Strontium [Sr, 38]
309
Most of the aquatic organisms may accumulate Sr. This process is an inverse correlation to Ca levels in water. Mussels from the Baltic Sea may accumulate Sr up to
100 mg/kg (Szefer 2002).
The average Sr content of rainwater collected in Sweden is 1.2 μg/L and the maximum is 3.3 μg/L (Eriksson 2001a).
45.4 AIR
The common concentration of Sr in the atmosphere varies within the range of
20–50 ng/m 3 . In remote regions, Sr average concentration is estimated to be 0.8 ng/m 3
(Table 45.1). In industrial regions, especially close to coal power plants, it may be
significantly enriched up to 50 ng/m 3 .
During thermal processes, Sr is released to air as oxide, SrO, which in contact
with water may be transferred into ionic species Sr 2+ , which is easily trapped by both
biotic and abiotic environmental components.
Strontium contents of moss (Hylocomium splendens) from the mountains in
Poland (mean 4.1 mg/kg) are lower than those of the same moss species from Alaska
(mean 20.0 mg/kg). This may suggest higher Sr atmospheric deposits in Alaska than
in mountains of Poland (Migaszewski et al. 2009). In mosses sampled in Norway,
in the period 1990–1995, Sr content ranges from 2.8 to 51 mg/kg, mean 15 mg/kg
(Berg and Steinnes 1997).
45.5 PLANTS
Although Sr is apparently not a plant’s micronutrient, it is absorbed by plants similar
to Ca, by mechanisms of both mass flow and exchange diffusion. It is easily taken up
by plants from acidic light sandy soils. Its content of plants is highly variable, from
the lowest in cereal grains (mean 1.5–2.5 mg/kg) to the highest in some vegetable
leaves (mean 45–74 mg/kg).
In the European forest ecosystems, Sr contents in blueberries (Vaccinium sp.)
range between 4.5–5.5 mg/kg in Russia and 2.9–3.09 mg/kg, in Germany (Markert
and Vtorova vide Kabata-Pendias 2011). The mean Sr content of forest crowberries
(Empetrum nigrum) from the Kola Peninsula is 8.9  mg/kg, whereas the mean Sr
content of crowberries grown close to the Monchegorsk plant is 0.8 mg/kg, which
indicates that this metallurgical industry does not emit Sr (Reimann et al. 2001).
Soil-to-plant transfer Sr ratios are relatively high and are calculated as 0.02–1.0
(ATSDR 2002b). Strontium is not readily transported from roots to shoots; thus, it is
likely to be accumulated in roots. However, the distribution of Sr in plants is highly
variable. However, in cereals plants, it is accumulated mainly in nonedible parts
(e.g., straw), and in the cell walls of roots. Relatively high Sr contents of plant tops
may be an effect of its aerial deposition.
Interactions between Sr and Ca are complex, and although they compete with each
other, Sr cannot replace Ca in biochemical functions. Increased levels of Ca in growth
media may both inhibit or stimulate Sr uptake, depending on several soil and plant factors.
Most often, however, addition of Ca to soil decreases Sr phytoavailability. Applications to
soils of other elements, such as Mg, K, and Na, also inhibit Sr uptake by plants.