Lead [Pb, 82]
173
Lead behavior in water depends on the pH and dissolved salts of other elements
and organic matter. In seawater, its species are mainly PbCO 3 and PbCl 2 . Surface
water and groundwater are predominated by Pb 2+ , PbOH + , PbHCO 3+ , and PbSO 4 .
However, all mobile Pb species will eventually precipitate in the bottom sediments,
especially in neutral or alkaline water. Lead entered into sediments may become
again resuspended, and enters as solid particles into the water column.
Lead contents in stream-bottom sediments of National Park, Montgomery
(Pennsylvania State) were, in 1995, within the range of 30–60  mg/kg (Reif and
Sloto 1997). Sediments of Sergipe River estuary (Brazil) contain Pb from 8.14 to
31.1  mg/kg (Garcia et  al. 2011). The Pb concentration in the wetland sediments
from the effluent at the Savannah River site (Aiken, SC) is 59 mg/kg; its highest
amounts, 18.4  mg/kg, are amorphous oxide species, and 16.7  mg/kg are fixed in
SOM fraction (Knox et al. 2006).
Bottom sediments are considered as the long-term sink for Pb, in which it is
stored in unavailable forms. Thus, the best indicator of the Pb pollution in river
water is its content in bottom sediments, where its background levels are estimated
at 30–45  mg/kg. The highest concentrations of Pb in polluted rivers, from industrial and mine areas, range between 700 and 2600 mg/kg, in Poland and the United
Kingdom, respectively (Kabata-Pendias 2011). Lead content of surface-bottom sediments of harbor in Klaipeda (Lithuania) also depends on granulometric composition,
and is (in mg/kg, average and maximum, respectively) as follows: in sand 10.9 and
25.1 and in mud 7.6 and 32.8 (Galkus et al. 2012).
The assessment limits for Pb in sediments are established as follows (in mg/kg):
effects range low (ERL), 47; effects range median, 220; probable effect level (PEL),
91.3; 250; and 179 (EPA 2000, 2013). The Environment Canada sediment-quality
guidelines (USGS 2001) gave a bit similar values for Pb in lake-bottom sediments
(in mg/kg): threshold effects level, 35; PEL, 91.3; and probable effect concentration, 128.
Lead concentrations in drinking water, where it occurs in the forms of Pb(OH) 2 ,
PbCO 3 , and Pb 2 O, have been of a great concern. Several products are used for its
removal, especially from tap water, where most Pb is the result of corrosion in the
water distribution and home-plumbing system. The volcanic rock from Northern
Rwanda is used for the Pb removal from polluted water in some countries, as it
reveals a great adsorption capacity for Pb, 9.52 mg/g (Sekomo et al. 2012).
Median Pb concentration in bottled water of the EU countries is 0.023 μg/L, and
is much lower than those in tap water, estimated at 0.118 μg/L (Birke et al. 2010). The
maximum Pb level in drinking water in the United States is 15 μg/L; above this level,
further treatment of tap water is necessary (EPA 1999). Provisional guideline value
for drinking water established by WHO is 10 μg/L (WHO 2011a). In most countries,
tap and well drinking water contains Pb within the levels of 2–3 μg/L.
Lead is easily taken up from water by phyto and zooplanktons, and may occur
in concentrations up to 3000 mg/kg in bryophytes. It is also likely to be accumulated in invertebrates. Its concentration above 0.19 and 0.30 mg/L is harmful to
Daphnia magna and Cyclop sp., respectively (Offem and Ayotunde 2008). Excess
lead is toxic to fish and water birds. Some bird populations (condors in particular)
are at risk of Pb poisoning. In fish, it may damage the respiratory system due to