1.3 Common Heavy Metals in the Marine Environment
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1.3.4 Lead (Pb)
Pb is naturally occurring in the environment (Garcia-Alix et al. 2013; Chiarelli
and Roccheri 2014) and a highly toxic metal whose widespread use has caused
extensive environmental contamination (Jaishankar et al. 2014). Pb is an extensively
used chemical for the preparation of large industry and household-based products
(Wang et al. 2014a). Important sources of environmental contamination of Pb include
mining, smelting, manufacturing and recycling activities (WHO 2017).
Pb usage is in car batteries, as a coloring element in ceramic glazes, as a base
metal for organ pipes, in the glass of computer as well as television screens, household
paints (Jaishankar et al. 2014); and hence is largely lost to the atmosphere and eventually finds its way to the marine environment via atmospheric deposition. Wuana
and Okieimen (2011), Tchounwou et al. (2012), and Jaishankar et al. (2014) reported
that other uses of Pb include house paint (lead based), bullets, solders, bearings, cable
covers, ammunition, plumbing, pigments, and caulking.
Leaded gasoline had been a major source of Pb dispersion in the environment.
Pb, in the form of tetraethyl lead, was previously added to gasoline to boost the
octane levels and protect exhaust valve seats from excessive wear in vehicles since
the 1920s (ATSDR 2017). However, their use was phased out in the United States
starting in the early 1970s, and banned for use in gasoline for motor vehicles in
January 1996 (ATSDR 2017) as a result of actions taken under the Clean Air Act of
1970. The Clean Air Act is the law that defines EPA’s responsibilities for protecting
and improving the nation’s air quality and the stratospheric ozone layer (EPA 2017).
The Clean Air Act of 1970 was prompted due to the presence of dense, visible smog
in many of the nation’s cities and industrial centers. Major revisions were made in
1977 and 1990 to the Act to improve its effectiveness and to target newly recognized
air pollution problems such as acid rain and damage to the stratospheric ozone layer
(EPA 2017).
Pb is a non-essential element (Jaishankar et al. 2014) and is potentially hazardous
to most forms of life. Pb can occur in four different forms in water and these include:
highly mobile and bioavailable form (ionic); in a bound form with limited mobility
and bioavailability (organic complexes); strongly bound with limited mobility
(attached colloidal particles such as iron oxide); and very limited mobility and availability (attached to solid particles of clay or dead remains of organisms) (ILA 2018).
Pb does not show biomagnifying characteristics (De Pooter 2013).
1.3.5 Zinc (Zn)
Zn is an essential element with biological significance (Depledge and Rainbow 1990)
and found in earth’s crust (McComb et al. 2014). It occurs only in the form of
sulfide, carbonate and silicate ores, mainly as calamine (Zn 2 SiO 4 H 2 O), smithsonite
(ZnCO 3 ), sphalerite (ZnS) and zincite (ZnO) (Namie´ snik and Rabajczyk 2010).
9
1.3.4 Lead (Pb)
Pb is naturally occurring in the environment (Garcia-Alix et al. 2013; Chiarelli
and Roccheri 2014) and a highly toxic metal whose widespread use has caused
extensive environmental contamination (Jaishankar et al. 2014). Pb is an extensively
used chemical for the preparation of large industry and household-based products
(Wang et al. 2014a). Important sources of environmental contamination of Pb include
mining, smelting, manufacturing and recycling activities (WHO 2017).
Pb usage is in car batteries, as a coloring element in ceramic glazes, as a base
metal for organ pipes, in the glass of computer as well as television screens, household
paints (Jaishankar et al. 2014); and hence is largely lost to the atmosphere and eventually finds its way to the marine environment via atmospheric deposition. Wuana
and Okieimen (2011), Tchounwou et al. (2012), and Jaishankar et al. (2014) reported
that other uses of Pb include house paint (lead based), bullets, solders, bearings, cable
covers, ammunition, plumbing, pigments, and caulking.
Leaded gasoline had been a major source of Pb dispersion in the environment.
Pb, in the form of tetraethyl lead, was previously added to gasoline to boost the
octane levels and protect exhaust valve seats from excessive wear in vehicles since
the 1920s (ATSDR 2017). However, their use was phased out in the United States
starting in the early 1970s, and banned for use in gasoline for motor vehicles in
January 1996 (ATSDR 2017) as a result of actions taken under the Clean Air Act of
1970. The Clean Air Act is the law that defines EPA’s responsibilities for protecting
and improving the nation’s air quality and the stratospheric ozone layer (EPA 2017).
The Clean Air Act of 1970 was prompted due to the presence of dense, visible smog
in many of the nation’s cities and industrial centers. Major revisions were made in
1977 and 1990 to the Act to improve its effectiveness and to target newly recognized
air pollution problems such as acid rain and damage to the stratospheric ozone layer
(EPA 2017).
Pb is a non-essential element (Jaishankar et al. 2014) and is potentially hazardous
to most forms of life. Pb can occur in four different forms in water and these include:
highly mobile and bioavailable form (ionic); in a bound form with limited mobility
and bioavailability (organic complexes); strongly bound with limited mobility
(attached colloidal particles such as iron oxide); and very limited mobility and availability (attached to solid particles of clay or dead remains of organisms) (ILA 2018).
Pb does not show biomagnifying characteristics (De Pooter 2013).
1.3.5 Zinc (Zn)
Zn is an essential element with biological significance (Depledge and Rainbow 1990)
and found in earth’s crust (McComb et al. 2014). It occurs only in the form of
sulfide, carbonate and silicate ores, mainly as calamine (Zn 2 SiO 4 H 2 O), smithsonite
(ZnCO 3 ), sphalerite (ZnS) and zincite (ZnO) (Namie´ snik and Rabajczyk 2010).