1.3 Common Heavy Metals in the Marine Environment
15
(Eisler 1997; Purcell and Peters 1998) and these have adversely impacted the
environment.
Ag is extremely toxic in its ionic form (Ag
+ ) (Luoma et al. 1995) to marine phytoplankton and invertebrates, and its increasing use as a biocide has raised concerns
about its potential as an environmental pollutant (Purcell and Peters 1998). Luoma
(2008) and Fabrega et al. (2011) have reported that Ag
+ ions have a great propensity to bioconcentrate in organisms since the chemical properties of Ag
+ ions make
them compatible for uptake via cell membrane ion transporters. Ag can be bioaccumulated from solution by phytoplankton, some algae and oysters, fish, shrimp and
a variety of gastropods (Clark 2001). Ag in sediments is bioavailable and despite
being bioaccumulated by a wide variety of animals, biomagnification is not evident
(Clark 2001).
1.3.12 Manganese (Mn)
Mn is one of the most abundant and broadly distributed metals in nature (Pinsino et al.
2012); occurring in the Earth’s crust in ores such as pyrolusite (MnO 2 ), rhodocrosite
(MnCO 3 ), manganite (Mn 2 O 3 .H 2 O), hausmannite (Mn 3 O 4 ), biotite mica (K (Mg,
Fe) 3 (AlSi 3 O 10 ) (OH) 2 (Moore 1991). Mn is the 12
th most abundant element in the
earth’s crust and the fifth most plentiful metal (Röllin 2011).
Hansel (2017) reported Mn is widely distributed throughout the global ocean as
an essential antioxidant (Mn
2+ ), a potent oxidant (Mn
3+ ) and strong adsorbent (Mn
oxides) sequestering disproportionately high levels of trace metals and nutrients in
comparison to the surrounding seawater. Dissolved Mn in oceanic waters range from
0.2 to 5.0 nmol/kg (Graham et al. 1988). Mn exhibits unique redox dynamics as
Mn
+2 , Mn
+3 , Mn
+4 ; with Mn
+4 being the most abundant form found in minerals
(Burdige 1993, Fischel et al. 2015). In fact, Mn is one of the key considerations used
as a tracer of ocean processes.
Mn is regarded as a biologically essential trace metal, a major global commodity
and an emerging marine contaminant for which ecotoxicological data are inadequate
(ANZECC and ARMCANZ 2016); with the oxidation of soluble Mn
2+ to insoluble
Mn
4+ form having significant ecotoxicological consequences (Summer et al. 2019).
Mn
2+ , being bioavailable and potentially toxic to marine organisms for prolonged
periods of time has high solubility and slow transformation rates to insoluble forms
(Pinsino et al. 2012; Summer et al. 2019).
Ocean spray, forest fires, vegetation, crustal rock and volcanic activity are the
major natural atmospheric sources of Mn (Röllin 2011). Anthropogenic sources of
Mn include mining, industrial emissions, fossil fuel combustion, and erosion of
manganese-containing soils. Hagelstein (2009) mentioned that Mn metal is vital to
metallurgical industries such as fabrication of steel and Al; with electrolytic Mn being
a constituent of nonferrous metals improving their strength and ductility. In addition,
Mn usage is also in the production of dry-cell batteries, plant fertilizer components,
animal feed and colorant for bricks (Hagelstein 2009).
15
(Eisler 1997; Purcell and Peters 1998) and these have adversely impacted the
environment.
Ag is extremely toxic in its ionic form (Ag
+ ) (Luoma et al. 1995) to marine phytoplankton and invertebrates, and its increasing use as a biocide has raised concerns
about its potential as an environmental pollutant (Purcell and Peters 1998). Luoma
(2008) and Fabrega et al. (2011) have reported that Ag
+ ions have a great propensity to bioconcentrate in organisms since the chemical properties of Ag
+ ions make
them compatible for uptake via cell membrane ion transporters. Ag can be bioaccumulated from solution by phytoplankton, some algae and oysters, fish, shrimp and
a variety of gastropods (Clark 2001). Ag in sediments is bioavailable and despite
being bioaccumulated by a wide variety of animals, biomagnification is not evident
(Clark 2001).
1.3.12 Manganese (Mn)
Mn is one of the most abundant and broadly distributed metals in nature (Pinsino et al.
2012); occurring in the Earth’s crust in ores such as pyrolusite (MnO 2 ), rhodocrosite
(MnCO 3 ), manganite (Mn 2 O 3 .H 2 O), hausmannite (Mn 3 O 4 ), biotite mica (K (Mg,
Fe) 3 (AlSi 3 O 10 ) (OH) 2 (Moore 1991). Mn is the 12
th most abundant element in the
earth’s crust and the fifth most plentiful metal (Röllin 2011).
Hansel (2017) reported Mn is widely distributed throughout the global ocean as
an essential antioxidant (Mn
2+ ), a potent oxidant (Mn
3+ ) and strong adsorbent (Mn
oxides) sequestering disproportionately high levels of trace metals and nutrients in
comparison to the surrounding seawater. Dissolved Mn in oceanic waters range from
0.2 to 5.0 nmol/kg (Graham et al. 1988). Mn exhibits unique redox dynamics as
Mn
+2 , Mn
+3 , Mn
+4 ; with Mn
+4 being the most abundant form found in minerals
(Burdige 1993, Fischel et al. 2015). In fact, Mn is one of the key considerations used
as a tracer of ocean processes.
Mn is regarded as a biologically essential trace metal, a major global commodity
and an emerging marine contaminant for which ecotoxicological data are inadequate
(ANZECC and ARMCANZ 2016); with the oxidation of soluble Mn
2+ to insoluble
Mn
4+ form having significant ecotoxicological consequences (Summer et al. 2019).
Mn
2+ , being bioavailable and potentially toxic to marine organisms for prolonged
periods of time has high solubility and slow transformation rates to insoluble forms
(Pinsino et al. 2012; Summer et al. 2019).
Ocean spray, forest fires, vegetation, crustal rock and volcanic activity are the
major natural atmospheric sources of Mn (Röllin 2011). Anthropogenic sources of
Mn include mining, industrial emissions, fossil fuel combustion, and erosion of
manganese-containing soils. Hagelstein (2009) mentioned that Mn metal is vital to
metallurgical industries such as fabrication of steel and Al; with electrolytic Mn being
a constituent of nonferrous metals improving their strength and ductility. In addition,
Mn usage is also in the production of dry-cell batteries, plant fertilizer components,
animal feed and colorant for bricks (Hagelstein 2009).