Barium is ubiquitous in soils, being found at concen-
trations ranging from 100-3000 µg/g (Schroeder, 1970;
Robinson et al., 1950). Brooks (1978) estimated an average
soil concentration of 500 mg/kg. Due to its abundance in
soils, barium may be present in the air in areas with high
natural dust levels.
Barium can be transported into ground-water aquifers
through the leaching and eroding of barium from sedimen-
tary rocks. The level of barium present in the ground
water is related to the hardness of the water, since
barium is always present with calcium (Kopp & Kroner,
1968). Cartwright et al. (1978) reported that the high
barium levels in ground water in Illinois, USA, were
derived from the sandstone formation of the Cambrian-
Ordovician aquifer. The highest concentrations occurred
in fine-grained and older sediments. Barium was found in
94% of the surface waters examined, the concentrations
range being 2-340 µg/litre (Kopp & Kroner, 1967).
4.1.1. Air
Examination of dust falls and suspended particulates
indicates that most contain barium. The presence of barium
is mainly attributable to industrial emissions, especially
the combustion of coal and diesel oil and waste inciner-
ation, and may also result from dusts blown from soils and
mining processes. Barium sulfate and carbonate are the
forms of barium most likely to occur in particulate matter
in the air, although the presence of other insoluble com-
pounds cannot be excluded. The residence time of barium
in the atmosphere may be several days, depending on the
particle size. Most of these particles, however, are much
larger than 10 µm in size, and rapidly settle back to
earth.
Particles can be removed from the atmosphere by rain-
out or wash-out wet deposition. These two forms of depo-
sition efficiently clear the atmosphere of pollutants, but they
are not well understood. Without knowing the amount
of barium in the atmosphere, it is difficult to evaluate
the processes of deposition, transport, and distribution.
5.1.4. Food
A review of the early literature summarizes the quan-
tity of barium present in many plants (Robinson et al.,
1950). Barium has been found in grain stalks, forage
plants, red ash leaves, and in the black walnut, hickory,
and Brazil nut trees. With the exception of the Brazil nut
tree, those parts of the plants that accumulate barium are
seldom eaten by man. Various studies document the concen-
trations of barium in Brazil nuts ranging from 1500-3000
mg/kg (Robinson et al., 1950; Smith, 1971a). Barium is
also present in wheat, although most is concentrated in
the stalks and leaves rather than in the grain (Smith,
1971b). Tomatoes and soybeans also concentrate soil
barium, the bioconcentration factor ranging from 2 to 20
(Robinson et al., 1950). Gormican (1970) determined the
barium content of a large number of food items, including
dairy products, cereals, fruits and vegetables, and meats
(Table 7). In the beverages group, tea and cocoa had the
highest barium content (2.7 and 1.2 mg/100 g, respect-
ively) on a dry-weight basis. Among breads, cereal prod-
ucts, and cracker products, bran flakes (0.39 mg/100 g)
and enriched instant cream of wheat (0.2 mg/100 g) had the
highest levels. Eggs were found to have 0.76 mg/100 g, and
swiss cheese 0.22 mg/100 g. Fruits and fruit juice had low
barium levels, the highest values being in raw, unpeeled
apples (0.075 mg/100 g). These levels are similar to those
found in grapes (<0.05 mg/100 g) and cooked prunes (0.064
mg/100 g). All meats showed concentrations of 0.04 mg per
100 g or less. Vegetables had relatively low barium
levels, with the exception of beets (0.26 mg/100 g) and
sweet potatoes (0.22 mg/100 g). Among nuts, pecans had the
highest barium content (0.67 mg/100 g).
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