6
1 Heavy Metals in the Marine Environment—An Overview
of food containing the chemical (Mondal et al. 2018). Metal bioaccumulation can be
complex and is influenced by multiple routes of exposure and geochemical effects
on bioavailability (Luoma and Rainbow 2005). Bioavailability on the other hand,
refers to the proportion of an element available for uptake from the environment
within a time frame. Biomagnification occurs when the chemical is passed up the
food chain to higher trophic levels, such that in predators it exceeds the concentration
to be expected where equilibrium prevails between an organism and its environment
(Neely 1980; Alexander 1999).
1.3.1 Cadmium (Cd)
Cd mostly occurs in sulfide minerals, which also contains Zn, Pb or Cu. Cd was first
used in World War I as a substitute for tin and in paint industries as a pigment (Jaishankar et al. 2014). It is also used in electroplating, batteries, paint dyes, stabilizers
for PVC (poly vinyl chloride) and alloys (Wuana and Okieimen 2011; Jaishankar
et al. 2014).
Cd is a highly toxic environmental pollutant (Ansari et al. 2004; Bat et al. 2012;
Chiarelli and Roccheri 2014; Wang et al. 2014a); and a non-essential metal as well
(Chiarelli and Roccheri 2014). It mostly enters the marine environment via atmospheric loading, riverine discharges and agriculture (elevated levels in most superphosphate fertilizers) (Wuana and Okieimen 2011); and through the use of detergents
and refined petroleum products (Gautam et al. 2014). It is noteworthy to mention that
Cd is largely associated with Zn extraction and phosphate fertilizers (Loganathan and
Hedley 1997; Howe et al. 2014). Furthermore, Reichelt-Brushett (2012) reported
that Cd is of particular concern for marine environments that receive runoff from
agricultural and mining operations.
Ansari et al. (2004) and Rieuwerts (2015) reported that surface seawater Cd acts as
a micronutrient in marine phytoplankton, facilitating photosynthesis. Cd interferes
with the metallothioneins (metal-binding proteins) activity and hence disrupts the
homeostasis in an organism’s body (Klaassen et al. 2009).
Cd is very bio persistent but has few toxicological properties and, once absorbed
by an organism, remains resident for many years (Wuana and Okieimen 2011) and
it does not have biomagnifying properties.
1.3.2 Copper (Cu)
Cu occurs naturally in rocks, soil, water, sediment and in air with generally low
concentrations. Cu is used in the production of alloys (such as bronze, brass and
copper-nickel alloy), electrical wiring, plumbing, roofing, machinery and electronics
(Rieuwerts 2015). Cu mostly enters the marine environment via activities such as
mining, smelting, discharge of wastewater, the use of wood preservatives for coastal
1 Heavy Metals in the Marine Environment—An Overview
of food containing the chemical (Mondal et al. 2018). Metal bioaccumulation can be
complex and is influenced by multiple routes of exposure and geochemical effects
on bioavailability (Luoma and Rainbow 2005). Bioavailability on the other hand,
refers to the proportion of an element available for uptake from the environment
within a time frame. Biomagnification occurs when the chemical is passed up the
food chain to higher trophic levels, such that in predators it exceeds the concentration
to be expected where equilibrium prevails between an organism and its environment
(Neely 1980; Alexander 1999).
1.3.1 Cadmium (Cd)
Cd mostly occurs in sulfide minerals, which also contains Zn, Pb or Cu. Cd was first
used in World War I as a substitute for tin and in paint industries as a pigment (Jaishankar et al. 2014). It is also used in electroplating, batteries, paint dyes, stabilizers
for PVC (poly vinyl chloride) and alloys (Wuana and Okieimen 2011; Jaishankar
et al. 2014).
Cd is a highly toxic environmental pollutant (Ansari et al. 2004; Bat et al. 2012;
Chiarelli and Roccheri 2014; Wang et al. 2014a); and a non-essential metal as well
(Chiarelli and Roccheri 2014). It mostly enters the marine environment via atmospheric loading, riverine discharges and agriculture (elevated levels in most superphosphate fertilizers) (Wuana and Okieimen 2011); and through the use of detergents
and refined petroleum products (Gautam et al. 2014). It is noteworthy to mention that
Cd is largely associated with Zn extraction and phosphate fertilizers (Loganathan and
Hedley 1997; Howe et al. 2014). Furthermore, Reichelt-Brushett (2012) reported
that Cd is of particular concern for marine environments that receive runoff from
agricultural and mining operations.
Ansari et al. (2004) and Rieuwerts (2015) reported that surface seawater Cd acts as
a micronutrient in marine phytoplankton, facilitating photosynthesis. Cd interferes
with the metallothioneins (metal-binding proteins) activity and hence disrupts the
homeostasis in an organism’s body (Klaassen et al. 2009).
Cd is very bio persistent but has few toxicological properties and, once absorbed
by an organism, remains resident for many years (Wuana and Okieimen 2011) and
it does not have biomagnifying properties.
1.3.2 Copper (Cu)
Cu occurs naturally in rocks, soil, water, sediment and in air with generally low
concentrations. Cu is used in the production of alloys (such as bronze, brass and
copper-nickel alloy), electrical wiring, plumbing, roofing, machinery and electronics
(Rieuwerts 2015). Cu mostly enters the marine environment via activities such as
mining, smelting, discharge of wastewater, the use of wood preservatives for coastal