Ammonia pollution is
pollution
Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the ...
by the chemical
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...
(NH
3) – a compound of
nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
and
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
which is a byproduct of agriculture and industry. Common forms include air pollution by the ammonia gas emitted by rotting agricultural
slurry
A slurry is a mixture of denser solids suspended in liquid, usually water. The most common use of slurry is as a means of transporting solids or separating minerals, the liquid being a carrier that is pumped on a device such as a centrifugal pu ...
and
fertilizer
A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...
factories while natural sources include the burning coal mines of
Jharia
Jharia is a neighbourhood in Dhanbad city in Dhanbad Sadar subdivision of Dhanbad district in Jharkhand state, India. Jharia's economy is heavily dependent on the local coal fields, used to make coke. However, fires in the coal fields have made ...
, the caustic
Lake Natron
Lake Natron is a salt or alkaline lake located in north Ngorongoro District of Arusha Region in Tanzania. It is in the Gregory Rift, which is the eastern branch of the East African Rift. The lake is within the Lake Natron Basin, a Ramsar Site ...
and the
guano
Guano (Spanish from qu, wanu) is the accumulated excrement of seabirds or bats. As a manure, guano is a highly effective fertilizer due to the high content of nitrogen, phosphate, and potassium, all key nutrients essential for plant growth. G ...
of seabird colonies. Gaseous ammonia reacts with other pollutants in the air to form fine
particles
In the physical sciences, a particle (or corpuscule in older texts) is a small localized object which can be described by several physical or chemical properties, such as volume, density, or mass.
They vary greatly in size or quantity, from su ...
of
ammonium
The ammonium cation is a positively-charged polyatomic ion with the chemical formula or . It is formed by the protonation of ammonia (). Ammonium is also a general name for positively charged or protonated substituted amines and quaternary a ...
salts, which affect human breathing. Ammonia gas can also affect the
chemistry of the soil on which it settles and will, for example, degrade the conditions required by the
sphagnum moss
''Sphagnum'' is a genus of approximately 380 accepted species of mosses, commonly known as sphagnum moss, peat moss, also bog moss and quacker moss (although that term is also sometimes used for peat). Accumulations of ''Sphagnum'' can store wa ...
and
heathers of
peatland
A mire, peatland, or quagmire is a wetland area dominated by living peat-forming plants. Mires arise because of incomplete decomposition of organic matter, usually litter from vegetation, due to water-logging and subsequent anoxia. All types ...
.
Ammonia detection is facilitated through the use of filter packs and fabric denuders (a gas separator). Techniques such as
satellite imaging
Satellite images (also Earth observation imagery, spaceborne photography, or simply satellite photo) are images of Earth collected by imaging satellites operated by governments and businesses around the world. Satellite imaging companies sell im ...
and
rainwater analysis are also used.
Much is still unknown about the impact of ammonia pollution, but rising emission rates concern scientists. The level of ammonia in the atmosphere was more than twice as large in 2010 as it was in 1940.
Ammonia is now recognized by many countries as a major pollutant and some have begun taking steps to limit their emissions.
Sources
The table below lists sources of ammonia pollution and their percent contribution to global ammonia emissions. The sources are also classified as either
anthropogenic
Anthropogenic ("human" + "generating") is an adjective that may refer to:
* Anthropogeny, the study of the origins of humanity
Counterintuitively, anthropogenic may also refer to things that have been generated by humans, as follows:
* Human im ...
(resulting from humans) or natural.
Effects
Ammonia decreases the
biodiversity
Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...
of terrestrial and aquatic
ecosystem
An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...
s and also forms
aerosol
An aerosol is a suspension (chemistry), suspension of fine solid particles or liquid Drop (liquid), droplets in air or another gas. Aerosols can be natural or Human impact on the environment, anthropogenic. Examples of natural aerosols are fog o ...
s in the atmosphere which can cause human health complications if inhaled.
Biodiversity
Gaseous ammonia emissions enter Earth’s soil and water through both wet and dry
deposition.
Aqueous
An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, or sodium chloride (NaCl), in water would be rep ...
ammonia, another form of the compound, may seep directly into the ground or flow into aquatic ecosystems. Both terrestrial and aquatic ammonia pollution decrease biodiversity mainly through the process of
nitrification
''Nitrification'' is the biological oxidation of ammonia to nitrite followed by the oxidation of the nitrite to nitrate occurring through separate organisms or direct ammonia oxidation to nitrate in comammox bacteria. The transformation of amm ...
.
Terrestrial Effects
In terrestrial settings, ammonia increases soil acidity (decreased pH) and causes
eutrophication
Eutrophication is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients, particularly nitrogen and phosphorus. It has also been defined as "nutrient-induced increase in phytopla ...
