Tin [Sn, 50]
331
Marine plants are important in the cycling of Sn; its contents in algae and
macrophytes vary within 0.5–101 mg/kg. Algae may immobilize Sn from seawaters
and stimulate the degradation of toxic methyl-Sn.
Tin is present in waters in divalent and/or tetravalent oxidation states, as well as
in organic compounds (OTCs). It is present in waters as neutral or cationic species,
which is highly controlled by water pH. Methylated OTCs from river estuaries and
their volatile forms are significant Sn sources in the marine environment.
There are various OTCs of Sn, such as monobutylin (MBT), dibutylin (DBT),
and tributylin (TBT). The main source of these compounds in waters is ship paints.
Variable concentrations of OTCs are present in waters, especially in harbor regions.
Their highest concentrations of harbor waters are reported (in ng Sn/L) as follows:
MBT, 70, DBT, 283, and TBT, 1000. The quality standard for seawaters at 2  ng
TBT/L has been recommended in the United Kingdom. In aquatic environments, all
OTCs are easily adsorbed by both suspended OM and particles of bottom sediments.
The highest contents are also reported for TBT; their amounts in bottom sediments
of harbors may be up to 10,780 μg Sn/kg (Kabata-Pendias and Mukherjee 2007).
All OTCs are easily available to aquatic organisms and affect the growth and
reproduction of both phyto- and zooplanktons. They are considered to be the most
hazardous known pollutants in the aquatic environment. The amounts of TBT in
various fishes differ within the range of <0.13–190 μg Sn/kg; however, their much
higher amounts are reported to be in livers of otters, 4–3020 μg Sn/kg (Sudaryanto
et  al. 2005). At relatively low concentration, <1  ng/L, TBT is harmful to some
marine biota. When fish contain Sn 10–55  μg/kg, aquatic birds accumulate TBT,
within the range of 42–160 ng/kg. Although the use of OTCs has been restricted,
there are still problems with these compounds in aquatic systems.
The median Sn concentration in bottled waters of the EU countries is 0.123 μg/L,
and is slightly lower than in tap water, estimated to be 0.185 μg/L (Birke et al. 2010).
50.4 AIR
The concentration of Sn in the atmosphere of remote regions is <70 ng/m 3 , whereas
it may be up to 5000 ng/m 3 in industrial regions (Table 50.1). Very high level of Sn,
up to 10,900 ng/m 3 , has been reported for air from the highway tunnel in Hamburg,
Germany (Dannecker et al. vide Kabata-Pendias and Mukherjee 2007).
The most significant sources of Sn are industrial emission and coal burning
plants. The worldwide industrial Sn emission, from various countries, in the 1980
was estimated to be 1.47–10.8 kt (Nriagu and Pacyna 1988). The global emission of
OTCs to the atmosphere ranges between 2000 and 6000 kg/yr. Relatively high Sn
deposition, at an average of 60 g/ha/yr, is reported for agricultural soils of Sweden
(Eriksson 2001a).
There are several sources of OTCs in the atmosphere, which include incineration
of organic waste, use of pesticides, and antifouling paints, as well as from glass
manufacturing facilities because of the tin used. Apparently, the precipitation of
elemental Sn from air is about 10 times higher than that of OTCs.
Tin contents of the moss carpet in Sweden decreased from 0.49 mg/kg in 1975 to
0.09 mg/kg in 2000 (Rühling and Tyler 2004). Moss sampled in Norway, during the