Role of Agriculture in Air pollution

8/7/2019 Role of Agriculture in Air pollution

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Muhamma

dTalhaKaifi

2011

Ro

leofAgricultureinAir

pollution

Human activities can release substances into the air, some of which

can cause problems for humans, plants, and animals causing airpollution. Agricultural practices also have such an impact on

environment which includes the chemical air pollution that result

from burning forest and crop residues, infectious agents and

allergens, and pesticides and other agricultural chemicals. The

documents look at the contribution of agriculture in air pollution in

detail.

PIMS Arid University


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January 13, 2011 [ROLEOF AGRICULTUREIN AIRPOLLUTION]

2 By : MuhammadTalha Kaifi -1502-Arid-10

Contents

Air pollution: ........................................................................................................................................... 3

Pollutants:............................................................................................................................................ 3

Classification ofPollutants: .............................................................................................................. 5

Sources of air pollution: ....................................................................................................................... 7

Agriculture: ............................................................................................................................................. 7

Production practices............................................................................................................................. 8

Tillage ............................................................................................................................................. 8

Pest control ...................................................................................................................................... 8

Nutrient management ....................................................................................................................... 8

Water management .......................................................................................................................... 8

Role of Agriculture in AirPollution: ........................................................................................................ 9

Agricultural Emissions:........................................................................................................................ 9

Agricultural technology: .................................................................................................................... 10

Emission of Nitrous oxide:................................................................................................................. 11

Emission of Ammonia: ...................................................................................................................... 12

Emission of Dust: .............................................................................................................................. 12

Agricultural Chemicals: ..................................................................................................................... 12

Emission of Hydrogen sulfide (H2S):................................................................................................. 12

Emissions ofParticles: ....................................................................................................................... 13

Conclusion: ........................................................................................................................................... 14


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Role of Agriculture on Air pollution:

Air pollution:

Oxygen is an essential requirement of body supplied by air while breathing. Air is 99.9%

nitrogen, oxygen, water vapor and inert gases. Human activities can release substances into the

air, some of which can cause problems for humans, plants, and animals. The release of such

inappropriate substance causes air pollution.

Air pollution is the introduction of chemicals, particulate matter, or biological materials that

cause harm or discomfort to humans or other living organisms, or cause damage to the natural

environment or built environment, into the atmosphere.

The atmosphere is a complex dynamic natural gaseous system that is essential to support life on

planet Earth. Stratospheric ozone depletion due to air pollution has long been recognized as a

threat to human health as well as to the Earth's ecosystems.

Indoor air pollution and urban air quality are listed as two of the worlds worst pollution problems

in the 2008 Blacksmith Institute World's Worst Polluted Places report

There are several main typesof pollution having hazardous effects on human body and theenvironment. The possible consequences of increasing air pollution include smog, acid rain, the

greenhouse effect, and "holes" in the ozone layer.

Pollutants:

An air pollutant is known as a substance in the air that can cause harm to humans and the

environment. Pollutants can be in the form of solid particles, liquid droplets, or gases. In

addition, they may be natural or man-made.


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Before flue gas desulfurization was installed, the emissions from this power plant in Mexico contained excessive amounts of sulfur

dioxide.

Growing public and regulatory concerns have recognized the emissions and discharges from

agriculture and adverse impacts of agriculture on the quality of the air and water, and on soil,

biodiversity, and the long-term sustainability of agricultural ecosystems. Public concerns about

current and predicted impacts to the environment pressure farmers to reduce intensive

agriculture. To develop policies to reduce environmental impacts from agriculture, one must

understand the behavior of agricultural emissions and the subsequent transformations, transport,

and fate of pollutants in the environment. As given in the below figure:

Schematic drawing, causes and effects of air pollution: (1) greenhouse effect, (2) particulate contamination, (3) increased UV radiation,

(4) acid rain, (5) increased ground level ozone concentration, (6) increased levels of nitrogen oxides.


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Classification ofPollutants:

Pollutants can be classified as primary or secondary. Usually, primary pollutants are directly

emitted from a process, such as ash from a volcanic eruption, the monoxide gas from a motor

vehicle exhaust or sulfur dioxide released from factories.

