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Trace Elements in Abiotic and Biotic Environments
The observations of Pb balance in soils of various ecosystems show that its input
greatly exceeds its output. Lead added to agricultural soils with various materials
vary from <3 to 96 g/ha/yr, from lime and sewage sludge, respectively. According
to Eckel et al. (2005), agricultural Pb input to soils varies from 1.3 to 139 g/ha/yr, in
Norway and France, respectively.
Lead, as pollutant, enters soils in various and complex compounds, thus its reactions with soil components highly differ. Due to low mobility and phytoavailability
of Pb in soils, there was little concern about soil pollution previously. However, soon
it was observed that Pb is easily taken up by roots, and may also be translocated to
shoots. Pb limitation of enzymatic activities of soil microbiota has also been reported.
Pb accumulation in surface soils has become a great ecological significance.
Remediation of Pb-contaminated soil was recently broadly investigated. Several
methods have been applied. Although Pb is slightly phytoavailable, there are some
hyperaccumulators (e.g., corn, sunflowers, and Thlaspi spp.) that are used for the
phytoextraction and/or phytostabilization. The phytoremediation is more effective
after the addition of chelators (ethylenediaminetetraacetic acid [EDTA], diethylenetriaminepentaacetic acid), which increase Pb mobility. Some plants may stabilize
Pb, for a certain period, by its fixation in rhizosphere zones.
Other methods are based on the Pb stabilization, for which lime (especially
Fe-rich lime) and P fertilizers, as well as some minerals (e.g. barite, BaSO 4 ) may
be applied (Courtin-Nomade et al. vide Kabata-Pendias 2011). Addition of a browncoal preparation (composed of coal, fly ash, and peat) decreased Pb phytoavailability
(Kwiatkowska-Malina and Maciejewska 2013).
24.3 WATERS
The worldwide median concentration of Pb in ocean water is calculated at 0.03 μg/L,
within the range of <0.03–0.27 μg/L (Reimann and de Caritat 1998). In the North
Pacific Ocean, it is lower, estimated at 0.003 μg/L (Nozaki 2005). The Baltic Sea
contains Pb at the range from 0.05 to 3.6 μg/L, with the highest being in coastal
water (Szefer 2002). The average worldwide Pb concentration in river water is estimated at 0.08 μg/L, within the range of 0.04–3.8 μg/L (Table 24.1). River water in
Pb-mineralized areas and near to Pb-polluted sources may contain this metal up to
about 45 μg/L (Monbesshora et al. vide Kabata-Pendias 2011).
The annual global input of Pb to marine basins with river water and atmospheric precipitations is estimated at 40 and 20 kt, respectively (Kitano vide Kabata-Pendias and
Mukherjee 2007). Annual Pb load to the Baltic Sea in 1990 was estimated at 2800 t, in
about equal proportion from river flux and atmospheric deposition (Matschullat 1997).
Above 90% of Pb discharged to this sea basin is of the anthropogenic origin.
Lead concentration in rainwater should be very low, at about 10 μg/L. However,
rainwater is very often polluted, by roofs and tanks, and therefore rainwater collected in towns may contain Pb up to >500 μg/L
The ratio of Pb isotopes in the northeast Pacific Ocean was used for the identification of pollution sources; the surface layer of water contained Pb of the industrial dust from Japan, whereas deeper layers were polluted by the North American
emissions (Flegal et al. vide Kabata-Pendias 2011).