1.3 Common Heavy Metals in the Marine Environment
11
Japanese coastal town (Minamata disease) due to consumption of contaminated fish
and seafood (discussed later in this section).
Natural Hg emission processes include weathering of mercury-bearing rocks,
degassing from Hg deposits; degassing from aquatic and terrestrial systems (through
reduction of Hg
2+ to Hg
0 ); geological activity-volcanic and geothermal processes
(underwater exhalations from geothermal vents); biomass burning (forest fires);
erosion of mercury –containing minerals and plant growth (Clark 2001; Baby et al.
2010; Okoro et al. 2012; Gworek et al. 2016; Rodrigues et al. 2019).
Anthropogenic uses of Hg include dentistry and in the pharmaceutical industry
(Okoro et al. 2012); whilst elemental Hg is used in the extraction of gold (Au) in
Artisanal small-scale gold mining (Reichelt-Brushett et al. 2017) and electronics,
light bulbs and thermometers. Anthropogenic emissions of Hg result from agricultural practices, municipal wastewater discharge, mining processes, combustion of
fossil fuels, electricity-generating power stations, use of Hg in precious metal extraction, manufacture of many commercial products such as thermometers, thermostats,
barometers, batteries and dental amalgams and discharges of industrial wastewater
(Chen et al. 2012; Driscoll et al. 2013; Jaishankar et al. 2014). When vaporized into
the air by factories producing these products, Hg is deposited into soils and later
discharged through rivers to the oceans. Anthropogenic emissions of Hg also result
from incineration of medical and municipal wastes (Suvarapu et al. 2013). Coal-fired
power plants emit Hg as gaseous elemental Hg, gaseous oxidised Hg and particulate
bound mercury into the atmosphere (Weigelt et al. 2016).
The health hazards of Hg became well-known and gained worldwide attention due
to the 1956 outbreak of Minamata disease in Japan (Ye et al. 2016). Methylmercury,
formed as a by-product of chemical compound (acetaldehyde) production in a fertilizer factory was discharged into the Minamata Bay for a long time; thus polluting the
marine ecosystem including the fish and shellfish. Upon consumption of the contaminated seafood, many residents from the area died or suffered injury to their nervous
system, brain, heart, lungs, kidneys and the immune system. Due to its adverse health
problems, the World Health Organization (WHO) considers Hg as one of the top 10
chemicals of major public health concern.
Methyl mercury has biomagnifying characteristics, while inorganic Hg does not.
Methylmercury dissolves well in water, crosses biological membranes and persists
in fatty tissues of organisms (Solomon 2008). Warmer water temperatures increase
bacterial Hg methylation and uptake by plankton and zooplankton (Costa et al. 2012).
1.3.7 Nickel (Ni)
Ni is a naturally occurring element that can exist in various mineral forms and is in
global demand as an industrially and commercially important commodity (Cempel
and Nikel 2006) due to its versatility and use as an alloying ingredient. Ni is used as
11
Japanese coastal town (Minamata disease) due to consumption of contaminated fish
and seafood (discussed later in this section).
Natural Hg emission processes include weathering of mercury-bearing rocks,
degassing from Hg deposits; degassing from aquatic and terrestrial systems (through
reduction of Hg
2+ to Hg
0 ); geological activity-volcanic and geothermal processes
(underwater exhalations from geothermal vents); biomass burning (forest fires);
erosion of mercury –containing minerals and plant growth (Clark 2001; Baby et al.
2010; Okoro et al. 2012; Gworek et al. 2016; Rodrigues et al. 2019).
Anthropogenic uses of Hg include dentistry and in the pharmaceutical industry
(Okoro et al. 2012); whilst elemental Hg is used in the extraction of gold (Au) in
Artisanal small-scale gold mining (Reichelt-Brushett et al. 2017) and electronics,
light bulbs and thermometers. Anthropogenic emissions of Hg result from agricultural practices, municipal wastewater discharge, mining processes, combustion of
fossil fuels, electricity-generating power stations, use of Hg in precious metal extraction, manufacture of many commercial products such as thermometers, thermostats,
barometers, batteries and dental amalgams and discharges of industrial wastewater
(Chen et al. 2012; Driscoll et al. 2013; Jaishankar et al. 2014). When vaporized into
the air by factories producing these products, Hg is deposited into soils and later
discharged through rivers to the oceans. Anthropogenic emissions of Hg also result
from incineration of medical and municipal wastes (Suvarapu et al. 2013). Coal-fired
power plants emit Hg as gaseous elemental Hg, gaseous oxidised Hg and particulate
bound mercury into the atmosphere (Weigelt et al. 2016).
The health hazards of Hg became well-known and gained worldwide attention due
to the 1956 outbreak of Minamata disease in Japan (Ye et al. 2016). Methylmercury,
formed as a by-product of chemical compound (acetaldehyde) production in a fertilizer factory was discharged into the Minamata Bay for a long time; thus polluting the
marine ecosystem including the fish and shellfish. Upon consumption of the contaminated seafood, many residents from the area died or suffered injury to their nervous
system, brain, heart, lungs, kidneys and the immune system. Due to its adverse health
problems, the World Health Organization (WHO) considers Hg as one of the top 10
chemicals of major public health concern.
Methyl mercury has biomagnifying characteristics, while inorganic Hg does not.
Methylmercury dissolves well in water, crosses biological membranes and persists
in fatty tissues of organisms (Solomon 2008). Warmer water temperatures increase
bacterial Hg methylation and uptake by plankton and zooplankton (Costa et al. 2012).
1.3.7 Nickel (Ni)
Ni is a naturally occurring element that can exist in various mineral forms and is in
global demand as an industrially and commercially important commodity (Cempel
and Nikel 2006) due to its versatility and use as an alloying ingredient. Ni is used as