(an overabundance of nutrients). Both of these occur as a direct result of nitrification. In this process, ammonia is converted into
nitrate
Nitrate is a polyatomic ion
A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zer ...
by bacteria (usually of genera
Nitrosomonas
''Nitrosomonas'' is a genus of Gram-negative bacteria, belonging to the Betaproteobacteria. It is one of the five genera of ammonia-oxidizing bacteria and, as an obligate chemolithoautotroph, uses ammonia (NH3) as an energy source and carbon diox ...
and
Nitrobacter
''Nitrobacter'' is a genus comprising rod-shaped, gram-negative, and chemoautotrophic bacteria. The name ''Nitrobacter'' derives from the Latin neuter gender noun ''nitrum, nitri'', alkalis; the Ancient Greek noun βακτηρία'','' βακτ ...
) performing the following two step reaction:
Step 1: Ammonia (NH
3 ) is
oxidized
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...
into
nitrite
The nitrite polyatomic ion, ion has the chemical formula . Nitrite (mostly sodium nitrite) is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name ...
(NO
2−) by:
NH3(aq) + O2(g) -> NO2- (aq) + 3H+(aq) + 2e-
Step 2: Nitrite (NO
2−) is oxidized into nitrate(NO
3−)
NO2- (aq) + H2O(l) -> NO3- (aq) + 2H+(aq) + 2e-
The products of this reaction include
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
(H
+)
ion
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...
s which lower the soil pH and lead to acidification. Increased soil acidity in the ecosystem leads to decreased protection against cold temperatures, drought, disease, and invasive species. The other product, nitrate (NO
3−), is a key nutrient for plant growth. This excess nitrate from ammonia nitrification favors
nitrophilous Nitrophily is a Botany, botanical term that indicates a preference of certain plant species for a habitat rich in nitrate. This term was first introduced by George Fuller (ecologist), George Fuller during the 1930s. The word is a contraction of the ...
plants (those that prefer high nitrate concentrations) and disadvantages others. For example, an increase in nitrophilous plant populations shade other plants from necessary sunlight. Sensitive plant groups such as
lichen
A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.[moss
Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) '' sensu stricto''. Bryophyta (''sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and hor ...]
are particularly susceptible to ammonia pollution and habitats such as
bog
A bog or bogland is a wetland that accumulates peat as a deposit of dead plant materials often mosses, typically sphagnum moss. It is one of the four main types of wetlands. Other names for bogs include mire, mosses, quagmire, and muskeg; a ...
s,
peatlands
A mire, peatland, or quagmire is a wetland area dominated by living peat-forming plants. Mires arise because of incomplete decomposition of organic matter, usually litter from vegetation, due to water-logging and subsequent anoxia. All types ...
,
grassland
A grassland is an area where the vegetation is dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur natur ...
s,
heath
A heath () is a shrubland habitat found mainly on free-draining infertile, acidic soils and characterised by open, low-growing woody vegetation. Moorland is generally related to high-ground heaths with—especially in Great Britain—a cooler ...
lands, and
forest
A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' ...
s are mainly affected.
Aquatic effects
In aquatic settings, ammonia causes nitrogenous oxygen demand, eutrophication, and changes in fish health. Nitrogenous biological oxygen demand (NBOD) occurs as a direct result of nitrification (see terrestrial effects). Dissolved oxygen (O
2) is used in nitrification to react with NH
3. This results in less O
2 available to organisms that depend on it. Nitrification also releases nitrate which leads to eutrophication as in terrestrial settings. Nitrophilous
algae
Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...
and
macrophytes
Aquatic plants are plants that have adapted to living in aquatic environments (saltwater or freshwater). They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes. A macrophyte is a plant that g ...
create large blooms in standing water. This puts stress on resources and also can indirectly poison organisms through toxic algae formation. In contrast, ammonia can also directly harm organisms with permeable skin if they absorb it. Fish kills and changes in fish growth, gill condition, organ weights, and hematocrit (red blood cell) levels are linked to ammonia exposure.
Human health
Gaseous ammonia that is not deposited forms aerosols by combining with other emissions such as
sulfur dioxide
Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...
(SO
2) and
nitrogen oxide Nitrogen oxide may refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds:
Charge-neutral
*Nitric oxide (NO), nitrogen(II) oxide, or nitrogen monoxide
*Nitrogen dioxide (), nitrogen(IV) oxide
* Nitrogen trioxide (), or n ...
s (NO
X). Atmospheric reactions among sulfur dioxide, nitrogen oxides, intermediate products, and other gases eventually result in formation of
ammonium nitrate
Ammonium nitrate is a chemical compound with the chemical formula . It is a white crystalline salt consisting of ions of ammonium and nitrate. It is highly soluble in water and hygroscopic as a solid, although it does not form hydrates. It is ...
(NH
4NO
3) and
ammonium bisulfate
Ammonium bisulfate, also known as ammonium hydrogen sulfate, is a white, crystalline solid with the formula (NH4)HSO4. This salt is the product of the half-neutralization of sulfuric acid by ammonia.
Production
It is commonly collected as a bypro ...
(NH
4HSO
4) by the following:
NH3(g) + HNO3 (g) -> NH4NO3(g)
NH3(g) + H2SO4 (g) -> NH4HSO4 (g)
These resulting ammonium (NH
4) aerosols are classified as fine
particulate matter
Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM) or suspended particulate matter (SPM) – are microscopic particles of solid or liquid matter suspended in the air. The ter ...
