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Trace Elements in Abiotic and Biotic Environments
soils also significant amounts of Cd. The output of Cd from agricultural soils is less
than its input, which affects in its yearly increases in surface soils. The balance of
Cd in various European soils was calculated as follows (in g/ha/yr): for forest ecosystems, 3.1–23, and for agricultural soils, 1.3–40 (Kabata-Pendias 2011).
According to the EU regulations, the use of compost materials on agricultural
lands is advisable when their Cd contents vary between 0.2 and 1.3 mg/kg (Eckel
et  al. 2005). The criteria for contaminated land (Dutch List 2013), following Cd
concentrations in soils and groundwater, are established (in mg/kg, and μg/L) as
follows: uncontaminated, 1 and 1; medium contaminated, 5 and 2.5; and heavily
contaminated, 20 and 10. Acceptable Cd levels in soils are estimated, based on various criteria, within the range of 3–3.7 mg/kg (Siebielec et al. 2012).
P fertilizers are also significant sources of Cd in soils; its doses to agricultural
soils increased from about 5 g/ha in 1920 to about 100 g/ha in 1980. Manure may
also be enriched in Cd, and according to Lourekari et al. (2000), about 50% of Cd
added to rural soils may be from this source. Sewage sludge and various composts
may add Cd up to 150 g/ha/yr (Kabata-Pendias 2011).
Cadmium contents in phosphate rocks may be very high (in mg/kg P 2 O 5 ), up to
180, but the common range (rounded) is 20–60. Its concentrations in P fertilizers
range from 22 to 90  mg/kg P 2 O 5 , in Finland and Belgium, respectively. Thus, its
input to agro-soils varies from 1.8 to 150 g/ha/yr. The guidelines for maximum Cd
levels in soils are from (in mg/kg) 0.5 (Finland) to 3.0 (United Kingdom) (Oosterhuis
et al. 2000).
Several methods, based on adsorption and desorption processes, solubility and
natural attenuation, as well as phytoremediation, have been applied for the remediation of soil contaminated with Cd, as well as with other trace metals (Hamon et al.
2006). Liming is an old practice to reduce phytoavailability of Cd, and it is still
effective (Adriano et  al. 2004). Addition of a brown coal preparation (composed
of coal, fly ash, and peat) decreased Cd phytoavailability (Kwiatkowska-Malina
and Maciejewska 2013). Some plant species reveal an unusual ability to uptake Cd
and transport it to upper parts. Among several plants, sugarcane is a candidate for
Cd phytoremediation; it concentrates much Cd in shoots, up to 451 mg/kg, without
symptoms of toxicity (Sereno et al. 2007).
9.3 WATERS
Concentration of Cd in ocean water is estimated at mean values from 0.07 to
0.11 μg/L (Table 9.1) Baltic Sea contains Cd within the range of 0.06–1.99 μg/L
(Szefer 2002). Average Cd concentration in river water is calculated as 0.08 μg/L,
and its riverine flux is 3  kt/yr (Gaillardet et  al. 2003). The annual input of Cd to
oceans with stream water is also given as 7.5 kt/yr (Nriagu 1980).
Cadmium contents of surface water may vary highly, especially ranging from 0.05
to 1.0 μg/L. However, much higher values have also been reported (e.g., 6–1000 μg/L)
for rivers and estuaries (Kabata-Pendias and Mukherjee 2007). The average range
of Cd in European rivers is <0.01–0.1 μg/L (Pan et  al. 2010). However, some
European rivers contain much higher amounts of Cd, up to 1000 μg/L, as results of
sewage sludge inputs (Kabata-Pendias and Pendias 1999). Atmospheric inputs may