FLUORIDE AS POLLUTANT IN

AIR, WATER AND SOIL AND

ITS IMPACTS ON PLANTS

Jannat Iftikhar

Roll # B11-16

8th

Semester

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Course Title: Agriculture And Environmental Pollution

Module Code Bot- 437

History Of Fluoride Pollution

Pliny the Elder died due to fluoridecontaining fumes

The study began much later in 16th

century, with the use of fluorspar(CaF2) as flux in metal smelting.

He described how miners used rockscalled fluores to aid the smelting ofores.

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History Of Fluoride Pollution

1790

20th century

1848, Stockhardt &

Schroder

• Fluorine was found to bepresent in rockphosphate deposits.

• It was used by thebiochemists as a tool tohelp them to determinethe biochemicalpathways.

• Published the firstdetailed description offluoride injury in plants.

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Properties Of Fluorine

• Not present in free elemental state

• Most reactive

• Most electronegative

• Fluorine can form both covalent and electrovalent bonds

• Fluorine forms very strong bonds with carbon

• They are resistant to biological and chemical attack

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Sources of Fluoride in Atmosphere

Natural sources

Anthropogenic

sources

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Natural Sources

Forest fires Volcanoes

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Minerals

•According to Fleischer (1953), fluoride accounts for

0.032% of the earth crust

•Major minerals are Fluorite (CaF2), Fluorapatite

(Ca10F2(PO4)6) and Caryolite (Na3AlF6).

•Identified world reserves of fluoride are around 500 million t and

annual mine production is in excess of 4.5 million t.

•13th (Smith and Hodge, 1979) or 17th (Fleischer, 1953) most

abundant element in the earth crust.

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Natural

waters

• Depends on the geology, chemistry, physical characteristics and

climate of the area.

• If water is not in contact with high fluoride minerals the

range of concentration is from 0.01 to 0.4mg/L.

• The highest fluoride concentration tend to occur in arid

regions.

• The Rift Valley of East Africa has the highest concentration on

record, upto 300 mg/l

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Volcanoes,

Forest Fires

And Oceans

• 600 known, active volcanoes

• Halmer et al. (2002) have estimated the global

annual emmision of HF from valcanoes are being

from 7000 to 8000 kt.

• The total atmospheric inorganic fluoride under 0.1

and mostly <0.05µg/m3. (WHO, 2002)

• HF main form, others are; SiF, ammonium

flourosilicates, sodium flourosilicates, potasium

fourosilictes and potasium flouroborate.

• Roholm (1973) also reported the presence of NaF, MgF2, KF, CaF2.

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Anthropogenic sources

Industrial Emission Of Fluoride

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Anthropogenic Sources

Industries

• Other sources are toothpastes, pharmaceuticals, wood preservatives and

agrochemicals

• Result in the emission of gaseous and particulate fluoride into the atmosphere

• The combustion of coal

• Phosphate fertilizer and elemental phosphorus

• Iron and steel manufacture.

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Fluoride Cycle

Deposition Of Pollutant From

Atmosphere

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EPA Licensing Of Fluoride

Emissions

• Portland Aluminium has an EPA Licence outlining

emission limits for fluoride.

• Licence limits set out in EPA licences require emissions to

be well within safe levels.

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Rate Of Fluoride Deposition

• Chamberlain (1996)

Rate of deposition(µg/m2/s) = conc. in air (µg/m3) × deposition

velocity (m/s)

• The deposition velocity, Vg, varies with the form of fluoride

(gas or particulate), particle size, wind speed, and the

nature of the plant canopy particularly its architecture and

wetness.

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Fluoride In Water

• Dissolve in water and split into ions.

• Speed of dissolution depend on pH, type of compound.

• Transport and transformation is influence by pH, hardness

and presence of clay.

• As they travel through the water cycle fluorides usually

combine with Aluminium.

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Fluoride In Soil

• Fluoride is so strongly adsorbed by the soil that the

leaching is slow.

• The most widespread source of soil contamination arise

from the use of phosphate fertilizers.

• In soils, fluoride is predominantly combined with

Aluminium or calcium.

• When the soil is slightly acidic, fluoride tends to adsorb

more strongly to soil particles.

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Fluoride In Plants

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• Absorbed through leaf stomata.

• Move by transpiration into the principal sites of accumulation at the tip and leaf margins.

Gaseous fluoride

• In plant roots through passive diffusion.

• Transported to the shoots via xylem.

Dissolved in water

• Onset symptoms depends on

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Type and age

of plant

Concentration

Time of

exposure

Composition of the air Rate of circulation

Temperature

Type of light

and intensity

Injury Symptoms

• The injury starts as a gray or light-green water-soaked

lesion, which turns tan to reddish-brown.

• With continued exposure

Necrotic areas increase in size

Spreading inward to the midrib on broad leaves

Downward on monocot leaves

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Fluoride injury symptoms on leaves of Gladiolus and Douglas fir.

Case Studies

• Effects of fluoride has been studied on Pinus ponderosa

by Solberg et al. (1955).

• Benedict and Breen (1955) have used weeds in evaluating

vegetation damage caused by air containing hydrogen

fluoride and other air pollutants.

• Fluoride is reported to cause adverse effects on plant

growth and yield.

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Biochemical And Physiological

Impacts Of Fluoride Contamination

• The high internal fluoride concentration disturbs almost

all physiological and biochemical process in plants.

• A number of cellular processes identified to cause

deleterious effects on plants disruption of enzymes

involved in

Metabolic activities

Protein secretion and synthesis

Generation of reactive oxygen species

Alteration of gene expression

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At micro molar

concentrationsAt milli molar concentrations

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Acts as an anabolic reagent

Promotes cell proliferation

It acts as enzyme inhibitor

• Fluoride disrupts enzyme activity by binding to functional

amino groups that surrounds the enzyme’s active center.

• Inhibition of protein synthesis and secretion interrupts the

signaling pathway involves involved in cell proliferation

and apoptosis.

• Fluoride can increase oxidative stress

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Conclusion

• Fluoride is a hazardous for both animal and plants.

• It causes serious damage to the crops grown in the

vicinity of fluoride.

• It effects almost all the biochemical and physiological

process of the plant that ultimately led to the reduction in

yield.

• Strict measures should be taken to avoid fluoride

contamination.

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References

• L.H. Weinstein, A.W. Davison; Fluoride in the Environment, CABI publishers, Cambridge, USA, 2004.

• Greenwood, Delbert A., "Some Effects of Inorganic Fluoride on Plants, Animals, and Man" (1956). USU Faculty Honor Lectures. Paper 41.

• M. Baunthiyal, S. Ranghara, P. Garhwal; Physiological And Biochemical Responses Of Plants Under Fluoride Stress: An Overview, Research review Fluoride 47(4)287–293 October-December 2014.

• M.N. Ahmad, et al., Hydrogen Fluoride Effects On Local Mung Bean And Maize Cereal Crops From Peri-Urban Brick Kilns In South Asia, Research report Fluoride 47(4)315–319 October-December 2014.

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• S. F. Yang And G. W. Miller, Biochemical Studies on the

Effect of Fluoride on Higher Plants, Biochem. J. (1963) 88,

505.

• P. C. Mishra, S. K. Sahu, A. K. Bhoi, S. C. Mohapatra,

Fluoride Uptake and Net Primary Productivity of Selected

Crops, Open Journal of Soil Science, 2014, 4, 388-398.

• Summary & Details: Green Facts, Scientific Facts on

fluoride, source document IPCS (2002).

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Thank you!!!

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Any question???