metal pollution in the environment. (Masindi and Khathutshelo 2018) Among the
listed heavy metals; Zn is mainly located in sedimentary rocks that includes limestone, dolostone, salt and shale. Zinc carbonate (ZnCO 3 ), known as calamine or
smithsonite is commonly found as Zn ore (Peter and Tharsika 2017). The host rocks
of Cu are Igneous, Sedimentary, Metamorphic types. In amalgamation with sulphur
oxides and oxygen, it is found as Sulphides and sulphur oxides respectively. Its
combination with cobalt, Ni, Pb, Ag and Fe forms complex Cu minerals. Pb is found
mainly in sedimentary rocks (including limestone, dolostone, salt and shale), igneous and metamorphic rocks. ZnCO 3 known as calamine or smithsonite is a common
Zn ore. A Pb sulphide mineral is known as Galena (Peter and Tharsika 2017).
Hg is found in pure form in found in volcanic rocks, but is usually occur in the
mineral called cinnabar which is chemically known as Hg sulphide. Cd is principally
found in rocks of sedimentary type, the amount being much higher than that in in
igneous or metamorphic rocks (except nonferrous metallic ores of Zn, Pb and Cu
(ICAD). It occurs naturally in Earth’s curst in combination with Zn. In air, it gets
released through volcanoes and forest fires. Rocks of Igneous and Metamorphic type
contain Ag. Native elemental mineral form is rare. In this state it is often associated
with quartz, gold, Cu, sulphides, arsenide of other metals and other Ag minerals.
Cr which is Naturally occurring is typically found associated with ultramafic
igneous and metamorphic rocks like peridotites and serpentinites, and their derived
soils (Chrysochoou et al. 2016). Earth’s most important Fe ore deposits are found in
sedimentary rocks. They are formed from chemical reactions which combines Fe and
oxygen in marine and fresh waters. Hematite (Fe 2 O 3 ) and magnetite (Fe 3 O 4 ) are the
two most important minerals found in the deposits as Fe oxides. The Heavy metal Se
is mainly concentrated in sedimentary rocks like shales, sandstones, limestones, and
phosphorite rocks. Ti metal is usually present in igneous rocks and in the sediments
derived from them and is not found as the free element. It is found in the minerals
rutile (TiO 2 ), ilmenite (FeTiO 3 ), and sphene, and is present in titanites and in many
Fe ores.
Barium (Ba) is a trace element occurring in igneous and sedimentary rocks in
association with potassium- bearing minerals in the Earth’s crust and it becomes
available to the aquatic environment through chemical weathering of rocks and
minerals (Liguori et al. 2016). Ultramafic rocks possess two principle minerals that
contain Ni. These are olivine (High amount of Ni) and orthopyroxene (small amount
of Ni). These minerals are the prime source of the Ni (Lightfoot 2017).
The heavy metal As is largely present in Sedimentary Rocks of Limestones,
Sandstones, Shales and clays Phosphorites and Sedimentary ores of iron and manganese. The highest amount of As is associated with sulphide minerals and metal
oxides, specifically iron oxides (Pal 2015).
Apart from this natural sources of Heavy metals, forest fires, volcanic eruption,
biogenic sources, sea salt spray and wind-borne particles cause natural emission of
heavy metals that may occur under different and indubitable environmental conditions. Anthropic activities such as industries, wastewater generated from different
sectors, agriculture, mining etc. has paramount share in polluting different
15 Potential of Free Floating Macrophytes for Bioremediation of Heavy Metals. . .
319
listed heavy metals; Zn is mainly located in sedimentary rocks that includes limestone, dolostone, salt and shale. Zinc carbonate (ZnCO 3 ), known as calamine or
smithsonite is commonly found as Zn ore (Peter and Tharsika 2017). The host rocks
of Cu are Igneous, Sedimentary, Metamorphic types. In amalgamation with sulphur
oxides and oxygen, it is found as Sulphides and sulphur oxides respectively. Its
combination with cobalt, Ni, Pb, Ag and Fe forms complex Cu minerals. Pb is found
mainly in sedimentary rocks (including limestone, dolostone, salt and shale), igneous and metamorphic rocks. ZnCO 3 known as calamine or smithsonite is a common
Zn ore. A Pb sulphide mineral is known as Galena (Peter and Tharsika 2017).
Hg is found in pure form in found in volcanic rocks, but is usually occur in the
mineral called cinnabar which is chemically known as Hg sulphide. Cd is principally
found in rocks of sedimentary type, the amount being much higher than that in in
igneous or metamorphic rocks (except nonferrous metallic ores of Zn, Pb and Cu
(ICAD). It occurs naturally in Earth’s curst in combination with Zn. In air, it gets
released through volcanoes and forest fires. Rocks of Igneous and Metamorphic type
contain Ag. Native elemental mineral form is rare. In this state it is often associated
with quartz, gold, Cu, sulphides, arsenide of other metals and other Ag minerals.
Cr which is Naturally occurring is typically found associated with ultramafic
igneous and metamorphic rocks like peridotites and serpentinites, and their derived
soils (Chrysochoou et al. 2016). Earth’s most important Fe ore deposits are found in
sedimentary rocks. They are formed from chemical reactions which combines Fe and
oxygen in marine and fresh waters. Hematite (Fe 2 O 3 ) and magnetite (Fe 3 O 4 ) are the
two most important minerals found in the deposits as Fe oxides. The Heavy metal Se
is mainly concentrated in sedimentary rocks like shales, sandstones, limestones, and
phosphorite rocks. Ti metal is usually present in igneous rocks and in the sediments
derived from them and is not found as the free element. It is found in the minerals
rutile (TiO 2 ), ilmenite (FeTiO 3 ), and sphene, and is present in titanites and in many
Fe ores.
Barium (Ba) is a trace element occurring in igneous and sedimentary rocks in
association with potassium- bearing minerals in the Earth’s crust and it becomes
available to the aquatic environment through chemical weathering of rocks and
minerals (Liguori et al. 2016). Ultramafic rocks possess two principle minerals that
contain Ni. These are olivine (High amount of Ni) and orthopyroxene (small amount
of Ni). These minerals are the prime source of the Ni (Lightfoot 2017).
The heavy metal As is largely present in Sedimentary Rocks of Limestones,
Sandstones, Shales and clays Phosphorites and Sedimentary ores of iron and manganese. The highest amount of As is associated with sulphide minerals and metal
oxides, specifically iron oxides (Pal 2015).
Apart from this natural sources of Heavy metals, forest fires, volcanic eruption,
biogenic sources, sea salt spray and wind-borne particles cause natural emission of
heavy metals that may occur under different and indubitable environmental conditions. Anthropic activities such as industries, wastewater generated from different
sectors, agriculture, mining etc. has paramount share in polluting different
15 Potential of Free Floating Macrophytes for Bioremediation of Heavy Metals. . .
319