4
Barium [Ba, 56]

4.1 INTRODUCTION
Barium (Ba) is an alkaline metal of the group 2 in the periodic table of elements and
occurs in the Earth’s crust at levels 550–668 mg/kg (mean 425 mg/kg). It has a lithophilic affinity and is likely to be concentrated in acidic igneous rocks (400–1200 mg/kg)
and argillaceous sediments (400–800 mg/kg). Barium follows the K fate in geochemical
processes and may be concentrated in phosphate rocks, and thus in P fertilizers, often as
barium phosphate, Ba 3 (PO 4 ) 2 . In coal, Ba contents vary within the range 150–500 mg/kg,
and in brown coal, it may concentrate up to about 1500 mg/kg. According to Finkelman
(1999), Ba concentration in some coals may be up to 22,000 mg/kg. In fly ash, its average
amount is estimated at 398 mg/kg.
Barium occurs at +2 oxidation state. Its common minerals are barite, BaSO 4 ;
whiterite, BaCO 3 ; and hollandite, Ba 2 Mn 8 O 16 .
Total barite production in 2010 was 6 900 kt, of which (in kt) China, 3600; India,
1000; and the United States, 670 (USGS 2011). Ba has varied industrial uses, and
mainly in the production of bricks, ceramics, and glasses. It is widely applied in
chemical industries, including rubber, paints, and plastics production. Nearly 95% of
the barite sold in the United States is used as a weighting agent in gas- and oil-well
drilling fluids. Barite is used in X-ray medical treatments, because it significantly
blocks X-ray and gamma-ray emissions. It is also used as aggregate in high-density
concrete for radiation shielding around X-ray units in hospitals, nuclear power plants,
and various nuclear research facilities.
4.2 SOILS
Barium contents in soils vary from 10 to 1500 mg/kg, with the lowest in organic soils
and the highest in loamy soils (Table 4.1). Mean content calculated for top soils in
the United States is 580 mg/kg (Burt et al. 2003), and this value for European soils
is 400 mg/kg (FOREGS 2005). Average Ba background concentration for worldwide
soils is estimated at 460 mg/kg. However, it may considerably vary, depending on the
geology of the parent materials.
The criteria for the contaminated land (Dutch List 2013), following Ba concentrations in soils and groundwater, are established (in mg/kg, and μg/L) as follows:
uncontaminated, 200 and 50; medium contaminated, 400 and 100; and heavily contaminated, 2000 and 500. An interim soil-quality criterion for Ba content in agricultural soils of Canada has been established at 750 mg/kg (Jaritz 2004).
During weathering processes, Ba precipitates easily with sulfates and carbonates,
and is also strongly adsorbed by clays, oxides, and hydroxides. It is relatively mobile,
especially in acidic soils, although it may be strongly adsorbed, especially by Mn
nodules. Also, some minerals, for example, mica, reveal a great sorption capacity
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