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Trace Elements in Abiotic and Biotic Environments
accumulate Zn up to 28,000 mg/kg, at the pH range of 4–7.5 (Perelomov et al. 2013).
The elevated Zn amounts may be toxic to some microorganisms, especially in acidic
soils. Zinc is relatively easily taken up by earthworms, and the content of this metal,
within the range of 114–369 mg/kg, depends on various soil amendments (Siebielec
et  al.  2013). In Zn-contaminated soils, earthworms may contain this metal up to
2000 mg/kg (Kabata-Pendias 2011).
The fate of Zn from various sources (e.g., atmospheric deposition, fertilizers, pesticides, sewage sludge, ashes) differs, depending on its chemical species and their
affinity for various soil components. The contents of Zn in crop-farm soils increase
(in g/ha/yr) from 115 in Germany to 838 in France (Eckel et al. 2005). Sewage sludges applied to agricultural land of EU countries contain Zn, at average values, from
606 to 1628 mg/kg (ICON 2001). Long-term irrigation (above 100 years) with municipal wastewaters influences Zn speciation in soils, increasing its fraction bound to
amorphous Fe oxides (Kabala et al. 2011). Decontamination of Zn from wastewaters
is proposed by electrochemical technology (Chen 2013).
Half life-time of Zn as a pollutant in soils may be quite long and has been estimated for about 70–80 years (Kitagishi and Yamane vide Kabata-Pendias 2011).
Amelioration of Zn-contaminated soils is commonly based on controlling its bioavailability by application of lime or OM, or both. Addition of a brown coal preparation
(composed of coal, fly ash, and peat) decreases Zn phytoavailability (KwiatkowskaMalina and Maciejewska 2013). However, various organic Zn complexes may also
increase its uptake by roots (Degryse et al. 2006).
55.3 WATERS
The median Zn concentrations in ocean and seawaters are estimated within the range
of 0.5–5.0 μg/L. The mean Zn amount in the North Pacific is 0.35 μg/L (Nozaki
2005), whereas in the Baltic Sea it ranges from 1.4 to 5.4 (Szefer 2002).
The worldwide mean Zn content of river waters is calculated for 0.6 μg/L, and its
riverine flux for 23 kt/yr (Gaillardet et al. 2003). In river waters its amounts may be
quite elevated, and range (in EU rivers) from <5 to 40 μg/L (Table 55.1). Terrestrial
waters are often contaminated by domestic wastewaters, in which Zn concentrations
range between 0.1 and 1.0 mg/L, but may be elevated up to 35 mg/L in the United
Kingdom, and up to 50 in France (ICON 2001).
Zinc in aquatic media dominates at divalent state, Zn 2+ . However, its speciation
varies with pH. At pH between 4 and 6, it exists in freshwater, mainly as aqua ion
(hydrated ion), Zn H O
2
6
2+
(
) ; at pH about 7 it dominates free cation, Zn 2+ ; and at pH 9
it occurs mainly as monohydroxide ion, HOZn + .
In lakes, rivers, and estuaries, Zn is bound by hydroxides, clay minerals, and other
sediment materials. Fine granulometric fraction of sediments in polluted rivers may contain elevated amounts of Zn, for example, up to around 355  mg/kg (Bojakowska vide
Kabata-Pendias and Mukherjee 2007). Much higher Zn accumulation, up to 2,000 and
14,000 mg/kg, in sediments of selected regions of Vistula and Odra rivers (Poland), respectively, are also reported (Helios-Rybicka et al. vide Kabata-Pendias and Mukherjee 2007).
Zinc contents in bottom sediments of streams in National Park, Montgomery
(Pennsylvania) were, in 1995, within the range of 80–5400 mg/kg (Reif and Sloto 1997).