Iram shahzadiM.Sc. 1ST

09-Arid-349

Contents…Definition of natural emissions.Sources.Natural emissions.Criteria pollutants.Air quality standards.Effects on air quality.References.

“Natural” is commonly defined as being “present in or produced by nature with relatively little modification by humans.

Natural emissions are the emissions during natural processes in soil, water and air.

Anthropogenic sources.Natural sources.

•Carbon dioxide(Co2).•Carbon monoxide(Co).•Sox.•NOx.•VOCs.(Benzene, pentane, etc…)•Hydrocarbons (Methane).•Aerosols.•SPM.

Vegetations. Respiration by vegetation emits around 220 Gt per year.Ocean. The ocean releases about 330 Gt. In contrast, human emissions are only around 26.4 Gt per year. Volcanoes. Volcanic activity now releases about 130 to 230 teragrams (0.13-0.23 gigatonnes or 145 million to 255 million short tons) of carbon dioxide each year.(Gerlach,1992).

Currently carbon dioxide is responsible for 57% of the global warming trend.(Tom Socha, 2007).

NOx production by lightning has been estimated in the range of 3-5 TgN/yr.

(Levy.H.,et.al.,1996)Has a role in reducing stratospheric ozone.30 to 50 million tons per year from human activities, and natural 10 to 20 million tons per year.

(Tom Socha, 2007).

Figure 1. Contribution and uncertainty of global anthropogenic and natural N emissions in 1990 [from Olivier et al. (1999)].

Wetlands.Gas hydrates.Permafrost.Termites.Oceans.Freshwater bodies.Wildfires.

Effects of natural emissions on air.Acidification.Green house effect.Ozone déplétion.Tropospheric ozone formation.Aérosols formation. Photochemical smog.

Acid rain is formed when sulfur dioxide and nitrogen oxides react with water vapor and otherchemicals in the presence of sunlight to form various acidic compounds in the air.

•SO2 + H2O + ½O2 = H2SO4

•NO2+H2O+1/2O2=HNO3

The chemical reaction between nitrogen oxides and volatileorganic compounds

(VOCs) in the presence of sunlight resultsin the photochemical smog; the tropospheric

ozone is an endproduct of this reaction and a component of the smog itself.

Santiago SmogPhoto: Phil Whitehouse

Greenhouse gases are gases in an atmospherethat absorb and emit radiation within the thermalinfrared range. This process is the fundamentalcause of the greenhouse effect.(IPCC,2008).water vapor, which contributes 36–72%.carbon dioxide, which contributes 9–26%.methane, which contributes 4–9%.ozone, which contributes 3–7%.(Kiehl,2006)

A depletion of the ozone layer will increase the UV-radiation at ground level.For each 10 percent depletion of the ozone layer, we can expect 20 percent more radiation in these damaging wavelengths. The ozone layer above the northern hemisphere has been reduced by 5-6 percent in spring per decade.

Ozone-depleting gases. gases The various ozone-

depleting substances vary in the degree to which they contribute to the reduction of the ozone layer.

Chlorofluorocarbons (CFCs).

HalonsMethyl chloroform.Methyl bromide.Carbontetrachloride.

Smoke and ozone pollution fromIndonesian fires, 1997.

Ozone-layer depletion seems likely to increase the rate of greenhouse warming, by reducing the effectiveness of the carbon dioxide sink in the oceans.

IPCCAR4SYRAppendixGlossary(http://www.ipcc.ch/pdf/assessmenteport/ar4/syr/ar4_syr_appendix.pdf(“PDF).ttp://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr_appendix.pdf. Retrieved 2008-12-14.Kiehl, J. T.; Kevin E. Trenberth (1997). "Earth’s Annual GlobaleanEnergyBudgethttp://www.atmo.arizona.edu/students/courselinks/spring04/atmo451b/pdf/RadiationBudget.pdf) " (PDF). Bulletin of the American Meteorological Society 78 (2): 197–208. DOI:10.1175/1520-0477(1997)078<0197:EAGMEB>2.0.CO;2 (http://dx.doi.org/10.1175%2F15200477%281997%29078%3C0197%3AEAGMEB%3E2.0.CO%3B2)http://www.atmo.arizona.edu/students/courselinks/spring04/atmo451b/pdf/RadiationBudget.pdf. Retrieved 2006-05-01.

JICA-Pak EPA, # 3, Review of Pak Environmental Air Quality and Emission Standards Promulgated, May 2, 2001, My Y Shigeta (JICA Env Expert stationed at Pak ).

Air Pollution Causes and Effects by Tom Socha,09/11/2007.

Gerlach, T.M., 1992, Present-day CO2 emissions from volcanoes: Eos, Transactions, American Geophysical Union, 72(23).June 4, 1991, pp. 249, and 254 – 255.