Nickel is a naturally occurring element that is found in soil, water, air, and food. It can enter the environment through natural processes like volcanic eruptions or weathering of nickel-containing rocks, as well as anthropogenic activities like mining, fossil fuel combustion, and waste incineration. Nickel is present in varying concentrations in different types of soils depending on their geological composition. In plants, nickel is taken up as Ni2+ and concentrations can vary significantly depending on plant species and soil nickel levels. While not essential in all plants, nickel plays a role in certain enzyme functions in some species. High levels of nickel exposure through food and water can cause toxicity effects in humans and animals. Phytoremediation

2. Outlines
 Characteristics and history
 Source of pollution
 Concentration in soil, Mobile forms in soil
 Concentration in plants, function and hypo
accumulators, excluders, indicator plants
 Concentration in food, has a harmful effect on human.
 Phytoremediation and examples

3. Characteristics
Chemical
symbol:
Ni
Atomic
number:
28
Atomic
weight:
58.69
Melting point: 1453 oC
Boiling point: 2730 oC
Color Silver White
Curie
temperature:
253 oC
History
In 1751, Axel Fredrik Cronstedt,
working at Stockholm,
investigated a new mineral now
called nickeline (NiAs) which
came from a mine at Los,
Hälsingland, Sweden. He
thought it might contain copper,
but he extracted a new metal that
he announced and named nickel
in 1754.

4. Sources of Pollution
Anthropogenic Sources
Nickel in the air; Combustion of fossil fuel (released 0.57m tons worldwide
1999).
326 tons were released from electric utilities, municipal incineration accounted for
12%, steel production produced 3% and other nickel-containing alloys.
Nickel in water; nickel emissions from industrial processes like mining,
industrial wastewater as well as domestic wastewater, and landfill leachate can
also contain nickel.
According to reports, approximately 0.5–2 ppb of nickel is present in seawater,
while rivers contain about 0.3 ppb of nickel species.
Nickel in Soil; Nickel levels in the soil come from anthropogenic sources such as
metal manufacturing waste, commercial waste, fallout, and sludge, coal fly ash,
coal bottom ash, mining, and smelting.

5. Natural sources
Nickel, a widely distributed metal in natural flora and fauna, is found in animals, plants,
soil, and varied water bodies.
Nickel in the atmosphere; Approximately 30 000 tons of nickel per year are emitted
from its natural sources.
Windblown sand, volcanic activity, wild forest fires, sea salt spray, continental
particulates and continental volatiles, and aerosols from oceanic dust, although volcanoes
and windblown dust from rocks and soil are of prime importance.
Surface and groundwater; weathering, dissolution, and atmospheric evaporation of
nickel-rich rocks and soils.
Surface water can become contaminated due to the dissolution of primary bedrock
minerals in rainwater.
In soil; Nickel is mainly released to the soil as a result of atmospheric emissions.
It is found in the highest concentrations in igneous rocks.

6. Concentration of Nickel in soil
Nickel comprises approximately 3% of the earth's crust composition and is the
twenty-fourth most abundant element (Hemantaranjan 2014).
Total Ni concentration commonly ranges from 5 to 500 mg kg-1, averaging 50 mg
kg-1 in soils.
Ni concentrations in dried biosolids (also referred to as treated sewage sludge) or
soil near metal refineries range from 24,000 to 53,000 mg kg-1.
Soils for crop production contain 3–1,000 mg kg-1 because Ni2+ is the available
form of Ni for plants, total Ni concentration is not a useful measure for Ni
bioavailability. Thus, plants grown in high-pH soils are vulnerable to Ni
deficiency. Additionally, excessive use of Zn and Cu may induce Ni deficiency in
soil because these three elements share a common uptake system.

7. Over-liming raises pH excessively and causes soil deficiency in plant-available
Ni. Thus, in soils that have to be high-pH, either naturally or artificially
According to Chen et al., (1999) Australia (60 ppm), Canada (150 ppm), China
(20 ppm), France (50 ppm), Germany (200 ppm), Japan (100 ppm) Netherlands
(210 ppm), South Africa (15 ppm), United Kingdom (60 ppm), and United State
of America (420 ppm).

9. Nickel is considered a mobile element and its availability is controlled by
such factors as PH, the quantity and quality of clay minerals, organic
matter, or soil reaction. In acid soils, Ni solubility increases considerably,
and its adsorption by Fe and Mn hydroxides increases with a decrease in
acidity.
In acidic soil, the mobility of Ni is more, while in alkaline soil, adsorption
is irreversible, which limits both availability and mobility of Ni in soil.
In acidic soil solution, the most common forms of Ni that have been
identified are Ni2+, NiSO4, and NiHPO4 and in the alkaline medium, are
Ni2+ Ni(OH)+
Mobile Forms of Nickel in Soil

