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1 Heavy Metals in the Marine Environment—An Overview
an alloying component in stainless steel, cast iron, nonferrous alloys and other nickelbased alloys used in challenging high temperature and corrosion resistant applications (Reichelt-Brushett and Hudspith 2016). Further prominent uses of Ni include
Ni coatings, components in battery systems and electrodes, coinage, filters and as
catalysts in commercially significant chemical processes (see Reichelt-Brushett and
Hudspith 2016).
Ni ore occurs as either magmatic sulphides or nickel laterites (Mudd 2010; Gissi
et al. 2017; Gillmore et al. 2020) with Ni laterite ore being extracted by opencast
mining, thus leading to major landscape alteration, enhanced soil erosion rates, and
the production of large volumes of waste material (Gillmore et al. 2020), which later
enters the marine environment.
Ni is released from both natural and anthropogenic sources; with input from
both stationary and mobile sources (Cempel and Nikel 2006). These sources include
weathering of rocks and soils, volcanic emissions, forest fires and vegetation, fossil
fuels (usually rich in Ni), combustion of oil and coal and incineration of waste and
sewage (Clark 2001; Cempel and Nikel 2006). Ni is a substantial contaminant in the
marine sediments of industrialized areas and has been used in steel, batteries and
as a catalyst. The major input of Ni to the sea is through rivers (Clark 2001). Ni
does not show any biomagnification characteristics and is regarded as a moderately
toxic metal. It can cause lethal effects to some algae species at concentrations above
600 µg/l (Clark 2001).
1.3.8 Chromium (Cr)
Cr is a naturally occurring element present in the earth’s crust and enters the environment from a wide variety of natural and anthropogenic sources (Tchounwou et al.
2012). Wuana and Okieimen (2011) mentioned that Cr is mined as a primary ore
product in the form of chromite, FeCr 2 O 4 . Sources for Cr in the oceans are mineral
weathering processes and riverine and atmospheric input (Geisler and Schmidt 1991;
Bielicka et al. 2005).
Industries with the largest contribution to Cr release in the environment include
metal processing, tannery facilities, chromate production, stainless steel welding, and
ferrochrome and chrome pigment production (Tchounwou et al. 2012) and textile
dyes, catalysts, wood and water treatment (Bielicka et al. 2005). Cr is a highly
toxic metal presenting various degrees of risk for coastal ecosystems mainly due to
dumping of untreated or poorly treated industrial residues (Chiarelli and Roccheri
2014).
Cr exists in variable oxidation states but only +3 and +6 oxidation states are
biologically and environmentally stable (Ducros 1992) and the hexavalent form of Cr
is 30 times more toxic than the trivalent form and can be mutagenic and carcinogenic
(Natale et al. 2000; Chiarelli and Roccheri 2014).
1 Heavy Metals in the Marine Environment—An Overview
an alloying component in stainless steel, cast iron, nonferrous alloys and other nickelbased alloys used in challenging high temperature and corrosion resistant applications (Reichelt-Brushett and Hudspith 2016). Further prominent uses of Ni include
Ni coatings, components in battery systems and electrodes, coinage, filters and as
catalysts in commercially significant chemical processes (see Reichelt-Brushett and
Hudspith 2016).
Ni ore occurs as either magmatic sulphides or nickel laterites (Mudd 2010; Gissi
et al. 2017; Gillmore et al. 2020) with Ni laterite ore being extracted by opencast
mining, thus leading to major landscape alteration, enhanced soil erosion rates, and
the production of large volumes of waste material (Gillmore et al. 2020), which later
enters the marine environment.
Ni is released from both natural and anthropogenic sources; with input from
both stationary and mobile sources (Cempel and Nikel 2006). These sources include
weathering of rocks and soils, volcanic emissions, forest fires and vegetation, fossil
fuels (usually rich in Ni), combustion of oil and coal and incineration of waste and
sewage (Clark 2001; Cempel and Nikel 2006). Ni is a substantial contaminant in the
marine sediments of industrialized areas and has been used in steel, batteries and
as a catalyst. The major input of Ni to the sea is through rivers (Clark 2001). Ni
does not show any biomagnification characteristics and is regarded as a moderately
toxic metal. It can cause lethal effects to some algae species at concentrations above
600 µg/l (Clark 2001).
1.3.8 Chromium (Cr)
Cr is a naturally occurring element present in the earth’s crust and enters the environment from a wide variety of natural and anthropogenic sources (Tchounwou et al.
2012). Wuana and Okieimen (2011) mentioned that Cr is mined as a primary ore
product in the form of chromite, FeCr 2 O 4 . Sources for Cr in the oceans are mineral
weathering processes and riverine and atmospheric input (Geisler and Schmidt 1991;
Bielicka et al. 2005).
Industries with the largest contribution to Cr release in the environment include
metal processing, tannery facilities, chromate production, stainless steel welding, and
ferrochrome and chrome pigment production (Tchounwou et al. 2012) and textile
dyes, catalysts, wood and water treatment (Bielicka et al. 2005). Cr is a highly
toxic metal presenting various degrees of risk for coastal ecosystems mainly due to
dumping of untreated or poorly treated industrial residues (Chiarelli and Roccheri
2014).
Cr exists in variable oxidation states but only +3 and +6 oxidation states are
biologically and environmentally stable (Ducros 1992) and the hexavalent form of Cr
is 30 times more toxic than the trivalent form and can be mutagenic and carcinogenic
(Natale et al. 2000; Chiarelli and Roccheri 2014).