(PM2.5 or particulate matter less than 2.5 microns in size). The small size of PM2.5 particles allows them to enter the lungs and bloodstream through inhalation. Ammonium particles can then cause complications including
asthma
Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...
,
lung cancer
Lung cancer, also known as lung carcinoma (since about 98–99% of all lung cancers are carcinomas), is a malignant lung tumor characterized by uncontrolled cell growth in tissue (biology), tissues of the lung. Lung carcinomas derive from tran ...
, cardiovascular issues,
birth defect
A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities can ...
s, and premature death in humans. The smaller ammonium PM2.5 can also travel further distances (100–1000 km) when compared to unreacted ammonia (less than 10–100 km) in the atmosphere.
Some countries like China have focused on reducing SO
2 and NO
X emissions, however increased NH
3 pollution still results in PM2.5 formation and reduces air quality.
Monitoring techniques
Ammonia pollution is most commonly measured by its presence in the atmosphere. It has no automatic relay system as with other pollutant measurements such as
carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
; therefore, ammonia samples must be collected through other methods including filter packs, fabric denuders, satellite imaging, and rainwater analysis.
Filter packs
Filter packs consist of an air pump fitted with a
Teflon
Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that has numerous applications. It is one of the best-known and widely applied PFAS. The commonly known brand name of PTFE-based composition is Teflon by Chemou ...
and
glass fiber
Glass fiber ( or glass fibre) is a material consisting of numerous extremely fine fibers of glass.
Glassmakers throughout history have experimented with glass fibers, but mass manufacture of glass fiber was only made possible with the inventio ...
filter. The pump sucks in air and the filters remove ammonia particles. The Teflon and glass fiber filter are coated in
citric acid
Citric acid is an organic compound with the chemical formula HOC(CO2H)(CH2CO2H)2. It is a colorless weak organic acid. It occurs naturally in citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, which occurs in t ...
which reacts with the slightly basic ammonia particles. This reaction essentially "glues" the ammonia in place. Later, the filter is tested with
Nessler’s reagent (an ammonia indicator) and a
spectrophotometer reads the amount of ammonia present.
Fabric Denuders
Fabric denuders function through
passive sampling
Passive sampling is an environmental monitoring technique involving the use of a collecting medium, such as a man-made device or biological organism, to accumulate chemical pollutants in the environment over time. This is in contrast to Environment ...
(no pump is used and collection depends only on airflow). A pipe fitted with cloth filters on either side serves as a tunnel for air to diffuse through. The cloth is coated in
phosphoric acid
Phosphoric acid (orthophosphoric acid, monophosphoric acid or phosphoric(V) acid) is a colorless, odorless phosphorus-containing solid, and inorganic compound with the chemical formula . It is commonly encountered as an 85% aqueous solution, w ...
which attracts ammonia gas (a base). Air flows through the tube and ammonia sticks to the filters which can then be tested for NH
3 concentrations using Nessler's reagent and a spectrophotometer.
Satellite imaging
Systems of satellites measure gas signatures in the atmosphere over time. Ammonia’s signature is charted giving an estimate of its prevalence in the air and where it is most concentrated.
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research.
NASA was established in 1958, succeeding t ...
has been using satellite imaging to monitor ammonia emissions since 2008.
Rainwater analysis
Buckets of rain are collected and then tested for ammonia using techniques described above. This provides the concentration of ammonia gas trapped in atmospheric water vapor.
Regulations
Although ammonia is now recognized as a potentially hazardous air pollutant, only some countries have taken further action to reduce their emission. Reduction strategies predominantly focus on controlling agricultural practices.
Policy
The
European Union
The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been des ...
has had two policies in place since 1999 to prevent ammonia pollution. These include the
Gothenburg Protocol (1999) and the Directive on Integrated Pollution Protection and Control (1999). The National Emission Ceilings Directive was also put into effect in 2001 by the EU to further reduce NH
3 emissions. The Gothenburg Protocol was revised in 2012 to set new, stricter, ceiling limits on ammonia until 2020 and to include all EU-27 countries. The
United Kingdom
The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...
in particular has announced that they plan to cut emissions by 16% by 2030, however no new policies have been enacted. Other countries like
China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
and the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
acknowledge ammonia as a pollutant, but have no policies in place to regulate it.
Ammonia pollution regulations mainly focus on mitigation through better farming practices. One suggested change is keeping manure and fertilizer in large storage tanks to prevent runoff and volatilization into the air. Another strategy involves feeding livestock diets less dense in protein. This would result in less nitrogen proteins (including ammonia) ending up in manure. A final idea is using less
urea
Urea, also known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid.
Urea serves an important r ...
and ammonium based fertilizers which are prone to volatilization into ammonia.
See also
*
Nitrogen cycle
The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmospheric, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biologi ...
*
Haber-Bosch process
The Haber process, also called the Haber–Bosch process, is an artificial nitrogen fixation process and is the main industrial procedure for the production of ammonia today. It is named after its inventors, the German chemists Fritz Haber and C ...
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Ammonia
Pollution