Cadmium [Cd, 48]
57
also be a significant source of Cd, especially in seawater. According to Nriagu and
Pacyna (1988), Cd atmospheric input to the oceans is 2.4 kt/yr.
Cadmium is more mobile in seawater than in other water, where it is present in
various forms such as Cd 2+ , Cd(OH) + , and CdCO 3
q , and as organic and inorganic
complexes (Sundby et al. 2004).
Cadmium in water is easily absorbed by aquatic biota, which sometimes may
be used for biomonitoring. In most marine biota, Cd contents range from 0.03 to
1.8 mg/kg, in flounder and oyster, respectively (Jeng et al. 2000). However, it might
be much higher, as in flounder liver, 2.5 mg/kg (Voigt 2004). Growth of algae is
stopped when Cd contents range from 0.05 to 2.0 mg/kg, depending on their sensitivity. Planktons from various lakes contain Cd from 5.6 to 15 mg/kg, indicating water
pollution (Kabata-Pendias and Mukherjee 2007). Some aquatic bacteria may absorb
high amounts of Cd, up to 55% of its concentration in water. Abyar et al. (2012) suggested that Achromobacter denitrificans may be used for Cd removal from polluted
water, at a relatively low cost. The great biosorption of Cd reveals Nordmann fir
cones (Abies nordmannaana), which is optimal at water pH 6.5 (Ozel 2012).
Cadmium content of bottom sediments is a good information on water contamination by this metal. Its average contents in bottom sediments of San River (Poland)
vary between <0.5 and 1.7 mg/kg, and is higher in mule sediments (mean 0.24 mg/
kg) than in the sandy ones (mean <0.1 mg/kg) (Bojakowska et al. 2007). Its content
(in 1995) in stream-bottom sediments of National Park, Montgomery (Pennsylvania
State) was <1  mg/kg (Reif and Sloto 1997). Cadmium content of surface-bottom
sediments of a harbor in Klaipeda (Lithuania) depends on granulometric composition, and is (in mg/kg, average and maximum, respectively) as follows: in sand, 0.4
and 0.9, and in mud, 0.8 and 1.4 (Galkus et al. 2012).
Assessment limits for Cd in sediments are established as follows (in mg/kg):
effects range low, 1.2; effects range median, 9.6; probable effect level (PEL), 3.5; 10;
and 3 (EPA 2000, 2013). The Environment Canadian Sediment Quality Guidelines
(USGS 2001) gave other values for Cd in lake-bottom sediments (in mg/kg): threshold
effects level, 0.6, PEL, 3.5, and probable effect concentration, 4.98.
Median Cd concentration in bottled water of the EU countries is 0.0032 μg/L,
and a little bit lower than in tap water, 0.0083 μg/L (Birke et al. 2010). The guideline
Cd concentration in drinking water is established at 3.0 μg/L by the WHO (2011a).
9.4 AIR
Cadmium concentration in the atmosphere changes (in ng/m 3 ) from 0.015 in Antarctica to over 4 in rural regions, and to 150 in urban areas (Table 9.1). This clearly
shows that anthropogenic Cd emission should be of a real concern. A great proportion of Cd in the air is emitted mainly from smelting and refining of nonferrous
metals, fossil fuel combustion, and municipal waste incineration. The natural source
of Cd is volcanic emissions. Earlier estimations of anthropogenic Cd versus natural
Cd emissions indicated that approximately 8–10 kt/yr is from anthropogenic sources
compared to 0. 8 to 1 kt/yr from natural emissions (Nriagu and Pacyna 1988). In the
European countries, and worldwide, approximately 85%–90% of total airborne Cd
emissions arise from anthropogenic sources.