Secondary pollutants are not emitted directly. Rather, they form in the air when primary

pollutants react or interact. An important example of a secondary pollutant is ground level

ozone one of the many secondary pollutants that make up photochemical smog. Some

pollutants may be both primary and secondary: that is, they are both emitted directly and formed

from other primary pollutants.

Primary Pollutants:

Major primary pollutants produced by human activity include:

Sulfur oxides (SOx) - especially sulfur dioxide, a chemical compound with the formulaSO2. SO2 is produced by volcanoes and in various industrial processes. Since coal and

petroleum often contain sulfur compounds, their combustion generates sulfur dioxide.

Further oxidation of SO2, usually in the presence of a catalyst such as NO2, forms H2SO4,

and thus acid rain. This is one of the causes for concern over the environmental impact of the

use of these fuels as power sources.

Nitrogen oxides (NOx) - especially nitrogen dioxide are emitted from high temperaturecombustion. Can be seen as the brown haze dome above orplume downwind of cities.

Nitrogen dioxide is the chemical compound with the formula NO2. It is one of the several

nitrogen oxides. This reddish-brown toxic gas has a characteristic sharp, biting odor. NO2 is

one of the most prominent air pollutants.

Carbon monoxide - is a colorless, odorless, non-irritating but very poisonous gas. It is aproduct by incomplete combustion of fuel such as natural gas, coal or wood. Vehicular

exhaust is a major source of carbon monoxide.

Carbon dioxide (CO2) - a colorless, odorless, non-toxic greenhouse gas associatedwith ocean acidification, emitted from sources such as combustion, cement production,

and respiration


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Volatile organic compounds - VOCs are an important outdoor air pollutant. In this fieldthey are often divided into the separate categories of methane (CH4) and non-methane

(NMVOCs). Methane is an extremely efficient greenhouse gas which contributes to

enhanced global warming. Other hydrocarbon VOCs are also significant greenhouse gases

via their role in creating ozone and in prolonging the life of methane in the atmosphere,

although the effect varies depending on local air quality. Within the NMVOCs, the aromatic

compounds benzene, toluene and xylene are suspected carcinogens and may lead to leukemia

through prolonged exposure. 1,3-butadiene is another dangerous compound which is often

associated with industrial uses.

Ammonia (NH3) - emitted from agricultural processes. Ammonia is a compound with theformula NH3. It is normally encountered as a gas with a characteristic pungent odor.Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving

as a precursor to foodstuffs and fertilizers. Ammonia, either directly or indirectly, is also a

building block for the synthesis of many pharmaceuticals. Although in wide use, ammonia is

both caustic and hazardous.

Odors such as from garbage, sewage, and industrial processes Radioactive pollutants - produced by nuclear explosions, war explosives, and natural

processes such as the radioactive decay of radon.

Secondary pollutants:

Particulate matter: formed from gaseous primary pollutants and compounds in photochemicalsmog. Smog is a kind of air pollution; the word "smog" is a portmanteau of smoke and fog.

Classic smog results from large amounts of coal burning in an area caused by a mixture of

smoke and sulfur dioxide. Modern smog does not usually come from coal but from vehicular

and industrial emissions that are acted on in the atmosphere by ultraviolet light from the sun

to form secondary pollutants that also combine with the primary emissions to form

photochemical smog.

Ground level ozone (O3): formed from NOx and VOCs. Ozone (O3) is a key constituent of thetroposphere (it is also an important constituent of certain regions of the stratosphere

commonly known as the Ozone layer). Photochemical and chemical reactions involving it


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drive many of the chemical processes that occur in the atmosphere by day and by night. At

abnormally high concentrations brought about by human activities (largely the combustion of

fossil fuel), it is a pollutant, and a constituent of smog.

Peroxyacetyl nitrate (PAN): - similarly formed from NOx and VOCs.

Minor air pollutants:

A large number of minor hazardous air pollutants. Some of these are regulated in USA underthe Clean Air Act and in Europe under the Air Framework Directive.

A variety of persistent organic pollutants, which can attach to particulate matter.Persistent organic pollutants (POPs) are organic compounds that are resistant to environmental

degradation through chemical, biological, and photolytic processes. Because of this, they havebeen observed to persist in the environment, to be capable of long-range transport,

bioaccumulate in human and animal tissue, biomagnify in food chains, and to have potential

significant impacts on human health and the environment.

