14
Copper [Cu, 29]
14.1 INTRODUCTION
Copper (Cu), a metal of the group 11 in the periodic table of elements, occurs in the
Earth’s crust within the range of 25–75 mg/kg. It is concentrated mainly in mafic
igneous rocks, up to 120 mg/kg, whereas in acidic igneous rocks its contents range
from 5 to 30 mg/kg. Its distribution in sedimentary rocks is as follows (in mg/kg):
argillaceous (shales), 40–60; sandstones, 2–30; and limestones, 2–10. Coal contains
Cu within the very broad range of 12–280 mg/kg. In fly ash, it may be accumulated
up to about 70 mg/kg.
Copper occurs mainly at +2 oxidation state, and sometimes +1. Due to its strong
affinity for S, it is likely to form minerals mainly with S, such as covellite, CuS; chalcosite, Cu 2 S; chalcopyrite, CuFeS 2 ; and bornite, Cu 5 FeS 4 . During the weathering of
Cu sulfides, Cu is incorporated in oxide and carbonate minerals, of which the most
common are tenorite, CuO; cuprite, Cu 2 O; malachite, Cu 2 CO 3 (OH) 2 ; and azurite,
Cu 2 (CO 3 ) 2 (H 2 O) 2 . There are several host minerals of Cu, such as mica, sphaleryt,
pyrite, galena, and magnetite. In some sedimentary deposits, it may occur as native
Cu. It may also be very easily adsorbed by freshly precipitated Al and Mn oxides
(Violante 2013).
World mine Cu production (rounded) in 2010 was 16.2 Mt, of which Chile, 5.5;
Peru, 1.3; China, 1.2; and the United States 1.2 (USGS 2011). Copper in all old and
new, refined or remelted scrap (160 kt) contributed to about 35% of its supply in the
United States. It reveals versatile properties, and therefore has a wide range of applications, very often as Cu alloys. It is used in building construction (50%), electronic
products (20%), transportation equipment (10%), consumer and general products
(10%), and industrial machinery and equipment (8%). It is also used in agriculture,
mainly as fertilizers and pesticides. It is also a fodder additive in livestock and poultry
nutrition.
14.2 SOILS
The worldwide average Cu content is estimated at 14 mg/kg. However, it highly varies for different countries, within the range between 14 and 110 mg/kg. Copper contents are closely associated with soil textures; in most cases, the lowest is in sandy
soils, 3–30 mg/kg, and the highest in loamy soils, 7–140 mg/kg. Some histosols may
also contain elevated amounts of Cu, up to about 120 mg/kg (Table 14.1). Some soils,
derived from parent rocks with high Cu levels, may contain much higher Cu, for example, soils in Carpathian rocks have Cu up to 22,360 mg/kg (Čurlik and Šefčik 1999).
Agricultural soils (3045 samples) of the United States contain Cu within the
range <0.6–495 mg/kg (mean, 18 mg/kg) (Holmgren et al. 1993). Agricultural soils
(32,000 samples) of Poland contain Cu from 0.2 to 725 mg/kg (mean, 6.5 mg/kg)
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