kg) for all investigated
soils (Nygard et al. 2012).
The ranges of mean Zn contents in soils of various countries are as follows
(in  mg/kg) Brazil, 4–20; Japan, 60100; Poland, 10–5800; South Africa, 12–115;
Slovak Republic, 45–14,925; Sweden, 6–152; the United States, 3–265; and Vietnam,
22–237. Its mean amounts in soils of uncontaminated areas of the EU countries vary
within the range of about 7–90 mg/kg (Kabata-Pendias 2011). The elevated Zn contents are in soils from industrial regions. Soils of the remote region in Spitzbergen
contain Zn from 0.5 to 12.7 mg/kg (Gulińska et al. 2003).
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