Sources of air pollution:

The main sources of air pollution are the industries, agriculture and traffic, as well as energy

generation. However most air pollution causes originate from human activities such as the

burning of fossil fuels and use of land for agricultural purposes.

Agriculture:

Agriculture is the production, processing, marketing, and use of foods, fibers and byproducts

from plant crops and animals. Agriculture encompasses a wide variety of specialties and

techniques, including ways to expand the lands suitable for plant raising, by digging water-

channels and other forms of irrigation. Cultivation of crops on arable land and

the pastoral herding of livestock on rangeland remain at the foundation of agriculture. In the past

century there has been increasing concern to identify and quantify various forms of agriculture.

In the developed world the range usually extends between sustainable agriculture and intensive

farming (e.g. industrial agriculture).


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Production practices

Road leading across the farm allows machinery access to the farm for production practices.

Tillage is the practice of plowing soil to prepare for planting or for nutrient incorporation or for

pest control. Tillage varies in intensity from conventional to no-till. It may improve productivityby warming the soil, incorporating fertilizer and controlling weeds, but also renders soil more

prone to erosion, triggers the decomposition of organic matter releasing CO2, and reduces the

abundance and diversity of soil organisms.

Pest control includes the management of weeds, insects/mites, and diseases. Chemical

(pesticides), biological (biocontrol), mechanical (tillage), and cultural practices are used. Cultural

practices include crop rotation, culling, crops, intercropping, composting, avoidance,

and resistance. management attempts to use all of these methods to keep pest populations belowthe number which would cause economic loss, and recommends pesticides as a last resort.

Nutrient management includes both the source of nutrient inputs for crop and livestock

production, and the method of utilization of manureproduced by livestock. Nutrient inputs can be

chemical inorganic fertilizers, manure, green manure, compost and mined minerals. Crop

nutrient use may also be managed using cultural techniques such as crop rotation or

a fallow period. Manure is used either by holding livestock where the feed crop is growing, such

as in managed intensive rotational grazing, or by spreading either dry or liquid formulations of

manure on cropland or pastures.

Water management is where rainfall is insufficient or variable, which occurs to some degree in

most regions of the world. Some farmers use irrigation to supplement rainfall. In other areas such

as the Great Plains in the U.S. and Canada, farmers use a fallow year to conserve soil moisture to


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use for growing a crop in the following year. Agriculture represents 70% of freshwater use

worldwide.

Role of Agriculture in AirPollution:

Air pollutants from agricultural practices that have an impact on agriculture, andon other

aspects of our society, include chemical air pollutants that result from burning forest and

crop residues, infectious agents and allergens, and pesticides and other agricultural

chemicals. Agricultural burning produces some nitrogen oxides and hydrocarbons from which a

small amount of photochemical air pollutants are, produced.

Agriculture is diverse, ranging from large, highly intensive, and specialized commercial holdings

to subsistence (i.e., family owned) farming, using mainly traditional practices. Consequently,impacts on the environment vary in scale and intensity and may be positive or negative (1).

However, increasing evidence shows that the greater size and intensity of farms and concentrated

animal-feeding operations (CAFOs) increase the emissions of odorous compounds (e.g., organic

acids) and trace gases (e.g., carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O),

nitrogen oxides (NOx), ammonia (NH3), and reduced sulfur compounds, such as hydrogen

sulfide (H2S)) to the atmosphere.

Globally the livestock sector (beef and dairy cattle, swine, and poultry) is estimated to be

responsible for 18% of all greenhouse gas emissions measured in CO2 equivalents, 65% of

anthropogenic nitrous oxide, 37% of anthropogenic methane, and 64% of anthropogenic

ammonia. It is a major driver of deforestation, as well as one of the leading drivers of land

degradation, pollution, climate change, coastal sedimentation, and invasion of alien species.

Few of the root causes are discussed below:

Agricultural Emissions:

Agricultural emissions play an important role in several atmospherically mediated

processes of environmental and public health concerns. These atmospheric processes

affect local and regional environmental quality, including odor, particulate matter (PM)

exposure, eutrophication, acidification, exposure to toxics, climate, and pathogens.

