1
1. GENERAL DESCRIPTION
1.1 Identity
Barium is present as a trace element in both igneous and sedimentary rocks. Although
it is not found free in nature (US EPA, 1985a), it occurs in a number of compounds,
most commonly barium sulfate (barite) and, to a lesser extent, barium carbonate
(witherite).
Compound
CAS No.
Molecular formula
Barium sulfide
21109-95-5
BaS
Barium chloride
10361-37-2
BaCl
2
Barium oxide
1304-28-5
BaO
Barium hydroxide
17194-00-2
Ba(OH)
2
Barium bromide
10553-31-8
BaBr
2
Barium nitrate
10022-31-8
Ba(NO
3
)
2
Barium nitrite
13465-94-6
Ba(NO
2
)
2
Barium sulfate
7727-43-7
BaSO
4
Barium acetate
543-80-6
Ba(C
2
H
3
O
2
)
2
1.2 Physicochemical properties (US EPA, 1985b; Lide, 1992–1993)
Compound
Melting point
(°C)
Boiling point
(°C)
Density (g/cm
3
)
Water solubility
(g/litre)
BaS 1200
–
4.25 readily
soluble
BaCl
2
960
1560
3.856 at 24 °C
310 at 0 °C
BaO
1923
2000
5.32–5.72
15 at 0 °C
Ba(OH)
2
77.9
800
2.18 at 16 °C
38.9 at 20 °C
BaBr
2
847
decomposes
4.781 at 24 °C
980 at 0 °C
Ba(NO
3
)
2
592
decomposes
3.24 at 23 °C
92 at 20 °C
Ba(NO
2
)
2
217
decomposes
3.23
675 at 20 °C
BaSO
4
1580
–
4.50 at 15 °C
0.000 285 at 30 °C
Ba(C
2
H
3
O
2
)
2
–
–
2.47
770 at 26 °C
1.3 Major uses
Barium compounds, including barium sulfate and barium carbonate, are used in the
plastics, rubber, electronics and textile industries,
in ceramic glazes and enamels, in
glass-making, brick-making and paper-making, as a lubricant additive, in
pharmaceuticals and cosmetics, in case-hardening of steel and in the oil and gas
industry as a wetting agent for drilling mud (Miner, 1969; Brooks, 1986).
1.4 Environmental fate
Barium in water comes primarily from natural sources. The acetate, nitrate and
halides are soluble in water, but the carbonate, chromate, fluoride, oxalate, phosphate
BARIUM IN DRINKING-WATER
2
and sulfate are quite insoluble. The solubility of barium compounds increases as the
pH level decreases (US EPA, 1985a). The highest levels to be found in drinking-water
are likely to be associated with groundwater of low pH from granite-like igneous
rocks, alkaline igneous and volcanic rocks and manganese-rich sedimentary rocks.
Concentrations are, therefore, expected to be relatively stable.
Organic barium compounds are ionic and are hydrolysed in water (Cotton &
Wilkinson, 1980). The concentration of barium ions in natural aquatic systems is
limited by the presence of naturally occurring anions and possibly also by the
adsorption of these ions onto metal oxides and hydroxides (Hem, 1959).
2. ANALYTICAL METHODS
Barium concentrations in water may be determined by atomic absorption
spectroscopy using either direct aspiration into an air–acetylene flame (detection limit
2 µg/litre) or atomization in a furnace (detection limit 100 µg/litre) (US EPA, 1985a).
Barium in water may also be determined by inductively coupled plasma atomic
emission spectrometry, the detection limits being equivalent or superior to those of
flame atomic absorption spectroscopy (OME, 1988).
3. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE
3.1 Air
Barium is generally present in air in particulate form as a result of industrial
emissions, particularly from combustion of coal and diesel oil and waste incineration.
Concentrations ranging from 0.000 15 to 0.95 µg/m
3
have been reported. The
estimated respiratory intake for an adult male is in the range of 0.03–22 µg/day (US
EPA, unpublished data, 1984).
3.2 Water
The concentration of barium in groundwater in the Netherlands was measured at 60
locations; the mean and maximum concentrations were 0.23 and 2.5 mg/litre,
respectively (Van Duijvenbooden, 1989).
Barium concentrations in distribution drinking-water in Canada were found to range
from detectable (detection limit 5 µg/litre) to 600 µg/litre, with a median value of 18
µg/litre; in 86% of the 122 locations surveyed, the concentrations were below 100
µg/litre (Subramanian & Meranger, 1984). In 83% of 262 locations surveyed in the
Netherlands in 1983, barium concentrations in drinking-water were below 50 µg/litre;
the maximum concentration found was below 200 µg/litre (Fonds et al., 1987). In a
study of water supplies of cities in the USA, a median value of 43 µg/litre was
reported; in 94% of all determinations, the concentrations found were below 100
µg/litre (IPCS, 1990). Levels of barium in municipal water supplies in Sweden ranged
from 1 to 20 µg/litre (IPCS, 1990). The median value for barium in drinking-water in
Norway was reported to be 9 µg/litre (Flaten, 1991); in the Tuscany region of Italy,