Iron [Fe, 26]
159
bottom sediments. Bacteriogenic, mainly amorphous, Fe hydrous oxides, together
with Mn oxides and organic matter (OM), play especially important role in the fate
and transport of dissolved metals in subterranean water systems. Some organic
ligands, present in seawater may strongly bind Fe, and prevent its deposition in bottom sediments. Iron is considered to be the most mobile metal among others deposited in bed sediments.
Iron is an essential micronutrient for phytoplankton, as an important component
in processes of photosynthesis and respiratory electron transports. In oxic seawater,
however, Fe is present predominantly in the insoluble species, and thus it may be
deficient for the phytoplankton. Thus, the addition of fine Fe particles may highly
generate the growth of plankton biomass.
Iron concentration may be increased in some aquatic environments (e.g., mine
drainage or iron pickling wastewater). Oxidation of Fe 2+ to Fe 2 O 3 × H 2 O is applied
for the deferrization of water.
Rainwater contains Fe within the range of 10–40 μg/L; the lowest value is for
the coastal region of Norway, and the highest for the contaminated region of Kola
Peninsula (Reimann and de Caritat 1998).
Median Fe concentration in bottled water of the EU countries is 1.26 μg/L, and
is a bit lower than those in tap water, estimated at 3.21 μg/L (Birke et al. 2010). No
guideline value for Fe in drinking water is proposed. Reason for not establishing
a guideline value is a lack of health concern, at Fe levels found in drinking water
(WHO 2011a).
Fe concentration in the wetland sediments from the effluent at the Savannah River
site (Aiken, SC) is 18,421  mg/kg, and its highest amounts, 8,089  mg/kg, is fixed
in soluble OM fraction. Iron in these sediments occurs also as crystalline oxides,
4652 mg/kg, and amorphous oxides, 3737 mg/kg (Knox et al. 2006).
Iron contents in stream-bottom sediments of National Park, Montgomery
(Pennsylvania State) were, in 1995, within the range of 11,000–430,000 mg/kg. The
assessment limits for Fe in these sediments are established as follows (in mg/kg):
effects range low, 200,000; effects range median, 280,000; probable effect level,
250,000; and threshold effects level, 190,000.
23.4 AIR
The origin of Fe in air is from both terrestrial and industrial sources. Concentrations
of Fe in the atmosphere of different cities, from various continents, range broadly
from 130 to 14,000  ng/m 3 , and are closely associated with industrial activities
(Table 23.1). It is extremely elevated in air of various regions, when compared to its
contents in air of remote regions, especially Antarctica.
Iron content in moss growing in Norway vary from 120 to 21,000 mg/kg (average
660 mg/kg), and resulted from atmospheric deposition (Berg and Steinnes 1997).
Aerial dust of urban regions is composed of 33%–38% (weight) of Fe particles,
for which annual deposition is estimated at 16,800–43,200  g/ha/yr. Iron particles
deposition in remote areas of Europe range from 300 to 5700 g/ha/yr (Manecki et al.
vide Kabata-Pendias and Pendias 1999).