Agricultural emissions also contribute to the global problems caused by greenhouse gas


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emissions. Agricultural emissions are variable in space and time and in how they interact

within the various processes and media affected. Most important are ammonia (where

agriculture accounts for 90% of total emissions),

1. reduced sulfur (unquantified),2. PM2.5 ( 16%),3. PM10 ( 18%), methane ( 29%),4. nitrous oxide ( 72%), and odor and5. emissions of pathogens (both unquantified)6. carbon dioxide (CO2),7. oxides of nitrogen (NOx),8. sulfur oxides (SOx), and9. particulates.

These compounds interact in atmospheric reactions (e.g., gas-to-particle conversion, are

transported by winds, and return to the surface by wet and dry deposition. Many of these

compounds have adverse effects on human health and the environment. Agriculture

provides major sources of reduced gases and particulate matter during livestock

production, fertilizer application, land use changes, and biomass burning.

Current research priorities include the quantification of point and nonpoint sources, the

biosphereatmosphere exchange of ammonia, reduced sulfur compounds, volatile organic

compounds, greenhouse gases, odor and pathogens, the quantification of landscape

processes, and the primary and secondary emissions ofPM. Given the serious concerns

raised regarding the amount and the impacts of agricultural air emissions, policies must

be pursued and regulations must be enacted in order to make real progress in reducing

these emissions and their associated environmental impacts. Eases and other soil-borne

pests, and also as a means for the disposal of crop residues.

Agricultural technology:

Contributions of agricultural technology to air pollution include pesticides, odours,

smoke, dust, allergenic pollens, and trash. The widespread public concern about


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pesticides makes it imperative that pesticide technology be carefully controlled and that

search for better methods be pursued vigorously.

Emission of Nitrous oxide:

Emissions of nitrous oxide (N2O) mainly stem from agriculture, because nitrogen in soils

can easily be denitrified by bacteria. Nitrous oxide is emitted during the denitrification

process. Additionally, the application of (artificial) fertilizers causes emissions of

ammonia (NH3), nitrogen oxides (NOx) and methane CH4), a greenhouse gas.

The agricultural sector is known for its extensive use of pesticides. This application

causes emissions of many toxic chemicals.

Nitrous oxide is a greenhouse gas with an atmospheric lifetime of approximately 120

years. Nitrous oxide is about 310 times more effective in trapping heat in the atmosphere

than CO2 over a 100-year period . It is produced naturally in soils through the microbial

processes of denitrification and nitrification. These natural emissions of N2O can be

increased by a variety of agricultural practices and activities, including the use of

synthetic and organic fertilizers, production of nitrogen-fixing crops, cultivation of

organic soils, and the application of livestock manure to croplands and pasture.

Moreover, Inadvertent additions of nitrogen to soils can also result in N2O emissions.

Indirect emissions occur when applied fertilizer or manure nitrogen volatilizes as

ammonia and oxides of nitrogen, which are then deposited in downwind regions in the

form of particulate ammonium, nitric acid, and oxides of nitrogen. Surface runoff and

leaching of applied nitrogen into groundwater and surface waters can also result in

indirect N2O emissions from downstream ecosystems.

Nitrous oxide emissions from croplands fertilized for the production of biofuels can

negate all of the benefits of this renewable source of energy on the Earths climate.


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Emission of Ammonia:

Ammonia is a pungent, hazardous caustic gas. Agriculture, specifically livestock

farming & animals waste, is the main source of ammonia emissions. NH3 plays a

significant role in PM2.5 formation, and increasing ammonia may enhance PM2.5

(aerosols with aerodynamic diameters of less than or equal to 2.5 m).

Emission of Dust:

Agriculture also contributes to the dust problem, created by wind-blown soil, the

result of improper agricultural practices, and unprotected fields. Agricultural dustsalso arise from processing operations, such as cotton gins and alfalfa mills. Some of the

adverse effects of airborne dust are illness; irritation; morbidity; and the accumulation

of silt in homes and on mechanical equipment.

Agricultural Chemicals:

When agricultural chemicals are misused or used carelessly, they cause harm. The

Adverse effects have been relatively minor in relation to the great benefits that have

resulted from safe and effective pest control and improved crop management.