10. Nickel concentration in plants
Plants take up Ni in the form of soluble Ni²+
The Ni concentration in most plant leaf material ranges from about 0.1 to 5 ppm (in dry
weight).
It can be highly variable depending on soil availability, plant species, and plant part.
Ni naturally occurs in a few plants (legumes) where it functions as an essential component of
some enzymes (e.g., ureases) involved in nitrogen assimilation.
Tea plants may contain high Ni levels (at concentrations up to 5.3 mg kg−1 in dried leaves),
whereas Ni levels in other plants vary like cacao powder (9.8 mg kg −1), cashews (5.1 mg kg
−1), soy protein (4.3 mg kg −1), walnuts (3.6 mg kg −1), filberts and peanuts (1.6 mg kg −1),
almonds (1.3 mg kg −1), wheat germ (1 mg kg −1), pistachios (0.8 mg kg −1), and rice (0.4 mg
kg −1) (Nielsen 1993). The nickel content in some vegetables varies from 0.26 mg kg −1
(beans) to 0.08 mg kg −1 (tomatoes). Some fruits, such as peaches (0.16 mg kg −1) and apples
(0.03 mg kg −1), may also contain moderate amounts of nickel (Nielsen 1993).

11. Function of Nickel in plants
While nickel is not considered an essential nutrient for all plant species, it does play some
important functions in certain plants.
Urease activation: Nickel is a critical component of the enzyme urease, which plays a vital
role in nitrogen metabolism. Urease facilitates the conversion of urea into ammonia, which
plants can use as a source of nitrogen for growth and development.
Enzyme co-factor: Nickel activates several plant enzymes, including certain hydrogenases,
carbon monoxide dehydrogenases, and acetyl-CoA decarboxylases.
Iron absorption and metabolism: Nickel can influence iron uptake and metabolism in some
plant species. It has been observed that nickel-deficient plants may show impaired iron
uptake, leading to iron deficiency symptoms such as chlorosis.

12. • Alyssum murale
• Helianthus annuus
• Hybanthus
floribundus
• Ocimum
centraliafricanum
• Yellow alyssum
• Sunflower
• Shrub violet
• Copper plant
Hyperaccumulator Plants
Botanical Name English name
Excluder plants
• Brassica napus
• Zea mays
• Triticum aestivum
• Oryza sativa
• Glycine max
• Canola
• Maize
• Wheat
• Rice
• Soybean
Botanical Name English name
Indicator Plants
• Equisetum arvense
• Acalypha indica
• Polygonum persicaria
• Pteris vittata
• Vernonia cinerea
• Field horsetail
• Indian nettle
• Lady's thumb
• Brake fern
• Ironweed
Botanical Name English name
Accumulator plants
• Brassica juncea
• Brassica napus
• Festuca rubra
• Holcus lanatus
• Phragmites australis
• Trifolium repens
• Indian mustard
• Canola
• Red fescue
• Velvet grass
• Common reed
• Ribwort plantain
• White clover
English name
Botanical Name

13. Concentration in food
Human beings are exposed to nickel regularly because of its high abundance in nature.
Nickel deficiency in the human body is difficult to occur rather, it is hard to maintain a
diet deficient in nickel due to its high occurrence in food.
There are plenty of nickel-containing foods like vegetables (spinach, cabbage, lettuce,
peas, lentils, etc.), fruits (almonds, plums, dates, pineapples, etc.), grains (buckwheat, 2.0
μg g−1; oats, 2.3 μg g−1; oatmeal, 1.8 μg g−1) cocoa beans, 9.8 μg g−1; soya beans, 5.2 μg
g−1; soya products, 5.1 μg g−1; peanuts, 2.8 μg g−1; walnuts, 3.6 μg g−1; hazelnuts, dark
chocolate, seafood (crab, oysters, shrimps, salmon, etc.) and many more.
The quantity of nickel in a particular food depends on the plant species and the level of
nickel in the soil.

14. According to the information from research conducted in the USA, the average daily
intake for adults is 101–162 μg per day, for males, it is 136–140 μg per day, and for
females, it is 107–109 μg per day.
Nickel intakes were determined to be 9, 39, 82, and 99 μg per day for children aged 0–
6 months, 7–12 months, 1–3 years, and 4–8 years. The average intakes for pregnant
and lactating women are higher at 121 μg per day to 162 μg per day, respectively.
Additionally, cooking utensils significantly contributed to nickel levels in cooked food
(e.g. oven pans, roasting pans). Calogiuri et al. (2016) found that stainless-steel pans
cause a rise in nickel concentrations in acidic foodstuffs.

15. Nickel Toxicity Effect on Humans and Rats

16. Toxicity effect on
plants
Impaired root development,
stunted root growth and
reduced root branching
Chlorosis and leaf
discoloration, low
chlorophyll production
Nickel can induce the
production of reactive
oxygen species (ROS)
Inhibition of seed
germination

17. Phytoremediation and Phyto mining
Heavy metals, unlike organic pollutants, cannot be chemically degraded or biodegraded
by microorganisms. An alternative biological approach to manage this problem is
phytoremediation, which removes pollutants, including toxic metals, from the
environment by using plants (Salt et al. 1995).
Extracting nickel, cobalt, and other metals, including the platinum and palladium metal
families, from soil by cropping it with hyperaccumulating plants that concentrate these
metals in aerial parts of the plants, which are then harvested, dried and smelted to
recover the metal in a process known as metal phytomining (Chaney et al. 2004)