Chromium [Cr, 24]
81
Cr is released form tannery, textile, and plating industries. All these industries release
especially large amounts of Cr to surface water (ATSDR 2002b). Several methods are
used for the Cr removal from wastewater, but the most common is the reduction of Cr 6+
to Cr 3+ , a stable form and easily precipitated, as Cr(OH) 3 (Chen 2013).
Aquatic plants can accumulate high amounts of Cr, as, for example, Vallisneria
spiralis may contain this metal above 1000 mg/kg, and thus is proposed for the bioremediation of Cr-contaminated wastewater (Sinha et al. 2002). Aquatic animals, some
fishes, and invertebrates (e.g., crabs) may contain elevated Cr levels. Its toxicity is
variable, depending on several factors, and especially on water pH (Stoecker 2004).
Chromium content in bottom sediments is a good information on the water pollution with this metal. Its mean content in bottom sediments of San River (Poland)
varies from 2 to 17 mg/kg, in sandy and mule sediments, respectively (Bojakowska
et al. 2008). Chromium content of surface-bottom sediments of harbor in Klaideda
(Lithuania) depends on the granulometric composition, and is (in mg/kg, average and
maximum, respectively) in sand 14.0 and 33.2, and in mud 31.5 and 67.1 (Galkus
et al. 2012). Its content in stream-bottom sediments of National Park, Montgomery
(Pennsylvania State) was, in 1995, within the range of 10–50 mg/kg (Reif and Sloto
1997). Sediments of Sergipe river estuary (Brazil) contain Cr from 3.25 to 74.7 mg/kg
(Garcia et al. 2011). Assessment limits for Cr in sediments are established as follows
(in mg/kg): effects range low, 81; effects range median, 9.6; probable effect level
(PEL), 90; 110; and 100 (EPA 2000, 2013). The Environment Canada sediment- quality
guidelines (USGS 2001) gave a bit similar values for Cr in lake-bottom sediments
(in mg/kg) as follows: threshold effects level, 37.3; PEL, 90; and probable effect
concentration, 111.
Median Cr concentration in bottled water of the EU countries is 0.123 μg/L, and is
a little bit lower than those in tap water, 0.185 μg/L (Birke et al. 2010). U.S. drinking
water contains Cr within the range 0.4–8.0 μg/L, with the mean value of 1.8 μg/L
(ATSDR 2002b). Provisional guideline value of Cr in drinking water is established
at 50 μg/L. The guideline value is designated as provisional because of uncertainties
in the toxicological database (WHO 2011a).
12.4 AIR
Worldwide median Cr content of air is estimated at 0.5–0.6 ng/m 3 , whereas in remote
areas (Antarctica) its concentration does not exceed 0.01 ng/m 3 (Table 12.1). In the
United States, Cr concentration in air above rural areas is <10 ng/m 3 , and in urban
regions it ranges in 10–30 ng/m 3 (ATSDR 2002b).
In 1999, atmospheric deposition of Cr on rural soils in some EU countries was as
follows (in g/ha/yr): Germany, 17.8; England, 8.7; Sweden: 2.5 (Eckel et al. 2005).
Data on the Cr deposition highly vary, depending on time of calculations. In general,
there is a noticed decrease, with time, in amounts of Cr emission and deposition.
The main natural Cr source in the atmosphere is continental dust flux. About
70% of Cr in air is of anthropogenic origin, mainly from metal industry emissions
and fuel combustion. Mean Cr contents of two moss species from mountains in
Poland are a little bit lower (0.84–0.90 mg/kg) than in the same moss species from
Alaska (1.02–1.14 mg/kg). This may suggest the atmospheric transfer of the metal