Emission of Hydrogen sulfide (H2S):

Hydrogen sulfide (H2S), a major emission from animal agriculture, is a colorless,

potentially lethal gas released from swine manure decomposition. It is produced as

manure decomposes anaerobically, resulting from the mineralization of organic sulfur

compounds as well as the reduction of oxidized inorganic sulfur compounds such as

sulfate by sulfur-reducing bacteria . The U.S. Center for Disease Control (CDC) warns

that brief exposures to high concentrations (>500 ppm) can cause unconsciousness or

death. Campagna et al. have reported a correlation between elevated ambient H2S

concentrations and hospital visits for respiratory diseases. Donham et al. reported that

hydrogen sulfide and manure gas appeared to be the main toxic substance associated


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with death and illness for people with acute exposure to gases emanating from liquid

manure. With an odor threshold ranging from 0.0005 to 0.3 ppm, it is one of the primary

gases released from swine facilities causing odor complaints due to its characteristic

rotten egg smell. H2S is the major sulfur compound emitted from concentrated animal-

feeding operations, but we know little about the emission of other gaseous sulfur

compounds, such as methyl mercaptan (CH3SH), dimethyl sulfide (DMS (CH3)2S),

dimethyl disulfide (DMDS (CH3)2S2), carbonyl sulfide (COS), and carbon disulfide

(CS2).

Emissions ofParticles:

Primary emissions of particles from agriculture contribute about 16% to the PM2.5

emissions, and 18% to PM10 emissions. However, there is no estimate for the

secondary formation ofPM fine from precursor gases emitted from agriculture. Current

investigations show that PM emissions from agriculture in regions of intensive ammonia

emission may have been previously underestimated, and a large part of the gap between

modeled and measured PM concentrations might be explained by previously

underestimated agricultural sources.

Ambient PM2.5 results from direct particle emissions (e.g., soil dust) and secondary

particles (generated by atmospheric reactions of precursor gas emissions). The major

precursor gases include SO2, NOx, VOCs, and NH3. The mass of ambient PM2.5 is thus

a mixture composed mostly of sulfate (SO42-), nitrate (NO3), ammonium (NH4+),

organic carbon (OC), black carbon (BC), and soil dust. A considerable and growing body

of evidence shows an association between adverse health effects and exposure to ambient

levels ofPM.

The reactions between NH3, sulfuric acid (H2SO4), nitric acid (HNO3), hydrochloric

acid (HCl), and water (H2O) are the most important equilibrium reactions for gas/particlepartitioning and the formation of ammonium (NH4+) salts, which make up 20% of the

PM2.5 in the atmosphere. Once formed, these particles act as cloud condensation nuclei,

which affect the Earths radiation budget and its climate through cloud formation,

lifetime, and precipitation. The aqueous phase chemistry of NH3 may also provide a


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mechanism for reduced nitrogen to repartition from larger particles to small particles,

thus forming new particles in ultrafine mode (< 0.1 m aerodynamic diameter).

Conclusion:

Agriculture is an important sector contributing to environmental effects and air quality.

Agricultural air pollutants contribute to human health problems through exposure to ammonia,

hydrogen sulfide, toxic organic compounds, pesticides, and particulate matter. Agricultural air

pollution contributes to climate change in the form of greenhouse gas emissions and aerosols.

Agricultural air pollution also contributes to odor. After deposition of reactive nitrogen,

eutrophication and acidification can result and biodiversity is endangered.

Ammonia, in particular, plays a role in a host of environmental problems (e.g., air quality, odor,climate change, soil acidification, eutrophication, biodiversity), often through interactions with

other compounds in the atmosphere. The central challenge is how to optimize the use of nitrogen

to sustain human life while minimizing its negative impacts on the environment and human

health.

Production agriculture has adopted modern technologies and science to maximize productivity,

but it has not yet been subjected to the same environmental regulations that other modern

industries must obey. Regulations and policies should also require that CAFOs and crop

production systems use all of the practical methods to reduce ammonia and other air emissions.

The potential health and environmental risks of intensified modern agriculture demand that we

develop emission abatement policies based on best available science.

Reducing uncertainties presents significant research challenges and charts the direction of

research for the next decade or beyond. Resolving them will have important policy implications

on local to global scales and will profoundly improve air quality, human health, the agricultural

environments, and biodiversity. Progress on these challenges will require an integrated and

multidisciplinary effort both nationally and globally from scientists, engineers, policy-makers,

managers, and the public.


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Documents

Role of Agriculture in Air pollution